Antibacterial effect of a brominated self-etch adhesive on carious dentin - An in vivo study

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: 10 patients showing deep primary carious lesions at two posterior teeth without pulpal symptoms were included. At visit I, 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 an MDPB-containing self-etch adhesive (Clearfil Protect Bond, Kuraray Noritake; PB). The other restoration served as a control (Clearfil SE Bond II, Kuraray Noritake; SE). At visit II after 8 weeks, carious dentin was sampled again. Bacterial growth in carious dentin was differentiated using microbial cultivation. Bacterial DNA from intact cells and cell-free DNA were quantified using 16S rRNA gene-based real-time PCR and the microbial community composition was analyzed by amplicon deep-sequencing. Wilcoxon test was applied for statistical analysis.Results: Both treatments showed a decrease of intact bacterial cells in carious dentin at visit II compared to visit I (PB: visit I: 1.1*10(6), visit II: 1.7*10(5) (p = 0.03); SE: visit I: 1.1*10(7), visit II = 2.4*10(5) (p = 0.002)). No statistically significant reduction of cell-free bacterial DNA was detected (PB: visit I: 6.1*10(5), visit II: 1.6*10(5) (p = 0.08); SE: visit I: 5.3*10(5), visit II: 2.9*10(5) (p = 0.10)). The decrease of intact cell-derived (p = 0.371) and cell-free DNA (p = 0.455) did not differ significantly between PB and SE. Lactobacillus was most abundant within the microbial community at both visits. Alpha-diversity was not affected by treatment and samples showed high intraand interindividual diversity.Conclusion and clinical significance: Both self-etch adhesives have an antibacterial effect due to a decrease of bacterial DNA after selective caries removal. However, the results do not reveal any additional antibacterial effect by MDPB.