Forsberg J, Halse A
Department of Oral Radiology, School of Dentistry, University of Bergen, Norway.
Int Endod J. 1994 May;27(3):133-8. doi: 10.1111/j.1365-2591.1994.tb00242.x.
Sixty apical areas of single-rooted teeth were examined in this study. A simulated periapical lesion was produced using an acrylic sphere (diameter 2.0 mm), the surface of which was covered with a thin layer of zinc cement. The sphere was placed in close contact with the apical foramen using a thin orthodontic wire inserted into the apical portion of the root canal. The correctly adjusted parallel projection depicted the simulated lesion with a very low degree of error. Overangulation of the central beam with maintenance of parallelism between tooth and film resulted in a moderate degree of magnification. When correctly adjusted, the bisecting-angle technique produced images with almost the same accuracy as the paralleling technique. Over-angulation resulted in most images showing a reduced size of the simulated lesion. Moderate under-angulation most often recorded the correct dimension of the globe. In some cases a magnified image of the sphere was produced. Generally, this was associated with a palatally curved root. The investigation thus clearly indicated that the paralleling technique provides the most reliable information about the extent of a pathological process.
本研究检查了60颗单根牙的根尖区域。使用一个丙烯酸球（直径2.0毫米）制作模拟根尖周病变，其表面覆盖有一层薄的锌粘固剂。通过插入根管根尖部分的细正畸钢丝将球放置在与根尖孔紧密接触的位置。正确调整的平行投照以非常低的误差程度描绘了模拟病变。在保持牙齿与胶片平行的情况下，中心束过度成角会导致中等程度的放大。正确调整时，平分角技术产生的图像与平行技术几乎具有相同的准确性。过度成角导致大多数图像显示模拟病变尺寸减小。适度的角度不足最常记录球体的正确尺寸。在某些情况下会产生球体的放大图像。一般来说，这与腭侧弯曲的牙根有关。因此，该研究清楚地表明，平行技术提供了关于病理过程范围的最可靠信息。
