Bacteriological Safety of Water Used in Dental Clinics in Lagos Island, Lagos State

Dental unit waterlines are known to harbour complex biofilm communities that can compromise water quality and pose infection risks to patients and dental healthcare workers. This study assessed the bacteriological safety of water used in dental procedures at 15 registered dental clinics on Lagos Island, Lagos State, South West Nigeria. Water samples were collected from dental unit waterlines, autoclave water reservoirs, and handwashing sinks at each facility. Total aerobic plate count, Legionella species isolation using BCYE agar, and identification of P. aeruginosa were the primary microbiological endpoints. Biofilm formation on tubing segments was assessed quantitatively using the crystal violet staining technique. Results showed that 80 percent of dental unit waterline samples exceeded the CDC/ADA recommended threshold of 500 CFU/mL for dental treatment water. Legionella pneumophila was isolated from 26.7 percent of waterline samples. P. aeruginosa was recovered from 33.3 percent of samples, and mature biofilm was visualized in tubing samples from all clinics. Clinics that used independent water reservoirs and antimicrobial waterline treatment tablets had significantly lower bacterial counts. These findings highlight a significant and underappreciated infection risk in Lagos dental settings and call for the formulation of national dental waterline maintenance standards as a priority regulatory action. Keywords: dental unit waterlines, Legionella pneumophila, biofilm, Pseudomonas aeruginosa, Lagos.