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After 20 seconds, the teeth were dried and a sec- icon rubber and green politip-polisher silicon rubber ond coat of single component was applied and immedi- Vivadent-Liechtenstein in a low-speed handpiece. One Intact Teeth The hybrid composite teeth were dried and light cured for 10 sec- Restored with The same procedure was repeated twice packable composite more. Definite was placed and cured in the Restored with ormocer Compressive loading using steel rods, Figure 2. Illustrative graphic of mean and standard deviations for the fracture resistance test.

Figure 3. Fracture at the interfacial area Figure 4. Fracture at the interfacial area Figure 5. Bulk fracture of restorative materials. Occsionally, a small fragment of resin compos- ite was found attached to the tooth. The same investigator performed all restorative procedures throughout the study. The instrument developed by Blaser and others and Joynt and others appears to provide precision in loading the specimen and, with modifi- cation, it was used as a model for this Figure 6.

Fracture involving only tooth struc- Figure 7. Fracture involving the tooth structure investigation. Two metal rods, each ture. A bidirectional joint was well, applied to the enamel and dentin walls for 30 sec- also added to the shaft between the crosshead and the onds and rinsed and air dried. Three drops of base, one metal rods to allow for appropriate adjustment to the drop of catalyst and one scoop of HPA High various occlusal surfaces.

The use of two rods instead of Performance Additive were dispensed into a mixing one assured contact with tooth structure alone without well and gently stirred. The mixture was applied in a loading the restorative material during the test proce- thin layer to the cavity walls.

Each tooth was restored dure Figure 1. The specimens were placed on a foam immediatelly following adhesive application with a cushion on the Instron platen, which permitted even spherical lathe-cut amalgam A metal matrix band was seating of the load. The teeth were preloaded to a max- placed in the same way as the other restorations. The plastic amalgam was times before testing to failure.

The preloading proce- hand condensed into the cavity while the adhesive liner dure was introduced to simulate intraoral forces and was still wet. The teeth were then tested to failure at a speed of 5 of teeth using five adhesive systems. Fractured tooth and restoration sur- than the unprepared group. Table 2 and Figure 2. The Tukey multiple com- restorations has generally been accepted.

This suggests parison tests showed that there were no statistically that in teeth that are etched, bonded and restored with significant differences among the means of the unpre- resin composite, the cusps are mechanically splinted pared group and the group restored with hybrid com- together. The reaction of these teeth to a load was simi- posite, packable composite and ormocer.

Also, no statis- lar to the reaction of unprepared teeth. However, statistically sig- hybrid composite, packable composite and ormocer nificant differences were noted between the restored materials were not statistically significant compared to group with amalgam and the unrestored control group the unprepared control group.

Occasionally, small frag- In this study, the Tukey multiple comparison tests ments of resin composite were found attached to the revealed no significant differences between the restora- tooth Figure 3.

The amalgam group showed lower cuspal fracture resistance compared to all the other between the tooth and the restorations were found in a groups.

However, this difference was not statistically small number of ormocer and amalgam specimens significant. Also, the unprepared group showed higher Figure 4 compared to hybrid and packable composite cuspal fracture resistance than the teeth restored with specimens.

Fewer fractures were observed in all tion were restored with hybrid composite, packable com- restored groups that involved only the tooth structure posite, ormocer and bonded amalgam. The data showed Figure 6 and also involved tooth structure and that the fracture resistance of teeth restored with etched restoration Figure 7.

Static loading of the amalgam restoration, irre- amalgam. Composites, therefore, may transmit less of versible deformation and crack propagation risk on the the applied load to the underlying tooth structure. Several in vitro studies have reported that weakened teeth restored with resin composite and teeth restored with amalgam bonded to etched enamel placed with a bulk and an incremental technique that with resin cement have a significantly greater fracture may reduce the effects of polymerization shrinkage.

In fracture than posterior resin placed with a bulk tech- this study, intact teeth had a significantly greater frac- nique. Since polymerization contraction stresses of the ture resistance than teeth restored with amalgam using packable composite and ormocer materials were higher Amalgam Bond Plus.

These findings of failure were sim- posite resins Dental Materials 17 3 For ormocer and through micromechanical bonding Journal of Prosthetic amalgam, the number of fractures seen in the tooth and Dentistry 36 2 Fracture resistance of teeth restored with the bonded amalgam technique Operative Dentistry 26 5 In view of the reinforcing ability of all the tooth-colored Eakle WS a Fracture resistance of teeth restored with restorative materials hybrid, packable, ormocer stud- Class II bonded composite resin Journal of Dental Research ied, it is suggested that where cavity cusp width is one- 65 2 A statistically significant difference was found strates Dental in Japan 36 FDI Commission Project restored with bonded amalgam.

International Dental Journal 48 1 Review. Differences among the unprepared teeth and Effects of composite restorations on resistance to cuspal frac- those restored with hybrid composite, packable ture in posterior teeth Journal of Prosthetic Dentistry 57 4 composite and ormocer were not statistically Journal of Dentistry 13 Journal 12 Operative Dentistry 21 3 Prosthetic Dentistry 61 2 Clinical Relevance Significant variations in radiopacity values were found among esthetic restorative mate- rials when compared to enamel.

All materials except for the microfilled resin composite Filtek A had radiopacity values greater than dentin. The results showed statisti- materials with reference to an aluminum step cally significant differences among materials. A total of samples measuring 6 and was higher than enamel.

All materials except mm in diameter and 1 mm in thickness, with for the microfilled resin composite Filtek A eight samples of each material, were prepared had radiopacity values greater than dentin and from restorative materials. Enamel and dentin possessed sufficient radiopacity to meet ISO samples 1-mm thick were also prepared by longi- standard. Significant differences were found tudinally sectioning eight extracted human per- among materials of the same composition when manent molars using a microslicing machine.

Up-to-date The optical density values of the specimens were resin composites and glass ionomer cements may be used to determine the aluminum thickness equiv- the most refined materials, as new versions are rou- tinely being developed. Of these, radiopacity is a valuable property that Although many new esthetic restorative materials allows the clinician to assess the adequacy of restora- have been introduced to the dental market, there have tions, distinguish secondary caries and evaluate mar- been only a few recent studies regarding their ginal adaptation, voids and interfacial gaps.

This study, therefore, determined the proximal contours, contacts and overhangs and serves radiopacity values of esthetic restorative materials an important role in detecting aspirated or dislocated and compared them to enamel and dentin.

Table 1 lists the 21 esthetic restorative materials used According to the International Standards in this study. All samples were polished using , , and one tooth section. Enamel and an aluminum step wedge This step wedge was used to enable accurate correlation of the optical density of the images of the speci- mens to that of the aluminum step wedge.

Films were exposed for 0. Optical densities of aluminum step wedge. A min- imum of four readings was Dyract AP 1. A Compoglass F 1. Filtek Z 1. Heliomolar Flow 1. Pyramid Dentin 1. Marginal defects and secondary caries materials. One-way analysis of variance ANOVA are usually located on the gingival part of Class II indicated significant differences both for the optical restorations. Heliomolar RO had a radiopacity value 2.

A radiograph of all the tested materials along with a tooth section and the aluminum A had radiopacity values 1. All materials except Filtek A 0. Figure 3 shows the bar chart repre- sentation of optical densities and Figure 4 shows the aluminum thick- ness equivalents of all tested materi- als with enamel and dentin. Heliomolar RO. Solitaire 2. Enamel Vitremer. Heliomolar Flow. Filtek Z Pyramid Dentin. F Ariston pHc.

Compoglass F Dentin. Chem Flex Syringeable. P Filtek. Adequate radiopacity has been considered a prerequisite for diagno- sis of secondary caries and marginal defects since it facilitates evaluating. Bar chart representation of optical density values of all materials.

Whether a restorative mate- for posterior restorative materials. It has been recom- ground of enamel and dentin since the contrast facili- mended that the radiopacity of resin composites tates the evaluation of restorations in every region of should be equal to or greater than enamel Van Dijken, the mouth. Of the Materials with a radiopacity less than enamel microfilled resin composites, Heliomolar RO had a were reported not to be suitable for use, especially as radiopacity greater than enamel.

In this study, there was considerable variation in the In addition to being used in permanent dentition, radiopacity values of esthetic posterior restorative glass ionomer cements and hybrid versions have materials. Syringeable, and the polyacid-modified resin compos- The popular materials for posterior esthetic restora- ites, Dyract AP, Compoglass F and F, had a tions, the packable resin composites, also showed dif- radiopacity higher than enamel but the resin-modified ferent radiopacity values.

Of the five packable compos- glass ionomer cement Vitremer had a lower radiopacity. Pyramid Dentin, Pyramid Enamel and Solitaire 2 had It was suggested that in order to fulfill clinical lower values than enamel. The marginal defects. Heliomolar Flow, the flowable com- posite used in the study, was higher in radiopacity compared to enamel, but in contrast, Composan LCM Flow was lower.

The radiopacity of a resin depends on selection of the polymer matrix, chemical nature of Solitaire 2 Ariston pHc Chem Flex Condensable. Composan LCM. TPH Spectrum.

Pyramid Enamel. Filtek A F This resulted in considerable varia- tions in radiopacity values of the restorative materials used in the study. Bar chart representation of aluminum thickness equivalents of all materials. A caries lesion near the buccal or lingual resin composite Filtek A were found to have margin of a Class II restoration may be masked by a radiopacity values greater than dentin and possessed highly radiopaque restorative material.

Moderate sufficient radiopacity standards of ISO This found among materials when compared to enamel. Prosthetic Dentistry 70 4 Although Akerboom and light-cured posterior composite resin: Results of a 3-year clini- others suggested using human teeth as a stan- cal evaluation Journal of the American Dental Association dard, they reported that variations in radiopacity of 5 Association 81 4 It was reported that variability in radiopacity values Cook WD An investigation of the radiopacity of composite restorative materials Australian Dental Journal 26 2 Clinical Relevance With respect to the adhesion properties of carbon fiber posts and glass fiber posts used in the restoration of endodontically-treated teeth, they perform equally well if used in combination with chemically cured luting cements or with light activated ones.

The post is Fiber posts are widely used in the restoration of cemented inside the root canal using low mod- endodontically treated teeth. Scientific evidence ulus elastic polymer resins. In this study, the demonstrates that the mechanical performance mechanical resistance of four different post- of teeth restored with fiber posts in combination cement systems was assessed by means of a with resin luting cements is improved with micro-mechanical pull-out test assisted by a sim- ulation using the finite element methodology.

The post is cemented inside the root canal and the Luigi Ambrosio, full professor, Institute of Composite Materials Technology, National Research Council and Interdisciplinary core is retained by an apical extension of the post.

The use of post and core restoration will Luigi Nicolais, full professor, Institute of Composite Materials continue to increase because of the current trend to pre- Technology, National Research Council and Interdisciplinary serve natural tooth structure in the mature years of life Research Center in Biomaterials CRIB, University of Naples, Christensen, Fiber posts are generally used with low modulus resin The stress distribution in the cement layer was studied cements in combination with dentin adhesive systems.

Four different combinations of mechanical viewpoint, the post acts as a bypass, con- fiber post—luting cement were used: carbon fiber posts centrating the chewing stresses at the root tip. Carbon fiber posts were initially used in combination with low modulus chemically cured luting cements.

