The Importance of Adhesive Area Delimitation in a Microshear Bond Strength Experimental Design

Purpose: The purpose of this study was to assess the influence of adhesive area delimitation on the microshear bond strength of different adhesives to dentin. Materials and Methods: Eighteen bovine incisors were sectioned and the exposed dentin surfaces were prepared with 600-grit SIC paper. These teeth were randomly divided into three groups, according to the adhesive to be applied: two-step etch-and-rinse Adper Single Bond 2 (3M ESPE), two-step self-etching Clearfil SE Bond (Kuraray), and one-step Clearfil S(3) Bond (Kuraray). On each dentin surface, 4 samples were built up with the composite resin Z100 (3M ESPE); on 2 of these, a suggested area delimitation technique was employed. After 24 h of storage in water at 37 degrees C, samples were subjected to the microshear bond strength test, and the failure modes were evaluated under optical and scanning electron microscopes. The obtained results were statistical analyzed using two-way ANOVA and Tukey`s test. Results: Groups without area delimitation presented significantly higher bond strength results (p < 0.05) and a higher incidence of cohesive failures. In these groups, fractures tended to occur beyond the limits of the actual adhesive area, while the area restriction technique succeeded in avoiding this phenomenon. The three adhesives performed similarly when area delimitation was employed (p > 0.05), but Clearfil S(3) Bond showed significantly higher bond strength results when no area delimitation was taken into account (p < 0.05). Conclusion: The extension of the adhesive area beyond the limits of the composite cylinder may play an important role in the results of microshear bond strength tests, while the suggested area delimitation technique may lead to less questionable outcomes.

Measuring Bond Strength Between Fiber Post and Root Dentin: A Comparison of Different Tests

Purpose The aim of this study was to evaluate the ability of bond strength tests to accurately measure the bond strength of fiber posts luted into root canals Materials and Methods The test methods studied were hourglass microtensile (HM), push-out (PS), modified push out (MP) and pull out (PL) The evaluated parameters were bond strength values, reliability (using Weibull analysis), failure mode (using confocal microscopy), and stress distribution (using finite element analysis) Forty human intact single rooted and endodontically treated teeth were divided into four groups Each group was assigned one of the test methods The samples in the HM and PS groups were 1 0 +/- 0 1 mm thick, the HM samples were hourglass shaped and the PS samples were disk shaped For the PL and MP groups, each 1 mm dentin slice was luted with a fiber post piece Three dimensional models of each group were made and stress was analyzed based on Von Mises criteria Results PL provided the highest values of bond strength followed by MP both of which also had greater amounts of adhesive failures PS showed the highest frequency of cohesive failures MP showed a more homogeneous stress distribution and a higher Weibull modulus Conclusion The specimen design directly influences the biomechanical behavior of bond strength tests

Direct comparison of the bond strength results of the different test methods: A critical literature review

Objective. The goal of this paper is to undertake a literature search collecting all dentin bond strength data obtained for six adhesives with four tests ( shear, microshear, tensile and microtensile) and to critically analyze the results with respect to average bond strength, coefficient of variation, mode of failure and product ranking. Method. A PubMed search was carried out for the years between 1998 and 2009 identifying publications on bond strength measurements of resin composite to dentin using four tests: shear, tensile, microshear and microtensile. The six adhesive resins were selected covering three step systems ( OptiBond FL, Scotch Bond Multi-Purpose Plus), two-step (Prime & Bond NT, Single Bond, Clear. l SE Bond) and one step (Adper Prompt L Pop). Results. Pooling results from 147 references showed an ongoing high scatter in the bond strength data regardless which adhesive and which bond test was used. Coefficients of variation remained high (20-50%) even with the microbond test. The reported modes of failure for all tests still included high number of cohesive failures. The ranking seemed to be dependant on the test used. Significance. The scatter in dentin bond strength data remains regardless which test is used confirming Finite Element Analysis predicting non-uniform stress distributions due to a number of geometrical, loading, material properties and specimens preparation variables. This reopens the question whether, an interfacial fracture mechanics approach to analyze the dentin - adhesive bond is not more appropriate for obtaining better agreement among dentin bond related papers. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Finite Element Analysis of Shear Versus Torsion Adhesive Strength Tests for Dental Resin Composites

