Objective:To evaluate the effects of maxillary protraction with or without rapid maxillary expansion in the treatment of Class Ⅲ malocclusion by Meta-Analysis.Methods:The randomized controlled trail,quasi-randomized controlled trail and the clinical controlled trail about the treatment of Class Ⅲ malocclusion by protraction with or without expansion were searched in the database of Cochrane Library,Embase,PubMed,Medline,CBM,Wan Fang,CNKI,VIP.2 authors qualified and extracted the data independently.Then the Meta-analysis was performed by using the RevMan 5.3 software.Results:7 studies with 228 cases were included,114 cases were treated by maxillary protraction with expansion and the other 114 cases by maxillary protraction without expansion.The Meta-analysis showed that:there was no significant difference in SNA,SNB,ANB and SN-PP except ANS-Me,U1-NA,SN-MP.A favorable improvement of the sagittal relationship between maxillary and mandibular was observed by using protraction whether with expansion or not.The expansion did not shorten the course of treatment,but it lowered the inclination of upper incisors,resulting in more clockwise rotation of mandibular plane and increase of the facial vertical dimension.Conclusion:Maxillary protraction with rapid maxillary expansion can be used in the treatment of class Ⅲ malocclusion with incisor labioclination.

Objective: To evaluate the change of tooth root volume and length after rapid maxillary expansion by CBCT three dimensional reconstruction method. Methods: 33 patients underwent rapid maxillary expansion were examined by CBCT before and after treatment. The CBCT images of the first,second premolars and the first molars were segmented and reconstructed by Mimics image processing software for the analysis of the changes of root volume and length. All data were analyzed by SPSS software statistically. Results: After maxillary expansion,all root volumes were reduced(P ＜ 0. 05),more reduction was observed in anchorage teeth than in non-anchorage teeth(P ＜ 0. 05). The length of most teeth roots was not decreased(P＞ 0. 05) except the buccal and distal roots of the first molars(P ＜ 0. 05). Conclusion: Rapid maxillary expansion may result in root resorption and this resorption is mainly based on the volume decrease.

Objective To compare the root resorption of posterior teeth between fixed orthodontic appliances and clear aligners in adult patients with skeletal Class Ⅲ malocclusion undergoing camouflage treatment by using cone-beam computed tomography(CBCT)measurements.Methods Thirty-two cases of skeletal Class Ⅲ malocclusion patients who had previously undergone camouflage treat-ment were retrospectively selected.Based on the type of orthodontic appliance used,they were divided into two groups(the fixed appli-ance group and the clear aligner group),each comprising 16 cases.CBCT images of the entire dental arch before and after treatment were collected for these patients,and three-dimensional reconstructions of the mandibular central incisors,first premolars,and first molars were generated using Mimics software.Changes in root volume and length of mandibular teeth before and after treatment were measured and compared between the two groups.Results Both groups showed significant reductions in measured root volume of the teeth after orthodontic treatment(P＜0.05).In the clear aligner group,the mean reduction in root length of mandibular central incisors was(0.52±0.60)mm,while in the fixed appliance group,the reduction in root length of mandibular central incisors and first premolars was(0.47±0.38)mm and(0.38±0.25)mm,respectively.These differences were statistically significant(P＜0.05).Except for the sig-nificantly lower reduction in root volume of mandibular central incisors in the clear aligner group compared to the fixed appliance group(P＜0.05),there were no statistically significant differences in other root resorption-related parameters between the two groups(P＞0.05).Conclusion In camouflage treatment of adult skeletal Class Ⅲ malocclusion patients,clear aligners can reduce the amount of root resorption in mandibular anterior teeth to a certain extent compared to fixed orthodontic appliances.However,there is no significant difference between the two appliances in the posterior teeth region.

Objective To compare dental and skeletal changes after rapid maxillary expansion in patients with different bone ages.Methods Thirty-seven patients in different growth period were divided into three groups according to cervical vertebral maturation (CVM).There were 13 patients in the growth acceleration group,13 patients in growth peak group,and 11 patients in growth deceleration group.Conebeam computed tomography(CBCT) images were segmented and reconstructed using Mimics image processing software to assess the change of palatal morphology before and after treatment.Statistical analysis was carried out using SPSS 17.0 software.Results After the expansion the posterior teeth and alveolar bone were tilted and the mid-palatal suture was opened in all three groups.The first molar angle in the three groups decreased by 2.66°±1.04°,3.53°±0.81° and 12.32°± 1.64°,respectively and no significant difference was found between the acceleration group and the peak group (P ＞ 0.05),but the changes in the acceleration group and the peak groups were significantly less than that in the deceleration group (P＜0.05).The palatal angle in the three groups increased by 6.01°±2.06°,4.79°± 1.31° and 6.73°± 1.71°,respectively and no significant difference was found between the acceleration group and the deceleration group (P ＞ 0.05),but the changes in the acceleration group and the deceleration group were significantly greater than that in the peak group (P ＜ 0.05).The palatal cemento-enamel junction (CEJ) width,the middle palate width and the mid-palatal suture width in the three groups increased by (7.37± 1.31),(6.68± 0.72) and (5.13± 1.42) mm;(5.72±1.68),(4.82± 1.66) and (3.42± 1.15) mm;(3.14±0.45),(2.98±0.51) and (0.96±0.83) mm,respectively and no significant difference was found between the acceleration group and the peak group (P ＞ 0.05),but the changes in the acceleration group and the peak group were significantly greater than that in the deceleration group (P ＜ 0.05).Conclusions The mid-palatal suture could be opened in patients in different CVM period.More skeletal and less dental effects were found in patients in the growth acceleration and peek group than in those in the growth deceleration group and the inclination of the alveolar bone could be avoided to a greater degree in patients in the growth peek group.