Biomaterials research introduced new materials for post manufacturing, for example, E-glass or quartz fiber embedded in transparent epoxy-resin matrix, to be used with newly developed light cured luting cements. The mechanical properties of fiber posts and data on adhesive retention strength of cemented fiber posts in root canals are widely reported in the scientific litera- ture.

However, little information is available regarding the interface between the fiber post and the resin lut- ing cement.

In fact, the direct measurement of the bond strength between the fiber posts and cement has been Figure 1. Mechanical pull-out test set-up. This Table 1 shows the average recorded maximum load and was done in order to investigate whether the adhesion the average bond shear strength for each post-cement properties were improved by photopolymerization. During the that the load increases quasi-linearly, then levels up, preparation, all samples were stored for no more than reaching the ultimate load F before drastically dropping 24 hours in an isotonic 0.

Coupled ANOVA statistical analysis suggests that there are no Teflon molds were used to keep each fiber post coaxial significant differences among samples at a probability with the dentin hole during the curing of the cement, level of 0. In the first case, the upper surface of layer the part in contact with the steel frame, see the dentin was constrained, while the cement was free Figure 1. The axial- the other systems being very similar. Since the state of symmetry of the geometry led to the development of a stress in the relevant parts of the cement is generally two-dimensional model that was solved using the pack- three-dimensional, the FEM analysis produced graphs age ANSYS 5.

The The pull-out tests were performed with an INSTRON distributions of the von Mises equivalent stresses in the testing machine and the pulling load was cement layer for each of the four post-cement systems increased at a cross-head speed of 2.

The axial displacement of the check for the locations where critical stress values were post was monitored using an INSTRON extensometer reached and are shown in Figure 4. As can be seen, the positioned between the dentin slice and the post-cement interface the left side of each distribution post Figure 1. The load and the extensometer dis- is more loaded by about a factor of 2 than the dentin- placement were acquired at a sampling rate of 10 points cement interface the right side of each distribution.

Ultimate strength The manufacturers provided all the N St dev 78 70 84 68 relevant data concerning the posts and Ultimate shear stress MPa St dev 6. The axial load-axial displacement graph obtained from the FEM analysis is shown in Figure 2, where it can be compared with the experimental data.

Thus, regarding the mechanical integrity of the restored tooth, Figure 2. The left and right side of each distribution represent the post-cement and the cement-dentin interfaces, respectively.

The upper part of each distribution is the region of the cement that is in contact with the stainless steel frame, as represented in Figure 1. As retention properties are essential from a clinical The mechanical tests demonstrated that all the vari- perspective, it is important to study the properties of ous systems withstood loads up to N, suggesting the interfaces involved in the restoration.

The differences cement and another between the cement and the among the various post-cement combinations were not dentin substrate. Moreover, as it is well stress distribution within the luting cement layer. The shear stress calculated using are higher. In the case of fiber post restorations, the equation 1 is an average value obtained, assuming highest differences are between the post and the luting that the shear stress distribution within the cement cement; thus, it is particularly important to investi- layer is uniform.

This value is basically equal to the average shear stress calculated using equation 1. The left side and the right side of each distribution represent the post-cement and the cement-dentin interfaces respectively. The upper part of each dis- tribution is the region of the cement that is in contact with the stainless steel frame, as represented in Figure 1.

Acknowledgements Thus, it can be concluded that using equation 1 leads to a gross underestimation of the maximum shear The financial support of POP Regione Campania Azione 5.

The authors also mechanical reliability of this interface in the fiber post acknowledge Mr Antonio Maggio for matching the specimens and restorations. Dr Fulvio Anselmi of Cabon-Denit Spa for supplying technical The non-uniform stress distribution obtained with information. FEM suggests that the post-luting cement system likely fails when a crack starts on the upper part of the Received 16 August cement layer Figure 1 and propagates downward along the post-cement interface.

The difference This is consis- tion modalities in structurally compromised premolars tent with the clinical observation of post debonding International Journal of Prosthodontics 8 3 Further Microtensile bond strength and confocal microscopy of dental studies should focus on the influence of these factors adhesives bonded to root canal dentin American Journal of on the strength of the fiber post cement interface.

Dentistry 14 4 Prosthetic Dentistry 78 1 Clinical Relevance Dentin surface topography created by various bur designs may influence the surface sealing quality of resin bonding agents and, therefore, affect post-operative sensitivity and microleakage associated with composite bonding procedures.

Dentin bonding agents do not appear to routinely seal the pulpal wall before application of resin composite and creation of polymerization shrinkage stress. A flow system was established through This study investigated the effects of bur cutting the pulp chamber and gravity pressurized phos- surface roughness and bonding systems on phate buffered saline PBS was forced into the dentin permeability.

Burs were used to prepare flat sur- sively serrated bur were utilized with two differ- faces in dentin, and after etching with phos- ent bonding systems. After applying the dentin bonding the permeability of dentin sealing after applica- agents, fluid flow from the pulp chamber into tion of bonding agents.

This study incorporated a dentin was again measured. The percentage of fluid flow model for measuring dentin permeabil- reduction in permeability following bonding ity. Seventy caries-free extracted molars were agent application was then calculated. The specimens were straight-edged bur.

No significant differences were mounted to plexiglass plates using cyanoacrylate detected between bonding systems and no combi- nation of surface topography or bonding agent Tanya Vaysman, year IV dental student, UMDNJ New Jersey completely sealed the surface. D, professor and chair, Biomaterials ciated with postoperative sensitivity.

Causes of The cynaoacrylate cement was applied to the milled post-operative sensitivity after bonding procedures apical portion of the cut crown segment, taking care include incomplete caries removal, desiccation of tooth not to introduce any cement into the root canal cham- structure by over-drying, over-etching the dentin, bac- ber. A flow system was established using two gauge terial contamination, improper restorative placement, hollow stainless steel cylinders connected through the incomplete polymerization and occlusal interferences pulp chamber.

The specimens were coated with a thin Hornbrook, This fluid is a filtrate of plasma tions. While there is provide intrapulpal pressure to tooth specimen. Eick and others Hume, Other of bonding resins is the surface topography of the pre- investigators have reported that intrapulpal pressure pared dentin and that a roughened surface creates a is known to vary in magnitude, is significantly higher greater surface area.

The left side of the circuit consisted of This study compared the effects of dentin surface the fluid reservoir joined to the specimen with roughness on dentin permeability using a fluid flow gauge polyurethane tubing.

As men- to the prepared dentin surface. A millimeter ruler tioned above, incomplete sealing of dentin tubules by approximated to the polyurethane tubing allowed for the bonding system has been implicated in the etiology visual measurements of air bubble travel. They were then stored in a phosphate buffered saline solution PBS until used for sample preparation. The specimens were sectioned 2 mm apical to the CEJ using a high-speed handpiece with copi- ous water.

The specimens were mounted with cyano- acrylate cement to 50 x 50 mm plexiglass plates. Schematic diagram of fluid flow apparatus. The connections were examined to ensure a surface. The thin layer of cyanoacrylate cement sealed fluid system and minimize visible leaks.

After the equilibration agents. The flow through establish a baseline sealed measurement. This allowed the etched surface was recorded over 15 minutes to each tooth to act as its own control. A flat surface was establish initial dentin permeability of the crown seg- then prepared on the dentin at a depth of 1. Based on this initial dentin permeability, speci- half the cutting length of a carbide bur from the mens were assigned to each of the six experimental central fossa using a diamond bur on a high-speed groups so that each group received a variety of initial handpiece.

The bur was held perpendicular to the long dentin permeabilities. The flow was measured over 15 minutes and recorded as the etched system measure- ment. After establishing the etched system permeability, the pressure in the fluid reservoir was reduced to zero to avoid moisture contamination during the bonding pro- cedure.

Photographs of burs used in the study. All sam- ples were stored in an air-tight, moist environment before and after the testing procedure. Removing these samples necessitated having unequal samples groups. The remaining specimen distribution is shown in Table 2.

Post-hoc t-tests were used to compare groups where a significant omnibus f-test was found. Experiment-wise error rates were controlled in these post-hoc tests by means of Tukey HSD pro- cedure Kirk, For scanning electron microscopy SEM , the spec- imens were removed from their plexiglass plates and the undersurfaces were further milled to facili- tate placement in the SEM chamber.

The samples were mounted on stainless steel studs and vacuum desiccated for approximately four days, then carbon coated. Measuring dentin permeabilites in this extracted tooth model yielded significant variability. Typical permeabilities of etched open tubules ranged from 0. Once the etched dentin was bonded with DBA, typical permeabilities ranged between zero and 0.

Using the formula described above, mean PPD values ranged from a low of Post-hoc t-tests showed that the average PPD for both serrated type burs was signifi- cantly more effective than the straight fissure bur, therefore, indicating that samples prepared with the Figure 4a. Fissure bur FB. Figure 4b. Cross-cut bur CC. Figure 4c. Extensively serrated bur ES. Bonded samples with lower PPD measurements were considered to have areas of unsealed etched dentin, causing localized fluid flow of the PBS solu- tion.

Specimens with initial etched permeability less than 2. Very high initial flow volumes were thought to result from microcracks or from limited dentin thickness in specimens pre- Figure 5.

Specimens producing very low etched permeability, baseline flow 2. Since shallow restorations to higher values with increased serration was evident, exhibit little post-operative sensitivity, this elimi- the cross-cut fissure bur was not different from the nation was thought to be inconsequential to the extensively serrated bur.

The effect of the two bonding outcome of the study. No interaction between bur and bonding sys- pressure was introduced at a pressure significantly tem was detected. In addition, no group exhibited higher than what exists in a healthy tooth. SEM observation revealed a relatively post-operatively sensitive tooth , the authors felt that smooth surface with limited surface roughness when a creating an increased pressure environment may more fissure bur was employed as depicted in Figure 4a.

It has been Cross-cut serrated burs created serrations and shown that polymerization shrinkage of resin compos- grooves that appeared uniform and widely separated ites during direct placement causes dimensional strains Figure 4b. A higher magnifi- as gaps at the tooth-restorative material interface due cation SEM examination of the extensively serrated to the separation of the resin-bonding agent from the surface revealed orientation of the grooves, peaks and underlying dentin, especially along the pulpal wall.

The valleys in the dentin, and patent dentin tubules volume of these internal gaps has been reported to be as Figure 5. Carvalho and others reported these poly- Examination of the dentin prepared with cross-cut merization stresses and resulting strain are expected serrated burs followed by application of Clearfil SE in Class I preparations where there is a high ratio of Bond revealed that the bonding agent covered the bonded to unbonded surfaces high C-factor peaks and valleys created by the bur.

In addition, bonds to the appeared uniform with some irregularities Figure pulpal floor are often lower because deep dentin is 6a. The presence of these gaps, regardless of the from the underlying dentin, especially in the region of bonding agent polymerization method or whether flow- irregularities. This resulted in separation of polymer- able or heavily filled resin composite formulations were ized resin tags and exposed dentin tubules Figure employed, was recently demonstrated in Class I dentin 6b.

