The Study On The Insertion Angle Of Miniscrews At The Infrazygomatic Crest

Objective:In this study,we measured the bone width at the implant site below the infrazygomatic crest and the three-dimensional insertion angle of a miniscrew in the infrazygomatic crest.This study was conducted to provide a more reliable guide for clinicians to select a suitable direction for miniscrew placement in the infrazygomatic crest.Materials and Methods:Our sample consisted of CT images from 9 women and 9 men aged from 19 to 30 years.Helical CT images were examined,and the CT data was imported into the Mimics10.01 software.The three-dimensional models were reconstructed in the software.Select the interested section at the infrazygomatic crest and then measured as follows:Part 1:measured the bone width at the implant site between the cortical bone surface and the first molar roots from 2 to 8mm below the alveolar crest at 2 mm intervals;Part 2:meassured the routine insertion angles to the sagittal plane and horizontal plane respectively when the miniscrew with the 6mm effective lenghth was inserted at 4mm,6mm,8mm level from the alveolar crest at the mesiobuccal root of the maxillary first molar.All data analyses were carried out using SAS 9.1 to measure the means and standard deviation。Results:Part 1:The bone width at 2mm,4mm,6mm,8mm level from the alveolar crest at the mesiobuccal root was2.34±0.57mm,2.37±0.47mm,2.51±0.46mm,2.68±0.54mm respectively;at the middle point of two buccal roots was2.64±0.57mm,2.76±0.42mm, 2.66±0.40mm,2.88±0.67mm respectively;at the distobuccal root was.2.81±0.60mm, 2.92±0.51mm,2.72±0.50mm,2.84±0.68mm respectively;The bone width was greater at the higher level from the alveolar crest.The bone width at the distobuccal root was greater than the mesiobuccal root and the middle point at the 2mm,4mm and 6mm level from the alveolar crest.Part 2:The insertion angle to the sagittal plane and to the horizontal plane was 17.9±9.6°,23.8±16.4°respectively,and the the angle rang to the sagittal plane and to the horizontal plane was 12.8±7.9°,38.5±22.1°respectively when the implant site was at the 4mm from the alveolar crest at the mesiobuccal root of the maxillary first molar;the angle to the sagittal plane and to the horizontal plane was 24.7±10.5°,26.7±15.2°respectively,and the angle rang to the sagittal plane and to the horizontal plane was 9.5±7.5°,42.2±11.9°respectively when the implant site was at the 6mm level;the angle to the the sagittal plane and to the horizontal plane was 18±11.5°,13.8±11.8°respectively,and the angle rang to the sagittal plane and to the horizontal plane was 11.0±6.8°,37.4±17.0°respectively when the implant site was at the 8mm level.The angle either to the sagittal plane or the horizontal plane was biggest at the 6mm level from the alveolar crest.Conclusion:Part 1:The implant site was possible at 4mm,6mm,8mm level from the alveolar crest at the mesiobuccal root and the middle position between the two buccal roots of the maxillary first molar.Part 2:1.The insertion angles and the angle rangs were different when the implant site was at different level from the alveolar crest at the mesiobuccal root of the maxillary first molar. 2.The insertion angle is variable with individual variation,the angle was suitable for some people.It was necessary to assess the bone volume and insertion angle before miniscrew implant.