Therapy Effects Analysis Of Early Skeletal Class Ⅲ Malocclusion Using Skeletal Anchorage Combined With Hybrid-Hyrax-Facemask

Objective Class Ⅲ malocclusion of the anterior crossbite is a developmental deformity,which is strongly linked to the growth and development of children.Its pathogenesis may be caused by maxillary hypoplasia、mandibular prognathism or both.For Class Ⅲmalocclusion with maxillary hypoplasia,the ideal treatment approach is to stimulate the growth of the maxilla,so as to achieve the purpose of correcting the malrelationship between the maxilla and mandible.However,the traditional tooth-borne maxillary protraction appliances often show some problems such as insufficient skeletal effects and obvious dental compensations.This study used two miniscrews as skeletal anchorage in the anterior palate combined with the maxillary protraction appliance to promote more skeletal effects and reduce adverse dental effects.To further explore the effects of the two treatments on bones and teeth by comparing the therapeutic effects with Hybrid-HyraxFacemask(FM)versus miniscrews in the anterior palate combined with Hybrid-HyraxFacemask(MIS/FM)for young patients with Class Ⅲ malocclusions and maxillary deficiencies in mixed dentition and early permanent dentition.Methods Eighteen skeletal Class Ⅲ malocclusion patients with maxillary deficiency in mixed dentition and early permanent dentition who visited the Stomatological Hospital of Anhui Medical University from January 2020 to January 2022 were selected,including 10 males and 8 females.Eighteen young patients were randomly divided into two groups:one group was treated with Hybrid-Hyrax-Facemask,and the other group was treated with miniscrews in the anterior palate combined with Hybrid-Hyrax-Facemask.To correct skeletal Class Ⅲ malocclusion,the Alternating Rapid Maxillary Expansion andConstriction(Alt-RAMEC)protocol was used in both groups and combined with a 400g maxillary protraction force applied on bilateral of all patients in a downward and forward direction of 30° to the occlusal plane.All patients were evaluated at the stage when the Class Ⅲ malocclusion was completely corrected and the Overjet reached 1 to 2 mm,after continuing to maintain maxillary protraction for three months.Iortho cephalometric software was used to overlap the lateral cephalograms of the two groups before and after treatment and analyze the changes in cephalometric indexes before and after treatment.And the measured relevant data were statistically analyzed.Results 1.The mean orthodontic time was 8.44±4.19 months for the FM group and 7.17±2.22 months for the MSI/FM group,with shorter mean orthodontic time for patients in the MSI/FM group.2.Comparison of the FM group before(T0)and after treatment(T1)showed a significant increase in midfacial length(Co-A),and mandibular length(Co-Gn)(P<0.05,P<0.01),and the differences were statistically significant.The MSI/FM group showed a significant increase in Co-A(P<0.01),and a significant decrease in combined maxillary and mandibular length difference(Co-Gn-Co-A)(P<0.05)in T0 and T1 comparisons,and the differences were statistically significant.The results showed that compared to the FM group,the MSI/FM group had more pronounced maxillary forward growth and significantly improved the sagittal malrelationship between the maxilla and mandible.3.The FM group showed a statistically significant increase in Wits appraisal and mandibular plane angle(MP-SN)in T0 and T1 comparisons(P<0.05,P<0.05).Comparison between T0 and T1 in the MSI/FM group showed a statistically significant increase in Wits appraisal,MP-SN,and Y-axis angle(Y-Axis)(P<0.01,P<0.05,P<0.01).It was suggested that the mandibular growth direction improved significantly in the MSI/FM group,and different degrees of downward and backward directional rotation of the mandible occurred in both groups.4.The FM group showed a significant increase in the angle between the long axis of upper central incisor and anterior cranial base plane(U1-SN),Overjet,and upper labial protuberance distance(UL-EP)(P<0.01,P<0.01,P<0.01)and a significant increase in the upper and lower central incisor angles(U1-L1)significantly decreased(P<0.01),and the differences were statistically significant.Comparison between T0 and T1 in the MSI/FM group showed a statistically significant increase in U1-SN,Overjet,and UL-EP(P<0.05,P<0.01,P<0.01)and a statistically significant decrease in U1-L1(P<0.05).The results showed that the facial profile and occlusion were significantly improved in both groups after orthodontic treatment.Compared to the FM group,the compensatory lip inclination of anterior teeth was reduced in the MSI/FM group.Conclusion For early skeletal Class Ⅲ malocclusion patients with maxillary deficiency,the Hyrax of dental anchorage or skeletal anchorage combined with Alt-RAMEC protocol and a maxillary protraction force both had marked effects.Compared with the FM group,the MSI/FM group had shorter mean treatment time,significant skeletal effects,and reduced dental compensations,including obvious forward growth of the midface,definite improvements in the growth direction of the mandible,and reduced compensatory lip inclination of anterior teeth.