Assessment of Marginal Integrity and Fracture Resistance of Nanographene-Reinforced Polymethyl Methacrylate Versus Conventional Polymethyl Methacrylate Single Crowns

Problem: CAD/CAM PMMA, as a provisional material, needs physical, mechanical, and biological improvements. Purpose: To compare graphene-reinforced PMMA crowns' marginal adaption and fracture resistance to CAD/CAM PMMA crowns under simulated oral conditions. Methods: A typodont mandibular first molar was prepared for an all-ceramic crown. Duplicating it yielded 20 dental epoxy resin dies. A 3D scanning was performed for each die to design 20 crowns. Ten crowns were milled from PMMA blanks (P) and 10 from graphene-reinforced PMMA blanks (G). Next, resin cement luted each crown to its die. Each specimen was digitally imaged for marginal gap assessment. Four equidistant landmarks at each specimen's cervical circumference were measured. A chewing simulator aged tested crowns for 120,000 cycles. The marginal gap evaluation was repeated after aging. Each crown was evaluated for fracture resistance in a universal testing machine that determined fracture load in Newton. All data were statistically analyzed. Results: The tested materials did not differ statistically before or after thermocycling. Group (P) showed no statistically significant difference in mean gap distance after thermocycling, while Group (G) showed a statistically significant rise (P-value = 0.033, Effect size = 0.719). The fracture resistance of the two groups was not significantly different (P-value = 0.839, Effect size = 0.132). Conclusions: The mean marginal gap between PMMA and G-PMMA was clinically acceptable. Neither material fractured beyond posterior maximal masticatory stresses, demonstrating clinical resistance. The clinical uses of graphene-reinforced PMMAs are similar to CAD/CAM PMMAs, considering them effective long-term interim materials rather than permanent restorative alternatives.