Effect of x-ray angulation on radiographic periodontal ligament space width

The aim of this study was to set up a model for quantitating a change in radiographic PDL width on variation of x-ray angulation within anticipated clinical limits. Four incisor and 4 molar sites of 6 human skulls were radiographed at varying angulation. Horizontal angulation changes were made over a 12 degrees range, in 3 degrees increments. Vertical angulation change was in one 10 degrees increment. Baseline radiographs were taken with the x-ray beam perpendicular to a buccal tooth surface in a horizontal direction and perpendicular or 10 degrees off the perpendicular in a vertical direction. The radiographs were converted to digitized images and PDL width measurements made utilizing a mouse-driven computer program. The mean PDL width differences between all possible horizontal and vertical combinations (n = 45) were compared with the mean of those obtained from differences observed in PDL width measurements on replicate baseline radiographs. Mean PDL width differences for incisor locations were statistically different from the mean baseline PDL width difference; posterior PDL width difference showed no statistical variation from the mean baseline PDL width difference. For radiographs taken within the range expected under clinical conditions, a significant change in PDL width may be observed in incisor locations. Posterior sites may not exhibit this significant change due to the anatomy of the region which may reduce the clarity of the radiographic image.