Curative Effect Analysis Of Mini-implant Reinforced Anchorage For Adult Patients With Class Ⅱ Division1Malocclusion

Objective:To compare the clinical efficiency of mini-implant anchorage and traditional anchorage in patients with Class II Division1malocclusion and to estimate the efficacy of mini-implant anchorage in orthodontic treatment.Methods:This is a retrospective review of twenty-five adult patients with Angle Class II malocclusion Division1undergonging orthodontic treatment by retracting the maxillary anterior teeth by using the extraction space of the bilateral maxillary first premolars. MBT preadjusted appliance and sliding mechanics for en masse retraction of the anterior teeth was used. Two anchorage systems were preformed. group A (n=13) received mini-implants for bony anchorage. Group B (n=12) received traditional molars anchorage preparation. Pretreatment and posttreatment lateral cephalograms were superimposed to compare the following parameters between groups:(1)the convexity of jaws (2) amount of maxillary central incisor retraction and reduction in maxillary central incisor angulation,(3) changes in soft tissues. Paired t tests and Student’s t-tests were performed to determine skeletal, dental and soft tissue changes during treatment.Results:(1) Changes in jaw:SNA diminished slightly before and after treatment in group A and B, while GoGn-SN and OP-SN increased. In group A, SNA has significant difference during treatment. According the OP-SN changes in group B, the increase of3.41°has a significant difference compared with group A.(2) Changes in teeth:All the measuremnts have positive changes except U6-Ptm, which occured undesired forward in both groups. U1-NA、U1-facial and U1-APg have significant statistical differences in intra-group comparison (p<0.05) while U1-APg only has statistical significance in inter-group comparisons. In group B, U6-Ptm has significant difference before and after treatment(p<0.05). (3) Changes in soft tissue:Siginificant upper and lower lips retraction was achieved in both groups, and Z angle show significant difference between two groups.(4)The treatment period is shorter in mini-implants anchorage group(p<0.05)。Conclusion:(1)In Class II Division1adult patients, the employ of mini-implants anchorage and traditional molar anchorage would retract siginificantly the maxillary incisors and upper lip. While have little effect on skeletal correction.(2) Compared with conventional anchorage, mini-implant anchorage achieved better results in the treatment of maxillary dentoalveolar protrusion and can lead to shorter treatment time. Greater retraction of the maxillary incisor and upper lip all facilitated the correction of the Class Ⅱ malocclusion.