Effects of Rinsing Water Temperature and Preheated Composites on Microleakage of Composite Restorations with Two Bonding Agents.

Objectives: The aim of this study was to evaluate the effects of rinsing water temperature and preheated composites on microleakage of class V restorations with two different bonding agents. Materials and Methods: Eighty class V cavities were prepared in the buccal and lingual surfaces of 40 molars. Single Bond and Prime and Bond NT bonding agents were used. The teeth were divided into four groups of 10. G1: After acid etching, cavities were rinsed with 23˚C water and filled with 23˚C composite resin. G2: Rinsing water and composite resin had 55˚C temperature. G3: Rinsing water had 55˚C and composite resin had 23˚C temperature. G4: Rinsing water had 23˚C and composite resin had 55˚C temperature. The specimens were immersed in 0.5% basic fuchsine dye. Microleakage scores were analysed with the Kruskal-Wallis, Mann-Whitney U, and Wilcoxon tests. Results: There were significant differences in microleakage of specimens prepared with Single Bond and Prime and Bond NT only in group 1 (P<0.05). There were no significant differences between the microleakage of groups rinsed with different water temperatures (P>0.05). There were significant differences between the unheated and preheated composite groups (P<0.05). Conclusion: Preheating of composite is a valuable method to increase its adaptability and decrease microleakage of composite restorations.

The effect of washing water temperature on resin-dentin micro-shear bond strength.

BACKGROUND: The purpose of this study was to evaluate the effect of washing water temperature on the micro-shear bond strength (µSBS) of composite resin to dentin using a two-step etch-and-rinse system and a two-step self-etching system. MATERIALS AND METHODS: In this in vitro study, the intact dentins of buccal and lingual surfaces of healthy third molars were exposed. Dentin surfaces were rinsed with different temperatures of distilled water (20 s) before applying Single Bond (SB) or Clearfil SE Bond(SE). After applying the adhesive, composite cylinders (0.8 mm diameter and 1 mm length) were bonded to the teeth surfaces. After storing the specimens in 37°C distilled water for 48 h and thermocycling, µSBS test was done. Data were analyzed using analysis of variance, post hoc Tukey tests, paired samples t-test, and Fisher exact test (α = 0.05). RESULTS: Temperature and interaction of temperature and type of bonding agent affected the bond strength. The bond strength of SB groups was significantly higher at 50°C washing than 5°C (P = 0.003) and 22°C (P = 0.019), but no significant difference was observed between SE groups. The bond strength of SE was significantly higher at 22°C than that of SB (P = 0.031), whereas the bond strength of SB was significantly higher at 50°C than that of SE (P = 0.007). CONCLUSION: The use of high-temperature washing water is an appropriate method to enhance bond strength in etch-and-rinse systems.

Shear bond strength of resin composite bonded with two adhesives: Influence of Er: YAG laser irradiation distance.

BACKGROUND: Dental surfaces prepared with different Er:YAG laser distance may have different characteristics compared with those prepared with conventional instruments. The aim of this study was to investigate the effect of Er:YAG laser irradiation distance from enamel and dentin surfaces on the shear bond strength of composite with self-etch and etch and rinse bonding systems compared with conventional preparation method. MATERIALS AND METHODS: Two hundred caries-free human third molars were randomly divided into twenty groups (n = 10). Ten groups were designated for enamel surface (E1-E10) and ten for dentin surface (D1-D10). Er: YAG laser (2940 nm) was used on the E1-E8 (240 mJ, 25 Hz) and D1-D8 (140 mJ, 30 Hz) groups at four different distances of 0.5 (standard), 2, 4 and 11 mm. Control groups (E9, E10, D9 and D10) were ground with medium grit diamond bur. The enamel and dentin specimens were divided into two subgroups that were bonded with either Single Bond or Clearfil SE Bond. Resin composite (Z100) was dispensed on prepared dentin and enamel. The shear bond strengths were tested using a universal testing machine. Data were analyzed by SPSS12 statistical software using three way analysis of variance, Tukey and independent t-test. P < 0.05 was considered as significant. RESULTS: There was a significant difference between enamel and dentin substrates (P < 0.001) and between lased and un-lased groups; the un-lased group had significantly higher bond strength (P < 0.001). Shear bond strength increased significantly with an increase in the laser irradiation distance (P < 0.05) on enamel surfaces (in both bonding agent subgroups) and on dentin surfaces (in the Single Bond subgroup). CONCLUSION: Laser irradiation decreases shear bond strength. Irradiation distance affects shear bond strength and increasing the distance would decrease the negative effects of laser irradiation.

Histologic evaluation of human pulp response to total etch and self etch adhesive systems.

BACKGROUND: To investigate pulp response to the application of two types adhesive systems (total-etch and self-etch) in human premolar teeth. MATERIALS AND METHODS: Cavities limited to enamel walls in all margins with 2.5 mm depth were prepared on buccal surfaces of thirty three human premolars. The cavities were treated with the following adhesive. Single Bond (SB) and Prompt L-Pop (PLP). The teeth were extracted after 30 days and prepared due to histological technique. RESULTS: Pulp responses were evaluated in three field including inflammatory cell response, pulp tissue disorganization and restorative dentin formation. There were no differences in histological response of the pulp tissue (P > 0.05). CONCLUSION: Both adhesive systems showed good biological compatibility.

Comparison of color stability of a composite resin in different color media.

BACKGROUND: Color change of composite restorations in different color media during the time is a common problem in esthetic dentistry, causing the need to replace the restoration, and spending a great deal of cost and time to patients. The aim of this study is to investigate the effects of different common drinks consumed by patients on one of the widely used composites in dentistry. MATERIALS AND METHODS: Sixty-five disk-shaped specimens were prepared with a light-cured composite (Z100-shade A2) and divided into five groups of 13 specimens. Samples of each group were immersed in staining solutions (tea, coffee, lemonade, and cola) and distilled water (as control). Color values (L*, a*, b*) were measured relative to the standard illuminant D65 over a white background, using the CIE L*a*b* system. Color change values were calculated before and after 1, 7, and 14 days of immersion. Repeated measures and one-way analysis of variance (ANOVA) and paired t tests were applied for statistical analysis. RESULTS: Tea and coffee produced the most discoloration, whereas, water exhibited the least color change after immersion for 14 days in Z100 (P < 0.05). After one day of immersion, coffee caused the lowest discoloration in the test composite, compared to tea, cola, distilled water, and lemonade (P < 0.05). CONCLUSION: Staining solutions and immersion time are significant factors that affect color stability of composite resins.

Effect of storage environment on the bond strength of reattachment of crown fragments to fractured teeth.

AIM: The aim of this study was to examine various storage environments for storing fragments before being bonded to the remaining teeth and also estimate the required force to fracture the restored teeth. MATERIALS AND METHODS: Sixty mandibular incisor teeth were fractured on the incisal one-third and were divided into five groups of 12 each to be stored in normal saline, water, milk, saliva and dry environments for 24 hours. All the fractured parts in each group were bonded to their relevant apical parts by an etch and rinse bonding system and a flowable composite resin. The fracture resistance was measured by a universal testing machine, and the results were analyzed using one-way ANOVA and Tukey statistical tests. RESULTS: The results revealed that the difference among the five groups was statistically significant (P<0.001). Tukey tests showed that the force required for fracturing fragments kept in the milk and saliva environments were significantly higher than those for the normal saline, water and dry environments (P<0.05 ). CONCLUSIONS: It was concluded that keeping the fractured parts in milk and saliva environments can increase the required force for fracturing teeth more than the other environments.