Microscale liquid droplets could act as the SARS carriers in air when released from an infected person through breathing, coughing, or sneezing. In this study, a dynamic model has been built to quantitatively investigate the effect of the relative humidity on the transport of liquid-droplets in air using coupled mass transfer and momentum equations. Under higher relative humidity, the exhaled liquid droplets evaporate slowly. Larger droplets fall faster, which could reduce the probability of the droplets inhalation. This may be one of the most important factors that influence the SARS transmission in air.

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Objective: This study evaluated the relationship between follow-up temporomandibular joint positional change and mandibular stability among patients who had orthognathic and orthodontic treatment for a skeletal Class II malocclusion. Methods:Thirty-seven patients who underwent 2-jaw surgery (Le Fort I osteotomy, bilateral sagittal split ramus osteotomy and genioplasty with rigid internal fixation)were included with an average follow-up length of 8.10 ± 2.06 years. They were categorized into a stable and unstable group according to follow-up mandibular change in the sagittal direction. Temporomandibular joint spaces were measured on serial magnetic resonance images, prior to orthodontic treatment (T0), upon completion of orthodontic treatment following surgery (T1), and at least 5 years post-completion of the treatment (T2).Results: While the maxillary position was stable during the follow-up period, the mandibular positional change was statistically significant (the relapse amount was −0.81 ± 1.52 mm at B point). An increase in the anterior joint space and superior joint space was found to correlate with the follow-up mandibular backward movement. Conclusions:Patients who underwent orthognathic and orthodontic treatment to correct mandibular retrognathism displayed follow-up mandibular relapse in the sagittal direction. The relapse is accompanied by condylar positional change. K E Y W O R D Sangle class II, malocclusion, mandibular advancement, mandibular reconstruction, orthognathic surgery, temporomandibular joint