A comparison of the diametral tensile strength, the flexural strength, and the compressive strength of two new core materials to a silver alloy-reinforced glass-ionomer material

Evaluation of Compressive and Flexural Strengths of Two Resin-based Core Materials with an Alkasite Material: An In Vitro Study

AIM

To compare and evaluate the compressive and flexural strengths of two resin-based core build-up materials with an alkasite material.

MATERIALS AND METHODS

ParaCore, Tetric N ceram Bulk-fill composite, and Cention N were used. A total of 90 specimens were prepared. Customized cylindrical split molds of dimension 6 ± 1 mm (height) × 4 ± 1 mm (diameter) were used to fabricate 15 samples of each core material for testing the compressive strength and rectangular split metal molds of dimensions 25 ± 1 mm (length) × 2 ± 1 mm (width) × 2 ± 1 mm (height) were used to fabricate 15 samples of each core material for testing the flexural strength. Then the samples were tested using a Universal testing machine (UTM).

RESULTS

The compressive and flexural strengths of Cention N were significantly less than ParaCore® but higher than Tetric® N-CeramTM Bulk-fill core build-up material.

CONCLUSION

Within the limitations of this study, it was concluded that Cention N may be used as an alternative to other core build-up materials after further in-vitro and in-vivo studies.

CLINICAL SIGNIFICANCE

Cention N had the added advantage that self-cure polymerization alone was sufficient to achieve good physical properties when compared to the other two resin-based core build-up materials.

An In Vitro Study Comparing the Diametral Tensile Strength of Composite Core Build-Up Material With Three Different Prefabricated Post Systems

Statement of problem

Dental restorations are subjected to tensile stresses from oblique or transverse loading of their complex geometric forms, making tensile strength a fundamental mechanical property. Since composite core build-up materials are brittle, the integrity of the post and core depends on their tensile strength and resistance to fracture when utilized with various prefabricated post systems. Therefore, it is essential to determine the tensile strength of the prefabricated metallic and nonmetallic posts used to reinforce the composite resin core.

Purpose

This study compared the diametral tensile strength (DTS) of three prefabricated post systems with composite core build-up material.

Material and methodology

Ten composite resin cores from four different groups were formed. The control group was the composite resin core without a post (group 1). Group 2 was composed of composites with metal posts, group 3 was composed of composites with glass fiber posts, and group 4 was composed of composites with carbon fiber posts. All the samples were kept in a humid place for seven days to mimic the conditions in the mouth. DTS was determined by recording the tensile force required to fracture the core material by performing a diametral compression test for tension after a week. The observations were analyzed using a one-way analysis of variance (ANOVA), followed by a post-hoc test.

Results

The tensile strength of the resin core material was decreased by 28.1%, 20.8%, and 10.4% by using posts made of stainless steel, carbon fiber, and glass fiber, respectively. Among the three post systems, stainless steel had the lowest mean DTS values, while glass fiber had the highest mean DTS values.

Conclusion

Composite core glass fiber post systems showed higher tensile strength than other post systems.

Comparative evaluation of the compressive, tensile, and flexural strengths of paracore®, flourocore®2+, and multicore® resin-based core build-up materials - An in vitro study

Aims

The study was aimed to evaluate and compare the compressive, diametral tensile, and flexural strengths of three different commercial resin based core materials and to single out the best resin-based core build-up material with respect to their physical properties among ParaCore® (Coltene Whaledent, USA), FlouroCore® 2+ (Dentsply International, USA), MultiCore® (Ivoclar Vivadent, Liechtenstein) with Miracle Mix® (GC America) core used as control.

Materials and Methods

One hundred and twenty samples were prepared, of which forty samples (10 of each material) were prepared in cylindrical stainless steel molds (height 6 mm, diameter 4 mm) for compressive strength measurements. Other forty samples (10 of each material) were prepared in cylindrical molds (diameter 6 mm, height 2 mm) for diametral tensile strength measurements. Forty samples (10 of each material) were prepared in stainless steel molds cuboidal in shape (length 25 mm, thickness 2 mm, and width 2 mm) for flexural strength measurements. The samples were tested on a Universal testing machine (Instron Machine 3366, made in the USA).

Statistical Analysis Used

One-way analysis of variance was performed to determine any statistically significant differences (P < 0.05) among the resin-based core build-up materials with respect to their three respective strengths. Further, the statistical comparison was made among the four materials using Student's t-test at a significance level of 5%.

