Development of an Antibacterial Dentin Adhesive

Abstract

Nisin is a peptide that possesses potent antibacterial properties. This study evaluated the antibacterial activity of a nisin-doped adhesive against Streptococcus mutans, as well as its degree of conversion and microtensile bond strength (μTBS) to dentin. Nisin was added to the adhesive Adper Single Bond 2 (3M ESPE), resulting in four groups: Control Group (Single Bond 2); Group 1% (1 wt% nisin-incorporated), Group 3% (3 wt% nisin-incorporated) and Group 5% (5 wt% nisin-incorporated). Antibacterial activity against S. mutans was evaluated using colony-forming unit counts (CFU). The degree of conversion was tested using FTIR. Forty human teeth were restored for μTBS evaluation. Data were statistically analyzed with ANOVA and Tukey tests at α = 0.05. The nisin-doped adhesives, for all concentrations, exhibited a significant inhibition of the growth of S. mutans (p < 0.05); Incorporation of 5% and 3% nisin decreased the degree of conversion of the adhesive (p < 0.05). The μTBS (in MPa): Control Group—38.3 ± 2.3A, Group 1%—35.6 ± 2.1A, Group 3%—27.1 ± 1.6B and Group 5%—22.3 ± 1.0C. Nisin-doped adhesives exerted a bactericidal effect on S. mutans. The μTBS and degree of conversion of adhesive were not affected after incorporation of 1% nisin.

Keywords: antibacterial activity; dentin; etch-and-rinse adhesive; nisin.

Figure 1

Representative SEM images of surface texture of resin polymerized disks from different groups and nisin particles. (A) control adhesive (without nisin); (B) nisin-doped adhesive with 1 wt% nisin; (C) nisin- doped adhesive with 3 wt% nisin; (D) nisin-doped adhesive with 5 wt% nisin. The CFU counts of S. mutans was roughly inversely proportional to the nisin concentration within the polymerized adhesive discs. (E) high magnification of the nisin particle, as we can see particle size is around 2 μm, however clusters can be larger.

Figure 2

Representative failure modes observed from the dentin side of fractured composite-dentin sticks. (A) control group: some of the tubules were empty and had resin tags pulled out during microtensile testing. (B) Adhesive with 1 wt% nisin: fractured adhesive with surface of the hybrid layer showing dentin tubules. (C) Adhesive with 3 wt% nisin: dentin tubules with nisin clustering (arrow) between the dentin and the hybrid layer. (D) Adhesive with 5 wt% nisin: large nisin clustering (arrow) on the hybrid layer.