Crack propensity of different direct restorative procedures in deep MOD cavities

ObjectiveThe purpose was to evaluate the crack formation associated with different direct restorative procedures of the utilized resin composites (RC) right after and 1 week later of the restoration.Materials and methodsEighty intact, crack-free third molars with standard MOD cavities were included in this in vitro study and randomly divided into four groups of 20 each. After adhesive treatment, the cavities were restored either with bulk (group 1) or layered (group 2) short-fiber-reinforced resin composites (SFRC); bulk-fill RC (group 3); and layered conventional RC (control). Right after the polymerization and a week later, crack evaluation on the outer surface of the remaining cavity walls was performed with a transillumination method utilizing the D-Light Pro (GC Europe) with the "detection mode." Between- and within-groups comparisons Kruskal-Wallis and Wilcoxon tests were used, respectively.ResultsPost-polymerization crack evaluation showed significantly lower crack formation in SFRC groups compared to the control (p<0.001). There was no significant difference within SFRC groups and non-SFRC groups (p=1.00 and p=0.11, respectively). Within group comparison revealed significantly higher number of cracks in all groups after 1 week (p <= 0.001), however, only the control group differed significantly from all the other groups (p <= 0.003).ConclusionsPost-polymerization shrinkage induced further crack formation in the tooth 1 week after the restoration. SFRC was less prone to shrinkage-related crack formation during the restorative procedure; however, after 1 week, besides SFRC, bulk-fill RC also showed less prone to polymerization shrinkage-related crack formation than layered composite fillings.