Comparative Insights Into the Degree of Conversion of a 3D‐Printed Photopolymer Occlusal Splint Resin Fabricated by Stereolithography and Masked Stereolithography Compared to Heat‐Polymerized Acrylics

ABSTRACT The degree of conversion (DC) is a critical determinant of the biocompatibility and long‐term performance of occlusal splints. However, limited evidence exists on how emerging three‐dimensional printing technologies, particularly masked stereolithography (MSLA), affect polymerization efficiency compared to established methods. This study investigated the DC of a photopolymer‐based occlusal splint resin fabricated using stereolithography (SLA) and MSLA technologies, compared to a conventional heat‐polymerized acrylic resin. DC was assessed by Fourier Transform Infrared Spectroscopy (FTIR) at three stages for printed specimens: the unpolymerized resin, after printing and washing (DC Print), and after post‐curing (final DC). The difference between DC Print and final DC (ΔDC) represented the contribution of the post‐curing step. Conventional specimens were evaluated after mixing and after polymerization. The final DC of the conventional group was significantly higher than both SLA and MSLA groups ( p < 0.001), although SLA and MSLA did not differ significantly ( p > 0.05). Post‐curing significantly enhanced polymerization in both printed groups. MSLA printing achieved comparable DC to SLA while reducing production time. These findings support MSLA as a promising and time‐efficient method for splint fabrication, though further improvements in resin formulation and post‐curing protocols are warranted to match the polymerization efficiency of conventional heat‐polymerized acrylics.