Flowable materials as an intermediate layer could improve the marginal and internal adaptation of composite restorations in Class-V-cavities

Objectives The purpose of this in vitro study was to evaluate the marginal and internal adaptation of restorative systems in combination with flowable materials as an intermediate layer in Class-V-cavities. Methods Thirty Class-V-cavities with occlusal margins in enamel and gingival margins in dentin/cementum were prepared and randomly assigned to five groups. The following five restorative systems were used: compomer, composite E, flowable compomer/composite E, composite RF and flowable composite/composite RF. The flowable materials were added between the restorative composites and the cervical margins of the cavities. Marginal and internal adaptation were quantitatively evaluated before and after thermal (2500 times between 5 and 55 °C) and mechanical load cycling (25,000 times 100 N) using standard SEM procedures. Statistical analysis was performed using the Kruskal–Wallis and Mann–Whitney U-Test. The morphology of the internal restorative interfaces was also evaluated. Results The present study revealed that the best marginal adaptation in dentin was attained with the compomer restoration (95.8% perfect margin). The marginal adaptation of composite restorative systems was improved by the use of a flowable compomer (45.5% vs. 68.2% perfect margin in dentin) or a flowable composite (46.7% vs. 80.7% perfect margin in dentin, p<0.05) as an intermediate layer. No differences were observed between the used materials for the parameter internal adaptation. Significance In Class-V-cavities compomers showed the best marginal adaptation and the marginal adaptation of composite fillings could be improved by the use of flowable materials as an intermediate layer.