One pos- sible explanation is that increased surface area on the dentin allows for a better infiltration of the bonding resins. In addition, the bur-cre- ated surface topogra- phy, if extended to the pulpal wall prepara- tion, may help to with- stand the polymeriza- Figure 6a. Arrow points to micro-cracks in bonded resin Figure 6b. SEM image of a micro-crack. Arrow points to a tion shrinkage stress layer. Resin bond- The results of this study indicate that if a uniform ing agents have a dual role when used under resin com- roughness could be created on the pulpal floor of cavity posites.

First, they provide micro-retention, primarily preparations, the initial sealing capability of existing through the peritubular dentin, for bonding to the com- bonding resins may be improved. In clinical practice, posite restorative. Therefore, an pulpal floor topography playing a role in improving ideal resin bonding agent should provide effective per- dentin bonding agent sealing ability.

While many pro- itubular bonding to facilitate retention of the composite cedures and techniques have been proposed to improve and complete sealing of the dentinal tubules to prevent bonding procedures, cavity surface topography is gen- permeability of dentinal fluid that may cause post-oper- erally not considered. As a result of this study, future ative sensitivity.

In clinical practice, amalgam restorations are seldom associated with post-operative sensitivity. The authors thank Malvin Janal, PhD for his assistance in sta- The results of this study indicated that samples pre- tistics and Elizabeth Clark, MS, for her technical assistance. Operative Dentistry 12 3 Journal of Dentistry 11 5 Dentin permeability: Effects of cavity varnishes and liners Analysis of sealing vs tensile bond strength of eight adhesive Journal of Prosthetic Dentistry 53 Clinical Relevance The effect of food-simulating liquids on the shear strength of resin-based filling mate- rials was product dependent.

Composites based on BisEMA may be more resistant to degradation by alcohol. After conditioning, the speci- [EX], Dentsply , a conventional Compoglass [CG], mens were restrained within the test apparatus Vivadent and a posterior polyacid-modified and subjected to shear punch strength testing Dyract Posterior [DP], Dentsply composite.

All materials with the excep- Dentistry, National University of Singapore, Republic of tion of EX were significantly weakened by Singapore ethanol solution. Composites may be defined as three-dimen- strength values, while glass ionomers and polycarboxy- sional combinations of at least two chemically different late provided the lowest.

Polyacid-modified composite materials with a distinct interface Phillips, This and coloring pigments. Polyacid-modified composites or study investigated the effects of food-simulating liquids compomers are resin composites that contain either or on the shear-punch strength of composites and poly- both of the essential components of glass ionomer acid-modified composites, including a recently intro- cements but at a level insufficient to promote acid-base duced posterior polyacid-modified composite material.

Composites are recommended for restoring all ious mediums was also performed. Konstanz, Germany , a conventional Compoglass Composites, conventional and resin-modified glass [CG], Vivadent and a posterior polyacid-modified ionomer cements are all susceptible to various modes of Dyract Posterior [DP], Dentsply composite were chemical degradation in vitro.

Reduction in hardness, selected for the study. Table 1 shows the technical pro- wear, fracture toughness and flexural strength had been files of the materials and their manufacturers.

All reported after exposure to various food-simulating liq- materials were of the A2 shade. In an in vivo situation, it can be assumed that by glass slides. A second glass slide was placed on top saliva, food components and beverages can degrade and of the washers and gentle pressure was applied to age dental restorations.

Wu and others reported extrude excess material. The mean intensity of the light degradation of these materials. Thirty-two dental restorations.

Although the effects of food-simulat- specimens of each material were made and randomly ing liquids on composites had been widely investigated, divided into four groups of eight. Dental amalgams At the end of the conditioning period, the shear ISO and water-based cement ISO are punch strength of the materials was assessed. A special evaluated using a compression test, while resin-based shear punch apparatus was designed and fabricated in filling materials ISO and light-activated water- collaboration with Instron, Singapore.

The apparatus based cements ISO are evaluated using a flexural Figure 1 allowed for restraining the specimens during test. A single standard test for all dental restorative testing, self-location of the specimens and testing in a materials is desirable. The shear punch test has previ- thermally-controlled liquid environment. The shear strength of TC to fracture the test specimens.

The thickness of each and CG were significantly reduced after conditioning in specimen was measured with a digital vernier calliper ethanol solution. For DP, a significant increase in shear prior to placement in the shear punch apparatus. The strength was observed after conditioning in water. The specimens tioning in water. No significant difference in shear were subsequently restrained by tightening the screw strength was observed between Group 1 air and Group clamp on top of the specimens. An M2 tool steel punch 3 ethanol solution specimens for DP.

For EX, no signif- with a flat end 3. A small disc from the center of each The shear strengths of EX, TC and CG were signifi- specimen was punched out and the maximum load cantly greater than DP after conditioning in air Group recorded.

Shear strength was then computed using the 1. In addition, EX was significantly stronger than TC. All statistical analysis was carried out at significance level 0. Results of the statistical analyses are shown in Tables 3 and 4. The effect of conditioning mediums on shear strength was Figure 1. Diagrammatic representation of the shear punch apparatus.

The shear strength of study the effects of solvent and environmental degra- EX was also significantly greater than CG after condi- dation on material properties in dental research tioning in ethanol solution. Heptane simulates butter, fatty the simplicity of specimen preparation. Results of flex- meats and vegetable oils, while the ethanol solution ural, diametral and compression testing are highly simulates certain beverages, including alcohol, vegeta- dependent on the production of high quality specimens.

The by saliva and water. The solubility parameters for these quality of the edges of the disc around the circumfer- organic food simulating liquids were 1. The only requirement is and water, respectively.

They hypothesized that unrestrained specimens are able to bend on application of the punch, creating localized stress concentration that leads to prema- ture failure. Although a cm kg increase in screw clamp torque resulted in an increase in shear Shear Strength MPa. Tetric Ceram Esthet X strength, the increase was not sta- 80 Compoglass tistically significant.

The punch Dyract Posterior diameter 3. The shear punch apparatus used in 0 this experiment gave highly repro- Air Distilled Water Ethanol Solution Heptane Conditioning Mediums ducible results, and the standard deviations observed were generally Figure 2. Mean shear strength of the materials.

Standard deviations indicated in parentheses. In view of the latter, a further solution. The shear strength of ethanol solution has a solubility parameter value all materials was not significantly affected by heptane.

Studies have reported a positive cor- strength observed. Materials with For EX and DP, no significant difference in shear higher filler volumes like EX, TC and CG are therefore strength was observed between conditioning in air expected to have higher shear strength than DP, which control and ethanol solution. This is probably due to the differences in EX more resistant to the softening effect of ethanol- resin matrix formulation.

The shear strength of EX water solution. This finding was consistent with that of remained significantly higher than DP after condi- Yap and others a , who found that BisEMA-based tioning in water, ethanol and heptane.

Despite its high composites were highly resistant to the degradation filler volume, TC was not significantly stronger than effect of food-simulating liquids including ethanol.

DP after conditioning in the aforementioned food-sim- BisEMA is hydrophobic, as it does not contain any ulating liquids. Although no significance in slight weakening of TC after conditioning in ethanol strength was observed between DP specimens condi- and heptane. EX was most resistant to the degradation tioned in air and ethanol, significant differences were effect of alcohol.

As EX was significantly stronger than observed between DP specimens conditioned in water all materials after conditioning in ethanol, it may be and ethanol. The strength of DP was significantly the composite of choice for the restoration of posterior increased by water storage. This increase in strength is teeth in patients who consume alcohol frequently and probably due to the acid-base reaction between the in large quantities.

Differences in shear strength hydrated acidic functional groups and fluoroalumino between materials after conditioning in heptane were silicate glasses present in DP. The acid-base reaction, similar to that of the control group with the exception however, occurs only at the surface layers uppermost of TC. The latter was due to a slight decrease in Table 3: Results of Statistical Analysis Based on Materials strength of TC after conditioning in heptane and a slight increase in strength of DP.

The shear punch test, however, offers a simple, effective and reliable Table 4: Results of Statistical Analysis Based on Conditioning means of screening resin-based filling materials and Mediums evaluating material-environment interactions. Ethanol solution 2. The shear punch test is a simple, reliable Journal of Dentistry 14 4 Dental Research 71 1 A method using a micro-punch apparatus British International Organization for Standardization Dental Journal 8 Specification for dental water-based cements ISO Materials 5 3 Clinical Relevance Luting cements differ considerably with respect to their mechanical properties.

These differences should be taken into consideration when selecting a material for clinical application. Resin cements had the on flexural strength FS and compressive highest flexural and compressive strengths, fol- strength CS of 12 luting cements from different lowed by self-adhesive universal resin cement.

In addition, the influence of the These materials were statistically stronger than curing method on the mechanical properties was resin-modified glass ionomer cements, glass investigated.

The materials examined were two ionomer cements and zinc phosphate cements. The samples were prepared and tested Traditionally, zinc phosphate cement has been the most according to ISO specifications. Specimens for popular dental cement and has been in use for more FS and CS were loaded to fracture at a constant than 90 years Ames, The mechani- are not adhesive to tooth substance or to restorative cal properties were measured after the materials materials.

The mixing technique is critical in develop- were stored in distilled water at a temperature of ing the optimal cement, because the strength is almost It also investigated the Glass ionomer cements GIC have been gaining in pop- effect of the curing method on mechanical properties. Handling of the materials was car- Ferracane, They exhibit high mechanical proper- the time recommended by the manufacturers 8 or 10 ties and have excellent esthetic shade-matching poten- seconds.

On the other hand, they require pre-measured delivery systems. Panavia F and skillful usage and multiple steps with respect to their Variolink II were mixed with a hard plastic spatula in handling characteristics, especially time-consuming a ratio of base to catalyst paste on a mixing block for bonding procedures and excess removal.

The self-adhe- approximately 20 and 10 seconds, respectively. The cements. Clinically, the tooth-cement interface can withstand To evaluate the influence of the curing method, the masticatory and parafunctional stresses for many years resin cements and the self-adhesive universal resin in a warm, wet oral environment. Stress may cause cement were polymerized using a dental light-curing recoverable elastic or permanent plastic deformation, unit Elipar Trilight; 3M ESPE, Seefeld, Germany.

When cements. These measurements enhances the surface deterioration of polymer resin were performed on 10 samples at each occasion. The mold was placed mechanical properties of luting cements. This study on a glass slab and freshly mixed cement was applied analyzed the influence that water has on three-point until the mold was slightly overfilled. Then, a trans- flexural strength FS and compressive strength CS parent matrix band was placed on top of the mold and a second glass slab was pressed on it.

After the mold and the glass slabs were put in the The specimens were prepared in split cylindrical rigid screw clamp and tightened, all specimens were placed plastic molds 6 mm in height and 4 mm in diameter, into an incubator Memmert model , Schwabach, which corresponds to ISO ISO, b. After 60 ural strength test above. Light-curing the cements was minutes the molds were removed and separated. The sam- or chipped edges. Defective specimens were discarded.

No surface protection was used on any of the mixing. The wet specimens were placed with the flat materials. Darmstadt, Germany. As the Material 24 hours days data were metrically scaled and Harvard cement Ketac-Cem 6. The statistical analysis demon- Panvavia F light-cured Compolute Among the other mate- Fuji Cem Panavia F For compressive strength, the Panvavia F light-cured Results of the mechanical tests only apply to the specific conditions in this study.

