Nanohybrid and microfilled hybrid versus conventional hybrid composite restorations: 5-year clinical wear performance

The 5-year findings of a randomized clinical trial testing the null hypothesis that there are no differences between the clinical-wear performances of nano-, microfilled-, and conventional hybrids placed in class I and class II cavities are reported. Effects of subject-, operator-, and restoration-related variables on wear were assessed. Sixteen Tetric-C, 17 Tetric-EC, and 16 Gradia-DP restorations were placed in human molars and recalled at baseline, 6 months and at yearly intervals. The gypsum replicas at each recall were scanned (3D laser scanning), epoxy resin replicas were observed under scanning electron microscope and linear mixed models were used to study the influence of different variables on wear. The generalized vertical wear rate/month were (1.4 μm Tetric-C and Tetric-EC; 1.8 μm Gradia-DP) and volume wear rate/month were (0.017 mm³ Tetric-EC; 0.018 mm³ Gradia-DP, and 0.011 mm³ Tetric-EC). Operator-cavity type interaction and surface area of restorations did significantly influence the volume wear rates (p < 0.05). The three wear patterns: fatigue cracks at heavy occlusal contact area/OCA, pitting at light OCA, and scratches/striations along the food escape pathways were evident. The three hybrids differed significantly in volume wear due to material and operator variables. Clinical relevance: Clinically, operators and cavity type can affect restorations' wear magnitude but do not contribute to increased functional risk of fracture or harmful effect on pulp and periodontal biocompatibility.