Objectives: This study investigates the effectiveness of three polishing systems on the surface roughness and gloss of different CAD/CAM reinforced resin composites, one of which is an experimental short fiber-reinforced composite (SFRC CAD). A secondary objective was to evaluate whether specific material-polishing system combinations could achieve clinically acceptable thresholds for surface roughness and gloss.

Materials and methods: Ninety plate-shaped specimens were prepared from three CAD/CAM reinforced resin composite blocks: experimental SFRC CAD, TRINIA (TR), and Lava Ultimate (LU). Surface roughness and gloss measurements for all specimens were determined at baseline. Then, material specimens were divided into three study groups (n = 10): Sof-Lex diamond polishing system (SOF), OptraGloss polishing system (OPT), and silicon carbide papers (1200-4000 grit) (SIC). Surface roughness and gloss were measured again after polishing. Scanning electron microscopic (SEM) images were taken for one representative specimen from each group pre- and post-polishing. Two-way ANOVA, Bonferroni-adjusted pairwise comparisons and Games-Howell post hoc tests were performed to determine the effectiveness of polishing on roughness and gloss on each material (p < 0.05).

Results: Polishing significantly reduced surface roughness (Ra) and increased gloss in CAD/CAM resin composites (p = 0.001), with wide variations ranging between 0.121 and 3.635 μm and from 5.9 to 124.9 GU, respectively. SFRC and LU showed smoother surfaces with SOF and SIC (p = 0.001), while LU exhibited higher gloss with OPT. TR had the roughest surfaces and lowest gloss, especially with OPT (p = 0.001).

Conclusions: Within the limitations of this study, the new SFRC CAD, polished with Sof-Lex or silicon carbide papers, achieved smoothness and gloss comparable to Lava Ultimate (LU), supporting its potential as an aesthetically restorative material. TR exhibited less favorable surface roughness and gloss upon polishing with the OptraGloss polishing system.

Clinical relevance: Polishing significantly improved the surface properties of CAD/CAM reinforced resin composites; however, the results were material- and protocol-dependent. The findings highlight the importance of selecting appropriate polishing systems to optimize the surface properties of different reinforced resin composites.