Dental unit waterlines disinfection using hypochlorous acid-based disinfectant

Antimicrobial action and cytotoxicity of hypochlorous acid obtained from an innovative electrolytic device - An in vitro study

OBJECTIVE

This study evaluated the antimicrobial effect and cytotoxicity of hypochlorous acid(HClO) obtained from an innovative electrolytic device.

DESIGN

The root canals of fifty extracted human teeth were inoculated with Enterococcus faecalis and divided into 5 groups (n = 10): DW (control); 2% chlorhexidine gel(CHX); 2.5% sodium hypochlorite(NaOCl); 250 ppm HClO and 500 ppm HClO. The counting of colony forming units evaluated the decontamination potential of each group. Cytotoxicity was evaluated after inoculation of tested protocols in fibroblastic cells for 3 min, calculating the cell viability. Specific statistical analysis was performed (α = 5%).

RESULTS

The highest bacterial reduction was observed in experimental groups, with no statistical differences from each other (p > 0.05). The highest number of viable cells was observed in control group, followed by 250 ppm HClO and 500 ppm HClO groups, with statistical differences from each other (p < 0.05).

CONCLUSIONS

It could be concluded that HClO presented high antimicrobial activity and low cytotoxicity at both tested concentrations.

Comparison of antimicrobial efficacy of different disinfectants on the biofilm formation in dental unit water systems using dip slide and conventional methods: A pilot study

OBJECTIVE

Biofilm formation in dental waterlines brings opportunistic infections, especially for immunosuppressive patients. This study aimed to determine biofilm-forming microorganisms by various methods and investigate disinfectants' effects on biofilm.

MATERIALS & METHODS

In the study, samples were obtained from the waterlines of 10-15 aged six dental units, before (0 min.) and after chlorine dioxide (ClO2) and hypochlorous acid (HOCl) treatment (1, 5, 10, 20, and 30 min.), and total colony counts were performed using conventional surface smear method (SSM) and dip slide method (DSM). The Congo red agar and Christensen methods were used to examine the biofilm-forming properties of the isolates. Monitoring of biofilm presence was also visualized by SEM scanning.

RESULTS

When DSM and SSM are compared in all units where ClO2 and HOCl are applied, DSM can detect bacterial growth even during periods of greater exposure to disinfectant application. Although DSM can achieve a value approaching 3% even at the 10th minute in units treated with HOCl; SSM does not show reproduction at the same disinfectant exposure and duration; It was observed that in the units where ClO2 was applied, the growth was no longer observed at the 10th minute with DSM, and SSM, 50% growth in the first minute of the units treated with ClO2 could not be detected in the 5th minute.

CONCLUSIONS

It is concluded that it can be advisable to routinely disinfect the dental unit water systems with non-toxic doses of ClO2 application before patient treatments in clinics and also to perform contamination controls at regular intervals with DSM, which is a sensitive and very practical method.

RESEARCH HIGHLIGHTS

It has been observed that the dip slide method can count bacteria more sensitively than conventional methods in dental water systems without the need for experienced personnel and equipment. The difference between biofilm formation in water systems before and after disinfectant exposure in SEM examinations is remarkable. The effects of ClO2 and HOCl on biofilm were investigated and bacterial growth was inhibited in dental units between 5 and 10 minutes with both disinfectants.

Electrolysed oxidising water as a multi-purpose biocide in dental healthcare-A scoping review

OBJECTIVES

The objective of this scoping review was to map evidence of electrolysed oxidising water (EOW) as a biocide for dental applications of relevance to older people and identify research gaps.

BACKGROUND

EOW is an emerging, "green," and cost-effective biocide. There are no reviews on the landscape of EOW research as either an antiseptic or disinfectant in dental healthcare or its suitability for the oral healthcare of older people.

MATERIALS AND METHODS

The review follows the PRISMA Extension for Scoping Reviews (PRISMA-ScR) guidelines. Database searches (Google Scholar, PubMed, Web of Science, Ovid, Scopus and Science Direct) were undertaken using MESH terms and Boolean operators with no date restrictions, to identify full-text, original reports published in English-language peer-reviewed journals.

RESULTS

The search yielded 114 papers that met the inclusion/exclusion criteria. Dental applications of EOW include its use as an endodontic irrigant (39%); mouth rinse/surgical irrigant (21%); disinfectant for dental unit water lines (19%) and dental biomaterials (17%); and for antimicrobial efficacy, effects on oral tissues and on dental material properties. Most studies (83%) evaluated a single EOW formulation (acidic, moderately acidic or neutral) that was either generated at 'point-of-use' (POU; 72%), bottled ('ready-to-use', RTU; 24%) or from unspecified (3%) sources. Six reports evaluated storage-related parameters and 25 evaluated clinical applications; 89 were in vitro studies and one investigated the cost-effectiveness of POU EOW.

