A Comparison Of Treatment Effect Of Molar Intrusion With Micro-implant In Different Facial Skelectal Types

Objective:The purpose of this study was to evaluate treatment effect of molar intrusion with micro-implant in different facial skeletal types.Methods:This retrospective study including 20 cases from 2007 to 2011. All the cases were divided into three groups:1.high angle group including patients whose SN-MP angle was larger than 38°; 2. average angle group including patients whose SN-MP angle was between 29°to 38°; 3.low angle group including patients whose SN-MP angle was lower than 29°.All the patients received molar intrusion with mocro-implant.Descriptive data of the cephalometric analysis was obtained with Win Cehp 8.0 software and Adobe Photoshop CS5. Measurements including SNA,SAB,ANB,NP-FH,NA-PA,MP-SN,MP-FH,PP-SN,PP-MP,Yaix,N-Me,B(x),B(y),A(x),A(y),Ns-Sn-Pos, Z angle,OB,OJ,U1(x),U1(y),UM angle,the amount of molar intruded. The statistical analysis was performed with SPSS 10.0 (SPSS, Chicago, IL).Results:All the molars were successfully intruded. Stacical analysis showed in high angle group, with molar intrusion, the mandible significantly rotated in a counterclockwise direction, and the mean mandibular plane angle tilted from 43.32°to 40.88°. With B and Po relocating upward and forward, patients showed better profile. Such changes were not detected in average group and low angle group. Conclusion:1 Significant molar intrusion did happen with the help of mocro-implant in all three groups.2 Molar intrusion cause mandible rotation in a counterclockwise direction, inducing a reduction in cant of occlusal plane.3 In high angle group, mandible rotated significantly, leading to significant changes in skeleton and soft tissue, which improved patients'profile. Such changes were not detected in average angle group and low angle group, because the amount of rotation was little.4 It's hypothesized that the way of molar intrusion in patients with different facial skeletal type maybe different.