Marginal adaptation of direct composite and sandwich restorations in ClassII cavities with cervical margins in dentine

Objectives: The aim of this study was to evaluate the marginal adaptation o f direct Class II sandwich restorations with resin-modified glass-ionomer c ements and compomers in comparison to base and total bond restorations. For sandwich restorations with a triple cure resin-modified glass-ionomer ceme nt the influence of different light curing techniques was also evaluated. Methods: Large butt-joint class II cavities with cervical margins 1 mm belo w the cemento-enamel junction were cut into 120 extracted human molars. The cavities (15 groups, n = 8) were filled using a sandwich, base or total bo nd technique with materials from five different manufacturers. A three-site d light curing technique was used in 13 groups. For the material combinatio n Vitremer/Z100 two additional groups with a different wand positioning and a metal matrix were evaluated. After water storage for 21 days and thermoc ycling (2000 x, 5-55 degrees C), replicas were quantitatively analysed in t he SEM. Statistical analysis was performed with the Kruskal-Wallis test and the Bonferroni test at p < 0.05. Results: The marginal adaptation of vertical enamel margins was not dependa nt on the restorative technique. For margins in dentine, marginal adaptatio n was significantly better with the sandwich technique than with a base or total bond technique for all materials. There were no significant differenc es between the base and total bond technique. Overall, resin-modified glass -ionomer cements showed somewhat better results than compomers in sandwich restorations, though differences were not significant for some criteria. Vi tremer/Z100 sandwich restorations applied with a metal matrix showed the hi ghest mean percentage of excellent margins of all experimental groups. Conclusions: Both resin-modified glass-ionomer cements and compomers can im prove the marginal quality when used in a sandwich technique. Further resea rch is necessary to determine the ideal material combination for sandwich r estorations. (C) 1999 Elsevier Science Ltd. All rights reserved.