| Skeletal ClassⅢ malocclusion is a common skeletal malocclusion. It notonly affects patients′profile but the function. Combination of orthognathicsurgery and orthodontics is an effective treatment method for adult with skeletalClassⅢ malocclusion at present. From clinical observation, the lingualinclination of the compentated lower incisors often result in thinner bonethickness at labial side and gingival recessions. It appears that the occurrence ofalveolar bone loss or fenestration was more common when the lower incisorswere decompensated during the presurgical treatment. The morphology of thealveolar bone in the mandibular incisor region had traditionally been evaluatedwith X-ray radiographs. But insufficient of the two-dimensional view, it wasdifficult to measure accuracy. With CBCT technology, this study can acquire the accurate radiographic images to investigate the characteristic of morphologyalveolar bone in the region of lower incisors and the change after presurgicalorthodontic treatment.ObjectiveThe comparison between the adult skeletal ClassⅢ malocclusion and thenormal occlusion samples and the comparison between before treatment andafter the presurgical orthodontic treatment were aimed to decet the change ofalveolar bone condition around mandibular incisors.MethodsExperiment1:The sample consisted of17patients with skeletal ClassⅢmalocclusion (10men,7women, average age:23.7years) and10Chinese normalocclusion subjects(5men,5women,, average age:24.0years). The CBCTimages covering the region of mandibular incisors were obtained.Thelabio-lingual inclinations of mandibular incisors, the thickness of the associatedalveolar bone and the vertical alveolar level were measured. Statistical testswere performed using SPSS15.0software package.Correlations and differencesbetween the measured variables were tested by t-test and linear regressionanalysis.Experiment2:15patients treated with orthodontic treatment and orthognathicsurgery (9men,6women, average age:23.6years) were taken CBCT beforetreatment(T0) and1month before orthognathic surgery(T1).The amount ofalveolar bone thickness, the vertical alveolar level and the root length were measured. Paired t-test was performed for the comparisons of the differencesbetween pre-and post-operative variables.Result1. The comparison between the adult skeletal ClassⅢ malocclusion andthe normal occlusion samples showed:①Alveolar bone thickness at the apexwas thinner than the normal group;②The vertical alveolar bone level at thelabial and lingual sides were both reduced than the normal group, especially atthe labial side;③There were statistically significant correlations between thelower incisors inclination and the alveolar bone thickness、the alveolar bonelevel at the labial side、the apex to labial side.2. The comparison between before treatment and after the presurgicalorthodontic treatment showed:①The lower incisors inclination and theincisors root apex were closer to the lingual side of alveolar bone(P<0.01);②The alveolar bone thickness at apex were not statistically changed;③Thevertical alveolar bone level at the labial and lingual sides were both significantlyreduced especially the lingual side after presurgical orthodontictreatment(P<0.01);④The root length were not significantly changed.ConclusionBased on the results, the alveolar bone thickness at apex were thinner andthe vertical alveolar level were reduced at the at the labial side. Forwardmovement of lower incisors during presurgical orthodontic treatment cause thethe lower incisors root apex were closer to the lingual side and the amount ofvertical alveolar level were continually reduced. With the results of this study, special care should be considered inindividuals with skeletal ClassⅢ malocclusion, according patients′periodontalhealth, the change of alveolar bone and the relationship between root andalveolar bone. Choose the right plan and avoid the excessive movement ofmandibular incisors during the treatment of skeletal ClassⅢ adults. |
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