Long-term maxillary stability after fixation with two or four plates: a 3-D prospective quasi-experimental evaluation

The purpose was to assess through a prospective, interventional and quasi-experimental study the long-term stability of maxilla fixed with two and four plates in Le Fort I osteotomies using computed tomography. A total of 63 patients (mean age 29,9 ± 9,3) with skeletal Class II-III dentofacial deformity were recruited. Thirty-six patients were fixed with two-plates and 27 patients with four plates. Preoperative, ≤6 months postoperative and ≥12 months postoperative tomography scans were taken. Data were imported to Dolphin Imaging®, superimposed and analyzed 3-dimentionally. Descriptive statistics were reported, quantitative variables were evaluated by the Kolmogorov Smirnov test, for categorical variables chi-square test with Yates' correction was used and Mann-Whitney test for those with asymmetric distribution. Spearman's test was used for correlation between quantitative variables. In the group of 4-plates, significant relapse was found in the vertical landmark A (p = 0.004). In the group of two plates, sagittal and vertical PNS and transversal A skeletal landmarks exhibited the highest relapse medians. Significant correlations between occlusal plane rotations and the vertical A landmark were found in the group of 2-plates (p = 0.043) and for all dental landmarks in the vertical axis in the group of 4-plates. (p = 0.024). Fixation with 2-plates was found to be stable in the long-term. Occlusal plane rotations and vertical maxillary repositioning must be taken under consideration when fixating with 2 or 4-plates respectively.