Viability of intra-tubular bacteria following chemomechanical caries removal methods

Abstract

Objectives: To assess the bacterial viability inside dentinal tubules following the application of sodium hypochlorite-based (Carisolv gel) and enzymatic-based (Papacarie gel) chemomechanical caries removal agents. Methods: Twenty-five caries-free dentine discs (2 mm thickness) prepared from 25 sound maxillary premolars were used. The discs were ultrasonically cleaned in 10% citric acid and 5% sodium hypochlorite (NaOCl) solution respectively for 4 minutes each to remove the smear layer. The discs were then infected with Streptococcus mutans suspension [3 x 106colony-forming unit (CFU)/mL] using the centrifugation method. The dentine discs were randomly divided into 5 groups according to the dentine treatments. In Group A, the discs were left untreated to act as negative control. Group B was treated with 5% NaOCl solution; Group C: 2% Chlorhexidine (CHX) solution; Group D: Carisolv gel and Group E: Papacarie gel. All agents were applied for 5 minutes. The dentine discs were fractured into two sections and stained with fluorescent LIVE/DEAD Baclight Bacterial Viability Stain (Molecular Probes, Eugene, OR). Each specimen was observed using confocal laser scanning microscopy (CLSM) (Fluoview 1000, Olympus, PA, USA) at five different randomly selected sites. Representative fractured specimens were observed under SEM for evaluation of intra-tubular bacterial penetration.

Results: One-way ANOVA and Tukey post hoc multiple comparison tests revealed that 5% NaOCl solution achieved the highest intra-tubular antibacterial effect; while Carisolv gel had the lowest antibacterial effect (P<0.05). No significant difference in antibacterial effect was observed between Papacarie gel and 2% CHX solution (P>0.05).

Conclusions: Papacarie enzymatic-based chemomechanical caries removal gel has an antibacterial effect similar to 2% chlorhexidine solution. Papacarie gel is effective in the reduction of residual cariogenic bacteria in the dentinal tubules.