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Objectives: The aim of the present study was to evaluate the effect of four different sandwich techniques on gingival microleakage of Class II direct composite resin restorations., Materials and Methods: Fifty sound human premolars were selected and randomly divided into five groups (n=10). Class II box only cavities were prepared in one of the proximal surfaces of each tooth with a gingival margin located approximately 0.5 mm below the cemento-enamel junction. Group A (control) was restored incrementally with composite resin (Tetric Ceram). Groups B, C, D, and E were restored with the sandwich technique using a compomer (Compoglass F), flowable composite resin (Tetric Flow), self-cure composite resin (Degufill SC), or resin modified glass ionomer (Fuji II LC), respectively. After thermal-load cycling, the specimens were immersed in 0.5% basic fuschin for 24 hours. Dye penetration (10(-1) mm) was detected using a sectioning technique. Data were analyzed with repeated measurements and Duncan test at α=0.05., Results: The least amount of microleakage was detected in the incremental group (1.28 ± 0.98). The sandwich technique using resin modified glass ionomer (7.99 ± 9.57) or compomer (4.36 ± 1.78) resulted in significantly more leakage than did the sandwich technique using flowable (1.50 ± 1.97) or self-cure composite (2.26 ± 1.52)., Conclusion: According to the results of this study, none of the four sandwich technique composite resin restorations used in this study could reduce gingival microleakage to a greater degree than the incremental technique.

Background: Fibre reinforced composites (FRC) can be used to join teeth as a rigid unit for anchorage purposes and/or for tooth movement. The utility of FRCs for these applications depends on the fracture characteristics and durability of the material under masticatory loads., Aims: To evaluate the effect of simulated masticatory loads on the fracture characteristics of FRC bars joining two bicuspids., Methods: Eighty extracted maxillary bicuspids were used. Pairs of bicuspids were joined with FRC bars on the buccal surfaces. The specimens were divided into two equal groups. In group A the fracture loads of the FRC bars were measured, and in group B the specimens were placed in a simulator and subjected to 4x10(5) chewing cycles, simulating a 2-year period of mastication. At the conclusion of this test the fracture loads of the FRC bars were measured in the intact specimens. All specimens were examined stereomicroscopically to determine the fracture pattern., Results: There were no bond failures in group B during the simulated masticatory forces. The mean fracture loads in groups A and B were 195.8 N and 190.6 N, respectively. Stereomicroscopic examination showed that most fractures occurred at the enamel-composite interfaces in both groups. There were no significant differences between the groups in the fracture loads and fracture patterns., Conclusions: Fibre reinforced composite bars bonded to bicuspids had sufficient durability to withstand the loads simulating a 2-year period of function. The fracture loads and fracture patterns of the FRC bars were not affected by the loads exerted by the simulator.