Effect of internal taper of endocrown preparation on the adaptation of ۳D-printed restorations

Objective: This study aimed to evaluate the influence of different internal taper angles in endocrown preparations on the marginal and internal adaptation of ۳D-printed restorations.Methods: Three standardized mandibular first molar models were prepared with internal taper angles of ۶°, ۱۰°, and ۲۲°. Each model was scanned ۱۲ times, and endocrown restorations were digitally designed and fabricated with a ۳D printer using Freeprint® Temp resin. All restorations were seated by a single operator, and the adjustment time and frequency were recorded. Adaptation was assessed using the replica technique, and marginal, axial, pulpal, and axio-pulpal line angle gaps were measured under a stereomicroscope. Data were analyzed using one-way ANOVA and Tukey’s post-hoc test at the significance level of P<۰.۰۵.Results: The pulpal gap was significantly larger in the ۲۲° taper group compared to both the ۶° (P<۰.۰۰۱) and ۱۰° (P=۰.۰۰۱) groups. The ۶° taper group exhibited significantly greater marginal misfit than the ۱۰° (P=۰.۰۳۵) and ۲۲° (P=۰.۰۲۱) groups. The axio-pulpal line angle misfit was significantly higher in the ۲۲° taper group than in the ۶° group (P=۰.۰۱۶). No significant difference was observed in axial misfit among the groups (P=۰.۱۶۹). Notably, the ۲۲° taper group required significantly less adjustment time and fewer adjustment attempts than the other groups (P<۰.۰۵).Conclusions: All three taper angles yielded restorations with clinically acceptable adaptation. Increasing the internal taper from ۶° to ۲۲° improved marginal fit and reduced clinical chairside adjustments; however, it resulted in a deterioration of pulpal adaptation.

کلیدواژه ها:

Dental Marginal adaptation ، Dental preparation ، dental prosthesis ، Permanent dental restoration ، Temporary dental restoration ، Three-dimensional printing