Journal of Research in Dental and Maxillofacial Sciences (Jun 2016)
Effect of Head Misalignment in Horizontal & Vertical Dimensions on the Magnification Rate of Digital Panoramic Radiography in Different Parts of the Jaws
Abstract
Background and aim: Considering the widespread development of implants in dental treatment plans, linear measurements on panoramic radiography are of especial importance. In the present study we investigated the effect of head misalignment up to 15° around vertical and horizontal axes on the magnification rate of digital panoramic radiography in each part of upper and lower jaws. Materials and methods: In this in vitro experimental study, five edentulous human skulls were used. Steel globes with 4mm diameter were placed inside each dental socket. Each skull was exposed twice at standard panoramic position and at 5, 10 and 15° upward, downward, left and right deviated positions with NewTom GIANO radiographic system with the least amount of kVp and mAs. All 50 images were saved in true size and the maximum horizontal and vertical diameter of each globe was measured by an oral and maxillofacial radiologist using linear measurement software. Data were statistically analyzed by Chi- square and ANOVA tests. Results: At standard panoramic position, linear measurements in both horizontal and vertical dimensions showed magnification and the results indicated 12-13% magnification in vertical dimension in all parts of both jaws. The least rate of horizontal magnification was seen in the molar area of both jaws (6%). (p0.05) Linear measurements in horizontal dimension showed the highest variations especially in the posterior parts of the jaws. (p>0.05) At upward and downward chin rotations, vertical measurements showed magnification rate comparable with that of standard panoramic position while horizontal measurements showed increased magnification at upward rotation and decreased magnification during downward rotation. (p>0.05) Conclusions: Vertical and horizontal linear measurements show magnification at standard panoramic position and also at lateral head rotation around Y-axis and at upward and downward rotations. Furthermore, even at deviations up to 15°, no minimized measurements were recorded in the obtained panoramic radiographs.