Stress distributions in torsion and wire-loop shear tests were compared using three-dimensional (3-D) linear-elastic finite element method, in an attempt to predict the ideal conditions for testing adhesive strength of dental resin composites to dentin. The torsion test presented lower variability in stress concentration at the adhesive interface with changes in the proportion adhesive thickness/resin composite diameter, as well as lower variability with changes in the resin composite elastic modulus. Moreover, the torsion test eliminated variability from changes in loading distance, and reduced the cohesive fracture tendency in the dentin. The torsion test seems to be more appropriate than wire-loop shear test for testing the resin composite-tooth interface strength. (c) Koninklijke Brill NV, Leiden, 2009

Microtensile vs Microshear Bond Strength of All-in-One Adhesives to Unground Enamel

Purpose To determine the bond strength to unground enamel of all in one adhesives in comparison with an etch and rinse system and to compare the reliability of microtensile and microshear methods in providing such measurements Materials and Methods The bonding procedure was performed on enamel of 64 extracted molars The tested all in one adhesives were Bond Force (Tokuyama), AdheSE One (Ivoclar Vivadent) and Xeno V (Dentsply) Prime&Bond NT (Dentsply) served as control Microtensile specimens were obtained from 4 teeth per group Twelve teeth per group were used for microshear testing Microtensile specimens that failed prior to testing were included in statistical calculations, they were assigned the lowest value measured in the respective group Failure modes were observed under light microscope and classified (cohesive within substrates, adhesive mixed) Statistically significant differences in bond strength were assessed among the adhesives within each testing method and between microshear and microtensile data for each adhesive Failure mode distributions were compared using the chi square test Results All in-one adhesives had similar microshear and microtensile bond strengths In both testing methods, the etch and rinse system achieved the strongest bond For all adhesives significantly higher bond strengths were measured with the microshear test In microtensile testing specimens bonded with the etch and rinse adhesive exhibited a significantly different distribution of failure modes The coefficients of variation were extremely high for microtensile bond strength data, particularly of all in one adhesives Conclusion The adhesive potential to intact enamel of recently introduced all in-one adhesives was inferior to that of an etch and rinse system When testing bond strength to enamel of all in one adhesives, microshear testing may be a more accurate method than microtensile

Push-out strength of methacrylate resin-based sealers to root canal walls

P>Aim To assess the push-out strength of Epiphany SE, Epiphany and Hybrid Root SEAL to the dentine walls of root canals. Methodology Sixty roots of canines were prepared and distributed to six groups (n = 10) according to the filling material: GI - Epiphany SE, GII - Epiphany primer and sealer, GIII - Epiphany primer, sealer and resinous solvent, GIV - Clearfil DC Bond and Epiphany sealer, GV - Clearfil, Epiphany sealer and solvent and GVI - Hybrid Root SEAL. Resilon cones were used in all groups. Roots were sectioned transversally to obtain three slices from each third. One slice was subjected to the push-out test (MPa), and results were analysed by anova and Tukey`s test (P < 0.05). The other two slices were prepared for scanning electron microscopy (SEM). Failure mode was also analysed. Results A statistically significant difference (P < 0.05) occurred between Hybrid Root SEAL (5.27 +/- 2.07) and the other materials, GI (0.40 +/- 0.23), GII (0.78 +/- 0.45), GIII (0.57 +/- 0.28), GIV (0.40 +/- 0.24) and GV (0.50 +/- 0.41), which did not differ significantly from each other (P > 0.05). Adhesive failures predominated in groups I, II, IV and V, whilst mixed and cohesive failures were the most frequent in groups III and VI, respectively. There were gaps in the adhesive interface of GI and GII, continuity areas of the filling material with dentine in GIV and GV and good adaptation of the interface of GVI. Conclusion Hybrid Root SEAL had greater push-out strength to root canal dentine than Epiphany SE and Epiphany. The use of primer, solvent and adhesive system did not influence the adhesion of Epiphany.

