Department of Oral Surgery, Oral Medicine, Oral and Maxillofacial Radiology, School of Dental Medicine, University of Geneva, Geneva, Switzerland.
Clin Oral Implants Res. 2011 Dec;22(12):1420-5. doi: 10.1111/j.1600-0501.2010.02131.x. Epub 2011 Mar 21.
Panoramic radiographs allow evaluation of the available bone height for implant treatment planning while imparting a low radiation dose. As panoramic radiography produces image distortion, reference objects are required to determine the exact magnification. This study aims to estimate a panoramic unit's vertical magnification factor (MF) by measuring the length of dental implants used as radiopaque reference objects on postoperative panoramic radiographs. We compared our findings to the vertical MF listed by the panoramic unit manufacturer, and studied the reproducibility and accuracy of our measuring method by analyzing the inter- and intraobserver agreements.
Using a digital calliper, we measured the length of 32 implants on 17 postoperative panoramic radiographs taken with a Scanora unit. The implants were 10mm-long standard Straumann implants placed in the posterior segments of mandibles. The MF was calculated by dividing the implant's radiological length by the implant's real length.
The mean calculated vertical MF was 1.27 ± 0.01 (1.245-1.295) and was lower than the manufacturer's MF (1.3). The vertical MF was 1.28 ± 0.01 in the premolar and 1.27 ± 0.01 in the molar regions. There was an excellent intraobserver reliability (0.96 for observer 1; 0.93 for observer 2) and a good interobserver reliability (0.85 at measurement session 1; 0.8 at measurement session 2)
The observed reliability of the MF confirms that a panoramic radiograph can be used for preoperative implant length evaluation in the posterior mandibular segments. MF stability should be verified with other panoramic units. In clinical practice, using the implant length as a reference object on postoperative panoramic radiographs is a simple and effective evaluation method to estimate a panoramic unit's MF.
全景放射影像允许评估可用于种植治疗规划的骨高度，同时提供低辐射剂量。由于全景放射照相术会产生图像失真，因此需要参考物体来确定确切的放大率。本研究旨在通过测量用作术后全景放射照片中的不透射线参考物体的牙科种植体的长度来估计全景单元的垂直放大因子（MF）。我们将我们的发现与全景单元制造商列出的垂直 MF 进行了比较，并通过分析观察者间和观察者内的一致性来研究我们的测量方法的可重复性和准确性。
使用数字卡尺，我们测量了 17 张 Scanora 单位拍摄的术后全景放射照片中 32 个种植体的长度。这些种植体是 10 毫米长的标准 Straumann 种植体，放置在下颌骨的后段。MF 通过将种植体的放射学长度除以种植体的实际长度来计算。
平均计算的垂直 MF 为 1.27 ± 0.01（1.245-1.295），低于制造商的 MF（1.3）。MF 在磨牙区为 1.28 ± 0.01，在前磨牙区为 1.27 ± 0.01。观察者 1 的内观察者可靠性为 0.96，观察者 2 的内观察者可靠性为 0.93，观察者 1 和观察者 2 的间观察者可靠性为 0.85（测量 1 次），观察者 1 和观察者 2 的间观察者可靠性为 0.8（测量 2 次）。
MF 的观察可靠性证实，全景放射照片可用于评估下颌后段的术前种植体长度。应使用其他全景单元验证 MF 的稳定性。在临床实践中，使用术后全景放射照片上的种植体长度作为参考物体是一种简单有效的评估方法，可以估计全景单元的 MF。
