Antibacterial Effect of a Brominated Self-etch Adhesive on Carious Dentin

Objectives: This in-vivo study compared the antibacterial effect of a self-etch adhesive with and without the brominated monomer 12-methacryloyloxydodecyl-pyridinium bromide (MDPB) on carious dentin after selective caries removal.
Methods: This randomized controlled clinical trial included 10 patients showing deep primary carious lesions at two posterior teeth without pulpal symptoms. Lesions penetrated radiographically to the inner third of dentin. At baseline (BL), carious tissue was selectively removed and carious dentin was sampled with a sterile roundbur (Komet No. 18). One cavity was restored with composite (SDR, Ceram X; DENTSPLY DeTrey) using a MDPB-containing self-etch adhesive (Clearfil Protect Bond, Kuraray Noritake; PB). The other restoration served as a control (Clearfil SE Bond II, Kuraray Noritake; CB). At re-entry (RE) after 8 weeks, carious dentin was sampled again. Bacterial growth in carious dentin was analyzed using cultural differentiation. Bacterial DNA from intact cells and cell-free DNA was quantified using 16S rRNA gene based real time PCR. Wilcoxon test was applied for statistical analysis.
Results: Both treatments showed a decrease of intact bacterial cells in carious dentin after 8 weeks compared to baseline (PB: BL=1.1*10⁶, RE=1.7*10⁵ (p=0.03); CB: BL=1.1*10⁷, RE=2.4*10⁵ (p=0.002)). No statistically significant reduction of cell-free bacterial DNA was detected (PB: BL=6.1*10⁵, RE=1.6*10⁵ (p=0.08); CB: BL=5.3*10⁵, RE=2.9*10⁵ (p=0.10)). The decrease of intact cell-derived (p=0.309) and cell-free DNA (p=0.330) did not differ significantly between treatment groups. After 8 weeks cultural growth was reduced by 20% (PB) and 30% (CB) (PB vs CB: p=0.605) and a microbial shift at RE was observed in PB as Lactobacilli were less abundant at RE compared to CB.
Conclusions: Both self-etch adhesives, Clearfil Protect Bond and Clearfil SE Bond, seem to have an antibacterial effect after selective caries removal. However, the results do not reveal an additional effect of MDPB.