[Effects of thermal cycling on mechanical properties of resin-ceramic composites]

Objective: To investigate the influence of thermal cycling on the mechanical properties of resin-ceramic composites. Methods: The different groups of resin-ceramic composites A (Lava Ultimate, 3M ESPE, USA), B (block HC, Shofu, Japan), C (Hyramic, Upcera, China), D (Vita Enamic, Vita, German), and the feldspar ceramic E (Mark Ⅱ, Vita, German) were included in this study. The properties of these groups (with 30 samples in each group), including flexural strength, flexural modulus and Vickers hardness were tested before and after thermal cycling (0, 10 000 and 20 000 cycles, respectively). The data were statistically analyzed. Results: Before thermal cycling, the flexural strength of groups A, B and C [(166.28±13.78) MPa, (170.21±11.36) MPa and (202.04±16.55) MPa] were higher than those of groups D and E [(137.09±8.83) MPa and (119.35±5.98) MPa], and the flexural modulus [(62.39±3.40) GPa] and Vickers hardness [(406.97±14.73) HV] of E group were higher than those of other groups (P<0.05). The flexural strength, flexural modulus and Vickers hardness of groups D and E did not change after thermal cycling (all P>0.05), while those of groups A, B and C decreased (all P<0.05). Conclusion: After thermal cycling, the mechanical properties of the A, B and C groups decreased, while those of the groups D and E were stable.