Bacterial Colonization in the Marginal Region of Ceramic Restorations: Effects of Different Cement Removal Methods and Polishing

Abstract

SUMMARY This study evaluated the effects of excess cement removal techniques, with or without subsequent polishing, on biofilm formation and micromorphology in the marginal region of the tooth/restoration. From bovine teeth, 96 dentin blocks (4 × 8 × 2 mm) were produced, molded, and reproduced in type IV gypsum, on which 96 pressed ceramic blocks (Vita PM9, Vita Zahnfabrik; 4 × 8 × 2 mm) were produced via the lost wax technique. The dentin blocks and their respective ceramic blocks were cemented with a self-adhesive resin cement (RelyX U200, 3M ESPE), and cement excess was removed from the margin using four different techniques, followed or not by polishing with silicone rubber tips: MBr, removal with microbrush and photoactivation; MBr-Pol, MBr + polishing; Br, removal with brush and photoactivation; Br-Pol, Br + polishing; Photo-Expl, 5 seconds of initial photoactivation, removal with explorer, and final curing; Photo-Expl-Pol, Photo-Expl + polishing; Photo-SB, 5 seconds of initial photoactivation, removal with scalpel, and final curing; and Photo-SB-Pol, Photo-SB + polishing. After 24 hours, the roughness in the marginal region was analyzed using a profilometer (three measurements on each sample). Micromorphological analyses of the region were performed by stereomicroscope and scanning electron microscopy (SEM). Then the samples were contaminated with sucrose broth standardized suspension with Streptococcus mutans, Staphylococcus aureus, and Candida albicans and incubated for a period of 48 hours. The samples were quantitatively analyzed for bacterial adherence in the marginal region by confocal laser scanning microscopy and counting of colony-forming units (CFUs/mL) and qualitatively analyzed using SEM. Roughness data (Ra) were submitted to two-way analysis of variance, Tukey test at a confidence level of 95%, and Student t-tests. CFU, biomass, and biothickness data were analyzed by Kruskal-Wallis, Mann-Whitney, and Dunn tests. The removing technique statistically influenced Ra (MBr, p=0.0019; Br, p=0.002; Photo-Expl, p=0.0262; Photo-SB, p=0.0196) when comparing the polished and unpolished groups. The MBr and MBr-Pol technique differed significantly for CFU/mL values (p=0.010). There was no significant difference in the amounts of biomass and biothickness comparing polished and unpolished groups and when all groups were compared (p>0.05). Different morphological patterns were observed (more regular surface for polished groups). We conclude that margin polishing after cementation of feldspar/pressed ceramic restorations is decisive for achieving smoother surfaces, as the excess cement around the edges can increase the surface roughness in these areas, influencing bacterial adhesion.