Effect of chairside polishing systems on the surface roughness of different CAD-CAM denture base materials.

Statement of problem: Adjusting and polishing a denture base affects surface roughness and, consequently, microbial adhesion. Since various computer-aided design and computer-aided manufacturing (CAD-CAM) denture base materials are available, the efficiency of chairside polishing systems to achieve a proper surface roughness should be investigated.

Purpose: The purpose of this in vitro study was to compare the surface roughness of milled and 3-dimensional (3D) printed denture base materials with that of heat-polymerized acrylic resin after the use of 2 different chairside polishing systems.

Material and methods: Heat-polymerized (control), milled, and 3D printed denture base materials were tested. Laboratory polished and unpolished denture bases served as positive and negative controls. Specimens were divided into 2 chairside silicone polishing systems (AcryPoint system and Exa technique). Surface roughness was measured before and after polishing. Surface morphology of the unpolished and polished specimens was observed via scanning electron microscopy. The surface hardness of unpolished specimens was measured using a Vickers hardness tester. Stress-strain behavior of the silicone matrix and abrasive filler size of each polisher was assessed. The effects of denture base materials and polishing systems on surface roughness and hardness were evaluated using 1-way, 2-way, and repeated measures analyses of variance (ANOVA) (α=.05), along with Weibull proportional hazards regression to assess the likelihood of achieving clinically acceptable surface roughness. The Spearman correlation assessed the relationship between the hardness of unpolished denture bases and final surface roughness.

Results: The surface roughness of all denture bases decreased with increased polishing duration, reaching a plateau after 60 seconds. For the heat-polymerized and milled dentures, the Exa technique consistently yielded lower roughness than the AcryPoint system (P<.001). Conversely, both polishing systems produced comparable surface roughness on the 3D printed denture base. The Vickers hardness of the unpolished milled denture was significantly higher than of the others (P=.010). The stress-strain behavior of the polisher matrix revealed distinct characteristics between coarse or medium and fine polishers within each polishing system. The abrasive filler size of the AcryPoint coarse polisher was relatively larger than that of the Exa technique.

Conclusions: Regardless of polishing protocols, the 3D printed denture base exhibited the highest surface roughness, followed by heat-polymerized and milled denture bases. The surface roughness of the polished denture was not related with the material hardness. For heat-polymerized and milled dentures, a chairside silicone polishing system can be used to attain a level of surface roughness similar to that of laboratory polishing, depending on the properties of the chairside silicone polishing system.

Data availability statement: The data that support the findings of this study are available upon request from the corresponding author.