A Comparative Study Of The Changes Of The Occlusal Plane And Mandibular Plane Before And After Orthodontic Treatment Of Skeletal Class Ⅲ Malocclusion

ObjectiveThe purpose of this article is to investigate the changes of occlusal plane and mandibular plane before and after orthodontic treatment in patients with skeletal Class III malocclusion of permanent dentition.and the correlation with surrounding soft and hard tissue changes.MethodsTen patients with voluntary orthodontic masking treatment with skeletal Class III malocclusion of permanent dentition were selected as the study objects.Their ages ranged from 16 to 26 years(mean age,20.8 ± 3.26 years),75?≤ SNA≤85?(mean 79.15 ± 3.76)?,77?≤ SNB ≤87?(mean 82.75 ± 3.63)?.-5.5?≤ ANB≤-2?(mean-3.60 ± 1.73)?,31?≤ SN-MP ≤44?(mean 38.2±4.35)?.Extraction of mandibular bilateral second molars or third molars with straight wire or edgewise appliance.In this study,two cases used multi-loop edgewise arch wire,one people’s anterior tooth bracket was reversed and two cases used micro-implant anchorage in mandibular bilateral buccal shed area,of which one case were combined with the micro-implant anchorage in maxillary bilateralzygomatic alveolar ridge.At the end of the orthodontic treatment,the overbite、overjet and the relationship of canine、molar are normal.The beauty of front and side looks improved.The cephalometry before and afte treatment of craniofacial items were measured.the measured data were analyzed by SPSS version 17.0.Paired t-test and Pearson correlation analysis were used.P < 0.05 represents a statistically significant difference.Results(1)After orthodontic treatment,the relationship of sagittal direction was improved,the angle of SNA and ANB increased,the inclination of the anterior and posterior teeth of the upper jaw increased.While,the lower jaw decreased.the N-Me and ANS-Me increased,S-Go and nasolabial angle decreased,the vertical distance of the upper lip to the aesthetic plane increased,The increase of the vertical distance between the nasolabial groove,the mentolabial sulcu and the H line.The difference was statistically significant(P < 0.05).(2)The posterior occlusion plane and functional occlusion plane decreased after orthodontic treatment in patients with skeletal Class III malocclusion,The difference was statistically significant(P < 0.05).There was no significant change in SN-MP angle and FH-MP angle before and after orthodontic treatment(P > 0.05).(3)Before and after treatment,the N-Me and ANS-Me were positively correlated with the mandibular plane.But,no significant correlation between changes.There is no significant correlation between anterior teeth overbite and mandibular plane.Conclusions(1)If the design is reasonable and the method is proper,the malocclusion can be corrected,the sagittal relationship of the maxilla and the mandible can beinproved,the vertical relationship can be controlled,the soft tissue is also adaptable,and the appearance is harmonious and beautiful.(2)For the cases of skeletal Class III malocclusion,as long as the design is correct,the right case is selected and the anchorage is used reasonably,the plane and mandibular plane can be well controlled.(3)There is a correlation between the S-Me,ANS-Me and the mandibular plane.It is suggested that the clockwise rotation of the mandible should be avoided as far as possible.