Assessing the Impact of Maxillomandibular Difference on the Success of Orthodontic Decompensation Preparation in Orthognathic Surgical Skeletal Class-III Patients

Background: Combined orthodontic-surgical treatment includes a thorough diagnosis and analysis of dental and facial deformities. Cephalometric analysis is a common tool for this, in which measurements of specific anatomical landmarks are performed. In order to achieve a successful surgery, orthodontic teeth preparation is mandatory, including dental decompensation before surgery. This should be planned and adequately executed to allow the surgeon to move the jaws to the correct ideal position. Aim: The current study aimed to check if the orthodontic decompensation amount is influenced and compromised by the maxillomandibular difference and if there is a correlation between the deformity's severity and the orthodontist's difficulty in achieving an accurate result in the orthodontic decompensation preparation. Methods: The study consisted of 50 pre-operational cephalometric radiographs of patients with Class-III (prognathic) deformity. The measurements included the angles of the upper incisor (U1) longitudinal axis to the Frankfort plane (FH) and palatal plane (PP), lower incisor (L1) longitudinal axis to the lower mandibular plane (MP), overjet (OJ), effective maxillary length, effective mandibular length, and the maxilla-mandibular difference (Diff); Pearson correlation coefficient was applied. Results: There was a significant correlation between the maxilla-mandibular difference and U1 to FH angle (r = 0.254, p = 0.037), U1 to PP angle (r = 0.447, p < 0.001), OJ (r = (-0.426), p < 0.001). There was no statistical significance for Diff and L1 to MP angle (p = 0.342). Conclusions: In Class-III patients, achieving adequate decompensation is more challenging with the maxillary incisors rather than with the mandibular incisors, especially in more severe cases.