Comparison of Panoramic and Cone Beam CT Radiography in the Assessment of Root Angulation

ABSTRACTOBJECTIVE: Traditionally, panoramic radiographs have been used to evaluate mesiodistal tooth angulation; however, with the development of 3-D CBCT technology, perhaps a better measurement of tooth angulation can be obtained. The purposes of this study were to: 1). Compare the mesiodistal tooth angulations determined from a typodont (gold standard) with measurements of tooth angulations from panoramic and CBCT radiographs. 2). Compare the differences in the quantity, location, and direction of mesiodistal bracket repositioning by CBCT and panoramic assessment by the same orthodontic examiner and between different examiners. 3). Assess which method of root assessment (CBCT or panoramic) examiners felt more confident using to diagnose root position.METHODS: A typodont with radiographic markings of each tooth's long axis was used as the gold standard. The root angulation measurements were compared to measurements from panoramic and CBCT images. Twenty-five consecutive subjects had a panoramic radiograph and CBCT scan taken on the same day. All 56 images (panoramic or CBCT) were randomized and evaluated by ten orthodontic examiners to identity each tooth they felt needed to be repositioned in order to obtain parallel roots. A questionnaire was given at the end of the study to rate their confidence level in using each method to assess root positioning.RESULTS: Compared to the typodont gold standard, the CBCT produced more accurate measurements of root angulation than the panoramic image (P<0.05). The two different radiographic methods provided a different assessment in the quantity, location, and direction of bracket repositioning. The teeth with the most disagreement between the two methods were the maxillary second premolar, canine, lateral incisor, and the mandibular first premolar. The panoramic image tends to over-report the maxillary lateral incisors and canines to need distal root tip, and under-report the maxillary premolars and mandibular 1st premolars to need distal root tip. In general, examiners felt more confident using CBCT to diagnose root position.CONCLUSION: The CBCT data provided a more accurate representation of mesiodistal tooth angulation when compared to the panoramic radiograph. Using a panoramic radiograph to evaluate root position is inaccurate and will cause the examiner to reposition the wrong teeth