The Morphometric Analysis of Maxillopalatal and Mandibular Changes of Skeletal Class III Malocclusion Treated with Orthopedic Therapy

The purpose of this study was to investigate the treatment effects on the maxillopalatal mandibular configuration by occipito-mental anchorage (OMA) (maxillary protraction) combined with chin cup appliance (CCA) therapy among growing children. The assessment of geometric morphometric, using Procrustes analysis, thin plate spline analysis, and growth-trended vectors, was applied and integrated to evaluate treatment effects on the maxillopalatal mandibular configuration of 22 children with skeletal Class III malocclusion. Taiwanese children (12 males and 10 females; 22 untreated stage of Class III subjects as pre-treated group; 22 treated stage of Class III subjects as post-treated group) were traced, and 9 landmarks digitized. Thin-plate spline analysis (TPSA) and growth-trended vectors (GTVs) of geometric morphometric technique were integrated and utilized to investigate the morphological differences of dentofacial growth and local effects of orthopedic treatment. Goodall’s analysis of morphometric statistics established statistical difference (p < 0.01) between the mean configurations of the pre-treated and post-treated groups. Significant morphological changes on the maxillopalatal mandibular configuration were detected that the skeletal Class III subjects following orthopedic therapy included the growth of forward extension on the maxillopalatal configuration and the growth of backward compression on the mandible. In addition, the mandible treated with the CCA therapy appeared to have a tendency of clockwise rotation. Median and transverse palatine sutures seem to play an important role to produce the antero-superior elongation on the maxillopalatal configuration when orthopedic force was applied. The results indicated that the therapy of the OMA+CCA was efficient for correcting developing Class III malocclusion. Moreover, the morphometric techniques of the TPSA and GTVs are efficient methods to investigate growth change and treatment effect for craniofacial studies.