Results

Based on the results obtained it can be summarized that the ParaCore is the strongest material among all the four materials, followed by MultiCore, FlouroCore2+, and Miracle Mix. The Miracle mix is the weakest among all the materials owing to its inferior strength values.

Conclusion

The results of the present study imply that, in consideration of their superior strength values, resin-based core build-up materials, ParaCore, MultiCore, and FlouroCore2+ should be a preferred for use as core build-up material over Miracle Mix in specific clinical situations, in the same order of preference.

Effect of Two Different Surface Treatments on Retention of Cosmopost with Two Different Core Materials

Objective

The objective of this study was to determine the effect of Cosmopost’s two different surface treatments (sandblasting and silica coating) on persistence to various core materials using push-out test set-up.

Material and Methods

A total of 30 Cosmoposts was used in this study. Cosmoposts were divided into three groups (10 samples each) according to the post-surface treatment received. Every category was additionally subdivided into two subgroups according to the type of core material (n = 5 samples). A specially designed copper mold was used for construction of different core materials with standardized dimensions around the posts, in such a way to ensure that the posts will be centralized. Surface roughness was estimated for all Cosmoposts, following different surface treatments using SEM. Cylindrical cores were fabricated of either composite resin or heat-pressed zirconia-containing glass-ceramic (IPS Empress Cosmo, Ivoclar Vivadent). Following the construction of different Core materials, samples were subjected to push-out test set-up to Evaluate the impact of various treatments on post/core bond strength. Data were collected, tabulated and statistically analyzed. SEM was performed on Cosmoposts following debonding of different post/core samples to determine their mode of failure.

Results

Results of push-out bond strength revealed that core material, surface treatment and the interaction between the two variables using Two-way ANOVA had a statistically significant effect on mean push-out bond strength. Regarding the effect of type of core material on Push-out bond strength, results showed that IPS Empress Cores showed statistically significant higher mean push-out bond strength to Cosmopost (36.4±9.7MPa) than composite cores (15.8±2.5 MPa).

Conclusion

Within the limitations of this study, direct heat-pressed ceramic core was more beneficial for zirconia post buildups, than Composite Cores, since they provided higher bond strength. Thanks to a double improvement: increase in fracture resistance and retentive capacity to post. Also, Tribochemical Silicacoating technique was proved to be more effective in Cosmopost treatments than sandblasting technique.

Surface and bulk properties of dental resin- composites after solvent storage

OBJECTIVES

To investigate the surface micro-hardness and the diametral tensile strength (DTS) of bulk-fill and conventional resin-composites after storage in food simulating solvents.

METHODS

Eight materials were investigated. For the micro-hardness measurement, Teflon mould with an internal dimensions of 10mm and 2mm (n=15). For the DTS measurement, Split stainless steel moulds were used to make disk-shaped specimens of 6mm diameter and 2mm thickness (n=15). Materials were subdivided in to three groups (water, 75% ethanol/water and MEK). Micro-hardness measurements were made under a load of 300gm with a dwell time of 15s at 7, 30, and 90ds after storage. DTS was measured after 30ds at a cross head speed of 0.5mm/min.

RESULTS

The storage time and type of solvent had a significant influence on the micro-hardness. MEK showed more drastic reduction in the material micro-hardness with an exception of G-aenial universal flo (GA-F) which showed similar results in water/ethanol and MEK. DTS values of materials stored in water ranged from 48.7MPa for the GA-F and 30.6MPa for Ever X posterior (EXP). Generally, the results are observed to decrease with increasing solvent power, except for GA-F.

SIGNIFICANCE

Bulk-fill materials showed no superior results compared with the other materials. For the bulk-fill materials that are designed to be used as a base, their penetration by the solvents may be shielded and thus the changes observed in this study may not be of clinical importance.

Effect of short glass fiber/filler particle proportion on flexural and diametral tensile strength of a novel fiber-reinforced composite

PURPOSE

To evaluate the effect of glass fiber/filler particles proportion on flexural strength and diametral tensile strength of an experimental fiber-reinforced composite.

