Evaluation of the adaptation, wear, and fracture strength of endocrowns manufactured by additive, subtractive, and conventional methods after thermomechanical aging

Objective: To investigate the internal and marginal adaptation, wear, and fracture strength of endocrown restorations manufactured using different techniques: additive, subtractive and conventional. Materials And Methods: Root canal treatment and endodontic preparation were performed on 36 mandibular molar teeth. Twelve endodontic restorations were fabricated for each group using VarseoSmile TriniQ (additive manufacturing), Cerasmart 270 (subtractive manufacturing), and Gradia Plus (conventional manufacturing) materials (n=12). Internal and marginal adaptation were evaluated using the silicone replica technique, a triple scan protocol, a 3D analysis program for volume measurement, and surface matching methods. The prepared endocrowns were cemented and subjected to thermomechanical chewing simulation (MOD Dental) with 49 Newton vertical occlusal force, 5°-55° thermal cycle and regular chewing for 400,000 cycles. Wear depth and volume values were measured using a 3D scanning method. Subsequently, the samples were subjected to a fracture strength test at a speed of 1 mm/min in a universal testing machine (MOD Dental), and fracture types were determined. The normality of the data distribution was evaluated using the Kolmogorov-Smirnov and Shapiro-Wilks tests. Then data were analyzed using One-way ANOVA, Tukey HDS test, and Bonferroni multiple comparison tests. Kruskal-Wallis test and Dunn's test were used for intergroup comparisons of data that do not show a normal distribution. Significance was evaluated at the p<0.05 level. Results: The study employed the silicone replica technique and a triple scan protocol to measure values related to pulp base, axial wall, internal, and marginal gaps. Statistically significant differences were observed between the groups (p<0.05). The Cerasmart 270 group exhibited the highest marginal gap values (p<0.05), while the Gradia Plus material group had the lowest marginal gap values (p<0.05). In terms of volume results assessed using 3D analysis software, the Cerasmart 270 group also demonstrated the highest volume values (p<0.05). However, no statistically significant differences were identified among the groups regarding wear volume and depth (p>0.05). Significant differences were noted in fracture strength values between the groups (p<0.05), with the VarseoSmile TriniQ group displaying the lowest fracture resistance (p<0.05). Conclusion: Endocrowns manufactured using various techniques can achieve proper adaptation and fracture strength for clinical use. Keywords: Endocrown, 3D Printing, Subtractive Manufacturing, Conventional Manufacturing, Adaptation, Wear, Fracture.