Such conditions included the exper- imental variables of specimen fabrication procedures, speci- men geometries, storage times, storage environments, test configurations and tem- Figure 1. The results of the three- point flexural strength tests demonstrated a significant variation 6. Generally, the luting cements followed a trend, with zinc phosphate cements, glass ionomer cements and resin- modified glass ionomer cements having the lowest flexural strength, followed by the self-adhesive universal resin cement and the resin cements.

These findings are in accordance with previous studies that ranked resin cements stronger than resin- modified glass ionomer cements or glass ionomer Figure 2. Fuji Cem. The resin-modified glass ionomer cements Fuji Plus and RelyX Luting revealed two times higher Resin cements were up to 10x stronger in flexural results compared to the latter group with low flexural strength than zinc phosphate cements, glass ionomer strength values.

The filler particles incorporated into the matrix been demonstrated in vitro Peutzfeldt, The goal of developing the self-adhesive reliant on the chemical reaction only, revealed mainly no universal resin cement RelyX Unicem was to combine significant differences.

The flexural strength did not the easy handling and non-pre-treatment steps of glass improve more than 16 MPa for RelyX ARC after 24 hours ionomer cements with the high mechanical properties and 9.

This study found that the flexural dual and chemically cured specimens. The highest strength of this cement achieved lower results up to enhancement after light-curing the dual-cure cements 0. On the other hand, with regard to the compressive strength was after 24 hours the self-adhesive universal resin cement was up to 4. These small differences after days of ionomer cements and one resin-modified glass ionomer water storage could be explained by the light-curing cement Fuji Cem.

In general, Conflicting reports have been published on the effects compressive strength was lowest for phosphate of water storage on mechanical properties. The results cements, glass ionomer cements and resin-modified of a study by Ortengren and others indicated glass ionomer cements, higher for self-adhesive univer- that water has an important effect on flexural proper- sal resin cement and highest for resin cements.

Cattani-Lorente and others because a high compressive strength is necessary to observed a decrease in flexural strength of five resin- resist masticatory forces, although the exact value is modified glass ionomer cements immersed in water.

A unknown. In con- specification No 96 ISO, b for dental water-based trast, McCabe found that water storage pro- cements requires a minimum compressive strength of duced a small initial decrease in strength but had little 70 MPa at 24 hours.

At the first measuring time after long-term effects. The other luting pressive strength of nearly all tested materials. Looking at the three-point flexural strength test, a The compressive strength of glass ionomer cements slight decrease in the measurements of the resin and resin-modified glass ionomer cements, in parti- cements and the self-adhesive universal resin cement cular, continues to increase over several weeks.

This usually resulted after days water storage. A factor that probably increase in compressive strength was found for four of influences mechanical properties, at least in the long five glass ionomer and resin-modified glass ionomer run, is stress corrosion of the filler particles, which cements. After days water storage, these cements takes place in water-stored composite materials achieved results ranging from On the other and The com- hand, the current study revealed a small increase in pressive strength of the self-adhesive universal resin flexural strength in the glass ionomer and resin-modi- cement ranged between However, as lower than the results of the resin cements It is unclear as to how valuable com- that were observed to occur in distilled water would not pressive strength data are in selecting a clinical mate- necessarily take place in an oral environment.

This study showed that specimens aged in dis- cements Journal of Oral Rehabilitation 22 1 Early and long-term wear of conventional and resin-modified glass ionomers Journal of Dental Research 75 8 However, the great diversity among the International Standards Organization a ISO standard material classes of luting cements indicates that Dentistry—polymer-based filling, restorative and luting materials.

Flexural and compressive Filling and restorative materials Geneva Switzerland strength are only two criteria for the selection of a lut- ISO Copyright Office. In Biomaterials 19 18 Fracture toughness of resin-based luting cements Journal of Prosthetic Dentistry 83 2 The three-point flexural and compressive strengths strength of resin-modified glass ionomer cements and their of luting cements varied widely.

Next came the self-adhesive universal cements Journal of Prosthetic Dentistry 81 5 Prosthetic Dentistry 71 1 Cosmos 34 Science: Materials Medicine 3 Prosthodontics 13 2 Dental Research 65 11 Journal of Dental Research 55 6 Clinical Relevance Light exposure of photo and dual-cure adhesives and dual-cure resin composites was nec- essary for optimum bonding to root canal dentin.

The post spaces of all the rial to root canal dentin using photo and dual-cure groups were filled with a dual-cure resin com- adhesives and different modes of polymerization. Chemical-cure and their root canals prepared to a depth of 8 mm resin composite was placed on the outer surfaces and a width of 1. They were serially sliced perpendicular roots were randomly divided into five groups and to the bonded interface into eight 0.

Kuraray Medical Co, Japan. When the bonding resin and dual-cure merized resin cement, there were no significant differ- resin composite were chemically-cured, failures ences in microtensile bond strength between the occurred cohesively within the resin. Photo-initi- coronal and middle-third of the post space.

Authors had ated polymerization of the adhesive resin and noted that these regions should be considered to be clin- dual-cure resin composite was necessary to ically relevant regions for bonding, since posts are com- achieve good bonding to root canal dentin, which monly cemented into post spaces prepared in the cer- was not dependent upon region.

Fibre posts are prefabricated and polymerization. If a fibre post is cemented into a extracted from adolescents for orthodontic reasons and flared canal, it might be difficult to maintain an even stored frozen, were used in this study. Their crowns thickness of resin cement between the canal wall and were removed at the cementoenamel junction using a the post. The thickness of the cement could be excessive low-speed diamond saw Isomet, Buehler, Ltd, in the coronal region of the post-space and may not Evanston, IL, USA with post spaces prepared in the possess the necessary mechanical properties to with- root canals using Gates drills Matsutani Seisakusho stand occlusal loading.

The roots were because of its limited working time, controlled place- then randomly divided into two groups, a group of 15 ment within the canal is difficult Lui, To over- for the microtensile bond strength test, and a group of come this problem, Lui proposed using light- four for microhardness testing. Table 1 shows the sate for the retention of parallel-sided and tapered chemical composition of these materials.

Currently, newer dual-cure resin composite core materials are being developed and may offer a longer The 15 roots were randomly divided into five groups of working time and an ability to polymerize in regions three and their walls treated with self-etching primer distant from the light source.

The dual-cure resin composite was then sent the apical region of the space Api corresponding injected into the canal using a centrix syringe Centrix to the middle third of the root canal. Chemical-cure resin composite Clearfil FII, Kuraray Medical Co, Tokyo, Japan was placed on the outer cementum surfaces of all the roots to make grips for testing and stored in Figure 1.

Each bond strength and Knoop hardness tests. A custom-molded acrylic base-plate was Kyoto, Japan and subjected to a tensile force at a slotted into the outer casing of the diamond saw. The load at failure Attached longitudinally to the base-plate was another divided by the cross-sectional area of the beam was glass slide positioned 0.

The edge of the glass side acted as a guide for the in units of stress MPa. In the case of the beams that each slab, only the central beam was designated for ten- failed during slicing pre-test failure , failure modes sile testing as shown in Figure 1.

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Optical densities of aluminum step wedge. A min- imum of four readings was Dyract AP 1. A Compoglass F 1. Filtek Z 1. Heliomolar Flow 1. Pyramid Dentin 1. Marginal defects and secondary caries materials. One-way analysis of variance ANOVA are usually located on the gingival part of Class II indicated significant differences both for the optical restorations.

Heliomolar RO had a radiopacity value 2. A radiograph of all the tested materials along with a tooth section and the aluminum A had radiopacity values 1. All materials except Filtek A 0. Figure 3 shows the bar chart repre- sentation of optical densities and Figure 4 shows the aluminum thick- ness equivalents of all tested materi- als with enamel and dentin. Heliomolar RO.

Solitaire 2. Enamel Vitremer. Heliomolar Flow. Filtek Z Pyramid Dentin. F Ariston pHc. Compoglass F Dentin. Chem Flex Syringeable. P Filtek. Adequate radiopacity has been considered a prerequisite for diagno- sis of secondary caries and marginal defects since it facilitates evaluating.

Bar chart representation of optical density values of all materials. Whether a restorative mate- for posterior restorative materials. It has been recom- ground of enamel and dentin since the contrast facili- mended that the radiopacity of resin composites tates the evaluation of restorations in every region of should be equal to or greater than enamel Van Dijken, the mouth.

Of the Materials with a radiopacity less than enamel microfilled resin composites, Heliomolar RO had a were reported not to be suitable for use, especially as radiopacity greater than enamel.

In this study, there was considerable variation in the In addition to being used in permanent dentition, radiopacity values of esthetic posterior restorative glass ionomer cements and hybrid versions have materials. Syringeable, and the polyacid-modified resin compos- The popular materials for posterior esthetic restora- ites, Dyract AP, Compoglass F and F, had a tions, the packable resin composites, also showed dif- radiopacity higher than enamel but the resin-modified ferent radiopacity values.

Of the five packable compos- glass ionomer cement Vitremer had a lower radiopacity. Pyramid Dentin, Pyramid Enamel and Solitaire 2 had It was suggested that in order to fulfill clinical lower values than enamel. The marginal defects. Heliomolar Flow, the flowable com- posite used in the study, was higher in radiopacity compared to enamel, but in contrast, Composan LCM Flow was lower. The radiopacity of a resin depends on selection of the polymer matrix, chemical nature of Solitaire 2 Ariston pHc Chem Flex Condensable.

Composan LCM. TPH Spectrum. Pyramid Enamel. Filtek A F This resulted in considerable varia- tions in radiopacity values of the restorative materials used in the study.

Bar chart representation of aluminum thickness equivalents of all materials. A caries lesion near the buccal or lingual resin composite Filtek A were found to have margin of a Class II restoration may be masked by a radiopacity values greater than dentin and possessed highly radiopaque restorative material.

Moderate sufficient radiopacity standards of ISO This found among materials when compared to enamel. Prosthetic Dentistry 70 4 Although Akerboom and light-cured posterior composite resin: Results of a 3-year clini- others suggested using human teeth as a stan- cal evaluation Journal of the American Dental Association dard, they reported that variations in radiopacity of 5 Association 81 4 It was reported that variability in radiopacity values Cook WD An investigation of the radiopacity of composite restorative materials Australian Dental Journal 26 2 Clinical Relevance With respect to the adhesion properties of carbon fiber posts and glass fiber posts used in the restoration of endodontically-treated teeth, they perform equally well if used in combination with chemically cured luting cements or with light activated ones.

The post is Fiber posts are widely used in the restoration of cemented inside the root canal using low mod- endodontically treated teeth. Scientific evidence ulus elastic polymer resins. In this study, the demonstrates that the mechanical performance mechanical resistance of four different post- of teeth restored with fiber posts in combination cement systems was assessed by means of a with resin luting cements is improved with micro-mechanical pull-out test assisted by a sim- ulation using the finite element methodology.

The post is cemented inside the root canal and the Luigi Ambrosio, full professor, Institute of Composite Materials Technology, National Research Council and Interdisciplinary core is retained by an apical extension of the post. The use of post and core restoration will Luigi Nicolais, full professor, Institute of Composite Materials continue to increase because of the current trend to pre- Technology, National Research Council and Interdisciplinary serve natural tooth structure in the mature years of life Research Center in Biomaterials CRIB, University of Naples, Christensen, Fiber posts are generally used with low modulus resin The stress distribution in the cement layer was studied cements in combination with dentin adhesive systems.