METHODS

Four experimental groups (N=10) were created using an experimental short fiber-reinforced composite, having as a factor under study the glass fiber (F) and filler particle (P) proportion: F22.5/P55 with 22.5 wt% of fiber and 55 wt% of filler particles; F25/P52.5 with 25 wt% of fiber and 52.5 wt% of filler particles; F27.5/P50 with 27.5 wt% of fiber and 50 wt% of filler particles; F30/P47.5 with 30 wt% of fiber and 47.5 wt% of filler particles. The experimental composite was made up by a methacrylate-based resin (50% Bis-GMA and 50% TEGDMA). Specimens were prepared for Flexural Strength (FS) (25 mm × 2 mm × 2 mm) and for Diametral Tensile Strength (DTS) (3×6 Ø mm) and tested at 0.5 mm/min in a universal testing machine.

RESULTS

The results (in MPa) showed significance (different superscript letters mean statistical significant difference) for FS (p<0.009) and DTS (p<0.001)--FS results: F22.5/P55: 217.24±20.64(B); F25/P52.5: 245.77±26.80(AB); F27.5/P50: 246.88±32.28(AB); F30/P47.5: 259.91±26.01(A). DTS results: F22.5/P55: 21.82±4.42(B); F25/P52.5: 22.00±7.40(B); F27.5/P50: 18.63±4.41(B); F30/P47.5: 31.05±2.97(A). In SEM analysis, areas without fiber reinforcement demonstrated to be more prone to the presence of bubbles and crack development. The group F30/P47.5 showed areas with a great quantity of fibers without empty spaces for crack propagation.

CONCLUSION

Increasing fiber content results in higher flexural and diametral tensile strength of an experimental composite reinforced with glass fibers.

Comparative study of mechanical properties of direct core build-up materials

Background and Objectives:

The strength greatly influences the selection of core material because core must withstand forces due to mastication and para-function for many years. This study was conducted to evaluate certain mechanical properties of commonly used materials for direct core build-up, including visible light cured composite, polyacid modified composite, resin modified glass ionomer, high copper amalgam, and silver cermet cement.

Materials and Methods:

All the materials were manipulated according to the manufacturer's recommendations and standard test specimens were prepared. A universal testing machine at different cross-head speed was used to determine all the four mechanical properties. Mean compressive strength, diametral tensile strength, flexural strength, and elastic modulus with standard deviations were calculated. Multiple comparisons of the materials were also done.

Results:

Considerable differences in compressive strength, diametral tensile strength, and flexural strength were observed. Visible light cured composite showed relatively high compressive strength, diametral tensile strength, and flexural strength compared with the other tested materials. Amalgam showed the highest value for elastic modulus. Silver cermet showed less value for all the properties except for elastic modulus.

Conclusions:

Strength is one of the most important criteria for selection of a core material. Stronger materials better resist deformation and fracture provide more equitable stress distribution, greater stability, and greater probability of clinical success.

An in vitro comparative evaluation of physical properties of four different types of core materials

Introduction:

Compressive and tensile stresses of core materials are important properties because cores usually replace a large bulk of tooth structure and must resist multidirectional masticatory forces for many years.

Material and Methods:

The present study was undertaken to find out the best core build up material with respect to their physical properties among resin-based composites. Individual compressive, tensile, and flexural strength of fiber-reinforced dual cure resin core build up material, silorane-based composite resin, and dual curing composite for core build up with silver amalgam core was used as control were evaluated and compared using universal testing machine. Data were statistical analysed using Kruskal-Wallis test to determine whether statistically significant differences (P < 0.05) existed among core materials. Both dual cure composite materials with nanofillers were found superior to amalgam core. The silorane-based material showed the highest flexural strength, but other mechanical properties were inferior to dual cure composite materials with nanofillers.

The Comparison of Shear Bond Strength Between Fibre Reinforced Composite Posts with Three Different Composite Core Materials - An In vitro Study

AIM

The aim of this study is to compare the shear bond strength between fiber reinforced composite post with three different composite core materials.

MATERIALS AND METHODS

The materials used for the study were: 30 maxillary central incisors, pre fabricated fiber reinforced composite post (postec plus posts), Multi-core heavy body, Ti-core, Fluoro-core, Etchant gel, Silane coupling agent, Dentin bonding agent, Standardized gutta percha points, Rely-X dual cure composite resin. A total of 30 human maxillary central incisor were selected for this study. They were divided into three groups of 10 specimens each namely A, B and C.

RESULTS

The results obtained were analyzed by using one way analysis (ANOVA) and Tukey Honestly Significant Difference and they showed highest mean shear bond strength for group C when compared with group A and group B. There is no significant difference in the shear bond strength values between group A and group B.

CONCLUSION

The teeth restored with multicore HB showed highest shear bond strength. The teeth restored with Fluoro core showed lowest shear bond strength. No statistically significant difference exists between the shear bond strength values between Ti-core and Fluoro-core.

