コーンビームCT 画像によるインプラント補綴装置歯冠設計と 欠損部顎骨との位置関係についての計測研究

抄録

The positional relationship between implant prosthetic crown designs made by the top-down method were measured on the basis of the remaining teeth and the actual defective part of the jawbone, to establish clinical guidelines for the surgical planning of dental implants and prosthetic therapy.
Cone-beam CT images were used to measure 469 sites in the mouths of 246 Japanese patients (133 males, 113 females;aged 26 to 83) who were diagnosed by CT scans during the period from April 2011 to July 2012. While referring to chair-side diagnosis and model diagnosis, cone-beam CT images were used to design appropriate prosthetic crown contours on the basis of the remaining teeth. In this study, appropriate continuity of the crown contour with the remaining teeth was taken as the criterion. The point of measurement was the center point between adjacent teeth in the curve formed by the row of teeth or the assumed position of the most posterior molar. At the measurement point, MPR images from a cone-beam CT scan that were both orthogonal to the row of teeth and parallel to the axis of the root of the mesial adjacent tooth were used to measure the labial or buccal displacement(mm) as the positional relationship between the position of the prosthetic crown design and the center of the defective part of the jaw.
The prosthetic crown design was positioned to the labial or buccal side of the center of the defective part of the jaw in the upper and lower anterior teeth and mandibular molars, as opposed to on the palatal side in the maxillary premolar area. In some cases, the position of the crown design in the maxillary molar area was the center of the jawbone or toward the palatal side.
In cases where there is insufficient amount of bone at the intended implant site for the prosthetic crown design, a bone transplant can be effective. Moreover, in cases where there is a distance between the planned implant position and the prosthetic position, it is possible to correct the tooth contour with a superstructure and abutment. However, bone transplantation is a highly invasive surgical procedure that often prolongs the treatment period. In addition, excessive over-contouring or angle revision with a superstructure and abutment can cause such problems as a dynamic burden on the implant body, breakage of the abutment or superstructure, or poor hygiene, and should accordingly be avoided.
For successful top-down treatment planning in dental implant therapy, it is imperative that the treatment be planned on the basis of a comprehensive diagnosis that takes into account the ideal crown contour and the anatomical features of the defective part of the jawbone.