The effects of Herbst two phase treatment on temporomandibular joint position analyzed by CBCT / 实用口腔医学杂志

ABSTRACT

Objective:To assess the effects of Herbst two phase treatment on temporomandibular joint(TMJ) position analyzed by CBCT.Methods:15 patients of permanent dentition with class Ⅱ malocclusion combined with mandibular retrusion were treated by Herbst appliance as the 1st phase,then the 4 1st premolars of each patient were extracted,the fixed appliance of edgewise was applied as the 2nd phase of treatment.CBCT examination was carried out at the following stages2 weeks before Herbst treatment(T1),at the start of the treatment when Herbst appliance was placed(T2),immediately after Herbst appliance was removed(T3) and immediately after the edgewise appliance was removed(T4).The InvivoDental software was used to calculate the joint space of TMJ from the three -dimensional CBCT images.The acquired data were then statistically analyzed.Results:During T1-T2-T3 stages,the anterior joint space was decreased and then increased,superior joint space and posterior joint space were increased and then decreased.During T3-T4 stages,the superior joint space and posterior joint space decreased further,but anterior joint space did not change.No significant difference was found in the anterior joint space,superior joint space and posterior joint space between T1 and T4 stage.Conclusion:At the start of treatment with Herbst appliance,the condyle is displaced in an anterior and inferior direction.At the end of functional treatment,especially the end of two phase treatment,the condyle is drawed back nearly to the original position.