Comparative evaluation of compressive strength and flexural strength of conventional core materials with nanohybrid composite resin core material an in vitro study

Several dental materials have been used for core build-up procedures. Most of these materials were not specifically developed for this purpose, but as a consequence of their properties, have found application in core build-up procedures. Improvements in composites and the development of nanocomposites have led to their use as a core build up material due to their superior mechanical properties, optical properties and ease of handling. However it is not clear if they have better mechanical properties than the conventional core build up materials like amalgam, GIC and dual cure composite core build up material. The strength of the core material is very important and this study was undertaken to compare the mechanical properties of materials used for direct core foundations. The differences between the compressive strength and flexural strength of Filtek Z350 nanocomposite with conventional core build up materials like Amalgam, Vitremer GIC and Fluorocore were tested. Cylindrical plexi glass split molds of dimension 6 ± 1 mm [height] x4 ± 1 mm [diameter] were used to fabricate 15 samples of each core material for testing the compressive strength and rectangular plexi glass split molds of dimension 25 ± 1 mm [length] x 2 ± 1 mm[height] x2 ± 1 mm [width] used for fabricating samples for flexural strength. The samples were stored a water bath at 250 °C for 24 h before testing. The samples were tested using a Universal Instron testing machine. The results of the study showed that Fluorocore had the highest compressive strength and flexural strength followed by Filtek Z350 [nanocomposite] Amalgam had the least flexural strength and Vitremer GIC had the least compressive strength. Thus flurocore and nanocomposite are stronger than other core build up materials and hence should be preferred over other conventional core build up materials in extensively damaged teeth.

Flexural and diametral tensile strength of composite resins

This study evaluated the flexural strength (sf) and the diametral tensile strength (st) of light-cured composite resins, testing the hypothesis that there is a positive relation between these properties. Twenty specimens were fabricated for each material (Filtek Z250- 3M-Espe; AM- Amelogen, Ultradent; VE- Vit-l-escence, Ultradent; EX- Esthet-X, Dentsply/Caulk), following ISO 4049 and ANSI/ADA 27 specifications and the manufacturers instructions. For the st test, cylindrical shaped (4 mm x 6 mm) specimens (n = 10) were placed with their long axes perpendicular to the applied compressive load at a crosshead speed of 1.0 mm/min. The sf was measured using the 3-point bending test, in which bar shaped specimens (n = 10) were tested at a crosshead speed of 0.5 mm/min. Both tests were performed in a universal testing machine (EMIC 2000) recording the fracture load (N). Strength values (MPa) were calculated and statistically analyzed by ANOVA and Tukey (a = 0.05). The mean and standard deviation values (MPa) were Z250-45.06 +/- 5.7; AM-35.61 +/- 5.4; VE-34.45 +/- 7.8; and EX-42.87 +/- 6.6 for st; and Z250-126.52 +/- 3.3; AM-87.75 +/- 3.8; VE-104.66 +/- 4.4; and EX-119.48 +/- 2.1 for sf. EX and Z250 showed higher st and sf values than the other materials evaluated (p < 0.05), which followed a decreasing trend of mean values. The results confirmed the study hypothesis, showing a positive relation between the material properties examined.

Diametral tensile strength of a resin composite core with nonmetallic prefabricated posts: an in vitro study

STATEMENT OF PROBLEM

A number of prefabricated nonmetallic posts are currently available for use in conjunction with resin composite cores before fabrication of crowns for endodontically treated teeth. Information is needed regarding the strength of the composite and the nature of attachment between its components.

PURPOSE

The aim of this study was to determine the influence of different types of posts on the fracture resistance of a resin composite core material using the diametral tensile strength (DTS) test.

MATERIAL AND METHODS

Cylindrical specimens, 6 mm in diameter and 3 mm high, were prepared from resin composite (Tetric Ceram) and a group of prefabricated posts (n=10) as follows: resin composite only (control); Vectrispost (VTS); FiberKor (FKR); AEstheti-Plus post (ATP); Light-Post (LTP); Dentorama post (DRM), and Para-Post (PRP) as a second control. Specimens were stored for 7 days in water at 37 degrees C and then subjected to DTS test in a universal testing machine until failure occurred and load was recorded (N). Mean values and SD for DTS values (MPA) were calculated, and data were analyzed statistically with 1-way analysis of variance, followed by the Tukey test (alpha=.05). Representative specimens from each group were examined with SEM to determine nature of failure.

