Objective: Evaluate the fracture resistance of maxillary premolars with MOD cavities restored with recent composites, and assess the biaxial flexural strength of those composites.
Methods and methods: Sixty maxillary premolars collected for fracture resistance evaluation, ten left intact (Group A).Remaining teeth received MOD preparations. Forty teeth divided into 4 subgroups (n=10); Subgroup B1 Filtek bulkfill posterior (3M ESPE). Subgroup B2 Ceram X Spheretec nanoceramic (Dentsply). Subgroup B3 Swisstec microhybrid (Coltene). Subgroup B4 Harmonize nanohybrid (Kerr). For group C, ten teeth were left unrestored. FR test was done with the Universal Testing Machine and failures evaluated.
BFS test, 40 composite discs were divided into 4 groups (n=10). Groups I, II, III and IV where discs made of (Filtek Bulkfill Posterior, 3MESPE), (Ceram X Spheretec, Dentsply), (Swisstec, Coltene) and (Harmonize, Kerr) respectively. Specimens were loaded till fracture using UTM. BFS was calculated and failures evaluated.
Results: FR values of Group A were the highest (1517.20), followed by Subgroup B2 (1179.00), Subgroup B4 (940.30), Subgroup B1 (813.70), Subgroup B3 (657.90) and Group C (559.50), with significant differences among the groups (p=0.001). BFS values were the highest in Group I (207.605) followed by Group III (165.241), Group IV (164.284) and Group II (151.221), with significant differences among the groups (p=0.001).
Conclusion: FR of nanoceramic composite was higher than all experimental groups, microhybrid was the lowest . BFS of bulkfill composite was higher than other groups, and that of nanocermic was the lowest. No direct correlation was found between FR and BFS of composite.