The length of the TISAD/TAD may be one of the factors that can affect the long-term success rate in the mandibles of 20- to 29-year-old women.

Background. Loading of the compromised periodontium with orthodontic forces produces different results than those achieved in patients with healthy periodontal support. Determining the force value at a level preventing further deterioration of the patient's periodontal status, thus delivering the most precisely individualized "dose" of loading, seems to be crucial for the successful intrusion of teeth with reduced periodontal support.

The mechanism of orthodontic teeth movement is not entirely explained. The principal reaction on tissues at the cellular and molecular level is initiated by the force applied to the tooth crown and transferred in turn upon the periodontal ligament (PDL). It seems, therefore, that the PDL and particularly its properties play a key role in bone remodelling. One of the more commonly used methods, which is capable of analysis of a wide range of orthodontic movements or distribution of stress and strain within teeth and periodontium, is the finite element method (FEM). Aiming to achieve the FEM model as close as possible to in vivo conditions, it is necessary to account for accurate material properties. The aim of the present study is to compare particular studies and descriptions of material characteristics of the PDL. The analysis of available articles shows how imperfect modern descriptions of PDL material properties available today are, which in the precise method could allow the analysis of the occurrences within the in vivo processes in a non-destructive manner. The complicated anatomy and physiology of PDL, which incur significant parameter changes with age and disease susceptibility, make the accurate description of this material so difficult. The available study results show that those characteristics should be precise and complicated, which undoubtedly impedes the calculation processes but generates reliable results.

Background: One of the goals of orthodontic treatment is to obtain maximum facial harmony. The sagittal position of the lower incisors plays a significant role in the planning of orthodontic treatment. The aim of the study was to evaluate the relationship between the sagittal position of lower incisors and facial profile esthetics with reference to the skeletal vertical dimension. Methods: There were 200 patients included in the study. Patients were allocated into three groups, depending on the vertical growth pattern: normal-angle, low-angle, and high-angle cases. Tweed–Merrifield cephalometric analysis was used to assess the sagittal and vertical position of the mandible, as well as to assess the sagittal position of the lower incisors. Results: Z-angle and Frankfort mandibular incisor plane angle (FMIA) decreased significantly (p < 0.001) with the increase of the skeletal vertical dimension. Incisor mandibular plane angle (IMPA) was significantly higher (p < 0.001) in low-angle patients compared to the high-angle ones. Z-angle appeared to be the most accurate parameter (area under curve, AUC = 0.957) describing patients with a convex profile. The cutoff value of Z-angle 68.0° was characterized by the sensitivity of 94.1% and the specificity of 84.3%. Conclusions: The sagittal position of the lower incisors significantly affects the facial profile convexity. The Z-angle is the parameter which most accurately describes the patients with a convex profile.

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