Effect Of Herbst Appliance On The Position Of Posterior Teeth Of Class Ⅱ Malocclusion With Scissors Bite

Objective:Analyzing and comparing three-dimensional position changes of the posterior teeth in patients who were treated with the Herbst appliance with Class II malocclusion characterized by posterior scissors bite in order to provide references for evaluating the clinical curative effect.Methods:The study selected 12 patients(male 7,female 5)with the average age of 12.6 years with Class II malocclusion characterized by posterior scissors bite.All patients were treated with Herbst appliance for 6-8 months.Cone-beam computed tomography(CBCT)images were taken two weeks before treatment(T1)and after treatment(T2).Imported the scan image into Mimics 17.0 software for three-dimensional reconstruction.After correcting the head position,determined the measurement markers and reference planes in the multi-plane reorganization view and measured the relevant parameters of maxillary and mandibular posterior teeth in the vertical,buccolingual and mesiodistal direction.The measured values were analyzed by SPSS 17.0.Results:Compared to pretreatment,the three-dimensional position changes of the scissors bite teeth are as following.1.Distance changes:In the vertical direction,the maxillary posterior teeth with scissors bite were intruded,the mandibular posterior teeth with scissors bite were extruded,the differences were statistically significant(P<0.05);otherwise,the overbite of posterior teeth with scissors bite is reduced,the differences were statistically significant(P<0.05).In the buccolingual direction,the buccal cusp of the maxillary posterior teeth with scissors bite were buccal moved slightly,the differences were statistically significant(P<0.05);and there was no statistical difference in the change of buccal position of the mandibular posterior teeth with scissors bite(P>0.05).In the mesiodistal direction,the maxillary posterior teeth with scissors bite moved distally and the mandibular posterior teeth with scissors bite moved mesially,the differences were statistically significant(P<0.05).Point A were mesical moved slightly while Point B remove were mesical moved obviously,the differences were statistically significant(P<0.05).2.Inclination changes:In the buccolingual direction,the buccal inclination of the maxillary posterior teeth with scissors bite were increased slightly,the differences were statistically significant(P<0.05).Otherwise,there was no statistical difference in the change of the buccolingual inclination of the mandibular posterior teeth with scissors bite(P>0.05).In the mesiodistal direction,although both the distal inclination of the maxillary posterior teeth and the mesial inclination of the mandibular posterior teeth with scissors bite were increased slightly,there was no statistical difference(P>0.05).3.After the treatment,the horizontal distance between the buccal cusp of the maxillary posterior teeth with scissors bite and the buccal salient point of the corresponding mandibular posterior teeth were reduced,the differences were statistically significant(P<0.05).Conclusion:After Herbst appliance treatment,the overbite of the posterior scissor bite was disengaged to an extent in the vertical direction,and the overjet of the posterior scissor bite was decreased to an extent in the horizontal direction,which were conducive to further correction of the scissor bite.