Investigation of the Transfer of Oral Bacteria from the mouth of the Patient to the Nasal Vestibule of the Clinician During Orthodontic Bracket Debonding

Abstract

Background: Despite the use of personal protective equipment (PPE), the possibility exists that dental aerosols generated during standard dental procedures may penetrate to the nasal regions of treating clinicians and staff. These aerosols may carry with them pathogenic oral bacteria. Orthodontic procedures, such as the removal of braces that employ the use of high-speed handpieces and water spray to remove excess bonding material, may release aerosols. When the procedure involves the removal of bracket adhesive material from subgingival areas of the tooth in patients with inflamed hyperplastic gingival, there is an increased risk that aerosols generated carry pathogenic aerobic and anaerobic oral bacterial. This study was designed to determine whether an orthodontist wearing an ear-loop mask is at risk of nasal inoculation of aerosols containing pathogenic oral bacteria released during routine removal of braces (debond). There were two phases to the present study. The first phase sought to (a) adapt DNA-based methods for the selective identification of particular bacterial strains in the mouth and nasal vestibule, (b) confirm the ability to detect these representative bacterial targets in patient saliva samples, and (c) develop an effective method for collecting samples from the nasal vestibular regions of the clinician. The second phase of the study was designed to test the ability of aerosols to transfer the patients’ oral bacteria into the nasal vestibules of treating orthodontists during a routine debonding procedure. Methods: In Phase 1, nasal and oral swab samples from the patients’ mouths and clinicians’ nasal vestibules were taken to establish sampling and assay protocols necessary to identify and assess the relative abundance of the selected target bacteria of oral origin. Bacterial DNA was extracted from the swabs using the Sigma-Aldrich GenElute Bacterial Genomic DNA kit and was analyzed through Real-time PCR. After developing the methods in Phase 1, Phase 2 involved one oral sample taken from a patient’s mouth and two nasal samples taken from the treating clinician’s nasal vestibule. The first nasal sample was taken as the start of the day, prior to any clinical contact with patients. The second nasal sample was taken directly after the patient’s braces were removed. At the same time, a sample was taken of the patient’s oral cavity prior to any rinsing. These three samples constituted a “case” of which there were twenty-eight in the study. Clinicians followed standard health and safety procedures. Bacterial DNA was extracted from the swabs using the Sigma-Aldrich GenElute Bacterial Genomic DNA kit and was analyzed through Real-time PCR. Only the bacteria detected in the patients’ oral cavities were analyzed in the nasal samples of the treating clinicians. Results: In Phase 1, nasal swab samples were obtained from seven residents using various collection methods to determine which of them yielded an adequate amount of bacterial DNA. The results indicated that detectable levels of individual bacterial DNA could be extracted from nasal swabs using the full nostril technique, twirled around ten times. The bacterial DNA signatures used as surrogates for the presence of orally derived bacteria were confirmed in the oral samples taken from the patients’ mouths. In Phase 2, twenty sets were analyzed from ten “cases.” The remaining eighteen “cases” were excluded because they didn't meet the inclusion criteria. Three out of the ten “cases” showed a transfer of bacteria from the patient’s mouth to the clinician’s nasal vestibule by a two-fold increase. In two out of the three cases, two bacteria Actinomycetes israelii and Fusobacterium nucleatum increased in relative abundance from the pre-nasal samples to the post-nasal samples, and in the third case, only Actinomycetes israelii showed an increase in relative abundance. Therefore, 30% of the “cases” showed a two-fold increase in relative abundance from the pre-nasal samples to the post-nasal samples. Two out of the ten “cases” showed a two-fold decrease in relative abundance. Conclusions: Oral microorganisms that are part of the aerosol cloud generated during the debond procedure may have the ability to pass around the edges of the protective mask into the clinician’s nasal vestibule and the results of this study show that a transfer of bacteria can occur. The use of personal protective equipment, if worn properly, may not always be effective in preventing aerosols that are generated during standard removal of braces, however it is important for clinicians to be aware of the potential health risk as a result of inhalation of aerosol contamination during dental procedures.