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

Effects of sodium hypochlorite gel and sodium hypochlorite solution on dentin bond strength

The aim of this study was to determine the effect of 10% NaOCl gel and 10% NaOCl solution on dentin bond strengths of four adhesive systems. One hundred eighty bovine incisors were ground to achieve a flat polished surface, then divided into 12 groups: Gluma One Bond [G1 - control; G2 - NaOCl solution; G3 - NaOCl gel]; Prime & Bond 2.1 [G4 - control; G5 - NaOCl solution; G6 - NaOCl gel]; Single Bond [G7 - control; G8 - NaOCl solution; G9 - NaOCl gel]; Prime & Bond NT [G10 - control; G11 - NaOCl solution; G12 - NaOCl gel]. Dentin was etched, rinsed, and blot dried. For the experimental groups, after acid etching, 10% NaOCl solution or 10% NaOCl gel was applied for 60 s, rinsed, and blot dried. Composite resin was inserted and light cured. Shear bond strengths were tested with a crosshead speed of 0.5mm/min. The mean values MPa (SD) were analyzed with two-way ANOVA and Tukey's tests (alpha < 0.01). Ten percent NaOCl solution significantly increased Gluma One Bond strength. No effect was observed for the other adhesives. The 10% NaOCl gel did not affect bond strengths. Ten percent NaOCl gel was less effective on collagen removal as compared to 10% NaOCl solution. The influence of collagen removal on bond strength is dependent on adhesive system, where both the solvent and the monomer can influence the results. (C) 2004 Wiley Periodicals, Inc.72B233934

The effect of sodium hypochlorite on microleakage of composite resin restorations using three adhesive systems

Purpose: The aim of this study was to evaluate the effect of three different adhesive systems on microleakage of Class V restorations after the use of sodium hypochlorite. Materials and Methods: One-hundred eighty bovine incisors were selected and randomly divided into 9 groups (n = 20): G1: Single Bond (SB); G2: 10% NaOCl solution (NS) + SB; G3: 10% NaOCl gel (NG) + SB; G4: Prime Bond NT (PB); G5: NS + PB; G6: NG + PB; G7: Gluma One Bond (GOB); G8: NS + GOB; G9: NG + GOB. Standardized Class V cavities were prepared. All teeth were etched with 37% phosphoric acid for 15 s. In groups 2, 5, and 8, a 10% NaOCl solution was applied for 60 s to the dentin, and in groups 3, 6, and 9, a 10% NaOCl gel was applied to dentin for 60 s. All cavities were restored with composite resin Definite. The specimens were thermocycled for 1000 cycles (5degreesC to 55degreesC) and then immersed in 2% buffered solution of methylene blue for 4 h. The specimens were sectioned and analyzed according to a ranking score (0 to 4). Kruskal-Wallis and Mann-Whitney non-parametric tests (p less than or equal to 0.05) were used for statistical analysis. Results: The NaOCl treatment significantly increased microleakage at the dentin margin (p = 0.0129) as shown by the following sums of ranks: G1 = 1008.0(a); G4 = 1301.5(ab); G3 = 1687.0(ab); G7 = 1744.0(bc); G2 = 1802.0(c); G9 = 1880.0(c); G5 = 1889.0(c); G8 = 1950.0(c); G6 = 1963.0(c) (different superscripts indicate significant differences). For enamel, there were no statistically significant differences among the groups (p > 0.05). Conclusion: Depending on the adhesive system used, the application of NaOCI increased microleakage along dentin margins.6212312

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

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 degreesC); G3, mechanical load cycling (100,000 cycles, 50 N); G4, thermal and mechanical load cyclinig group (2000 cycles 5 to 5 degreesC/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.6322122

Influence of different tests used to measure the bond strength to dentin of two adhesive systems

