Antimicrobial action of sodium hypochlorite and castor oil solutions for denture cleaning – in vitro evaluation

The objective of this in vitro study was to evaluate the antimicrobial action of sodium hypochlorite (0.25% and 0.50%) and 10% castor oil solutions against specific microorganisms, by counting Colony Forming Units (CFU) of clinically important bacteria and Candida species. Acrylic resin specimens (n = 320; Lucitone 550) were obtained from square metal matrices (10 x 10 x 2 mm), sterilized by microwave (650W, for 6 minutes) and contaminated by Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Bacillus subtilis, Escherichia coli, Streptococcus mutans, Enterococcus faecalisand Candida glabrata. The specimens were immersed for 20 minutes in one of the following hygiene solutions (n = 10/each): A – 0.25% Sodium hypochlorite; B – 0.5% Sodium hypochlorite; C – 10% Castor oil solution; and D (Control) – saline. Adhered cells were suspended and inoculated into a selective solid medium (37ºC for 24 h). The Student’s t-test (α = 0.05) was performed to compare log10(CFU+1)/mL between Groups C and D. The results showed that sodium hypochlorite (0.25% and 0.5%) completely eliminated all detectable microorganisms. The castor oil solution eliminatedB. subtilisand reduced counts for other strains. Differences between C and D were significant (p < 0.05) for all species except for E. faecalis. Both sodium hypochlorite solutions (0.25% and 0.5%) were effective in eliminating all microorganisms evaluated, and may be useful as cleaning solutions for complete dentures. The castor oil solution provided moderate efficacy and performed differently on the tested species, with the strongest effect on B. subtilis and with non-significant action on E. faecalis.

本体外研究旨在通过计数临床重要细菌及念珠菌属的菌落形成单位（Colony Forming Units, CFU），评估0.25%、0.5%次氯酸钠溶液与10%蓖麻油溶液的抗菌作用。
丙烯酸树脂标本（n=320；Lucitone 550）采用方形金属模具（10×10×2 mm）制备，经微波炉（650W，6分钟）灭菌后，接种金黄色葡萄球菌、铜绿假单胞菌、白色念珠菌、枯草芽孢杆菌、大肠埃希菌、变形链球菌、粪肠球菌及光滑念珠菌。
将标本分为4组（每组n=10），分别浸入以下清洁溶液中静置20分钟：A组：0.25%次氯酸钠；B组：0.5%次氯酸钠；C组：10%蓖麻油溶液；D组（对照组）：生理盐水。
将黏附于标本表面的菌落洗脱并重悬，随后接种至选择性固体培养基中，于37℃培养24小时。采用t检验（α=0.05）比较C组与D组的log₁₀(CFU+1)/mL值。
结果显示，0.25%及0.5%次氯酸钠溶液可完全清除所有可检出的微生物。蓖麻油溶液可清除枯草芽孢杆菌，并降低其余菌株的菌落数。除粪肠球菌外，C组与D组其余所有受试菌种的差异均具有统计学意义（p<0.05）。
两种浓度的次氯酸钠溶液（0.25%、0.5%）均可有效清除所有受试微生物，可作为全口义齿的清洁溶液。蓖麻油溶液抗菌效果中等，对不同受试菌种的作用存在差异：对枯草芽孢杆菌的抗菌效果最强，而对粪肠球菌无显著抗菌作用。