Antimicrobial Photodynamic Therapy (aPDT) for decontamination of high-speed handpieces: A comparative study

Background: Cross-transmission is a major concern in dental offices. Various disinfection methods have been frequently used to reduce its incidence. Standard procedures include decontamination and sterilization. Traditional decontamination methods include: Alcohol 70 % and chlorhexidine digluconate, however, antimicrobial photodynamic therapy (aPDT) could be added as an option. The objective was to evaluate the effectiveness of aPDT on decontamination of high-speed handpieces, contaminated by Staphylococcus aureus (SA) and Escherichia coli. (EC), and compare it to autoclave sterilized and to conventional chemical decontamination methods. Methods: Sterilized, SA and EC contaminated high-speed handpieces were divided in 7 groups: G1- sterilized in an autoclave. G2- contaminated untreated control. G3- contaminated and decontaminated using Alcohol 70 %. G4- contaminated and decontaminated using chlorhexidine digluconate 2%. G5- contaminated and laser treated. G6- contaminated and photosensitizer treated. G7- contaminated and photodynamic therapy. Results: The groups G3, G4, G7 did not show bacterial growth, G5 and G6 showed bacterial growth similar to G2. The study did not find SA or EC sensible to laser irradiation only, differently from some authors and did not consider biofilm in our experiments. Conclusion: Our experiment showed that, laser and photosensitizer isolated were not effective to inhibit Staphylococcus aureus (SA) and Escherichia coli. (EC) growth, but when associated in aPDT technique, can be compared to chemical disinfection agents that are traditionally used and effective against this pathogen.