Purpose: To investigate the behavior of two bonding systems: self-etching primer Clearfil Liner Bond 2V (CLB) and total-etch Single Bond (SB) when submitted to two bond strength tests: shear bond strength (SBS) and microtensile (MTBS). Methods: Flat dentin surfaces were obtained at the facial surface of extracted bovine incisors. mu TBS started with adhesive application and incremental resin composite insertion. Samples were then sliced into 1 mm slabs parallel to the long axis of the tooth. Half of the specimens from each group were trimmed in order to obtain 2 dumbbell-shaped (D) specimens with a cross-sectional area of 1 mm, and in the other half of the group, the slabs were cut into beams (3) with a cross section of I mm. 2 area. Specimens were individually fractured on a microtensile apparatus. For SBS, crown segments were embedded in polyester resin and a flat dentin surface was exposed for bonding. After adhesive and restorative procedures were accomplished, the specimens were kept in water for 24 hours prior to bond testing. The tests were performed in a universal testing machine. MPa values were analyzed by Tukey's test (P < 0.05), two-way ANOVA (mu TBS) and Student's t-test (SBS). Results: Mean values (SD) on mu TBS were: SB/B: 42.6 (15.1), SB/D: 35.4 (6.8), CLB/B: 14.3 (10.3) and CLB/D: 27.0 (7.9). SBS values (SD) were: SB: 17.3 (5.6) and CLB 15.9 (7.2). Beam specimens bonded with CLB presented the lowest results. SBS did not show statistical differences between groups. The results showed that the shear bond test seemed to lack the sensitivity that is required to detect subtle differences between bonding agents or procedures.191374

Influence of load cycling on marginal microleakage with two self-etching and two one-bottle dentin adhesive systems in dentin

Purpose: To evaluate the influence of occlusal load cycling on cervical microleakage of proximal slot restorations located in dentin, using two self-etching and two one-bottle dentin adhesive systems. Materials and Methods: 240 proximal slot cavities were prepared in 120 bovine teeth and divided into two groups, one with load cycling and one without. The groups were then subdivided into four subgroups according to the adhesive system used (Experimental EXL 547 Self-etching 3M, Clearfil SE Bond, Single Bond, and Optibond Solo Plus) and restored following the manufacturers' instructions. The teeth were then submitted to mechanical load cycling with a force of 80 N and a frequency of 5 Hz, simultaneously over both restorations of each tooth, for a total of 50,000 cycles per specimen. All specimens were subsequently immersed in a 2% methylene blue solution (pH 7.0), and sectioned to examine the extent of dye penetration under a stereomicroscope (40X). Results: There was no statistically significant difference (p = 0.00002) between the loaded and unloaded teeth. However, a statistically significant difference was observed between the adhesive systems used. The experimental self-etching EXL 547 presented the lowest mean microleakage, but was only statistically significantly different from the Single Bond loaded and unloaded groups and the Clearfil SE Bond unloaded group. Conclusion: The application of 50,000 loading cycles did not affect the microleakage of the two self-etching and the two one-bottle adhesive systems evaluated. In vitro mechanical load cycling is an important factor to consider when evaluating the performance of adhesive systems under simulated masticatory conditions.5320921

Effect of different light-curing devices and aging procedures on composite knoop microhardness

The aim of this study was to evaluate the effect of light-curing devices (Halogen/HAL, Light Emitting Diodes/LED, Argon Laser/LAS and Plasma Arc/PAC) and aging procedures (Mechanical Cycling/MC, Thermal Cycling/TC, Storage/S, MC+TC and MC+TC+S) on the micro-hardness of bottom/B and top/T surfaces of 2-mm-high composite resin cylinders. The Knoop microhardness test (25 g, 20 s) on both B and T was performed before and after each aging procedure. For B and T, before aging procedures, PAC showed reduced polymerization effectiveness when compared with HAL. In the T, after TC, PAC and LAS had also showed reduced polymerization effectiveness when compared to HAL and LED. For all light-curing devices, MC+TC+S and S affected the Knoop microhardness values. In the B, no difference could be observed among the aging procedures for PAC. From all light-curing units, PAC may have rendered composites of reduced quality and the storage aging procedures were the most harmful to the polymer hardness