Bond Strength of Fiber Posts to Weakened Roots After Resin Restoration With Different Light-Curing Times

Introduction: This study evaluated the bond strength of translucent fiber posts to experimentally weakened radicular dentin restored with composite resin and polymerized with different light-exposure time. Methods: Roots of 60 maxillary incisors were used. Twenty-four hours after obturation, the filling materials of root canals were removed to a depth of 12 mm, and 4 groups were randomly formed. In 3 groups, root dentin was flared to produce a space between fiber post and canal walls. In the control group, the roots were not experimentally weakened. The flared roots were bulk restored with composite resin, which was light-activated through the translucent post for 40, 80, or 120 seconds. Posts were cemented, and after 24 hours, all roots were sectioned transversely in the coronal, middle, and apical regions, producing 1-mm-thick slices. Push-out test was performed, and failure modes were observed. Results The quantitative analysis showed significant statistical difference only among groups (P <.001). Comparing the weakened/restored groups, composite light-exposure time did not influence the results. Overall, adhesive failures occurred more frequently than other types of failures. Cohesive failures occurred only in the weakened/restored roots. Conclusions Intracanal root restoration with composite resin and translucent fiber posts provided similar or higher bond strength to dentin than the control group, regardless of the light-exposure time used for polymerization. (J Endod 2009;35:1034-1039)

Bond strength of fibre glass and carbon fibre posts to the root canal walls using different resin cements

The aim of the study was to evaluate the bond strength of fibre glass and carbon fibre posts in the root canal walls cemented with self-adhesive (RelyX-Unicem) and chemical (Cement-Post) resin cements. Forty maxillary canines were divided into four groups according to the cement and post used and submitted to the push-out test (0.5 mm min(-1)). The data were submitted to statistical analysis (2-way ANOVA, Bonferroni - P < 0.05) and fracture analysis by Scanning Electronic Microscopy. Fibre glass presented the best results when cemented with RelyX-Unicem and Cement-Post (P < 0.05). RelyX-Unicem presented the highest bond strength values for both posts (P < 0.05). Fracture analysis showed predominance of cohesive fracture of post for RelyX-Unicem and adhesive fracture between dentin/cement and mixed for Cement-Post. The bond strength values were significantly affected by the type of post and cement used and the highest values were found for fibre glass posts and RelyX-Unicem.

Bond Strength of Fiber Posts in Different Root Thirds Using Resin Cement

Purpose: The aim of the study was to assess the in vitro bond strength (BS) of glass fiber posts (GF) and carbon fiber posts (CF) in the cervical, middle, and apical thirds of root canals cemented with RelyX-Unicem (RX) and Cement-Post (CP). Materials and Methods: Forty maxillary canines were divided into 4 groups (n = 10) according to the cement and post used: group 1: GF and RX; group 2: CF and RX; group 3: GF and CP; group 4: CF and CP. The push-out test was applied in the cervical, middle and apical thirds of each specimen to assess bond strength of the cement/post complex to the root canal wall. The data obtained were submitted to ANOVA (Bonferroni test, p < 0.05), and fracture analysis was done with SEM. Results: The GF posts presented the best results when cemented with RX and with CF (p < 0.05). RX presented the highest BS values for both GF and CF (p < 0.05). For all the groups, BS was higher in the cervical third, followed by the middle and apical thirds. Fracture analysis showed a predominance of cohesive fracture of posts for RX, and a predominance of adhesive fracture between dentin/cement, and mixed failure mode for CP. Conclusion: GF posts cemented with RX presented the highest BS values in all root thirds.

Bond Strength of Dental Adhesive Systems Irradiated with Ionizing Radiation

Purpose: The aim of the present paper was to determine the effect of different types of ionizing radiation on the bond strength of three different dentin adhesive systems. Materials and Methods: One hundred twenty specimens of 60 human teeth (protocol number: 032/2007) sectioned mesiodistally were divided into 3 groups according to the adhesives systems used: SB (Adper Single Bond Plus), CB (Clearfil SE Bond) and AP (Adper Prompt Self-Etch). The adhesives were applied on dentin and photo-activated using LED (Lec 1000, MMoptics, 1000 mW/cm(2)). Customized elastomer molds (0.5 mm thickness) with three orifices of 1.2 mm diameter were placed onto the bonding areas and filled with composite resin (Filtek Z-250), which was photo-activated for 20 s. Each group was subdivided into 4 Subgroups for application of the different types of ionizing radiation: ultraviolet radiation (UV), diagnostic x-ray radiation (DX), therapeutic x-ray radiation (TX) and without irradiation (control group, CG). Microshear tests were carried out (Instron, model 4411), and afterwards the modes of failure were evaluated by optical and scanning electron microscope and classified using 5 scores: adhesive failure, mixed failures with 3 significance levels, and cohesive failure. The results of the shear bond strength test were submitted to ANOVA with Tukey`s test and Dunnett`s test, and the data from the failure pattern evaluation were analyzed with the Mann Whitney test (p = 0.05). Results: No change in bond strength of CB and AP was observed after application of the different radiation types, only SB showed increase in bond strength after UV (p = 0.0267) irradiation. The UV also changed the failure patterns of SB (p = 0.0001). Conclusion: The radio-induced changes did not cause degradation of the restorations, which means that they can be exposed to these types of ionizing radiation without weakening the bond strength.

