Radiographic assessment of impacted maxillary canine position using CBCT: A comparative study of 2 methods

Objectives: The aim of this study was to compare and evaluate the guidelines proposed by Counihan et al 2013 and the KPG index method for assessment of maxillary impacted canine position using CBCT images from a radiographic point of view.
Subjects & methods: Thirty-six CBCT scans of 36 patients (6 males and 30 females), with a total number of 45 impacted maxillary canines, were recruited from the database of the Oral and Maxillofacial Radiology Department, Faculty of Dentistry, Cairo University. KPG index, for each impacted canine, was calculated by giving both its cusp and root tips a score on a 0–5 scale along the x, y, and z planes. The summation of these six scores would predict the treatment difficulty, classified as easy (0–9), moderate (10–14), difficult (15–19), and extremely difficult (20 and above). Moreover, Counihan et al 2013 guidelines were applied on each studied impacted tooth in which the tooth position in four categories was considered: overlap with adjacent incisor, vertical height, angulation to midline and position of root apex. For each category, either good, average or poor prognostic outcome was selected. Data were collected and statistically analyzed.
Results Upon comparing both studied methods of radiographic assessment of impacted maxillary canines, a statistically significant difference was found: KPG index categorized more cases (9 cases) as easy (20%) while Counihan et al guidelines categorized only 2 cases (4.4%) as having good prognosis. Similarly, KPG index categorized more cases (15 cases) as moderate (33.3%) while Counihan et al guidelines categorized 13 cases (28.9%) as having average prognosis. On the other hand, Counihan et al guidelines categorized more cases (30 cases) as poor prognosis (66.7%) while KPG index categorized only 21 cases (46.7%) as being difficult. Nonetheless, on comparing the treatment difficulty and prognosis of impacted maxillary canines found on the right and left sides, unilaterally or bilaterally, in males and females, a non-statistically significant difference was found using both methods of radiographic assessment.
Conclusion From a radiographic point of view, the KPG index, with some minute modifications, has demonstrated to be an effective and competent method for classification of maxillary impacted canine’s treatment difficulty in accordance to their position, as compared to the guidelines proposed by Counihan et al at 2013.