The Three-dimensional CT Clinical Analysis Of Distalizing Dentition As A Whole With Micro-implant Anchorage

[Objective] In this study, micro-implants were used to move the upper and lower whole dentition distal. Three-dimensional CT,3D Imaging Techniques and Mimics software were used to measure the thickness of buccal cortical bone and the quantity of trabecular bone to analyze the relation between micro-implants and adjacent roots and surrouding tissue. The aim of this study was to investigate the security and stability of micro-implants which were used in distalizing dentition as a whole.[Methods] Seven adult with mild and moderate bimaxillary protrusion cases were selected to be treated with straight wire technique after the third molar extracted Four draw hooks were welded on the 0.019×0.025 stainless steel between the canines and lateral incisors. A NiTi coil springs was attached to the micro-implants and draw hook, and 300g force each side was applied to the micro-implants, dragging the upper and lower whole dentition distal movement. Three- dimensional CT was taken before we took out of the micro-implants.The thickness of buccal cortical bone and the quantity of trabecular bone were measured. The SPSS17.0 software was used to analyze.[Result]1.Seven cases had remarkable changes of soft and hard tissue after treatment. 2. Micro-implants:28 micro-implants in seven cases(1)21 micro-implants remained stable during treatment.(2)Total 2 micro-implants in the maxilla and 1 micro-implant in the mandible fell off.(3)The micro-implants in 2 cases (total 4) were inserted into maxillary sinus without obvious clinical symptoms.3.The thickness of buccal cortical bone in posterior area(1)①In the maxillary,the thickness of buccal cortical bone in the distal second molar,between the second molar and the first molar and between the first molar and the second premolar was not significantly different;②In the mandible,The thickness of buccal cortical bone in the distal second molar,between the second molar and the first molar and between the first molar and the second premolar was statistically different;③Both in the maxillary and in the mandible,the higher the height was,the thicker the thickness of buccal cortical bone was.[Conclusion](1) In the same height,the thickness of buccal cortical bone in distal maxillary second molar was the thinnest, the thickness of buccal cortical bone between the maxillary first molar and the maxillary second premolar was the thickest. This is opposite in mandible.(2)It is better to know the distance between micro-implants and adjacent tooth roots and maxillary sinus through three-dimensioned CT.(3)It is improved that the thickness of buccal cortical bone was an important factor affecting the stability of micro-implants by measuring the thickness of buccal cortical bone and observing the stability of micro-implants in the clinic.