Electrolyzed saline coolant mitigates bacterial airborne deposition in dental procedures

Dental procedures generate dental spray that can transmit microorganisms. Substituting conventional coolants with antiseptics may mitigate this risk by preventing the transmission of infectious particles at the source. The aim of this in vitro study was to evaluate the efficacy of electrolyzed saline (EOS), a hypochlorous acid (HOCl) based antiseptic as a coolant for mitigating bacterial spray deposition during ultrasonic scaling (USS) in stimulated dental procedure.

The bactericidal activity of EOS (pH 7.0, 200 ppm) and 0.2% chlorhexidine digluconate (CHX) was tested against Streptococcus mitis, Streptococcus pneumoniae, Streptococcus pyogenes, and Haemophilus influenzae using a static antibacterial assay. Changes in bacterial morphology were visualized using transmission electron microscopy. A bacteria-laden dental spray model was used to simulate a patient undergoing plaque debridement procedure with ultrasonic scaler in standardized airborne transmission tunnel. Due to safety concerns, pathogen-free consortium of oral streptococci was used. Mitigation of bacterial deposition was quantified using a culture-based method. In addition, the biocompatibility of antiseptics was tested with exposure to human gingival fibroblasts (hGF) and human gingival keratinocytes (hOK).

In the static assay, CHX reduced all tested bacteria species to ≤10 CFU/mL within 10 s of exposure, irrespective of the presence of saliva. In contrast, EOS was generally less effective after 10 s but exhibited near-complete antibacterial activity after 30-60 s, with delayed efficacy in the presence of saliva. During USS procedures, no culturable bacteria were detected in splatter generated with either CHX or EOS. However, compared with saline EOS reduced bacteria-laden droplets/aerosol (CFU/cm²) deposition by 92% vs. 81% with CHX (both, p < 0.001), with no significant difference between the antiseptics (p = 0.607). Both antiseptics effectively reduced bacterial deposition at short range. Nevertheless, only EOS maintained consistent mitigation efficacy over greater distances dominated by aerosol. EOS exhibited minimal cytotoxicity to hGF and moderate effects on hOK, while CHX substantially reduced viability of both cell types.

EOS demonstrated rapid contact-bactericidal activity and comparable dental spray deposition reduction to CHX. As a reasonably biocompatible, broad-spectrum agent, EOS may represent a promising coolant candidate for infection prevention control, warranting further clinical evaluation.