Paper Title
Development of Elasticity Measurement for Perioral Soft Tissues

Abstract
In the field of orthodontics, patients are examined and assessed prior to treatment to ensure accurate treatment. In addition to the assessment of intraoral findings such as tooth alignment and gum condition, extraoral findings such as perioral soft tissue are also assessed morphologically and functionally using facial photographs and radiographs. One method of assessment is to check the anterior-posterior position of the upper and lower lips in relation to the E-line, a straight line connecting the tip of the nose and the most anterior point of the mandible. However, there is no quantification of normal perioral soft tissue stiffness or change in the amount of soft tissue, and the evaluation of extraoral findings has relied on rough standards and the subjective opinions of the attending physician and the patient themselves1). This is not limited to the perioral area, but is due to the fact that skin soft tissue is flexible tissue and it is difficult to define measurement points, measurement methods, etc., and the amount of change in perioral soft tissue due to facial muscle movement and mouth opening and closing during eating is minute. In this study, we focused on the stiffness of perioral soft tissue, which has not been quantified and prepared skin model materials with different plasticizer concentrations, and constructed a device and analysis method that can accurately measure it as an elastic modulus. To obtain the accurate modulus, the optimized condition for the indentation depth and the diameter of the intender was cleared. We believe that the device developed here would be a powerful tool to evaluate the elasticity around the mouth. 1) T. Shimomura, H. Ioi, S. Nakata, A. L. Countsd, Am. J. Orthod. Dentofacial Orthop., 139, 4, E291 (2011).