The Assessment Of Dental Implant Site On Panoramic Radiographs

Purpose: The success of dental implant restorations is, in part, dependent on adequate diagnostic information about bony structures of the oral region. Although regarded as a standard radiographic examination for preoperative assessment of an implant site, the use of panoramic radiography as an evaluation tool is still a matter of debate. The aim of this study was to quantify the vertical and horizontal distortion in panoramic radiographs in various implant regions of the jaws and thus to assess the dental implant site. Materials and Methods: Part one: Five implants with same length were placed in alveolar sockets of two human cadavers, in vitro. When implants were installed in the incisor and premolar and molar region of the jaws respectively, the specimens were taken radiographs at three different positions by moving the specimens anterior and posterior on the base of routine position. For each image, the length and diameter of each implant were measured. Part two: 47 panoramic images, 54 implants of 32 patients were selected from 137 images of 62 patients who had accepted dental implants. Using a software program and measure tool, the length and diameter of each implant were measured by three observers. Results: It was found that the images of implants were enlarged or lessened in the two human cadavers. The mean ratios ofhorizontal and vertical distortion of panoramic radiographs were -16.4% and 14.6%, -7.1% and 15.8%, -4.2% and 17.9% in the incisor and premolar and molar region, respectively. In all regions, the horizontal and vertical distortion altered with moving the specimen to different position, but the change of the horizontal distortion was more severe. When changed the position to a large degree, the images displayed obviously different distortions in different regions even the same dimension of implants involved. In clinical patients, the mean ratios of horizontal and vertical distortion of panoramic radiographs were 25.7% and 27.0%, 16.2% and 23.8%, 17.7% and 27.3% in the incisor and premolar and molar region, respectively. The ratio of horizontal distortion was the largest in incisor region and with a maximum variation of 49%. Statistically significant difference demonstrated that indirectly digital panoramic images exhibited lesser horizontal and vertical distortions as compared to films with 18.21% and 22.09%, respectively. Conclusion: Taking panoramic radiographs before implantation is indispensable for selecting suitable fixture. Distortion of panoramic radiograph easily can occur as a result of patient positional errors or other factors. As far as each individual person is concerned, distortion of panoramic radiograph is not the same in different region. The use of a software program to correct for distortion is more reliable and also very promising.