Is Preoperative Maintenance of the Curve of Spee Associated With an Increase of Facial Height in Class II Short Face Orthognathic Patients? A Never Answered Dogmatic Question

Abstract

To determine the association of maintaining the curve of Spee (COS) before surgery with post-treatment facial height in patients with Class II short face syndrome undergoing combined orthodontic and orthognathic treatment. In this retrospective cohort study, the clinical and radiologic data of all patients with Class II short face syndrome who underwent combined orthodontic and orthognathic treatment were reviewed. The primary outcome variables were 1) preoperative COS and 2) post-treatment facial height. Depth of the COS and skeletal and soft tissue relations were measured on digital lateral cephalometric radiographs. Descriptive and bivariate statistics were performed. The sample was composed of 20 patients. Statistical analysis showed a significant increase of soft tissue facial height after treatment (P<.02). Preoperative depth of the COS was significantly associated with changes in sagittal skeletal relations (angle formed by the sella, nasion, and B point [SNB], correlation [cor]=-0.54, P<.02; angle formed by the A point, nasion, and B point [ANB], cor=0.43, P<.06). These changes and changes in overjet were associated with the post-treatment increase of lower facial height (SNB, cor=0.70, P<.001; ANB, cor=-0.69, P<.001; overjet, cor=-0.55, P<.049). The ratios of upper to lower soft tissue facial height and upper to lower lip height were improved to near normal values (1.0 and 0.5, respectively) for most patients. In patients with Class II short face orthognathism, the present study found that maintaining the COS before surgery was associated with 1) an increase of soft tissue facial height and 2) an improvement of the ratio of upper to lower facial height and the ratio of upper to lower lip height to near normal values. Moreover, the depth of the COS was correlated with the post-treatment increase of facial height through changes in skeletal relations and was related to the degree of severity of the mandibular deficiency.