Effect of magnification and press-on force on resin composite polishing

Objective To evaluate surface roughness (Ra) and gloss (GU) of two resin composites after polishing with two systems, using a novel press-on force guided (PFG) polishing simulator. Materials and methods Eighty specimens were prepared using Essentia Universal (EU) and G-aenial Universal Injectable (GUI) composites. Surface roughness and gloss were assessed by a profilometer (Marsurf Ps10), and a glossmeter (Novo-Curve). They were polished with Sof-Lex and Twist Dia systems with or without magnification and PFG. Each polishing material was used for 30 s. Ra1 and GU1 measurements were repeated by the same operator. Data were analyzed using One-way ANOVA, Three-way ANOVA, and Robust ANOVA with Bonferroni Correction for multiple comparisons and Spearman’s rho Correlation Coefficient (<0.050). Results Higher Ra values were observed in GUI group for Twist Dia (0.33±0.05z ) compared to SofLex (0.22±0.08y ). Roughness was higher when PFG was uncontrolled (0.31±0.07x ), compared to the controlled (0.25±0.09w). No Ra difference was observed in EU group between SofLex (0.33±0.04) and Twist Dia (0.29±0.04)(P=.440). Uncontrolled PFG provided higher gloss for GUI and EU composites (69.7±2.91x , 54.63±18.68x , respectively). Twist Dia presented higher gloss for GUI and EU composites (72.3±2.57z ,58.88±13.73z , respectively). Magnification did not affect the roughness or gloss for both composites (P≥.05). A moderate negative correlation was found between roughness and gloss in GUI (r=-.546)(P<.001), while no correlation was observed in EU (r=-.110)(P=.449). Conclusion Higher surface roughness and gloss were observed with uncontrolled (not constant) press-on force. Even though SofLex may provide a lower surface roughness, Twist Dia can generate a greater surface gloss regardless of the composite type. 3.5X loupe magnification was not effective on surface roughness and gloss within a limited polishing time. Clinical Relevance Press-on force is an important factor affecting the composite polishing quality. Spiral polishing wheels can be advantageous for composite restoration polishing, as they better preserve the secondary and tertiary anatomies and provide a higher gloss. The effect of magnification on composite polishing can be related to the time spent using it.