Four different combinations of mechanical viewpoint, the post acts as a bypass, con- fiber post—luting cement were used: carbon fiber posts centrating the chewing stresses at the root tip. Carbon fiber posts were initially used in combination with low modulus chemically cured luting cements. Biomaterials research introduced new materials for post manufacturing, for example, E-glass or quartz fiber embedded in transparent epoxy-resin matrix, to be used with newly developed light cured luting cements.

The mechanical properties of fiber posts and data on adhesive retention strength of cemented fiber posts in root canals are widely reported in the scientific litera- ture. However, little information is available regarding the interface between the fiber post and the resin lut- ing cement.

In fact, the direct measurement of the bond strength between the fiber posts and cement has been Figure 1. Mechanical pull-out test set-up. This Table 1 shows the average recorded maximum load and was done in order to investigate whether the adhesion the average bond shear strength for each post-cement properties were improved by photopolymerization.

During the that the load increases quasi-linearly, then levels up, preparation, all samples were stored for no more than reaching the ultimate load F before drastically dropping 24 hours in an isotonic 0. Coupled ANOVA statistical analysis suggests that there are no Teflon molds were used to keep each fiber post coaxial significant differences among samples at a probability with the dentin hole during the curing of the cement, level of 0.

In the first case, the upper surface of layer the part in contact with the steel frame, see the dentin was constrained, while the cement was free Figure 1. The axial- the other systems being very similar. Since the state of symmetry of the geometry led to the development of a stress in the relevant parts of the cement is generally two-dimensional model that was solved using the pack- three-dimensional, the FEM analysis produced graphs age ANSYS 5. The The pull-out tests were performed with an INSTRON distributions of the von Mises equivalent stresses in the testing machine and the pulling load was cement layer for each of the four post-cement systems increased at a cross-head speed of 2.

The axial displacement of the check for the locations where critical stress values were post was monitored using an INSTRON extensometer reached and are shown in Figure 4. As can be seen, the positioned between the dentin slice and the post-cement interface the left side of each distribution post Figure 1. The load and the extensometer dis- is more loaded by about a factor of 2 than the dentin- placement were acquired at a sampling rate of 10 points cement interface the right side of each distribution.

Ultimate strength The manufacturers provided all the N St dev 78 70 84 68 relevant data concerning the posts and Ultimate shear stress MPa St dev 6. The axial load-axial displacement graph obtained from the FEM analysis is shown in Figure 2, where it can be compared with the experimental data. Thus, regarding the mechanical integrity of the restored tooth, Figure 2. The left and right side of each distribution represent the post-cement and the cement-dentin interfaces, respectively.

The upper part of each distribution is the region of the cement that is in contact with the stainless steel frame, as represented in Figure 1. As retention properties are essential from a clinical The mechanical tests demonstrated that all the vari- perspective, it is important to study the properties of ous systems withstood loads up to N, suggesting the interfaces involved in the restoration.

The differences cement and another between the cement and the among the various post-cement combinations were not dentin substrate. Moreover, as it is well stress distribution within the luting cement layer. The shear stress calculated using are higher.

In the case of fiber post restorations, the equation 1 is an average value obtained, assuming highest differences are between the post and the luting that the shear stress distribution within the cement cement; thus, it is particularly important to investi- layer is uniform. This value is basically equal to the average shear stress calculated using equation 1. The left side and the right side of each distribution represent the post-cement and the cement-dentin interfaces respectively.

The upper part of each dis- tribution is the region of the cement that is in contact with the stainless steel frame, as represented in Figure 1. Acknowledgements Thus, it can be concluded that using equation 1 leads to a gross underestimation of the maximum shear The financial support of POP Regione Campania Azione 5.

The authors also mechanical reliability of this interface in the fiber post acknowledge Mr Antonio Maggio for matching the specimens and restorations. Dr Fulvio Anselmi of Cabon-Denit Spa for supplying technical The non-uniform stress distribution obtained with information.

FEM suggests that the post-luting cement system likely fails when a crack starts on the upper part of the Received 16 August cement layer Figure 1 and propagates downward along the post-cement interface. The difference This is consis- tion modalities in structurally compromised premolars tent with the clinical observation of post debonding International Journal of Prosthodontics 8 3 Further Microtensile bond strength and confocal microscopy of dental studies should focus on the influence of these factors adhesives bonded to root canal dentin American Journal of on the strength of the fiber post cement interface.

Dentistry 14 4 Prosthetic Dentistry 78 1 Clinical Relevance Dentin surface topography created by various bur designs may influence the surface sealing quality of resin bonding agents and, therefore, affect post-operative sensitivity and microleakage associated with composite bonding procedures. Dentin bonding agents do not appear to routinely seal the pulpal wall before application of resin composite and creation of polymerization shrinkage stress.

A flow system was established through This study investigated the effects of bur cutting the pulp chamber and gravity pressurized phos- surface roughness and bonding systems on phate buffered saline PBS was forced into the dentin permeability. Burs were used to prepare flat sur- sively serrated bur were utilized with two differ- faces in dentin, and after etching with phos- ent bonding systems.

After applying the dentin bonding the permeability of dentin sealing after applica- agents, fluid flow from the pulp chamber into tion of bonding agents.

This study incorporated a dentin was again measured. The percentage of fluid flow model for measuring dentin permeabil- reduction in permeability following bonding ity. Seventy caries-free extracted molars were agent application was then calculated. The specimens were straight-edged bur. No significant differences were mounted to plexiglass plates using cyanoacrylate detected between bonding systems and no combi- nation of surface topography or bonding agent Tanya Vaysman, year IV dental student, UMDNJ New Jersey completely sealed the surface.

D, professor and chair, Biomaterials ciated with postoperative sensitivity. Causes of The cynaoacrylate cement was applied to the milled post-operative sensitivity after bonding procedures apical portion of the cut crown segment, taking care include incomplete caries removal, desiccation of tooth not to introduce any cement into the root canal cham- structure by over-drying, over-etching the dentin, bac- ber.

A flow system was established using two gauge terial contamination, improper restorative placement, hollow stainless steel cylinders connected through the incomplete polymerization and occlusal interferences pulp chamber.

The specimens were coated with a thin Hornbrook, This fluid is a filtrate of plasma tions. While there is provide intrapulpal pressure to tooth specimen. Eick and others Hume, Other of bonding resins is the surface topography of the pre- investigators have reported that intrapulpal pressure pared dentin and that a roughened surface creates a is known to vary in magnitude, is significantly higher greater surface area.

The left side of the circuit consisted of This study compared the effects of dentin surface the fluid reservoir joined to the specimen with roughness on dentin permeability using a fluid flow gauge polyurethane tubing. As men- to the prepared dentin surface. A millimeter ruler tioned above, incomplete sealing of dentin tubules by approximated to the polyurethane tubing allowed for the bonding system has been implicated in the etiology visual measurements of air bubble travel.

They were then stored in a phosphate buffered saline solution PBS until used for sample preparation. The specimens were sectioned 2 mm apical to the CEJ using a high-speed handpiece with copi- ous water.

The specimens were mounted with cyano- acrylate cement to 50 x 50 mm plexiglass plates. Schematic diagram of fluid flow apparatus. The connections were examined to ensure a surface. The thin layer of cyanoacrylate cement sealed fluid system and minimize visible leaks. After the equilibration agents. The flow through establish a baseline sealed measurement.

This allowed the etched surface was recorded over 15 minutes to each tooth to act as its own control. A flat surface was establish initial dentin permeability of the crown seg- then prepared on the dentin at a depth of 1. Based on this initial dentin permeability, speci- half the cutting length of a carbide bur from the mens were assigned to each of the six experimental central fossa using a diamond bur on a high-speed groups so that each group received a variety of initial handpiece.

The bur was held perpendicular to the long dentin permeabilities. The flow was measured over 15 minutes and recorded as the etched system measure- ment. After establishing the etched system permeability, the pressure in the fluid reservoir was reduced to zero to avoid moisture contamination during the bonding pro- cedure.

Photographs of burs used in the study. All sam- ples were stored in an air-tight, moist environment before and after the testing procedure. Removing these samples necessitated having unequal samples groups. The remaining specimen distribution is shown in Table 2. Post-hoc t-tests were used to compare groups where a significant omnibus f-test was found.

Experiment-wise error rates were controlled in these post-hoc tests by means of Tukey HSD pro- cedure Kirk, For scanning electron microscopy SEM , the spec- imens were removed from their plexiglass plates and the undersurfaces were further milled to facili- tate placement in the SEM chamber. The samples were mounted on stainless steel studs and vacuum desiccated for approximately four days, then carbon coated.

Measuring dentin permeabilites in this extracted tooth model yielded significant variability. Typical permeabilities of etched open tubules ranged from 0. Once the etched dentin was bonded with DBA, typical permeabilities ranged between zero and 0. Using the formula described above, mean PPD values ranged from a low of Post-hoc t-tests showed that the average PPD for both serrated type burs was signifi- cantly more effective than the straight fissure bur, therefore, indicating that samples prepared with the Figure 4a.

Fissure bur FB. Figure 4b. Cross-cut bur CC. Figure 4c. Extensively serrated bur ES. Bonded samples with lower PPD measurements were considered to have areas of unsealed etched dentin, causing localized fluid flow of the PBS solu- tion. Specimens with initial etched permeability less than 2. Very high initial flow volumes were thought to result from microcracks or from limited dentin thickness in specimens pre- Figure 5.

Specimens producing very low etched permeability, baseline flow 2. Since shallow restorations to higher values with increased serration was evident, exhibit little post-operative sensitivity, this elimi- the cross-cut fissure bur was not different from the nation was thought to be inconsequential to the extensively serrated bur.

The effect of the two bonding outcome of the study. No interaction between bur and bonding sys- pressure was introduced at a pressure significantly tem was detected.

In addition, no group exhibited higher than what exists in a healthy tooth. SEM observation revealed a relatively post-operatively sensitive tooth , the authors felt that smooth surface with limited surface roughness when a creating an increased pressure environment may more fissure bur was employed as depicted in Figure 4a. It has been Cross-cut serrated burs created serrations and shown that polymerization shrinkage of resin compos- grooves that appeared uniform and widely separated ites during direct placement causes dimensional strains Figure 4b.

A higher magnifi- as gaps at the tooth-restorative material interface due cation SEM examination of the extensively serrated to the separation of the resin-bonding agent from the surface revealed orientation of the grooves, peaks and underlying dentin, especially along the pulpal wall.

The valleys in the dentin, and patent dentin tubules volume of these internal gaps has been reported to be as Figure 5. Carvalho and others reported these poly- Examination of the dentin prepared with cross-cut merization stresses and resulting strain are expected serrated burs followed by application of Clearfil SE in Class I preparations where there is a high ratio of Bond revealed that the bonding agent covered the bonded to unbonded surfaces high C-factor peaks and valleys created by the bur.

