馬蹄形骨切り術を併用した分割Le FortⅠ型骨切り術による上顎歯列弓拡大

Purpose: To assess the maxillary dental arch width expansion and postoperative stability of segmental Le Fort Ⅰ osteotomy combined with horseshoe osteotomy. <br>Materials and methods: Seventy consecutive cases of segmental Le Fort Ⅰ osteotomy that underwent expansion of the maxillary dental arch width during the two years from January 2018 to December 2019, were examined retrospectively. Two segmental Le Fort Ⅰ osteotomy （Group A）, two segmental Le Fort Ⅰ osteotomy with parasagittal palatal osteotomy （Group B） and two segmental Le Fort Ⅰ osteotomy with additional horseshoe osteotomy （Group C） were performed to relieve the tension of the palatal mucosa. To evaluate the maxillary dental arch width expansions and expansion rates of the three groups, posteroanterior cephalograms were employed before surgery and immediately after surgery. The maxillary dental arch width was measured as the distance between the left and right outermost points of the dental arch. In addition, the maxillary dental arch widths were measured on plaster models of group C before surgery, immediately after surgery, at the end of orthodontic treatment, and at more than 1 year after the end of orthodontic treatment. To assess the postoperative stabilities of group C, the Wilcoxon signed-rank test was used to compare the relapse rates at the end of orthodontic treatment and at least 1 year after the end of orthodontic treatment. <br>Results: The number of cases in groups A, B and C were 32, 29 and 9, respectively. The mean expansion values of groups A, B and C on posteroanterior cephalograms were 2.3 （1.1-3.6）±0.6, 4.1 （2.9-5.4）±0.7 and 6.6 （4.8-8.8）±1.0mm; the mean expansion rates were 3.4 （1.7-5.4）±0.8, 6.1 （4.0-8.0）±1.0 and 10.0 （8.2-14.4）±1.7％, respectively. The mean relapse rates of 8 cases in group C on plaster models at two stages, the end of orthodontic treatment and at least 1 year after the end of orthodontic treatment, were 10.9 （−4.1 to 41.8）±14.9 and 15.1 （−13.3 to 35.6）±14.1％, respectively. No significant difference was observed in the relapse rates between the two stages （p＝0.547）. <br>Conclusion: In the segmental Le Fort Ⅰ osteotomy with horseshoe osteotomy group, more than 6mm or 8％ dental arch width expansions were obtained in the posterior part of the maxilla and good postoperative stabilities were observed.