Microtensile bond strength of two different adhesive systems to dentin (an in vivo and in vitro study)

Abstract no. 496published_or_final_versio

Effects of a peripheral enamel bond on the long-term effectiveness of dentin bonding agents exposed to water in vitro

This study evaluated the effects of water exposure on the in vitro microtensile bond strength (pTBS) of etch-and-rinse and self-etching adhesives to human dentin over a 1-year storage period. Five adhesive systems used were as follows: a one-step self-etching adhesive (One-up Bond F-OB), two two-step self-etching primers (Clearfill SE Bond-SE and Clearfil Protect Bond-CP), and two etch-and-rinse adhesives (Single Bond-SB and Prime&Bond NTPB). Dentin surfaces were bonded, restored, and assigned to four subgroups, according to the degree of water exposure: 24 h of peripheral water exposure (24 h-PE) (having circumferential enamel); and 1 year of peripheral exposure (1 yr-PE), direct exposure (1 yr-DE) (dentin directly water-exposed), or directly exposed to oil only (no water exposure) (1 yr-DOE). A composite-enamel bond adjacent to the restoration is determined if the water exposure was peripheral or direct. After storage periods, specimens were serially sectioned, trimmed to an hourglass shape with a cross-sectional area of I turn 2 at the interface, and tested in tension. Results were analyzed by two-way ANOVA and Tukey test (a = 0.05). No difference was found between 24 h-PE and I yr-PE for OB, CP, SB, and PB. However, pTBS values significantly dropped after 1 yr-DE for SE, CP, SB, and PB. A decreased pTBS was seen in SE after 1 yrPE, but no differences existed between I yr-PE and 1 yr-DE. Similar or increased pTBS values were noted in 1 yr-DOE for all adhesives. Water-storage for I year significantly decreased pTBS for all adhesives. However, except for SE, the presence of a peripheral composite-enamel bond seemed to reduce the degradation rate in resin-dentin interfaces for all materials. (c) 2007 Wiley Periodicals, Inc.85B1101

Influence of water-storage time on the sorption and solubility behavior of current adhesives and primer/adhesive mixtures

This study evaluated the effects of water-storage on the water sorption and solubility behavior of five commercially available dental adhesive systems and two primer/adhesive mixtures. The adhesives comprised three different approaches to bonding to hard tooth tissues: a one-step self-etching adhesive (One-up Bond F), two two-step self-etching primers (Clearfil SE Bond and Clearfil Protect Bond) and two etch-and-rinse systems: a water/ethanol-based (Single Bond) and an acetone-based filled adhesive (Prime&Bond NT). The bonding agents and primers of the two-step self-etching systems were mixed in a 1:1 volume ratio. Water sorption and solubility values were determined after 1, 7, 30, 90 and 180 days. The results showed that, except for SB, all adhesives presented increased water sorption with increased storage time. The one-step self-etching adhesive and self-etching primer/adhesive mixtures presented the highest water sorption and solubility values. Equilibrium in the water sorption values was observed for all adhesives after 90 days of water-storage. However, solubility values continued to increase for some materials until 180 days. The sorption and solubility behavior of the materials tested seem to be related to hydrophilicity of the adhesive resin solution and might influence the long-term performance of resin-based composite restorations.321535

Long-term bond strength of restorations subjected to thermo-mechanical stresses over time

Purpose: To evaluate the long-term effect of thermal and mechanical cycling on dentin bond strength to cervical margins of Class II restorations. Methods: Sixty Class II slot cavities were prepared in bovine incisors. The cavities were restored with Single Bond and Z-250 composite according to manufacturer's instructions. The teeth were then divided into two groups (n=30): specimens that would receive thermo-mechanical load cycling (2,000 cycles 550degreesC/ 100,000 cycles of 50 N loading) (TM) and the control (C). Fifteen specimens from each group were tested at baseline and the remaining 30 specimens were stored in distilled and deionized water at 37degreesC and tested after 1 year. For microtensile evaluation, the restorations were sectioned perpendicular to the cervical bonded interface into 0.7 +/- 0.2 mm thick slabs. The slabs were further trimmed at the interface to 1.4 +/- 0.2 mm with a fine diamond bur to produce a cross-sectional surface area of ca. 1 mm(2). Specimens were then subjected to microtensile bond testing. The bond strength data were analyzed using two-way ANOVA and Fisher's PLSD test (P< 0.05). Fracture mode analysis was performed using SEM. Results: At baseline, bond strength of the TM group was significantly lower when compared to the C group (P= 0.012). However, after 1 year storage, a significant decrease in bond strength was observed for the C group compared to baseline. No significant differences were noted between the C and TM groups at 1 year. No interaction was observed between groups (C and TM) and storage time (P= 0.098). For the fracture mode evaluation, at baseline, mixed failure was predominant for the C group, and increased after TM. Decreased mixed failure was observed after 1-year storage, with a concomitant increase in interphase failure.17533734

The effect of a "resin coating" on the interfacial adaptation of composite inlays

