Assessment of Surface Roughness and Microhardness of Resin Composites after different Finishing and Polishing Procedures
The aim of this in vitro study was to evaluate the influence of three different finishing and polishing (F&P) procedures on the surface roughness and microhardness of four resin composite restorative materials. A total of 160 disc-shaped specimens (10 mm × 2 mm) were prepared in metal mold using four resin composites and stored in distilled water at 37˚C for 24 h. The specimens were then divided into four experimental groups (n=40) according to the type of resin composite. Gp1: Microhybrid composite (Dynamic plus), Gp2: Nanohybrid composite (Nexcomp), Gp3: Supernano composite (ESTELITE Σ QUICK), and Gp4: Nanoceramic composite (ZENIT). For each type of resin composite the forty specimens were further divided into four sub-groups (A, B, C, & D) based on the type of finishing and polishing procedure as follow: A- Sandpaper, B- Fine diamond bur, C- Astropol cups and discs (two-step) F&P system, and D- Sof-lex discs (four-step) F&P system. Surface roughness measurements were made for all specimens using a USB digital surface profile gauge, and data were recorded using computer software (Elcomaster 2, Elcometer Instruments). The surface Microhardness of the specimens was measured using Digital Display Vickers Microhardness Tester. The obtained data statistically analyzed using SPSS software. Significant differences in surface roughness and microhardness were found according to the type of F&P systems and resin composite (P<0.05). The smoothest surface value was recorded for nanoceramic composite. The highest microhardness value was obtained with mi-crohybrid composite finished with the Soflex discs (four-step) F&P systems. Based on the limitations of this in vitro study, the following conclusions were drawn. The surface roughness and microhardness of the tested resin composites were greatly influenced by the F&P procedure. Among the tested composites, nanoceramic and supernano composites exhibited the lowest surface roughness, while the nanohybrid composite had the highest surface roughness when finished with the Soflex F&P system. The microhybrid composite had the highest microhardness. The smoothest surface finish was achieved when using a fine diamond bur, particularly with the supernano and nanoceramic composites. One-step procedures showed the best results.