Department of Pediatric Dentistry, School of Dentistry of Ribeirão Preto - University of São Paulo, Avenida do Café s/n, Ribeirão Preto, SP 14040-904, Brazil.
Department of Physics and Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Avenida do Café s/n, Ribeirão Preto, SP CEP 14040-903, Brazil.
Photodiagnosis Photodyn Ther. 2017 Dec;20:234-237. doi: 10.1016/j.pdpdt.2017.10.025. Epub 2017 Oct 31.
Several studies have reported the use of antimicrobial photodynamic therapy (aPDT) to control biofilm but its efficacy depends on several factors, such as biofilm model used. This study aims to examine whether exposure to diode laser combined with methylene blue affects the bacterial viability and polysaccharide content in a Streptococcus mutans cariogenic biofilm model, which simulated 'feast-famine' episodes of exposure to sucrose that occur in the oral cavity.
S. mutans biofilms were formed on acrylic resin discs and exposed to a 10% sucrose solution for 1min, eight times/day. After growing for 48h, the biofilms were submitted to the following treatments, twice daily (n=4): (i) 0.9% NaCl (NaCl) as the negative control; (ii) 0.12% chlorhexidine digluconate (CHX) as the positive antibacterial control; (iii) diode laser combined with methylene blue, using an energy density of 320J/cm (aPDT). After 120h of growth, the biofilm formed on each disc was collected to determine the viable bacterial counts and concentration of insoluble exopolysaccharides (IEPS) and intracellular polysaccharides (IPS).
Bacterial counts in the biofilms formed differed among the treatments. Compared with NaCl, aPDT significantly destabilized biofilm (p<0.0001). aPDT and CHX equally lowered the concentration of IEPS and IPS in biofilms.
Under the experimental conditions assessed, our findings indicate that a twice-daily treatment with diode laser combined with methylene blue effectively decreased bacterial viability and the intra- and extracellular polysaccharide concentration in biofilms of S. mutans, a cariogenic bacterium.
几项研究报告称，使用抗菌光动力疗法（aPDT）来控制生物膜，但它的疗效取决于几个因素，例如使用的生物膜模型。本研究旨在检查二极管激光联合亚甲蓝照射是否会影响变形链球菌致龋生物膜模型中的细菌活力和多糖含量，该模型模拟了口腔中蔗糖暴露的“饱食-饥饿”期。
将变形链球菌生物膜形成在丙烯酸树脂盘上，并每天暴露于 10%蔗糖溶液 1 分钟，共 8 次。生长 48 小时后，将生物膜每天两次（n=4）接受以下处理：（i）0.9%氯化钠（NaCl）作为阴性对照；（ii）0.12%葡萄糖酸氯己定（CHX）作为阳性抗菌对照；（iii）二极管激光联合亚甲蓝，使用 320J/cm 的能量密度（aPDT）。生长 120 小时后，收集每个培养皿上形成的生物膜以确定活菌计数和不可溶性胞外多糖（IEPS）和细胞内多糖（IPS）浓度。
生物膜中形成的细菌计数在不同处理之间存在差异。与 NaCl 相比，aPDT 显著破坏了生物膜（p<0.0001）。aPDT 和 CHX 同样降低了生物膜中 IEPS 和 IPS 的浓度。
在评估的实验条件下，我们的研究结果表明，每天两次用二极管激光联合亚甲蓝处理可有效降低致龋菌变形链球菌生物膜中的细菌活力和细胞内及细胞外多糖浓度。