RESULTS

Mean values (SD) in MPa for DTS were as follow:

CONTROL GROUP

49.64 (3.36); VTS: 29.77 (3.36); FKR: 31.9 (2.39); ATP: 28.92 (2.2); LTP: 34.26 (3.37); DRM: 33.45 (2.46), and PRP: 27.90 (2.40). Analysis of variance indicated significant differences among the groups (P<.05). SEM examination indicated that for PRP failure was adhesive in nature, whereas with all nonmetallic posts, cohesive failure was more predominant.

CONCLUSION

The use of posts did not result in reinforcement of resin composite core when diametral tensile force was applied. When used with the core material, LTP, DRM, and FKR resulted in the highest DTS values, whereas PRP resulted in the lowest values.

In vitro assessment of retention of four esthetic dowels to resin core foundation and teeth

STATEMENT OF PROBLEM

Several new esthetic dowel systems are currently available for the restoration of endodontically treated teeth. These dowel systems enhance the esthetic quality of all-ceramic restorations better than metallic dowel systems.

PURPOSE

The purpose of this study was to evaluate the retentive strength of composite and ceramic endodontic dowel systems to the tooth and to the core foundation.

MATERIAL AND METHODS

The following dowel systems were tested: resin dowels (Fibrekor [FR]; Luscent [LU]; Twin Luscent Anchor [TLU]); ceramic dowels (Cerapost [CR]; Cosmopost [CO]); and a titanium dowel (ParaPost XH [Ti]). In Part I of the study, core retention was tested by forming Bis-Core resin (n=12) cores around dowels followed by separation using a universal testing machine. In Part II, 60 (n=12) extracted human canines were endodontically treated, and dowel spaces were prepared using the corresponding drill for each dowel system. Nine-millimeter resin and ceramic dowels were cemented with C & B resin luting agent. Additionally, 2 groups (n=12) of Ti dowels cemented with C & B resin luting agent and zinc phosphate luting agent served as control groups. Retention was tested using a universal testing machine to separate the dowels from teeth. One-way analysis of variance and Student Newman-Keuls tests were conducted for statistical analysis (alpha=.05). Surface texture of all dowel systems tested was examined using SEM at original magnification x25 and x250.

RESULTS

Core retention of Ti was higher than all esthetic dowels tested (alpha<.05), but FR had higher core retention than the other esthetic dowels tested. Resin dowels had better retention to teeth than ceramic dowels (alpha<.05).

CONCLUSION

The esthetic dowel systems were less retentive for the resin core material than the titanium control. Resin dowel systems were more retentive in the root than the ceramic dowels but were similar to the titanium control.

Comparison of flexural properties of composite restoratives using the ISO and mini-flexural tests

The purpose of this study was to investigate the flexural properties (flexural strength and flexural modulus) of four commercial composite restoratives (Silux Plus, Z100, Ariston and Surefil) using the ISO 4049 flexural test (IFT) and a mini-flexural test (MFT). Both tests involved the use of three-point loading and the same fixture. The difference between the tests was in the length of the composites specimens and the distance between the supports [20 mm (IFT) and 10 mm (MFT)]. Six specimens were made for each material and flexural test. Test specimens [25 x 2 x 2 mm (IFT) and 12 x 2 x 2 mm (MFT)] were fabricated according to manufacturers' recommendations. After light-polymerization, the specimens were stored in distilled water at 37 degrees C for 24 h. The specimens were subsequently blotted dry, measured and subjected to flexural testing using an Instron Universal Testing Machine with a crosshead speed of 0.75 mm min(-1). Data was analysed using anova/Scheffe's, paired samples test (P < 0.05) and Pearson's correlation (P < 0.01). For both IFT and MFT, results of statistical analysis of flexural strength were identical. Silux had significantly lower flexural strength compared with the other composites and the flexural strength of Ariston was significantly lower than Z100 and Surefil. For IFT, the flexural modulus of Z100 was significantly higher than Silux, Ariston and Surefil while for MFT, Silux had significantly lower modulus compared with Z100, Ariston and Surefil. A significant, strong and positive correlation (r = 0.95) was observed for flexural strength between IFT and MFT. Correlation for flexural modulus was also significant and positive but was weaker (r = 0.53). As MFT has the advantage of ease of specimen fabrication and is more clinically realistic, it is suggested for the testing of composite restoratives.

