A Conebeam Computed Tomographic Imagestudy On The Anatomical Character Of Maxillary Buccal Area For Mini-implants Insertion

Objective:To study the anatomical character of the maxillary posterior region and to provide guidance for the miniscrew implant.Methods:21juvenile and21adult patients were divided into two groups. A CBCT examination was applied for each sample. Two horizontal planes which were4mm and7mm respectively from the CEJ at the distal-buccal of the maxillary first molar were selected as the study planes. Cortical bone thickness, bone density, narrowest interradicular distances, shortest distance from cortical bone surface to the narrowest interradicular space and distance from implant point to the bottom of the maxillary sinus in30°were measured and analyzed by Paired t test. Result:There were significant differences between adolescents and adults, with adults cortices significantly thicker and cortical bone density significantly higher from mesial to distal. Significantly more narrowest interradicular distances was observed at the buccal region mesial to the first molar than at the distal. Average distance from the surface of the cortical bone to the area of the closest interradicular space was over5mm in the most region. The average distance from drilling point to the bottom of maxillary sinus was8mm in30°insertion angle.Conclusion:A guidelines for safe and stable placement of a mini-implant as follow:mesial or distal to the first molar, the safest length is6mm of thread with a diameter of1.3mm-2mm; the best angulation is30°to the surface of bone. The findings of this study suggest implanting is very prudent when the paient is adolescent because the Cortical bone is thin and bone density is low.