To investigate the effect of different ventilation schemes on the concentration of aerosol pollutants in independent space during dental diagnosis and treatment.

Independent dental treatment room equipped with ventilation systems and air disinfectors was selected. A total of nine working conditions including three different dental treatments (supragingival scaling, root canal preparation and tooth preparation) were carried out respectively in three different ventilation schemes (natural ventilation, dedicated outdoor air system and dedicated outdoor air system combined with air disinfector) . The aerobic bacterial counts were measured at different heights and time points. Spatiotemporal distributions of aerosol pollutants in different ventilation schemes were analyzed quantitatively. The differences and equilibrium states of aerobic bacterial counts were examined using Spearman′s rank correlation analysis, generalized linear mixed models, analysis of variance (ANOVA) , Wilcoxon rank sum tests, and multiple comparisons following rank order transformation.

The results of the ANOVA test revealed no statistically significant variations in the aerobic bacterial counts at each site (F = 1.45, P = 0.182) , indicating that the aerobic bacterial counts were spread uniformly across sites. Compared to natural ventilation, the aerobic bacterial counts (N_{working condition1} = 25.8 CFU/cm²; N_{working condition2} = 10.4 CFU/cm²; N_{working condition7} = 35.7 CFU/cm²; N_{working condition8} = 6.5 CFU/cm²) under dedicated outdoor air system during supragingival scaling and tooth preparation decreased over time (t_{supragingival scaling} = 2.27, P_{supragingival scaling} = 0.024; t_{tooth preparation} = 2.30, P_{tooth preparation} = 0.022) . There is no significant difference between aerobic bacterial counts of the treatment after 30 minutes to 60 minutes and that after 60 minutes to 120 minutes, indicating the dynamic equilibrium of bacterial accounts was reached at 30 minutes after the spraying treatment, which met the class Ⅳ environmental requirements in the Hygienic Standard for Disinfection in Hospitals GB 15982-2012.

It can effectively reduce aerosol pollutants in a specific space in a certain period of time under the dedicated outdoor air system. The risk of the next patient can be greatly reduced when entering the dental treatment room at 30 minutes after the previous treatment.