Effect of Thermal Processing on Surface Roughness of Injection-Molded Denture Base Polymers

Surface roughness and mechanical performance are critical determinants of the clinical behavior, hygiene, and longevity of denture base materials. This study investigated the influence of two extrusion temperatures—280 °C and 300 °C—on both the surface roughness and compressive strength of ThermoSens thermoplastic polymer specimens over a 7-day immersion period. Surface roughness was evaluated at baseline, 24 h, and 7 days using a contact profilometer, while compressive strength was measured after 7 days following ISO 604 guidelines. Samples processed at 300 °C exhibited a significantly greater reduction in surface roughness over time (28.3%) compared with those processed at 280 °C (18.3%). However, although specimens processed at 300 °C showed a greater percentage reduction, their absolute roughness values remained higher than those processed at 280 °C. Compression testing demonstrated higher strength and modulus values in the 300 °C group (91.6 ± 1.8 MPa; 1887.9 ± 42.3 MPa) compared to the 280 °C group (82.3 ± 2.1 MPa; 1755.4 ± 38.7 MPa). These findings indicate a trade-off between improved mechanical performance at higher processing temperatures and lower surface roughness at lower temperatures, highlighting the need for the careful optimization of processing conditions.