EFFECT OF HEAD POSITIONING IN PANORAMIC RADIOGRAPHY ON VERTICAL MEASUREMENTS - AN IN-VITRO STUDY

Objective. To assess whether it is possible to make accurate vertical measurements of the jaws from panoramic radiographs. Methods. Five dry skulls were shifted 5 mm forwards and backwards and tilted 5 degrees up and down in the sagittal plane. Panoramic radiographs of each skull were obtained in nine different positions. In the maxilla, three refe rence lines were used and vertical measurements were made at the dista l surfaces of the first premolar and first molar and in the midline. I n the mandible, measurements were made at the distal surfaces of the f irst premolar and first molar, and at the mental foramen on both sides , and in the midline. The points and lines were marked manually and th e radiographs were digitized, magnified and measured. Results. Sagitta l shifting and tilting had only a slight effect on measurements in the mandible. Sagittal tilting of the head had the greatest effect on all the measurements made from the line between the articular eminences t o the alveolar crest, as well as measurements in the maxillary midline . Conclusions. The line between the articular eminences is unsuitable as a reference line for measurements of the tooth-bearing areas. A sli ght misalignment of the head does not significantly affect the vertica l measurements in the mandible or of the posterior maxilla if the refe rence lines are in the same vertical plane as the teeth.