Remote Corticotomy Accelerates Orthodontic Tooth Movement in a Rat Model

Abstract

Introduction: With an increasing demand for orthodontic treatment for adult patients, orthodontic professionals are constantly seeking novel strategies and technologies that can accelerate tooth movement in order to shorten the treatment period. For instance, in recent years, the influences of different surgical techniques on orthodontic tooth movement in the ipsilateral side of surgery were intensively investigated. Here, we attempt to examine if corticotomy could also affect the rate of tooth movement in the contralateral side of the surgery by using a rodent model.

Materials and methods: 72 eight-week-old Sprague-Dawley rats were randomly divided into three groups as follows: the Control group (orthodontic treatment devices delivered only, no tooth movement), the orthodontic tooth movement (OTM) group (orthodontic treatment devices delivered and orthodontic treatment performed), and the Corticotomy + OTM group (remote corticotomy performed, orthodontic treatment devices delivered, followed by orthodontic treatment). The surgical procedure was conducted on the right side of the maxilla at the time of appliance placement and a force of 60 g was applied between the maxillary left first molar and maxillary incisors using nickel-titanium springs to stimulate OTM. The OTM distance and speed were tracked at 3, 7, 14, and 28 days post-surgery, followed by histological and immunohistochemical assessments.

Results: In comparison with orthodontic treatment only, the contralateral corticotomy significantly accelerated OTM. Furthermore, animals undergoing corticotomy + OTM presented with a greater number of osteoclasts on the compression side, stronger staining of the osteogenic marker on the tension side, and higher expression of an inflammatory marker than the OTM group animals.

Conclusion: Our current study demonstrates that remote corticotomy effectively accelerates alveolar bone remodeling and OTM. The study enriches our understanding of the regional acceleratory phenomenon (RAP) and offers an alternative strategy for accelerating OTM to shorten the orthodontic treatment period.

Figure 1

Schematic drawing showing the experiment design for the Corticotomy + OTM group. (a) Occlusal view, L: left, R: right. (b) Right buccal view. (c) Left buccal view, C: compression side, T: tension side. (d) The timeline of experimental performance.

Figure 2

Corticotomy increased the moving rate and distance of the orthodontic teeth on the contralateral side. (a) The distance and (b) speed of orthodontic teeth movement during the 28-day experimental period. N = 6. Two sample t-test was used for statistical analysis. ∗: P < 0.05 when compared with the OTM group; ∗∗: P < 0.005 when compared with the OTM group.

Figure 3

Corticotomy increased Osteocalcin expression in the periodontal tissue on the tension side of the orthodontic teeth. The immunofluorescent staining of osteocalcin (OCN) in the periodontal tissue around the distal surface of the distal buccal root of orthodontic teeth on day 3, day 7, day 14, and day 28. Larger staining positive area was noticed in the Corticotomy + OTM group at day 7, day 14, and day 28 when compared to that in the OTM group. B: alveolar bone; P: periodontal ligament; T: tooth. Scale bar = 100 μm.

Figure 4

Corticotomy increased the osteoclast number in the periodontal tissue on the compression side of the orthodontic teeth. (a) The TRAP staining in the periodontal tissue around the mesial surface of the distal buccal root of orthodontic teeth. Red solid arrows: osteoclasts with TRAP staining. (b) The number of osteoclasts in the periodontal tissue around the mesial surface of the distal buccal root of orthodontic teeth per observation field. N = 6. Mann-Whitney test was used for statistical analysis. ∗: P < 0.05 when compared with the Control group. ∗∗: P < 0.005 when compared with the Control group. #: P < 0.05 when compared with the OTM group.

Figure 5

Corticotomy increased IL6 expression in the periodontal tissue around the orthodontic teeth. The immunofluorescent staining of IL6 in the periodontal tissue around the distal buccal root of orthodontic teeth on day 3, day 7, day 14, and day 28. OTM group has stronger staining intensity when compared to the Control group. The Corticotomy + OTM group has the strongest staining intensity at day 7 when compared to other groups. B: alveolar bone; P: periodontal ligament; T: tooth. Scale bar = 100 μm.