Effect of anti-biofilm glass–ionomer cement on Streptococcus mutans biofilms

Dental restorative materials with antimicrobial properties can inhibit bacterial colonization, which may result in a reduction of caries at tooth-filling interaction zones. This study aimed to develop antibacterial glass-ionomer cements （GIC） containing a quaternary ammonium monomer （dimethylaminododecyl methacrylate, DMADDM）, and to investigate their effect on material performance and antibacterial properties. Different mass fractions （0, 1.1% and 2.2%） of DMADDM were incorporated into the GIC. The flexure strength, surface charge density, surface roughness and fluoride release were tested. A Streptococcus mutans biofilm model was used. Exopolysaccharides （EPS） staining was used to analyze the inhibitory effect of DMADDM on the biofilm matrix. In addition, biofilm metabolic activity, lactic acid metabolism and the expression of glucosyltransferase genes g/fB, gtfC and gtfD were measured. GIC containing 1.1% and 2.2% DMADDM had flexural strengths matching those of the commercial control （P〉0.1）. DMADDM was able to increase the surface charge density but reduced surface roughness （P〈0.05）. The incorporation of 1.1% and 2.2% DMADDM elevated the release of fluoride by the GIC in the first 2 days （P〈0.05）. The novel DMADDM-modified GIC significantly reduced biofilm metabolic activity （P〈 0.05） and decreased lactic acid production （P〈 0.05）. The quantitative polymerase chain reaction （qPCR） results showed that the expression of gtfB, g/fC and gtfD decreased when mass fractions of DMADDM increased （P〈0.05）. EPS staining showed that both the bacteria and EPS in biofilm decreased in the DMADDM groups. The incorporation of DMADDM could modify the properties of GIC to influence the development of S. mutans biofilms. In this study, we investigated the interface properties of antibacterial materials for the first time. GIC containing DMADDM can improve material performance and antibacterial properties and may contribute to the better management of secondary caries.

Evaluation of three-dimensional biofilms on antibacterial bonding agents containing novel quaternary ammonium methacrylates

Antibacterial adhesives are promising to inhibit biofilms and secondary caries. The objectives of this study were to synthesize and incorporate quaternary ammonium methacrylates into adhesives, and investigate the alkyl chain length effects on three-dimensional biofilms adherent on adhesives for the first time. Six quaternary ammonium methacrylates with chain lengths of 3, 6, 9, 12, 16 and 18 were synthesized and incorporated into Scotchbond Multi-Purpose. Streptococcus mutans bacteria were cultured on resin to form biofilms. Confocal laser scanning microscopy was used to measure biofilm thickness, live/dead volumes and live-bacteria percentage vs. distance from resin surface. Biofilm thickness was the greatest for Scotchbond control; it decreased with increasing chain length, reaching a minimum at chain length 16. Live-biofilm volume had a similar trend. Dead-biofilm volume increased with increasing chain length. The adhesive with chain length 9 had 37% live bacteria near resin surface, but close to 100% live bacteria in the biofilm top section. For chain length 16, there were nearly 0% live bacteria throughout the three-dimensional biofilm. In conclusion, strong antibacterial activity was achieved by adding quaternary ammonium into adhesive, with biofilm thickness and live-biofilm volume decreasing as chain length was increased from 3 to 16. Antibacterial adhesives typically only inhibited bacteria close to its surface; however, adhesive with chain length 16 had mostly dead bacteria in the entire three-dimensional biofilm. Antibacterial adhesive with chain length 16 is promising to inhibit biofilms at the margins and combat secondary caries.

Ag2O/TiO2微球对变异链球菌生物膜形成的影响

生物膜状变异链球菌(Streptococcus mutans)是导致龋齿的主要细菌,为抑制该细菌,采用沉积沉淀法制备Ag2O/TiO2复合物,并以X射线衍射、电感耦合等离子体质谱和透射电镜对所合样品的组成和形貌进行表征。通过抑菌圈和最低抑菌浓度(MIC)法测定Ag2O/TiO2对Streptococcus mutans的抗菌活性,此外Ag2O/TiO2对Streptococcus mutans生物膜形成、产酸和胞外多糖(EPS)的影响进行测定。结果显示所合成的Ag2O/TiO2复合物为直径2~3 mm的微球,其中Ag2O在Ag2O/TiO2中所占质量分数为24.80%。Ag2O/TiO2对浮游状Streptococcus mutans的MIC值为64 mg/L,且能显著抑制Streptococcus mutans产酸。125 mg/L Ag2O/TiO2能减少61.9%生物膜形成,水可溶性的EPS和水不可溶性的EPS的产生分别减少56.1%和69.5%。结果表明Ag2O/TiO2可能是一种有效的预防龋齿材料。