Impact of resin tank, polishing, and thermal aging on the surface and optical properties of additively manufactured hard occlusal device resins.

Statement Of Problem Additively manufactured occlusal devices typically require labor-intensive polishing to achieve clinically acceptable surfaces. However, limited evidence exists on whether newer resin tanks that are claimed to improve surface and optical properties can reduce this need or how polishing and aging interact to affect surface and optical outcomes. Purpose The purpose of this in vitro study was to investigate the effects of resin type, resin tank selection, polishing procedures, and aging on the surface roughness (Ra), gloss, and light transmittance of additively manufactured occlusal device resins. Material And Methods Eighty disk-shaped specimens (Ø30×2 mm) were additively manufactured from 2 hard occlusal device resins (Freeprint Splint 2.0, FPS and KeySplint Hard, KSH) using 2 different resin tanks (Universal [conventional] and Ultragloss [modified]) of a digital light processing 3-dimensional printer (MAX UV). After fabrication, the specimens were divided into 2 subgroups (nonpolished and polished) (n=10). Specimens in the polished group were manually polished with a pumice-water slurry followed by a polishing paste. After initial Ra, gloss, and light transmittance measurements, all specimens were subjected to thermocycling (10 000 cycles, 5 °C and 55 °C), and these measurements were repeated. Generalized linear model analyses and Bonferroni-corrected post hoc tests were used for statistical analysis (α=.05).Results Polished specimens showed lower Ra than nonpolished specimens, and the modified tray led to lower Ra than the conventional tray for nonpolished specimens (P≤.005). FPS showed higher gloss than KSH when fabricated with the conventional tray and polished (P=.031). Nonpolished FPS and KSH specimens and polished KSH specimens had higher gloss when the modified tray was used (P<.001). Polishing increased the gloss of all specimens, while aging increased the gloss of polished specimens (P≤.026). The modified tray provided higher light transmittance irrespective of resin or polishing, while polishing increased transmittance for FPS with the modified tray and KSH with the conventional tray (P≤.012). Conclusions The modified tray improved the Ra, gloss, and light transmittance of nonpolished specimens; however, surface roughness remained clinically unacceptable, whereas polished specimens met acceptable thresholds. Polishing consistently increased gloss across all conditions and improved light transmittance in specific resin-tray combinations. The modified tray enhanced light transmittance regardless of polishing, and accelerated aging had no significant effect on Ra or light transmittance.