Bond Strength and Etching Pattern of Adhesive Systems to Enamel: Effects of Conditioning Time and Enamel Preparation

Statement of the problem: The performance of self-etch systems on enamel is controversial and seems to be dependent on the application technique and the enamel preparation. Purpose of the Study: To examine the effects of conditioning time and enamel surface preparation on bond strength and etching pattern of adhesive systems to enamel. Materials and Methods: Ninety-six teeth were divided into 16 conditions (N = 6) in function of enamel preparation and conditioning time for bond strength test. The adhesive systems OptiBond FL (Kerr, Orange, CA, USA), OptiBond SOLO Plus (Kerr), Clearfil SE Bond (Kuraray, Osaka, Japan), and Adper Prompt L-Pop (3M ESPE, St. Paul, MN, USA) were applied on unground or ground enamel following the manufacturers` directions or doubling the conditioning time. Cylinders of Filtek Flow (0.5-mm height) were applied to each bonded enamel surface using a Tygon tube (0.7 mm in diameter; Saint-Gobain Corp., Aurora, OH, USA). After storage (24 h/37 degrees C), the specimens were subjected to shear force (0.5 mm/min). The data were treated by a three-way analysis of variance and Tukey`s test (alpha = 0.05). The failure modes of the debonded interfaces and the etching pattern of adhesives were observed using scanning electron microscopy. Results: Only the main factor ""adhesive"" was statistically significant (p < 0.001). The lowest bond strength value was observed for OptiBond FL. The most defined etching pattern was observed for 35% phosphoric acid and for Adper Prompt L-Pop. Mixed failures were observed for all adhesives, but OptiBond FL showed cohesive failures in resin predominantly. Conclusions: The increase in the conditioning time as well as the enamel pretreatment did not provide an increase in the resin-enamel bond strength values for the studied adhesives. CLINICAL SIGNIFICANCE The surface enamel preparation and the conditioning time do not affect the performance of self-etch systems to enamel. (J Esthet Restor Dent 20:322-336, 2008)

Influence of different catilever extensions and glass or polyamaramid reinforcement fibers on fracture strength of implant-supported temporary

In long-term oral rehabilitation treatments, resistance of provisional crowns is a very important factor, especially in cases of an extensive edentulous distal space. The aim of this laboratorial study was to evaluate an acrylic resin cantilever-type prosthesis regarding the flexural strength of its in-balance portion as a function of its extension variation and reinforcement by two types of fibers (glass and polyaramid), considering that literature is not conclusive on this subject. Each specimen was composed by 3 total crowns at its mesial portion, each one attached to an implant component (abutment), while the distal portion (cantilever) had two crowns. Each specimen was constructed by injecting acrylic resin into a two-part silicone matrix placed on a metallic base. In each specimen, the crowns were fabricated with either acrylic resin (control group) or acrylic resin reinforced by glass (Fibrante, Angelus) or polyaramide (Kevlar 49, Du Pont) fibers. Compression load was applied on the cantilever, in a point located 7, 14 or 21 mm from the distal surface of the nearest crown with abutment, to simulate different extensions. The specimen was fixed on the metallic base and the force was applied until fracture in a universal test machine. Each one of the 9 sub-groups was composed by 10 specimens. Flexural strength means (in kgf) for the distances of 7, 14 and 21 mm were, respectively, 28.07, 8.27 and 6.39 for control group, 31.89, 9.18 and 5.16 for Kevlar 49 and 30.90, 9.31 and 6.86 for Fibrante. Data analysis ANOVA showed statistically significant difference (p<0.05) only regarding cantilever extension. Tukey's test detected significantly higher flexural strength for the 7 mm-distance, followed by 14 and 21 mm. Fracture was complete only on specimens of non-reinforced groups.