In addition, bonds to the appeared uniform with some irregularities Figure pulpal floor are often lower because deep dentin is 6a. The presence of these gaps, regardless of the from the underlying dentin, especially in the region of bonding agent polymerization method or whether flow- irregularities. This resulted in separation of polymer- able or heavily filled resin composite formulations were ized resin tags and exposed dentin tubules Figure employed, was recently demonstrated in Class I dentin 6b.

One pos- sible explanation is that increased surface area on the dentin allows for a better infiltration of the bonding resins. In addition, the bur-cre- ated surface topogra- phy, if extended to the pulpal wall prepara- tion, may help to with- stand the polymeriza- Figure 6a. Arrow points to micro-cracks in bonded resin Figure 6b. SEM image of a micro-crack. Arrow points to a tion shrinkage stress layer. Resin bond- The results of this study indicate that if a uniform ing agents have a dual role when used under resin com- roughness could be created on the pulpal floor of cavity posites.

First, they provide micro-retention, primarily preparations, the initial sealing capability of existing through the peritubular dentin, for bonding to the com- bonding resins may be improved. In clinical practice, posite restorative. Therefore, an pulpal floor topography playing a role in improving ideal resin bonding agent should provide effective per- dentin bonding agent sealing ability.

While many pro- itubular bonding to facilitate retention of the composite cedures and techniques have been proposed to improve and complete sealing of the dentinal tubules to prevent bonding procedures, cavity surface topography is gen- permeability of dentinal fluid that may cause post-oper- erally not considered.

As a result of this study, future ative sensitivity. In clinical practice, amalgam restorations are seldom associated with post-operative sensitivity. The authors thank Malvin Janal, PhD for his assistance in sta- The results of this study indicated that samples pre- tistics and Elizabeth Clark, MS, for her technical assistance.

Operative Dentistry 12 3 Journal of Dentistry 11 5 Dentin permeability: Effects of cavity varnishes and liners Analysis of sealing vs tensile bond strength of eight adhesive Journal of Prosthetic Dentistry 53 Clinical Relevance The effect of food-simulating liquids on the shear strength of resin-based filling mate- rials was product dependent.

Composites based on BisEMA may be more resistant to degradation by alcohol. After conditioning, the speci- [EX], Dentsply , a conventional Compoglass [CG], mens were restrained within the test apparatus Vivadent and a posterior polyacid-modified and subjected to shear punch strength testing Dyract Posterior [DP], Dentsply composite.

All materials with the excep- Dentistry, National University of Singapore, Republic of tion of EX were significantly weakened by Singapore ethanol solution. Composites may be defined as three-dimen- strength values, while glass ionomers and polycarboxy- sional combinations of at least two chemically different late provided the lowest. Polyacid-modified composite materials with a distinct interface Phillips, This and coloring pigments.

Polyacid-modified composites or study investigated the effects of food-simulating liquids compomers are resin composites that contain either or on the shear-punch strength of composites and poly- both of the essential components of glass ionomer acid-modified composites, including a recently intro- cements but at a level insufficient to promote acid-base duced posterior polyacid-modified composite material.

Composites are recommended for restoring all ious mediums was also performed. Konstanz, Germany , a conventional Compoglass Composites, conventional and resin-modified glass [CG], Vivadent and a posterior polyacid-modified ionomer cements are all susceptible to various modes of Dyract Posterior [DP], Dentsply composite were chemical degradation in vitro. Reduction in hardness, selected for the study. Table 1 shows the technical pro- wear, fracture toughness and flexural strength had been files of the materials and their manufacturers.

All reported after exposure to various food-simulating liq- materials were of the A2 shade. In an in vivo situation, it can be assumed that by glass slides. A second glass slide was placed on top saliva, food components and beverages can degrade and of the washers and gentle pressure was applied to age dental restorations.

Wu and others reported extrude excess material. The mean intensity of the light degradation of these materials. Thirty-two dental restorations. Although the effects of food-simulat- specimens of each material were made and randomly ing liquids on composites had been widely investigated, divided into four groups of eight. Dental amalgams At the end of the conditioning period, the shear ISO and water-based cement ISO are punch strength of the materials was assessed. A special evaluated using a compression test, while resin-based shear punch apparatus was designed and fabricated in filling materials ISO and light-activated water- collaboration with Instron, Singapore.

The apparatus based cements ISO are evaluated using a flexural Figure 1 allowed for restraining the specimens during test. A single standard test for all dental restorative testing, self-location of the specimens and testing in a materials is desirable. The shear punch test has previ- thermally-controlled liquid environment. The shear strength of TC to fracture the test specimens. The thickness of each and CG were significantly reduced after conditioning in specimen was measured with a digital vernier calliper ethanol solution.

For DP, a significant increase in shear prior to placement in the shear punch apparatus. The strength was observed after conditioning in water. The specimens tioning in water. No significant difference in shear were subsequently restrained by tightening the screw strength was observed between Group 1 air and Group clamp on top of the specimens.

An M2 tool steel punch 3 ethanol solution specimens for DP. For EX, no signif- with a flat end 3. A small disc from the center of each The shear strengths of EX, TC and CG were signifi- specimen was punched out and the maximum load cantly greater than DP after conditioning in air Group recorded.

Shear strength was then computed using the 1. In addition, EX was significantly stronger than TC. All statistical analysis was carried out at significance level 0. Results of the statistical analyses are shown in Tables 3 and 4. The effect of conditioning mediums on shear strength was Figure 1. Diagrammatic representation of the shear punch apparatus. The shear strength of study the effects of solvent and environmental degra- EX was also significantly greater than CG after condi- dation on material properties in dental research tioning in ethanol solution.

Heptane simulates butter, fatty the simplicity of specimen preparation. Results of flex- meats and vegetable oils, while the ethanol solution ural, diametral and compression testing are highly simulates certain beverages, including alcohol, vegeta- dependent on the production of high quality specimens.

The by saliva and water. The solubility parameters for these quality of the edges of the disc around the circumfer- organic food simulating liquids were 1. The only requirement is and water, respectively. They hypothesized that unrestrained specimens are able to bend on application of the punch, creating localized stress concentration that leads to prema- ture failure.

Although a cm kg increase in screw clamp torque resulted in an increase in shear Shear Strength MPa. Tetric Ceram Esthet X strength, the increase was not sta- 80 Compoglass tistically significant. The punch Dyract Posterior diameter 3. The shear punch apparatus used in 0 this experiment gave highly repro- Air Distilled Water Ethanol Solution Heptane Conditioning Mediums ducible results, and the standard deviations observed were generally Figure 2. Mean shear strength of the materials.

Standard deviations indicated in parentheses. In view of the latter, a further solution. The shear strength of ethanol solution has a solubility parameter value all materials was not significantly affected by heptane. Studies have reported a positive cor- strength observed. Materials with For EX and DP, no significant difference in shear higher filler volumes like EX, TC and CG are therefore strength was observed between conditioning in air expected to have higher shear strength than DP, which control and ethanol solution.

This is probably due to the differences in EX more resistant to the softening effect of ethanol- resin matrix formulation. The shear strength of EX water solution. This finding was consistent with that of remained significantly higher than DP after condi- Yap and others a , who found that BisEMA-based tioning in water, ethanol and heptane.

Despite its high composites were highly resistant to the degradation filler volume, TC was not significantly stronger than effect of food-simulating liquids including ethanol. DP after conditioning in the aforementioned food-sim- BisEMA is hydrophobic, as it does not contain any ulating liquids. Although no significance in slight weakening of TC after conditioning in ethanol strength was observed between DP specimens condi- and heptane.

EX was most resistant to the degradation tioned in air and ethanol, significant differences were effect of alcohol. As EX was significantly stronger than observed between DP specimens conditioned in water all materials after conditioning in ethanol, it may be and ethanol. The strength of DP was significantly the composite of choice for the restoration of posterior increased by water storage.

This increase in strength is teeth in patients who consume alcohol frequently and probably due to the acid-base reaction between the in large quantities.

Differences in shear strength hydrated acidic functional groups and fluoroalumino between materials after conditioning in heptane were silicate glasses present in DP. The acid-base reaction, similar to that of the control group with the exception however, occurs only at the surface layers uppermost of TC.

The latter was due to a slight decrease in Table 3: Results of Statistical Analysis Based on Materials strength of TC after conditioning in heptane and a slight increase in strength of DP. The shear punch test, however, offers a simple, effective and reliable Table 4: Results of Statistical Analysis Based on Conditioning means of screening resin-based filling materials and Mediums evaluating material-environment interactions.

Ethanol solution 2. The shear punch test is a simple, reliable Journal of Dentistry 14 4 Dental Research 71 1 A method using a micro-punch apparatus British International Organization for Standardization Dental Journal 8 Specification for dental water-based cements ISO Materials 5 3 Clinical Relevance Luting cements differ considerably with respect to their mechanical properties.

These differences should be taken into consideration when selecting a material for clinical application. Resin cements had the on flexural strength FS and compressive highest flexural and compressive strengths, fol- strength CS of 12 luting cements from different lowed by self-adhesive universal resin cement.

In addition, the influence of the These materials were statistically stronger than curing method on the mechanical properties was resin-modified glass ionomer cements, glass investigated. The materials examined were two ionomer cements and zinc phosphate cements. The samples were prepared and tested Traditionally, zinc phosphate cement has been the most according to ISO specifications. Specimens for popular dental cement and has been in use for more FS and CS were loaded to fracture at a constant than 90 years Ames, The mechani- are not adhesive to tooth substance or to restorative cal properties were measured after the materials materials.

The mixing technique is critical in develop- were stored in distilled water at a temperature of ing the optimal cement, because the strength is almost It also investigated the Glass ionomer cements GIC have been gaining in pop- effect of the curing method on mechanical properties. Handling of the materials was car- Ferracane, They exhibit high mechanical proper- the time recommended by the manufacturers 8 or 10 ties and have excellent esthetic shade-matching poten- seconds.

On the other hand, they require pre-measured delivery systems. Panavia F and skillful usage and multiple steps with respect to their Variolink II were mixed with a hard plastic spatula in handling characteristics, especially time-consuming a ratio of base to catalyst paste on a mixing block for bonding procedures and excess removal. The self-adhe- approximately 20 and 10 seconds, respectively. The cements.

Clinically, the tooth-cement interface can withstand To evaluate the influence of the curing method, the masticatory and parafunctional stresses for many years resin cements and the self-adhesive universal resin in a warm, wet oral environment. Stress may cause cement were polymerized using a dental light-curing recoverable elastic or permanent plastic deformation, unit Elipar Trilight; 3M ESPE, Seefeld, Germany.

When cements. These measurements enhances the surface deterioration of polymer resin were performed on 10 samples at each occasion. The mold was placed mechanical properties of luting cements.

This study on a glass slab and freshly mixed cement was applied analyzed the influence that water has on three-point until the mold was slightly overfilled.

Then, a trans- flexural strength FS and compressive strength CS parent matrix band was placed on top of the mold and a second glass slab was pressed on it. After the mold and the glass slabs were put in the The specimens were prepared in split cylindrical rigid screw clamp and tightened, all specimens were placed plastic molds 6 mm in height and 4 mm in diameter, into an incubator Memmert model , Schwabach, which corresponds to ISO ISO, b.

After 60 ural strength test above. Light-curing the cements was minutes the molds were removed and separated. The sam- or chipped edges. Defective specimens were discarded. No surface protection was used on any of the mixing. The wet specimens were placed with the flat materials. Darmstadt, Germany. As the Material 24 hours days data were metrically scaled and Harvard cement Ketac-Cem 6.

