The effect of reduced-step finishing and polishing protocols on roughness, gloss, and surface quality of bulk-fill resin-based composites

BACKGROUND: The surface condition of bulk-fill resin-based composites plays an essential role in their clinical durability and esthetic performance; however, the combined effect of composite viscosity and finishing and polishing approach has not been fully clarified. This study assessed the influence of composite type (sculptable versus flowable bulk-fill materials) and reduced-step finishing and polishing strategies (one-step versus two-step systems) on surface gloss, roughness, and overall surface quality. MATERIALS AND METHODS: Four bulk-fill resin composites-two sculptable (Filtek One Bulk-Fill and Tetric Power Fill) and two flowable (Charisma Bulk Flow One and Fill-Up! )-were finished and polished using one-step systems (Opti1Step and OneGloss) and two-step systems (Sof-Lex diamond spiral wheels and Diacomp Plus Twist). Surface gloss, roughness, and topographic characteristics were assessed using a glossmeter, three-dimensional optical microscopy, and scanning electron microscopy, respectively. Data were analyzed using two-way ANOVA and Tukey's post hoc test. RESULTS: Statistically significant differences were observed among polishing protocols and composite types (p < 0.001). Across all polishing protocols, sculptable bulk-fill composites demonstrated higher gloss values and lower surface roughness compared with flowable materials. Polishing systems incorporating diamond abrasives yielded more favorable surface characteristics than the aluminum-oxide-based system. Notably, for nano-filled sculptable bulk-fill composites, the one-step diamond system Opti1Step produced gloss (up to 89.4 ± 2.8 GU) and roughness outcomes (Sa as low as 0.06 μm) comparable to, and in certain cases superior to, those achieved with two-step protocols. CONCLUSION: Within the limitations of this in vitro investigation, polishing performance was shown to be influenced by the interaction between composite viscosity, filler characteristics, and abrasive type. These results highlight the importance of selecting finishing and polishing protocols based on material-specific properties to optimize surface quality and esthetic outcomes of bulk-fill resin composites. CLINICAL SIGNIFICANCE: The surface quality of bulk-fill resin composites is influenced by both material composition and polishing protocol. Sculptable bulk-fill materials demonstrate superior polishability compared with flowable composites. Diamond-based polishing systems produce smoother and glossier surfaces, and one-step diamond polishing systems can provide surface quality comparable to multi-step protocols, particularly for nano-filled sculptable bulk-fill composites, while reducing clinical time.