環口放射線攝影在牙科植體術前對下顎骨齒槽骨高度評估的準確性

Accuracy of Panoramic Radiography in Estimating Mandibular Ridge Height Before Dental Implantation

評估環口放射線攝影於牙科植體手術前量測下顎骨高度的準確性，本研究對象為臺大醫院牙科部2000年3月至2000年9月期間，連續30位考慮接受下顎骨植牙之病人。手術前，病人口腔戴著手術定位板，在上述位置接受環口放射線攝影及口腔顎面多功能斷層放射線攝影檢查。由於口腔顎面多功能斷層放射線攝影擷取下顎骨切面及矢狀放射線影像，因此順著手術定位板的長軸分別測量從齒槽骨脊至下顎神經管最上緣之高度，以口腔顎面多功能斷層攝影所量測的長度當標準值，並評估由環口放射線攝影機器所測高度的差異性。環口放射線攝影的放大率變化範圍在23%至62%之間（平均值37.4%，標準差8.8%），與斷層攝影機器放大率26%有統計上明顯差異（p<0.001）。而且在相同的位置（例如：#47），環口放射線攝影亦會有不同的放大率，其變化範圍在28%至43%之間。此研究結果顯示環口放射線攝影法所測得的三十位病人下顎齒槽骨平均垂直放大率大於斷層攝影機器，且同一部位放大率因案例而異，以此方式估算之下顎骨高度若鄫用於需精確量測下顎骨高度之牙科植體手術時需注意此限制。

To evaluate the accuracy of ridge height estimation of posterior mandible from panoramic radiography before dental implant placement placement. Thirty patients were included in the study. These patients received dental implant treatment at the National Taiwan University Hsopital (NTUH) between March and September of 2000. Panoramic radiography and cross-sectional and sagittal hypocycloidal tomography were performed on each patient with surgical stent in place. With the fixed magnification in the hypocycloidal tomography, the ridge height at the implant sites of posterior mandible can be measured with tomography as a standard to evaluate the magnification of panoramic radiography at the same sites. Accuracy of estimating ridge height, calculated according to the literature on panoramic radiography was also evaluated. The vertical magnification factor of the panoramic radiography range from 23% to 62% (mean: 37.4%, standard deviation:8.8%) which was significantly larger than 26% in tomography. In panoramic radiography, different vertical magnification (28% to 43%) could be observed at similar sites (e.g. #47) of the mandible. The ridge height estimated on the panoramic radiography was larger than the true ridge height. The magnification factor of panoramic radiography varied from case to case. Therefore, clinicians should be very careful in judging the ridge height of mandible from panoramic radiography when accuracy is required during implantation.