CONCLUSIONS

Neutral-pH, EOW is effective as an antimicrobial agent without deleterious effects on oral tissues. However, research on the impact of storage conditions, anti-Candida biofilm efficacy and mechanism of action against yeasts, long-term effects on denture materials and cost-effectiveness is required to establish the suitability of EOW as a multipurpose biocide for dental healthcare, including infection-control requirements relating to older people.

Construction of ZnO/PCL Antibacterial Coating Potentially for Dental Unit Waterlines

The formation of bacterial biofilms and the contamination of treatment water within dental unit waterlines can lead to a risk of secondary bacterial infections in immunocompromised patients. Although chemical disinfectants can reduce the contamination of treatment water, they can also cause corrosion damage to dental unit waterlines. Considering the antibacterial effect of ZnO, a ZnO-containing coating was prepared on the surface of polyurethane waterlines using polycaprolactone (PCL) with a good film-forming capacity. The ZnO-containing PCL coating improved the hydrophobicity of polyurethane waterlines, thus inhibiting the adhesion of bacteria. Moreover, the continuous slow release of Zn ions endowed polyurethane waterlines with antibacterial activity, thus effectively preventing the formation of bacterial biofilms. Meanwhile, the ZnO-containing PCL coating had good biocompatibility. The present study suggests that ZnO-containing PCL coating can realize a long-term antibacterial effect on the polyurethane waterlines by itself, providing a novel strategy for the manufacture of autonomous antibacterial dental unit waterlines.

Hypochlorous acid inactivates oral pathogens and a SARS-CoV-2-surrogate

BACKGROUND

Droplets and aerosols produced during dental procedures are a risk factor for microbial and viral transmission. Unlike sodium hypochlorite, hypochlorous acid (HOCl) is nontoxic to tissues but still exhibits broad microbicidal effect. HOCl solution may be applicable as a supplement to water and/or mouthwash. This study aims to evaluate the effectiveness of HOCl solution on common human oral pathogens and a SARS-CoV-2 surrogate MHV A59 virus, considering the dental practice environment.

METHODS

HOCl was generated by electrolysis of 3% hydrochloric acid. The effect of HOCl on human oral pathogens, Fusobacterium nucleatum, Prevotella intermedia, Streptococcus intermedius, Parvimonas micra, and MHV A59 virus was studied from four perspectives: concentration; volume; presence of saliva; and storage. HOCl solution in different conditions was utilized in bactericidal and virucidal assays, and the minimum inhibitory volume ratio that is required to completely inhibit the pathogens was determined.

RESULTS

In the absence of saliva, the minimum inhibitory volume ratio of freshly prepared HOCl solution (45-60 ppm) was 4:1 for bacterial suspensions and 6:1 for viral suspensions. The presence of saliva increased the minimum inhibitory volume ratio to 8:1 and 7:1 for bacteria and viruses, respectively. Applying a higher concentration of HOCl solution (220 or 330 ppm) did not lead to a significant decrease in the minimum inhibitory volume ratio against S. intermedius and P. micra. The minimum inhibitory volume ratio increases in applications of HOCl solution via the dental unit water line. One week of storage of HOCl solution degraded HOCl and increased the minimum growth inhibition volume ratio.

CONCLUSIONS

HOCl solution (45-60 ppm) is still effective against oral pathogens and SAR-CoV-2 surrogate viruses even in the presence of saliva and after passing through the dental unit water line. This study indicates that the HOCl solution can be used as therapeutic water or mouthwash and may ultimately reduce the risk of airborne infection in dental practice.

Water Contamination Risks at the Dental Clinic

Dental clinics, furnished with an array of specialized equipment, are commonplace, particularly in industrialized countries. Minimizing the risk of infection at the dental practice requires the formulation and implementation of strict protocols. These protocols must address the real risk posed by water contamination, particularly given that water is both integral to the function of some dental equipment, and is typically administered directly to the patient. The water in the dental clinic may be of local origin or from a water main, this can be problematic since the clinician often has little assurance regarding the quality of water reaching the dental chair. Though most modern dental equipment includes self-sterilization protocols, care must be taken that water does not stagnate anywhere in the dental equipment or clinic. The management of water quality at the dental clinic is an important part of respecting the protocols needed to manage the risk of patient infections.