Abstract
BACKGROUND: Previous studies have indicated severe contamination in dental unit waterlines (DUWLs), yet systematic investigations remain limited. METHODS: This cross-sectional study examined bacterial contamination in DUWLs across three tertiary hospitals, collecting water samples from seven dental specialties and four DUWL outlets at two sampling times (Time 1 and 2). Heterotrophic Bacteria Counting method was performed and the percentage of compliant water samples (≤100 CFU/mL) was used to assess the contamination level. Bacterial diversity and community structure were analyzed using 16S rDNA sequencing. RESULTS: Among 1,454 samples from 188 dental chair units (DCUs), 74.3% (Time 1) and 73.5% (Time 2) were compliant. The percentage of compliant water samples varied by specialties and outlets, with the highest in Periodontics (96.4%, 94.6%) and water cup filler (84.0%, 85.9%), while the lowest in Oral and Maxillofacial Surgery (28.0%, 31.7%) and nurse air/water syringe (63.4%, 63.5%). 16S rDNA sequencing revealed significant differences in bacterial species richness, diversity, and community structure among specialties at Time 1 (all p < 0.05). The core genera identified included Vibrio, Halomonas, Ralstonia, and Sphingomonas. CONCLUSIONS: The bacterial concentration and diversity of DUWLs were influenced by dental specialties, and refined disinfection and management strategies should be used to control bacterial contamination.