Contact damage to root surfaces of premolars touching miniscrews during orthodontic treatment

Our aim in this clinical study was to examine premolar root surfaces after intentional contact with miniscrews.

Ten patients (5 male, 5 female; mean age, 15.8 years; range, 13.5-23.2 years) with 2 maxillary first premolars to be extracted as part of their orthodontic treatment participated in the study. Two miniscrews were placed in each patient, and the first premolar roots were tipped into contact with the miniscrews by using tipping springs with a standardized force. Half of the experimental teeth were kept in contact with the screws for 4 weeks (mild resorption) and the other half for 8 weeks (severe resorption). In 5 patients, the screws were removed, and, in the remaining 5, the springs were removed to allow the roots to move back. The roots were allowed to recover for 4 or 8 weeks before extraction. Two premolars with accidental direct contact were used as controls. All teeth were prepared, coated, and examined with scanning electron microscopy.

In the control group, the periodontal ligament was removed and the dentin surface denuded. The experimental groups showed signs of resorption with structural surface irregularities. However, no apparent denuded dentin surfaces were seen. Although some resorption lacunae were still discernible at 8 weeks, the collagen fibers fully covered the affected areas. The immature fiber organization in the deepest crater represented the ongoing process of fiber reorganization, compared with the fully matured surface areas surrounding the crater.

The results indicate that root surfaces that touch miniscrews show swift repair and almost complete healing within a few weeks after removal of the screw or the orthodontic force. These findings are based on 10 patients only; verification in a larger study sample is needed.