Abstract: OBJECTIVE To evaluate the effect of super-alkaline reducing solution (SRS) with different pH values on eliminating biofilms of Pseudomonas aeruginosa and Candida albicans on the surfaces of polyvinyl chloride (PVC), a commonly used material in dental unit water lines (DUWLs). METHODS Biofilms of P. aeruginosa and C. albicans were cultivated on the surface of PVC. The experimental group was treated with SRS at pH 12 and pH 13, while the negative control group was treated with sterile distilled water, the biofilms sheets were immersed for 14 hours. The total bacterial colony counts were compared among the groups after the disinfection for 14 hours; the effects of SRS at different pH values on the biofilm thickness and total volume of bacterial adhesion were observed by confocal laser scanning microscopy (CLSM). The surface morphology of the biofilms and the status of corroded PVC surface were observed by scanning electron microscopy (SEM). RESULTS The total bacterial colony counts were less in the experimental group than in the negative control group, and there was significant between-group difference (P＜ 0.001). The result of CLSM showed that the thicknesses of biofilms of the experimental groups were decreased with the increase of the pH value, the total amount of bacterial adhesion on the surface was significantly diminished, with the differences being statistically significant (P＜ 0.001). SEM images revealed that as the pH value increased, the bacteria on surfaces exhibited a scattered distribution in the experimental groups, and the bacterial cells suffered varying degrees of damage. Almost no intact bacterial morphology could be observed in the pH 13 group. In contrast, the negative control group showed intact structures with relatively concentrated bacterial distribution. Surface morphology analysis indicated that there was almost no change in the surface morphology of the experimental groups after the treatment. CONCLUSION SRS can effectively kill and strip the simulated bacterial biofilms in dental unit waterlines, and SRS at pH 13 has the most remarkable effect on removal of biofilms.