The relatively low bond strengths of resin cements to dentin may result in poor interfacial adaptation of composite inlays. This study determined whether the interfacial adaptation of composite inlays could be improved by applying an adhesive system and a low viscosity microfilled resin to the prepared cavity walls before making an impression. Ten MOD cavities were prepared on extracted human premolars with gingival margins located above and below the cemento-enamel junction. A "resin coat" consisting of a self-etching primer system (Clearfil SE Bond) and a low viscosity microfilled resin (Protect Liner F) was applied to the cavities of half of the prepared teeth, while the remaining teeth served as non-coated control specimens. All the teeth were restored with composite inlays (Estenia) fabricated by the indirect method and cemented with a dual-cured resin cement (Panavia F). After finishing the margins with superfine burs, the bonded inlays were thermocycled between 4°C and 55°C for 400 cycles. Specimens were sectioned with a diamond saw and the tooth-restoration interfaces were observed with a confocal laser scanning microscope. The data were analyzed with two-way ANOVA and Fisher's PLSD test (p<0.05). The percentage length of gap formation at the dentinrestoration interface of the "resin coated" teeth (7.1 ± 3.5) was significantly less than that of the non-coated teeth (85.7 ± 6.7) (p<0.05). The concept of coating the prepared cavity with an adhesive system and a low viscosity microfilled resin resulted in observing fewer gaps at the internal dentin-restoration interface compared with the non-coated specimens.link_to_subscribed_fulltex

Effect of thermal and mechanical load cycling on microtensile bond strength of a total-etch adhesive system

To evaluate the effect of thermal and mechanical cycles on dentin bond strength to cervical margins of Class II restorations, 80 box-type Class II cavities were prepared on the surfaces of bovine incisors. The cavities were restored with Single Bond (3M-ESPE) and Z-250 composite (3M-ESPE) according to manufacturer's instructions. The incisors were divided into four groups: G1-Control, G2- Thermal cycling (2,000 cycles, WC 55 degreesC), G3- Mechanical cycling (100,000 cycles; 50N) and G4- Thermal and mechanical cycling (2,000 cycles 5 degreesC-55 degreesC/100,000 cycles; 50N). The restorations were sectioned perpendicular to the cervical bonded interface into 0.7 +/- 0.2 mm-thick slabs. The slabs were further trimmed at the interface to 1.4 +/- 0.2 mm with a fine diamond bur to produce a cross-sectional surface area of 1 mm(2). All specimens were then subjected to microtensile bond testing. Means and standard deviations were expressed in MPa. The bond strength data were analyzed by one-way ANOVA and Fisher's PLSD test (p < 0.05). Fracture mode analysis was performed using SEM. Bond strengths were significantly lower when thermal and mechanical cycling were performed [G4-2.41 (8.57)] when compared to the other groups [G128.15 (14.03); G2-27.60 (10.14); G3- 27.59 (8.67)]. No differences were observed among Groups 1, 2 and 3. Interfacial fracture of the control (G1) and thermocycling (G2) groups mainly occurred between the deepest portion of the adhesive resin and the top layer of the demineralized dentin (Interphase). Mixed failure was predominant and increased when mechanical cycling was applied (G3 and G4).29215015

Effect of thermal and mechanical load cycling on nanoleakage of Class II restorations.

PURPOSE: To evaluate the effect of thermal and mechanical cycling on the degree and pattern of nanoleakage on cervical margins of Class II restorations. MATERIALS AND METHODS: Forty box-type Class II cavities were prepared on bovine incisors. The cavities were restored with Single Bond and Z-250 composite resin (3M-ESPE) according to manufacturer's instructions. The teeth were randomly assigned to 4 groups: G1, control; G2, thermal cycling (2000 cycles, 5 to 55 degrees C); G3, mechanical load cycling (100,000 cycles, 50 N); G4, thermal and mechanical load cycling group (2000 cycles 5 to 5 degrees C/100,000 cycles, 50 N). The specimens were then sealed leaving a 1 mm window around the cervical margin interface. Samples were immersed in a 50% w/v ammoniacal silver nitrate solution for 24 h, and exposed to a photodeveloping solution for 8 h. Specimens were sectioned longitudinally, embedded in epoxy resin, polished and mounted on stubs, gold sputter coated, and examined under SEM using backscattered electron mode. Silver particle penetration length was measured directly on the SEM monitor and calculated as the percentage of the total length of cut dentin surface that was penetrated by silver nitrate. The data were analyzed with ANOVA and Fisher's PLSD test (p < 0.05). RESULTS: The degree of nanoleakage significantly increased when thermal and mechanical cycling was performed on the same specimens, as compared to the other groups (p < 0.05). No differences were observed between the control, thermal cycling, and mechanical cycling groups. No difference in nanoleakage pattern was observed between the groups. CONCLUSION: Thermal and mechanical cycling combined adversely affected nanoleakage values. Simulation of the oral condition might be crucial to better evaluate and understand the performance of adhesive materials