Investigation of the effect of post-curing time on the surface trueness of endocrowns manufactured with 3D printer and different permanent resins

Objective: The aim of this thesis is to investigate the effect of post-curing time on the surface trueness of endocrowns manufactured using a three-dimensional printer and different permanent resins. Materials and Methods: The endocrown preparation and restoration design of the right mandibular first molar were created using a three-dimensional modeling program and saved as a reference file. The reference endocrown design was prepared for printing by adjusting the manufactured parameters in the slicing software according to the properties of the permanent restoration resins [VarseoSmile Crown Plus (VS) (Bego, Germany), Saremco Print Crowntec (CR) (Saremco, Switzerland), and P-crown Version 3 (PC) (Senertek, Turkey)]. The sample size for each resin subgroup, divided by three different post-curing durations, was set as n=20 (Power=80%, effect size=0.30, α=0.05). Endocrowns were fabricated using a high-resolution three-dimensional printer operating with liquid crystal display (LCD) technology at a layer thickness of 50 μm and a build orientation of 0°.Unpolymerized resin residues on the surface of the endocrowns were removed using 99% isopropyl alcohol. Final polymerization was performed under a nitrogen atmosphere at three different post-curing durations (2000, 4000, and 6000 flashes). The completed samples were digitized using an intraoral scanner. The digitized samples were compared with the reference design using reverse engineering software. Surface trueness was evaluated by analyzing the Root Mean Square (RMS), Ort-, Ort+ and Total (%) values. Statistical analysis was conducted using Two-Way ANOVA and Kruskal-Wallis tests, followed by post-hoc Tukey and Tamhane T2 tests. Results: According to the RMS averages, CR showed the least deviation (0.037±0.006) at 6000 flashes, while PC exhibited the highest deviation (0.084±0.009) at 4000 flashes. Statistical analysis of different post-curing durations revealed no significant differences between groups (p>0.05). The highest Total (%) values were observed in the CR group (99.47±0.71). The lowest positive deviation (Ort+; 0.032±0.005) and negative deviation (Ort-; 0.010±0.002) values were also found in the CR group. Conclusion: Post-Curing time was found to have no significant effect on surface trueness; however, the type of resin was observed to influence the outcomes. All groups were determined to possess surface trueness acceptable for clinical use. Keywords: Three-Dimensional Printers, Permanent Resins, Post-Curing Time, Trueness