The novel coronavirus pandemic has resulted in an urgent need to study the risk of infection from aerosols generated during dental care and to conduct a review of infection controls. However, existing studies on aerosol particles related to dental treatment have mainly evaluated only the scattering range. Few studies have been conducted on the specifics of the generation of aerosol particles in clinical settings, their mechanisms and patterns of distribution throughout open or enclosed spaces, the duration that they remain suspended in air, and the amount and size of particles present. To minimize the influence of background particles, laser lights, a high-sensitivity camera, and particle counters were used in a large super clean laboratory to investigate the dynamics of aerosols generated during the operation of dental micromotors. The results indicate that aerosols tend to scatter upward immediately after generation and then gradually disperse into the surroundings. Most of the particles are less than 5 µm in size (only a few are larger), and all particles are widely distributed over the long term. Our research clearly elucidates that aerosols produced in dental care are distributed over a wide area and remain suspended for a considerable time in dental clinics before settling.

To assess the rate and risk factors of postoperative complications following tooth extraction in HIV-infected patients by CD4 count. The study subjects were 231 HIV-infected patients who underwent tooth extraction at our institution between January 2007 and December 2011. Results of blood test, underlying diseases, surgical site, extraction method, and postoperative complications were obtained from the medical records. The risk factors potentially involved in postoperative complications were analyzed by multivariate logistic regression. Patients were divided into two groups, 61 (26%) patients with CD4 count of <200 /μL, and 170 (74%) patients with ≥200 /μL. Of the 231 patients, 12 (5.2%) developed postoperative complications (alveolar osteitis, n=10; surgical site infection, n=2).The rate of complications was not different between the CD4<200 /μL group (1.6%), and the CD4≥200 /μL group (6.5%) (adjusted odds ratio (aOR): 9.328, 95% confidence interval (CI):(0.470, 185.229), p=0.1431). Surgical extraction method with bone excavation, but not CD4 count, were identified as risk factors for post-extraction complications (aOR: 22.037, 95%CI:(1.519, 319.617), p=0.0234). A low CD4 count is not a risk factor for post-extraction complications in HIV-infected patients. We advise that tooth extraction should be performed based on dental/oral condition, rather than delayed until improvement of CD4 count.

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There is an urgent need to examine the risk of infection from aerosols generated during dental treatment and to review infection control. However, existing research on aerosol particles associated with dental treatment is by no means sufficient, and little research has been done on the details of aerosol particle generation in the clinical environment, the mechanisms, and patterns of distribution in open and closed spaces, the time they are suspended in the air, the amount and size of particles present. Therefore, to minimize the influence of background particles, laser beams, a high-sensitivity camera, and a particle counter were used in a large super-clean laboratory (SCL) to investigate the dynamics of aerosols generated during dental micromotor operation. The large number of aerosol particles generated by the use of the micro-engine rose rapidly within 30 seconds and were suspended in the room atmosphere. Within a 100 cm radius of the user, the scattering