The statistical analysis demon- Panvavia F light-cured Compolute Among the other mate- Fuji Cem Panavia F For compressive strength, the Panvavia F light-cured Results of the mechanical tests only apply to the specific conditions in this study. Such conditions included the exper- imental variables of specimen fabrication procedures, speci- men geometries, storage times, storage environments, test configurations and tem- Figure 1.

The results of the three- point flexural strength tests demonstrated a significant variation 6. Generally, the luting cements followed a trend, with zinc phosphate cements, glass ionomer cements and resin- modified glass ionomer cements having the lowest flexural strength, followed by the self-adhesive universal resin cement and the resin cements.

These findings are in accordance with previous studies that ranked resin cements stronger than resin- modified glass ionomer cements or glass ionomer Figure 2. Fuji Cem. The resin-modified glass ionomer cements Fuji Plus and RelyX Luting revealed two times higher Resin cements were up to 10x stronger in flexural results compared to the latter group with low flexural strength than zinc phosphate cements, glass ionomer strength values.

The filler particles incorporated into the matrix been demonstrated in vitro Peutzfeldt, The goal of developing the self-adhesive reliant on the chemical reaction only, revealed mainly no universal resin cement RelyX Unicem was to combine significant differences.

The flexural strength did not the easy handling and non-pre-treatment steps of glass improve more than 16 MPa for RelyX ARC after 24 hours ionomer cements with the high mechanical properties and 9. This study found that the flexural dual and chemically cured specimens.

The highest strength of this cement achieved lower results up to enhancement after light-curing the dual-cure cements 0. On the other hand, with regard to the compressive strength was after 24 hours the self-adhesive universal resin cement was up to 4.

These small differences after days of ionomer cements and one resin-modified glass ionomer water storage could be explained by the light-curing cement Fuji Cem. In general, Conflicting reports have been published on the effects compressive strength was lowest for phosphate of water storage on mechanical properties. The results cements, glass ionomer cements and resin-modified of a study by Ortengren and others indicated glass ionomer cements, higher for self-adhesive univer- that water has an important effect on flexural proper- sal resin cement and highest for resin cements.

Cattani-Lorente and others because a high compressive strength is necessary to observed a decrease in flexural strength of five resin- resist masticatory forces, although the exact value is modified glass ionomer cements immersed in water. A unknown. In con- specification No 96 ISO, b for dental water-based trast, McCabe found that water storage pro- cements requires a minimum compressive strength of duced a small initial decrease in strength but had little 70 MPa at 24 hours.

At the first measuring time after long-term effects. The other luting pressive strength of nearly all tested materials. Looking at the three-point flexural strength test, a The compressive strength of glass ionomer cements slight decrease in the measurements of the resin and resin-modified glass ionomer cements, in parti- cements and the self-adhesive universal resin cement cular, continues to increase over several weeks.

This usually resulted after days water storage. A factor that probably increase in compressive strength was found for four of influences mechanical properties, at least in the long five glass ionomer and resin-modified glass ionomer run, is stress corrosion of the filler particles, which cements.

After days water storage, these cements takes place in water-stored composite materials achieved results ranging from On the other and The com- hand, the current study revealed a small increase in pressive strength of the self-adhesive universal resin flexural strength in the glass ionomer and resin-modi- cement ranged between However, as lower than the results of the resin cements It is unclear as to how valuable com- that were observed to occur in distilled water would not pressive strength data are in selecting a clinical mate- necessarily take place in an oral environment.

This study showed that specimens aged in dis- cements Journal of Oral Rehabilitation 22 1 Early and long-term wear of conventional and resin-modified glass ionomers Journal of Dental Research 75 8 However, the great diversity among the International Standards Organization a ISO standard material classes of luting cements indicates that Dentistry—polymer-based filling, restorative and luting materials.

Flexural and compressive Filling and restorative materials Geneva Switzerland strength are only two criteria for the selection of a lut- ISO Copyright Office. In Biomaterials 19 18 Fracture toughness of resin-based luting cements Journal of Prosthetic Dentistry 83 2 The three-point flexural and compressive strengths strength of resin-modified glass ionomer cements and their of luting cements varied widely.

Next came the self-adhesive universal cements Journal of Prosthetic Dentistry 81 5 Prosthetic Dentistry 71 1 Cosmos 34 Science: Materials Medicine 3 Prosthodontics 13 2 Dental Research 65 11 Journal of Dental Research 55 6 Clinical Relevance Light exposure of photo and dual-cure adhesives and dual-cure resin composites was nec- essary for optimum bonding to root canal dentin. The post spaces of all the rial to root canal dentin using photo and dual-cure groups were filled with a dual-cure resin com- adhesives and different modes of polymerization.

Chemical-cure and their root canals prepared to a depth of 8 mm resin composite was placed on the outer surfaces and a width of 1. They were serially sliced perpendicular roots were randomly divided into five groups and to the bonded interface into eight 0.

Kuraray Medical Co, Japan. When the bonding resin and dual-cure merized resin cement, there were no significant differ- resin composite were chemically-cured, failures ences in microtensile bond strength between the occurred cohesively within the resin. Photo-initi- coronal and middle-third of the post space.

Authors had ated polymerization of the adhesive resin and noted that these regions should be considered to be clin- dual-cure resin composite was necessary to ically relevant regions for bonding, since posts are com- achieve good bonding to root canal dentin, which monly cemented into post spaces prepared in the cer- was not dependent upon region. Fibre posts are prefabricated and polymerization. If a fibre post is cemented into a extracted from adolescents for orthodontic reasons and flared canal, it might be difficult to maintain an even stored frozen, were used in this study.

Their crowns thickness of resin cement between the canal wall and were removed at the cementoenamel junction using a the post. The thickness of the cement could be excessive low-speed diamond saw Isomet, Buehler, Ltd, in the coronal region of the post-space and may not Evanston, IL, USA with post spaces prepared in the possess the necessary mechanical properties to with- root canals using Gates drills Matsutani Seisakusho stand occlusal loading.

The roots were because of its limited working time, controlled place- then randomly divided into two groups, a group of 15 ment within the canal is difficult Lui, To over- for the microtensile bond strength test, and a group of come this problem, Lui proposed using light- four for microhardness testing. Table 1 shows the sate for the retention of parallel-sided and tapered chemical composition of these materials.

Currently, newer dual-cure resin composite core materials are being developed and may offer a longer The 15 roots were randomly divided into five groups of working time and an ability to polymerize in regions three and their walls treated with self-etching primer distant from the light source.

The dual-cure resin composite was then sent the apical region of the space Api corresponding injected into the canal using a centrix syringe Centrix to the middle third of the root canal. Chemical-cure resin composite Clearfil FII, Kuraray Medical Co, Tokyo, Japan was placed on the outer cementum surfaces of all the roots to make grips for testing and stored in Figure 1.

Each bond strength and Knoop hardness tests. A custom-molded acrylic base-plate was Kyoto, Japan and subjected to a tensile force at a slotted into the outer casing of the diamond saw. The load at failure Attached longitudinally to the base-plate was another divided by the cross-sectional area of the beam was glass slide positioned 0.

The edge of the glass side acted as a guide for the in units of stress MPa. In the case of the beams that each slab, only the central beam was designated for ten- failed during slicing pre-test failure , failure modes sile testing as shown in Figure 1. The remaining beams were determined visually. Failure modes of the tested were discarded. In addition, in etching primer, and the adhesive resin Bd A, which was the case of microhardness, there was a significant inter- light cured.

Each block was positioned on the traveling and apical regions. A posite was dual-cured than when curing was chemical load of 50 g was applied for a dwell time of 15 seconds.

Representative SEM views of the upper and lower apical regions of the post space. On the other hand, when the bonding resin ness data were analyzed by two-way ANOVA factorial was light or dual-cured, some beams were found to fail analysis chemical-vs dual-curing of DC Core and cohesively within the hybrid layer or dentin. Moreover, of the failure modes was performed using the Kruskal- when the bonding resin was light cured and the resin Wallis rank test.

For this, each failure mode was given composite dual cured, some beams in the coronal region a score from 1 to 4 prior to statistical analysis. A score exhibited cohesive failure in dentin. The microhardness data are presented in Table 5, with Presently, very limited information is available on the the failure modes of the beams shown in Table 6. Group showing cohesive fail- ure within the bonding resin and composite resin.

The area marked by an arrow is shown at higher magnification. Regarding Figures 2c and d: SEM photographs of the opposing side of the fractured beam shown in 2a. These results agree with those from a study by and apical regions of the post space irrespective of Gaston and others , that evaluated the microten- whether polymerization was light or chemically acti- sile bond strength of two chemically-cured resin cements vated, which agrees with the findings of Giannini and to root canal dentin in teeth that had not been endodon- others using coronal dentin.

Therefore, the tically-treated. This may have been due to the root canal dentin and concluded that bond strength is self-etching primer used in this study having a pH of related more to the area of solid dentin than to tubule around 2. The area marked by an arrow is sub-groups were shown at higher magnification c x d x. In addition, the Knoop Hardness est.

These findings indicate that the mechanical proper- Number of DC Core was significantly lower when poly- ties of the adhesive resin Bd A, when photo-cured, may merization was chemically initiated as opposed to have been greater than those of the adhesive resin Bd photo-initiated.

When Bond A and Bond B were properties of both the bonding resin and resin compos- mixed, a reduction in the concentration of photoinitators ite. In contrast, the was chemically initiated. Figure 4 ically-cured composites, resulting in sig- nificantly lower bond strengths. However, when an adhesive resin was placed after applying and curing the single-step adhesive, no Figures 4c and d: SEM photographs of the opposing side of the fractured beam shown in 4a.

The area marked by an arrow is adverse interac- shown at higher magnification. In addition, when light irradiation may have been at the apical region. This may be due to the insensitivity of obtain the optimum mechanical properties for bonding. No regional differences were found in Journal of Dentistry 12 4 Ltd Materials 17 6 Dentistry 4 1 Journal of Adhesive Dentistry 3 4 Clinical Relevance Delaying polishing for one day resulted in improved gap formation for Class V restora- tions of conventional and resin-modified glass ionomers and a microfilled composite.

Delaying polishing was not necessary for a compomer. Significant differences This in vitro study evaluated the effect of the ini- were observed between polishing immediately tial polishing period through 30 minutes, 3 hours, and polishing after 12 hours of storage in the two 12 hours, 24 hours and 1 week after setting on the glass ionomer restorative materials. The com- gap formation around Class V restorations.

Three pomer did not show this pattern. No significant resin-modified glass ionomers, one compomer, differences were observed among the six polishing one conventional glass ionomer and one micro- periods of the sum number of gaps at the cavity- filled composite were used as controls. The tendency of Silux Plus was similar to the two types of glass ionomer When specimens of the two types of glass materials; namely, when the specimen was pol- ionomers and a microfilled composite were pol- ished and inspected after storage in water for 24 ished immediately after the setting procedure, hours or one week, the authors observed almost this study showed gaps around the X-sec- 30 gaps around the restorative cavities.