CLINICAL RELEVANCE

The mini-flexural test may be better than the ISO flexural test for screening of composite restoratives for clinical applications.

Foundation restorations in fixed prosthodontics: current knowledge and future needs

PURPOSE

The Ad Hoc Committee on Research in Fixed Prosthodontics established by the Academy of Fixed Prosthodontics publishes a yearly comprehensive literature review on a selected topic. The subject for this year is foundation restorations.

METHODS

Literature of various in vitro and in vivo investigations that included technical and clinical articles was reviewed to provide clinical guidelines for the dentist when selecting methods and materials for restoration of structurally compromised teeth. Topics discussed and critically reviewed include: (1) desirable features of foundation restorations, (2) foundations for pulpless teeth, (3) historic perspectives, (4) cast posts and cores, (5) role of the ferrule effect, (6) prefabricated posts, (7) direct cores, (8) foundation restorations for severely compromised teeth, (9) problems and limitations, (10) future needs, and (11) directions for future research.

CONCLUSION

This comprehensive review brings together literature from a variety of in vitro and in vivo studies, along with technique articles and clinical reports to provide meaningful guidelines for the dentist when selecting methods and materials for the restoration of structurally compromised teeth.

Diametral and compressive strength of dental core materials

STATEMENT OF PROBLEM

Strength greatly influences the selection of core materials. Many disparate material types are now recommended for use as cores. Cores must withstand forces due to mastication and parafunction for many years.

PURPOSE

This study compared the compressive and diametral tensile strengths of 8 core materials of various material classes and formulations (light-cured hybrid composite, autocured titanium containing composite, amalgam, glass ionomer, glass ionomer cermet, resin-modified glass ionomer, and polyurethane).

MATERIAL AND METHODS

Materials were manipulated according to manufacturers' instructions for use as cores. Mean compressive and diametral strengths with associated standard errors were calculated for each material (n = 10). Analyses of variance were computed (P <.0001) and multiple comparisons tests discerned many differences among materials.

RESULTS

Compressive strengths varied widely from 61.1 MPa for a polyurethane to 250 MPa for a resin composite. Diametral tensile strengths ranged widely from 18.3 MPa for a glass ionomer cermet to 55.1 MPa for a resin composite. Some resin composites had compressive and tensile strengths equal to those of amalgam.

CONCLUSION

Light-cured hybrid resin composites were stronger than autocured titanium containing composites. The strengths of glass ionomer-based materials and of a polyurethane material were considerably lower than for resin composites or amalgam.

Mechanical properties of direct core build-up materials

OBJECTIVE

This work was undertaken to measure mechanical properties of a diverse group of materials used for direct core build-ups, including a high copper amalgam, a silver cermet cement, a VLC resin composite and two composites specifically developed for this application.

METHODS

Compressive strength, elastic modulus, diametral tensile strength and flexural strength and modulus were measured for each material as a function of time up to 3 months, using standard specification tests designed for the materials.

RESULTS

All the materials were found to meet the minimum specification requirements except in terms of flexural strength for the amalgam after 1 h and the silver cermet at all time intervals.

SIGNIFICANCE

There proved to be no obvious superior material in all respects for core build-ups, and the need exists for a specification to be established specifically for this application.

Shear bond strength of several new core materials

This study compared the shear bond strengths of three core materials: a light activated glass-ionomer cement (VariGlass VLC), a fluoride-release dual cure composite resin (Fluoro Core), and a conventional silver-reinforced glass-ionomer cement (Miracle Mix) when cured to dentin. Fifty-four noncarious molar teeth were extracted, cleaned, mounted in acrylic resin, and sectioned horizontally to expose the dentin surface. Each material was mixed according to manufacturer's instructions, applied in a premade mold to the exposed dentin, and then cured. The specimens were randomized into three group (six teeth from each material) and stored (37 degrees C, 100% humidity) for 15 minutes, 24 hours, and 24 hours and were then thermocycled (5 degrees to 55 degrees C) for 125 cycles. The specimens were tested for shear bond strength with the Instron universal testing machine. The differences among time groups were not statistically significant except for Miracle Mix and VariGlass VLC cements, which showed a greater improvement with thermocycling. This study indicated that the FluoroCore resin exhibited the greatest shear bond strength of the core materials and that VariGlass VLC cement had greater bond strength than Miracle Mix cement except after thermocycling, when VariGlass VLC cement and FluoroCore resin were not significantly different.