異なるシステムと速度で研磨された複合樹脂の表面粗さの評価：in vitro比較研究

The surface smoothness of resin composite restorations is critical for their esthetic appeal and clinical longevity because rough surfaces may promote bacterial adhesion and compromise durability. This study aimed to compare the surface roughness of nanofilled resin composite restorations polished with Enhance, Sof-Lex Diamond, and Shape Guard systems at high and low speeds using Mylar strip-finished samples as a control. The objectives were to evaluate intergroup differences in surface roughness via profilometry, assess the impact of polishing speed, and identify the most effective system for achieving minimal roughness to enhance clinical outcomes.

Seventy cylindrical composite discs (8 mm diameter × 4 mm depth) were fabricated using a nanofilled resin composite, polymerized with a curing unit, and stored in distilled water at 37°C for 24 h. Ten samples cured against Mylar strips served as the control group (Group 4) without further polishing. The remaining 60 samples were roughened with 600-grit sandpaper and randomly assigned to three groups (20 samples each): Group 1 (Enhance), Group 2 (Sof-Lex Diamond), and Group 3 (Shape Guard). Each group was subdivided into high-speed (15,000 revolutions per minute (rpm)) and low-speed (5,000 rpm) subgroups (10 samples each). Polishing was performed for 20 s under dry conditions using a micromotor with a contra-angle hand piece. The surface roughness (Ra, µm) was measured using a calibrated stylus profilometer, using three readings per sample to calculate the mean values. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's post hoc test (p < 0.05).

The Mylar control group exhibited the lowest mean surface roughness (0.21 ± 0.07 µm). Among polished groups, Sof-Lex at high speed produced the smoothest surface (0.23 ± 0.07 µm), followed by Shape Guard at high speed (0.27 ± 0.09 µm). The Enhance system at low speed yielded the highest surface roughness (0.42 ± 0.14 µm). ANOVA confirmed significant differences among the groups (p = 0.001), thus rejecting the null hypothesis. Sof-Lex and Shape Guard at high speed matched the smoothness of the control, whereas Enhance performed inferiorly.

The Sof-Lex Diamond and Shape Guard systems, particularly when utilized at elevated velocities, achieved superior surface smoothness that closely competed with Mylar-finished controls. These systems are recommended for clinical use to optimize restoration esthetics and durability, although further in vivo studies are needed to confirm their long-term performance.