Effect of cement type and water storage time on the push-out bond strength of a glass fiber post

This study investigated the effects of the cement type and the water storage time on the push-out bond strength of a glass fiber post. Glass fiber posts (Fibrekor, Jeneric Pentron) were luted to post spaces using a self-cured resin cement (C&B Cement [CB]), a glass ionomer cement (Ketac Cem [KC]) or a resin-modified glass ionomer cement (GC FujiCEM [FC]) according to the manufacturers’ instructions. For each luting agent, the specimens were exposed to one of the following water storage times (n=5): 1 day (T1), 7 days (T7), 90 days (T90) and 180 days (T180). Push-out tests were performed after the storage times. Control specimens were not exposed to water storage, but subjected to the push-out test 10 min after post cementation. Data (in MPa) were analyzed by Kruskal-Wallis and Dunn`s test (α=0.05). Cement type and water storage time had a significant effect (p<0.05) on the push-out bond strength. CB showed significantly higher values of retention (p<0.05) than KC and FC, irrespective of the water storage time. Water storage increased significantly the push-out bond strength in T7 and T90, regardless of the cement type (p<0.05). The results showed that fiber posts luted to post spaces with the self-cured resin cement exhibited the best bonding performance throughout the 180-day water storage period. All cements exhibited a tendency to increase the bond strength after 7 and 90 days of water storage, decreasing thereafter.

Influence of intraradicular post and crown ferrule on the fracture strength of endodontically treated teeth

The aim of this study was to investigate the fracture strength of endodontically treated teeth restored with different posts and variable ferrule heights. Sixty freshly extracted human canines were treated endodontically and randomly assigned to 6 groups (n=10), being restored with custom-made cast post-and-core (CP0 and CP3 groups), prefabricated post and composite resin core (PF0 and PF3 groups), and composite resin (CR0 and CR3 groups). The CP0, PF0 and CR0 groups presented no ferrule and the CP3, PF3 and CR3 presented 3 mm of coronal structure. All teeth were restored with full metal crowns. The fracture strength was measured in a universal testing machine at 45o to the long axis of the tooth until failure. Data were analyzed statistically by 2-way ANOVA and Tukey's test (?=0.05). When the mean fracture strength values were compared (CP0 group - 820.20 N, CP3 group - 1179.12 N; PF0 group - 561.05 N; PF3 group - 906.79 N; CR0 group - 297.84 N; and CR3 group - 1135.15 N) there was statistically significant among the groups (p<0.05), except for the three groups with 3 mm of coronal remaining, which were similar to each other. The results of this study showed that the ferrule in crowns promoted significantly higher fracture strength in the endodontically treated teeth.

Influence of different adhesive systems on the pull-out bond strength of glass fiber posts

This in vitro study evaluated the tensile bond strength of glass fiber posts (Reforpost - Angelus-Brazil) cemented to root dentin with a resin cement (RelyX ARC - 3M/ESPE) associated with two different adhesive systems (Adper Single Bond - 3M/ESPE and Adper Scotchbond Multi Purpose (MP) Plus - 3M/ESPE), using the pull-out test. Twenty single-rooted human teeth with standardized root canals were randomly assigned to 2 groups (n=10): G1- etching with 37% phosphoric acid gel (3M/ESPE) + Adper Single Bond + #1 post (Reforpost - Angelus) + four #1 accessory posts (Reforpin - Angelus) + resin cement; G2- etching with 37% phosphoric acid gel + Adper Scotchbond MP Plus + #1 post + four #1 accessory posts + resin cement. The specimens were stored in distilled water at 37°C for 7 days and submitted to the pull-out test in a universal testing machine (EMIC) at a crosshead speed of 0.5 mm/min. The mean values of bond strength (kgf) and standard deviation were: G1- 29.163 ± 7.123; G2- 37.752 ±13.054. Statistical analysis (Student's t-test; a=0.05 showed no statistically significant difference (p<0.05) between the groups. Adhesive bonding failures between resin cement and root canal dentin surface were observed in both groups, with non-polymerized resin cement in the apical portion of the post space when Single Bond was used (G1). The type of adhesive system employed on the fiber post cementation did not influence the pull-out bond strength.