Journal of Oral Microbiology · Available online 17 Mar 2026 · In press · DOI 10.1080/20002297.2026.2645306
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.
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