Evaluation of Transverse, Bodily Tooth Movement and Its Effects on the Surrounding Hard Tissue

Abstract

Orthodontic expansion has been associated with uncontrolled tipping and alveolar bone loss. Recent research evaluating orthodontic expansion has shown osteoblastic activity on the buccal cortical bone apical to the dehiscence. We hypothesize that the negative effects seen during orthodontic expansion is a result of tipping rather than expansion. The aim of the present study was to produce buccal translation, with little or no coronal tipping, and evaluate hard tissue changes of the dental-alveolar complex. A prospective, randomized, split-mouth study was conducted with 11 patients (average age 14.1 years, range 12.5-16.9 years) requiring maxillary first premolar extractions for comprehensive orthodontic treatment. Pre and post-treatment records included models, photographs, and small field of view cone beam computed tomographic images (FOV CBCT) of the right and left maxillae. One maxillary first premolar was randomly chosen and moved to the buccal with 50 grams of force applied approximately at the tooth’s center of resistance. The other premolar served as the control tooth. Forces were re-activated every 3 weeks for approximately 9 weeks of active movement, after which the tooth was held in place for 3 weeks to allow for maturation of the surrounding tissue. Pre and post treatment records were analyzed and superimposed to evaluate changes in the dental-alveolar complex. The results showed significant movement (0.96 mm, p=0.008) of the experimental premolar occurred 3 mm apical to the CEJ. There was minimal buccal tipping (2.2°, p=0.003). Maximum and minimum buccal bone heights decreased 0.60 mm (p=0.003) and 0.25 mm (p=0.262) respectively. The distribution of the maximum bone height measurement was bimodal, with 6 patients showing 0.42 mm (IQR -0.25 mm to 0.52mm) and 5 patients showing 8.3 mm (IQR 7.15 to 10.05) of vertical bone loss. Buccal bone thickness at the midline 3 mm apical to the CEJ decreased 0.63 mm (p=0.016). Based on direct measurements and CBCT superimpositions, buccal bone grew 0.46 mm (p=0.005) and 0.51 mm (p=0.036), respectively. Using light continuous forces, it is possible to produce buccal tooth movement with only limited amounts of tipping. With such movements buccal bone growth occurs, but there are potential limitations