Rheological properties should be considered when developing new whitening formulations.

As expected, fourth- and sixth-generation DBAs generally showed stronger SBS values than the seventh-generation all-in-one DBAs. The new sixth-generation DBA OptiBond XTR (Kerr) showed strong SBS values to both substrates and performed well in comparison to the other DBAs tested.

The sandwich technique results in more microleakage than classically bonded composite resin restorations. SUMMARYObjectives: 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 À1 mm) was detected using a sectioning technique. Data were analyzed with repeated measurements and Duncan test at a=0.05.Results: The least amount of microleakage was detected in the incremental group (1.28 6

Diastema closure with direct resin composites should be free of voids and establish proper contact formation. Good results can be achieved with the pull-through technique and the use of prefabricated matrices. SUMMARYThis study evaluated the influence of three different application techniques on contact formation and voids in anterior resin composite restorations. Artificial ivorine teeth were randomly assigned to three experimental groups, with 20 specimens in each group. One operator performed all restorations using the Teflon tape, pull-through, or bioclear matrix technique. The treatment time required for each restoration was recorded. An examiner blinded to the treatment group performed the visual evaluation of six criteria, including proper contact formation. The restored teeth were cut to yield a total of 180 sections for microscopic evaluation. The Kruskal-Wallis procedure was performed to evaluate the significance of treatment time, number of voids, percent porosity area, and void diameter. There were significant differences in treatment time among the three groups (p,0.05). The bioclear matrix technique required the least time for the treatment of one diastema closure (p,0.05). The Teflon tape technique resulted in proper contact formation in 80% of specimens, a rate that was significantly lower than that associated with the pull-through and bioclear matrix techniques (p,0.05). Out of 540 imaging areas 160 images were free of voids. The number of voids and the percent porosity area were not significantly different among the three techniques (p.0.05). However, the mean void diameter was greater with the bioclear matrix technique compared to the other two techniques (p,0.05).