Comparison of the mechanical and optical properties of resin teeth produced by conventional methods and 3D printing

In prosthetic restorations, the aesthetic appearance of artificial teeth is as important as their physical properties, such as wear resistance. Factors like wear and discoloration of artificial teeth can directly affect the clinical performance of these materials. Moreover, color stability is a significant criterion in the selection of artificial teeth, as materials may undergo color changes over time due to intrinsic and extrinsic factors. The aim of this in vitro study is to compare the mechanical and optical properties of prefabricated acrylic artificial teeth with those of resin-based artificial teeth produced using three-dimensional (3D) printing technology. In this study, three different artificial tooth materials were evaluated: conventional PMMA (Gnathostar), dual cross-linked PMMA (SR Orthotyp S DCL), and a 3D printed resin (NextDent C&B MFH). Before 3D printing, the samples were designed using a 3D modeling software (Blender, Amsterdam, Netherlands). The designed samples were fabricated using a 3D printer (NextDent 5100, NextDent, Soesterberg, Netherlands) according to the manufacturer's instructions. Mandibular first molar teeth with sufficient surface area were selected for mechanical and optical testing. The conventional and dual cross-linked PMMA molars (n=8) were embedded in epoxy resin with their occlusal surfaces exposed. All specimens were polished using a grinding device (Mikrotest, Istanbul, Türkiye) with silicon carbide abrasive papers of 120, 400, 600, 1200, and 2500 grit under continuous water cooling. This process was performed to simulate clinical finishing and polishing procedures and to obtain a flat surface with a thickness of 3 mm ± 0.03 mm for mechanical testing. All specimens were scanned with a laboratory scanner (AutoScan DS-EX PRO, Shining 3D, China) prior to the wear test. After being subjected to wear using a chewing simulator (Chewing Simulator CS-4.8 - SD Mechatronik, Germany), the specimens were rescanned. The pre- and post-wear scans were superimposed using specialized software (GOM Inspect, Germany), and the amount of wear was calculated in millimeters. Before aging, color measurements were taken using a spectrophotometer (Vita Easyshade V, VITA Zahnfabrik, Bad Säckingen, Germany) against a grey background. After thermal cycling, the color measurements were repeated, and the CIEDE2000 color difference (ΔE) was evaluated. For statistical analysis of the obtained data, the non-parametric Kruskal-Wallis test was used. While a statistically significant difference was found among the groups in terms of wear values, no significant difference was observed in terms of discoloration. According to the results of our study, the wear resistance and discoloration levels of artificial tooth materials vary depending on their chemical composition, which may influence the clinical longevity and patient comfort associated with the prostheses. It is recommended that clinicians consider these findings when selecting appropriate artificial tooth materials for prosthetic restorations.