Researchers at the University of Bergen have found that dental invagination is not a risk factor for root resorption during orthodontic treatment.

The study included 91 patients (32 males, 59 females) with a mean age of 13.1 years. Researchers took complete orthodontic records, including periapical radiographs of the maxillary incisors before and after treatment.

According to M. Mavragani and colleagues, 49 patients had at least one maxillary incisor invaginated, while  the remaining 42 patients were free of dental invaginations. Variables recorded for each patient included gender, age, Angle classification, extraction or nonextraction therapy, ANB angle, overjet, overbite, trauma, habits, agenesis, tooth exfoliation, treatment duration, Class II elastics, body-build, general factors, impacted canines, and root form deviation.

Crown and root length of the maxillary incisors were measured on pre- and post-treatment long-cone periapical radiographs corrected for image distortion. The percentage of root shortening and root length loss in millimeters was then calculated. Most of the invaginated teeth were minor type 1.

The results of the study revealed no significant difference in the severity of apical root resorption between invaginated and noninvaginated incisors in patients without dental invaginations, nor was the extent of dental invagination related to the severity of apical root resorption. However, invaginated teeth had malformed roots more often than noninvaginated teeth.

The researchers concluded that dental invagination, and particularly type 1, cannot be considered a risk factor for apical root resorption during orthodontic tooth movement.

[Biotech Business Week, November 27, 2006]