Evaluation of the mechanical effects of thermal aging on Resin-Based indirect restoration materials produced by additive and subtractive manufacturing

The aim of this study is to evaluate the mechanical properties such as microhardness, surface roughness, water sorption and water solubility for initial condition and after thermal aging of 10,000 and 30,000 cycles on resin based materials produced with different manufacturing techniques. 245 disc shaped specimens of 5 different resin materials with 3 different manufacturing technique are evaluated. (n=47) 2 milled (Voco Grandio, Voco, Vita Enamic, Vita Zahnfabrik), 1 conventional (Gradia Plus, GC Dental) 2 3D-Printed (Bego Varseo Smile Crown Plus, Bego, Formlabs Permanent Crown Resin, Formlabs ) resin materials are produced. Specimens polished under water cooling on an automatic polishing machine at 600 rpm with 600-800-1200 grit silicon carbide papers for standardization. Final dimension was adjusted to 10mm in diameter and 2 mm in thickness. Total of 47 specimens are prepared for each group; 39 specimens used for surface roughness and microhardness evaluations. 3 specimens were used for surface topography evaluation using SEM, AFM and SEM EDS, 5 specimens from each group evaluated for water sorption and solubility tests. Surface roughness (Ra), Vickers hardness (VHN), water sorption, water solubility, and surface topography were analyzed. The tests were carried out at initial, after 10,000 and 30,000 thermocycle aging at 5oC/55oC. Data collected were statistically analyzed using two-way analysis of variance (p<0.05) after verification of data normality and homogeneity of variances. Increases in mean Ra values were statistically significant after 10,000 and 30,000 thermal cycle aging in all groups. (p<0.05) The only incerase were not statistically significant after 10,000 thermal cycles in the Voco Grandio groups. (p<0.05) Increases in mean VHN values after 10,000 cycle thermal aging statistically significant increased the microhardness values of Voco Grandio, Bego Varseo Smile Crown Plus and Formlabs Permanent Crown Resin. Vita Enamic and Gradia Plus showed statistically significant decrease in microhardness values after 10,000 cycle thermal aging. (p<0.05) Microhardness values decreased statistically significant in all groups after 30,000 cycle thermal aging in comparison to 10,000 thermal cycle aging. (p<0.05) Increase in the mean water sorption values were statistically significant at after 10,000 and 30,000 thermal cycle aging for Voco Grandio, Vita Enamic and Bego Varseo Crown Plus Resin groups. (p<0.05) The difference at mean solubility values was statistically significant only in the Bego Varseo Crown Plus Resin group. (p<0.05) Subtractive and conventionally manufactured resins can be considered equivalent in terms of their material properties. Relative to the subtractive and conventionally manufactured resins, the additive manufactured resins had lower microhardness values and higher surface roughness, different water sorption and solubility values. Thermal cycle aging had affect on all produced specimens.