Choi Hang-Moon, Han Jin-Woo, Park In-Woo, Baik Jee-Seon, Seo Hyun-Woo, Lee Joo-Hyun, Park Ho-Won
Department of Oral and Maxillofacial Radiology and Research Institute of Oral Science, College of Dentistry, Gangneung-Wonju National University, Gangneung, Korea.
Imaging Sci Dent. 2011 Jun;41(2):63-9. doi: 10.5624/isd.2011.41.2.63. Epub 2011 Jun 23.
The purpose of this study was to evaluate a new technique for localizing impacted mesiodens using its horizontal magnification ratio on panoramic radiographs.
Location-magnification equation of a panoramic equipment was obtained from horizontal magnification ratio of a metal ball which was located variable positions from the center of image layer at interval of 2 mm. Panoramic radiographs were obtained from a skull phantom with a metal ball which was a substitute for impacted mesiodens and was embedded 10mm(Group 1), 15mm(Group 2), and 20mm(Group 3) posterior to the central incisor. Each group obtained 7 panoramic radiographs at variable positions and one periapical radiograph. Three methods were used to estimate the actual width of the incisors and the balls which were used to calculate the magnification ratio. The methods included using the actual incisor width and the calculated ball width (Method 1), using the actual incisor width and the ball widths measured on periapical radiograph (Method 2), and using the incisor and the ball widths measured on periapical radiograph (Method 3). The location of the metal ball was calculated by using the location-magnification equation.
The smallest difference between the calculated and the actual distance was 0.1±0.7 mm in Group 1/Method 3. The largest difference was -4.2±1.6 mm in Group 3/Method 2. In all groups, method 3 was the most accurate.
Quantitative localization of impacted mesiodens is possible by using panoramic radiograph.
本研究的目的是评估一种利用全景X线片上的水平放大率来定位埋伏正中多生牙的新技术。
通过一个金属球的水平放大率来获取全景设备的位置-放大方程，该金属球位于距图像层中心不同位置，间隔为2mm。从一个颅骨模型获取全景X线片，该模型中有一个替代埋伏正中多生牙的金属球，分别埋于中切牙后方10mm（第1组）、15mm（第2组）和20mm（第3组）处。每组在不同位置获取7张全景X线片和1张根尖片。使用三种方法来估计用于计算放大率的切牙和金属球的实际宽度。这些方法包括使用实际切牙宽度和计算出的金属球宽度（方法1）、使用实际切牙宽度和根尖片上测量的金属球宽度（方法2）以及使用根尖片上测量的切牙和金属球宽度（方法3）。通过位置-放大方程计算金属球的位置。
在第1组/方法3中，计算距离与实际距离之间的最小差异为0.1±0.7mm。在第3组/方法2中，最大差异为-4.2±1.6mm。在所有组中，方法3最准确。
利用全景X线片对埋伏正中多生牙进行定量定位是可行的。
