根尖片平行投照定位装置的研制

A positioning device for oral paralleling technique

研究目的：使根尖片的投照标准化，以使根尖片上所显示的牙槽骨骨量的细微变化实现稳定的纵向可比性。材料和方法：设计和制作了根尖片平行投照定位装置，并利用本装置及传统的平行投照装置对颅骨标本不同目标牙分别投照，将获得的两组根尖片（分别为２９对、１４对）投照角度误差以及减影后灰度的标准差进行统计学处理。结果：在平行投照时定位与否，对照片的重复性有着明显差别，采用定位装置可明显提高根尖片图像的可重复性。

Objective: To design a reliable method for standardized parallelling dental projection, for comparison of the tiny variations of alveolar bone during the treatment of the periodontal disease. Methods and Material: Periapical radiographs in 29 pairs of films with this device and 14 pairs of films with traditional method on dried skulls were comparatively analysed by digital subtraction. Standard deviations and angle variations of subtracted image were studied comparatively between this method and traditional paralleling technique. Results: Significant difference of reproducibility between two groups was showed. The reproducibility of the successive pictures was apparently increased when projected with positioning device.