Evaluation of Long-term Stability of Vertical Control in Hyperdivergent Patients Treated with Temporary Anchorage Devices

摘要

This study aims to evaluate,the long-term stability of vertical control in hyperdivergent patients treated with temporary anchorage devices.The sample included 20 hyperdivergent patients without anterior open bite.The temporary anchorage devices were used to intrude the upper incisor and molars for vertical control.Lateral cephalograms were established prior to treatment,immediately after treatment,and during retention. The upper molars and incisors were intruded by 1.33 mm and 1.41 mm after treatment (P<0.05).U6-PP increased by 0.11 mm and 0.23 mm during the first and second stages of retention (P>0.05).U1-PP was found to possess a significant extrusion of 1.2 mm during the first stage (P<0.05),which increased by 0.68 mm during the second stage (P>0.05). The mandibular plane angle (MP-SN)decreased by 2.58 degrees following treatment, and underwent a relapse of 0.51 degree and 0.42 degree during the first and second stages of retention respectively (P>0.05).No significant soft tissue changes occurred,with the exception of increased upper lip length during the second stage (P<0.05).Maxillary anterior and posterior intrusions,counter clockwise rotation,of the mandibular plane,and improved profiles can be successfully achieved following treatment with vertical control. During the first stage of retention (less than three years),intruded molars and incisors both exhibited some extrusion,and molars had better long-term stability than incisors. During the second stage of retention (three to six years),the therapeutic effects appeared stable,with the exception of some increase in upper lip length.Rotated mandibular plane remained stable during the entire retention period.