The final set materi- Due to the structure of glass ionomers and their als have been described as having a complex structure hydrophilic nature, water sorption and subsequent in which glass particles are sheathed in a matrix con- swelling may lead to partial compensation of the sisting of two networks—one derived from the glass shrinkage.

The preservation of sealing around a ionomer, the other from the resin Wilson, ; Mitra, restoration would benefit most if water sorption and In these dual-setting systems, the resin rein- setting shrinkage could occur simultaneously.

It consists of a resin matrix and a flu- were used for the experiment. After extraction, each oroaluminosilicate glass filler. The monomer in resin matrix ionizes fol- Tables 1 and 2. The released hydrogen ions then react with the Capsules of Photac-Fil were triturated using a high- glass filler to ini- tiate an acid-base Table 1: Restorative Materials Investigated reaction. For light activation of the priming or diameter: 8 mm was used.

The curing distance from tip sealing agents and of the restorative materials, a curing to material surfaces was as near as possible. For each material and stor- age period, 10 specimens were made. Class V Restoration Cavity preparations were made in the premolars on the facial surface.

A cylindrical cavity was prepared with a tungsten carbide bur ,rpm and a fissure bur 8,rpm under wet conditions to a depth of 1. A cavity preparation was placed parallel to the cementoenamel junction CEJ with the preparation extended 1. Cavosurface walls were finished to a butt joint. One cavity was prepared in each tooth. In total, cavities were prepared in teeth 6 materials X 6 pol- ishing times X 10 repeats. Dentin Conditioner and Ketac Conditioner were applied for 20 and 10 seconds, respec- tively, and rinsed with water.

Vitremer Primer was applied for 30 seconds, air dried and light cured for 20 seconds. Class V restoration and each measured point in the Class V and left undisturbed for 30 seconds. Excess solvent was restorations. E: Enamel substrate, D: Dentin substrate.

The light curing time was 10 seconds. Significant differences were observed between irradiation times of 20 seconds, 40 seconds, 20 seconds, the two conditions. No significant differences were 40 seconds and 40 seconds, respectively. However, humidity for four minutes after mixing to allow for polished points, 1 and 14 enamel substrate , showed chemical-curing to occur and was coated with a varnish half the number of gaps in the restorative cavities.

The Fuji Varnish, Tokyo, Japan. With the three stor- 12 hours, 24 hours and 1 week, the restorations were age periods immediately, after 30 minutes and after polished with abrasive points Silicone Mide, Shofu, three hours , the authors observed , and 95 Kyoto, Japan in wet condition to avoid desiccation and gaps, respectively, around the restorative cavities. At breakdown. Each tooth was sectioned in a buccolingual the severest points, 1 and 14, all showed gaps in the direction through the center of the restoration with a three conditions.

The coronal and cervical areas also low-speed diamond saw Isomet, Buehler Ltd, Lake mostly showed gaps.

Thus, the presence or absence of mar- than half the number of gaps in the same condition. This was performed using a 37 gaps around the restorative cavities. Significant dif- traveling microscope x1,, Measurescope, MM, ferences were observed among the three storage periods Nikon, Tokyo, Japan positioned parallel with the cavi- immediately, after 30 minutes and after three hours ty wall and bottom on each half of the sample Figure and after the 12 hour-storage period. Most of the comment forms I see look like this.

I find it confusing to figure out where a conversation ends. The bottom line is more and more sites are turning to third party comment systems because of the features they have out of the box. IntenseDebate had some cool features for comments at the time such as threaded comments and reply by email. Fast forward six years later and IntenseDebate is now on hiatus. But there has been a lot of work on the Jetpack comment features such as subscriptions and interactions with social networks.

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The choices are iOS, Android, or other. Stay tuned. With iGravatar, users can manage their Gravatar account from their mobile device. With that said, I want to hear from you in the comments on what functionality do you think will be part of the official Gravatar app? The goal of the service is to eliminate the stress and hassles of selling WordPress products allowing the developer to concentrate on the product itself. Some of the most difficult aspects of running a business such as licensing, memberships, refunds, secure download links, and refunds are handled through SellWP.

The customer and license is then managed through SellWP. If SellWP experiences downtime, it could result in lost sales. SellWP is transparent about the fact that their uptime is dependent upon the uptime of Fortrabbit. The service also creates daily, weekly, and monthly backups hosted at an offsite location. Back filling of customer data is not currently supported but will be available in an upcoming update. SellWP is a managed solution for selling WordPress products.

Once the beta ends, sellers will be charged the standard fees per transaction. Will existing sellers outsource this area of their business to a third party? Place any feedback you have in the comments as John Turner will be monitoring them to answer any questions you have.

The challenge is to make design changes in the child theme, without breaking the purpose of the parent theme. It supports all post formats and is translation-ready. By nature of being a child theme, it automatically includes all the features found in the Stargazer parent theme, ie. Given that the directory now contains 2, themes, a name with two words in it is less likely to be taken. Props go out to Weston Ruter and his team of dedicated developers who helped make this feature a reality.

Instead, the team opted to generalize this functionality so that any feature utilizing the customizer controls can do partial preview updates. Widgets still get live previews, but the window will refresh in an unobtrustve way as you make changes. But what if you want to use multiple categories? It allows you to select multiple categories to assign to uncategorized posts.

When network activated, it allows site administrators to select default categories for their own sites. When I asked him why he made the plugin, he said that it was originally part of a custom project. This is one of those rare plugins that is potentially useful to the vast majority of WordPress websites that make use of categories.

It provides a comprehensive set of user-friendly features that will transform your site into a collaborative hub for creating wiki content. Wiki participation privileges are based on user capabilities and can be manually set for each wiki.

If a user accesses a non-existent wiki page, the plugin will prompt him to create a new page. The plugin also offers an array of wiki-related widgets: search, new wikis, popular wikis, recent wikis, categories and tags, a tag cloud, and a subscription button.

The plugin allows users to compare changes to documents diff and gives the option for editors to attach a note with each revision. For example, one might flag an article for poor attribution, readability or spam. It fits in seamlessly with the user profile menu. However, the plugin will work with any WordPress theme. The automatic activation of the theme upon installation of the plugin helps users to discover that there is a theme available, but it might be disturbing if the administrator is not expecting it.

Its feature set is geared towards making collaboration more efficient and productive for wiki participants. WordPress hosting providers that cater to a specific niche are the latest trend. Due to the high demand for more CMS features, the Edublogs team decided to differentiate the services with CampusPress focused on providing multisite network hosting for schools and universities. I created this chart a few months ago when GoDaddy announced their managed WordPress hosting package.

I asked MediaTemple if there was any additional information they could give me regarding their theme marketplace. Essentially, the sky is the limit with the market place. However, security and or maintenance releases are usually applied the same day.

The automatic updates only apply to WordPress, not plugins and themes. Most of the WordPress managed hosting services I know of are extensions of established companies. Customers can upload plugins, change themes, edit their themes, and perform tasks that are locked down on WordPress.

Plus, they have a team of people ready to help at a moments notice which places them a step above most shared webhosting services. They cater to customers who just need a quick and easy way to publish content online. I see managed WordPress hosting companies as the next step for users when they outgrow the constraints of WordPress.

No question appears to be off-limits. Among the five answers within the category was WordPress. My smartphone is my camera, my flashlight, my connection to the world, and my crutch.

Yes, that includes SxSW. Any suggestions? DW Timeline was designed to showcase your blog or portfolio site.

The theme lets you define two colors for the header mask, as well as a background color for the site title. Clicking these will scroll you further down to the next set of posts. If the image is not large enough, it will be stretched. There are other plugins that have similar functionality but this plugin forces the user to check the search engine visibility settings with no alternative way to dismiss the warning box.

If so, how long did it take before you discovered the error? The survey provided an opportunity for participants to post feature requests as well as identify important areas for improvement. Further down the road, the media component may be used to manage all attachments for other components, i.

In this case attachments would refer to uploads that have BP metadata attached. The development survey indicated that 65 respondents from 31 countries are eager to contribute to BuddyPress in some way. Hopefully, the core team will be able to successfully use the features-as-plugins model to make it easier for new testers and contributors to get involved.

In the meantime, for most people, switching to the Visual view before publishing works. Three hundred thirty-eight developers from fifty-two countries completed the survey. Thank you all. Discover current and actual BuddyPress usage. Provide users the opportunity to post their feature requests. Identify key areas for improvement. Prioritize areas of BuddyPress development. Set benchmarks to streamline development processes.

Identify volunteers who are interested in contributing to BuddyPress development. The idea was to engage users in BP development for version 2. We will be contacting you soon. In addition, adopting the WordPress features-as-plugin process, some new BP features will be developed as plugins first to get more people involved in the frontend and backend requirements. Thinking about it? Live in the Salem, Oregon, or nearby areas?

Improve the security of any WordPress site in seconds. Automatically inserts the tracking code in every page of your website. After managing the meetup for a couple of months, Driver noticed interest grew along with memberships which is when he decided to begin the process of creating a WordCamp. It begins. I was told around 65 people participated in the workshop where they were introduced to WordPress and learned about eCommerce as well as SEO. Deep dive into WordPress daytonwp with MarcBenzak wcdayton pic.

Lewis theRamenNoodle March 8, The tragedy of life is what dies inside a man while he lives. Tracking with corymiller wcdayton pic. As soon as you get the green light from WordCamp Central go for it. Dazzling Features: This theme comes packaged with its own options panel for customizing the design, including the ability to edit the footer copyright information, set up the slider, customize typography and more.

Logo upload support Customizable call-to-action section Color customization for every aspect of the theme Retina ready Support for Font Awesome icons Popular posts widget Translation ready Infinite Scroll powered by Jetpack Multiple widget areas Dazzling also includes extra optimization for many popular plugins such as Contact Form 7, WordPress SEO, Jetpack and more to follow in subsequent theme updates.

Check out the live demo to see Dazzling in action. Download Dazzling for free via the theme administration panel in the WordPress admin. Patrick will be taking on the position of Developer here at WDS.

Patrick first started using WordPress with version 2. While freelancing he found he had an affinity for e-commerce development, and started building commercial plugins for WordPress powered e-commerce websites. Though that was short lived, after only a few months he is now joining the WDS team where he hopes to learn from some of the best in the industry while also bringing his own experience. Louis, Brian Messenlehner will be speaking, Sarah Pressler will be volunteering, and Cristina Cannon will be in attendance!

WordCamp St. We will go over how to rapidly build scalable and secure applications and how to save time and money doing so. We will also showcase some really cool applications and examples of building things with WordPress while thinking out of the box.

Louis this year! We love supporting the WordPress community, and sponsoring events is one of our favorite ways to show it! Stacy comes on board as our newest Front End Designer and today is her first day at WebDev, so wish her well.

She has been freelancing full-time since , is an active member of the Aurora WordPress Meetup Group and attends WordCamps every chance she gets. She was originally hired as a print designer, but they needed more help in web, so she began to do both. As her skills began to develop, she found herself wanting to learn more. Stacy believes she is a kick ass designer.

As she has grown in her profession she has realized she REALLY enjoys the actual development of the site and thinks the problem solving aspect is a fun challenge. She has worked hard to become an expert in both visual design and front-end development.

By working in small agencies and then doing freelance, she found that you are forced to wear many hats and uses these skills to make great sites for her clients.

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