Local orthodontic force initiates widespread remodelling of the maxillary alveolar bone

Xinyi Gong,Xiangru Huang,Qinggang Dai,Siru Zhou,Lingyong Jiang,Yiling Yang

doi:10.21307/aoj-2020-020

Xinyi Gong, Xiangru Huang + Show 4 more

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https://doi.org/10.21307/aoj-2020-020

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Abstract

Abstract Objectives To clarify the effects of a local orthodontic force on alveolar bone by analysing bone remodelling in different regions of the maxilla during orthodontic tooth movement (OTM). Methods An OTM model was established in rats. Histological changes in the maxilla were analysed using TRAP staining, IHC staining for CTSK and haematoxylin and eosin (H and E) staining. The root bifurcation region of the alveolar bone of the first (M1), second (M2) and third (M3) molars were selected as the regions of interest (ROIs), which were further divided into a cervical and an apical level. Sequential fluorochrome labelling was performed to analyse bone deposition rates. Results The maxillary left first molars were moved mesially. TRAP staining and IHC staining for CTSK showed orthodontic force increased osteoclast numbers in all six ROIs at both the cervical and apical levels. H and E staining indicated elevated osteoblast numbers in the OTM group in all induced regions. Sequential fluorochrome labelling exhibited increased bone deposition rates around M1, M2 and M3 in the OTM group. Conclusions An orthodontic force applied to the first molar could initiate widespread remodelling of the maxillary alveolar bone, which was not restricted to the tension and pressure sites. This may revise the orthodontic biomechanical theory and provide new insights for clinical work.

Highlights

Changes in bone resorption during orthodontic tooth movement (OTM) were determined by tartrate-resistant acid phosphatase (TRAP) staining and IHC staining of CTSK
IHC staining of CTSK indicated an increased number of osteoclasts in the cervical and apical level of the alveolar bone of M1 during OTM (Figure 3A–G, p < 0.05)
The results demonstrated that in the regions of interest (ROIs) of M2 and M3, the number of osteoclasts in the OTM group increased when compared with the corresponding control group and the day 0 group at both the cervical and apical levels (Figure 2 and 3, p < 0.05)

Summary

Introduction

Biomechanical alveolar bone remodelling induced by an orthodontic force lays the physiological foundation for orthodontic treatment.[1,2] Previous studies have revealed the effects of orthodontic stress in the periodontal ligament (PDL)[3,4] or on the alveolar bone surrounding a moving tooth.[5,6] Most of the previous studies have focused on local alveolar bone remodelling associated with the loaded tooth during OTM, indicating bone resorption at the compression site and deposition at the tension site.[7,8,9] the bone around the tooth roots is only a small percentage of the total alveolar bone and whether all of the According to Wolff ’s law, established in 1892, mechanical loading is crucial to maintaining the internal architecture and the external form of bone in living beings.[10] Bone is able to remodel itself under mechanical stress, while loading reduction could break the balance of remodelling and induce bone metabolic diseases such as osteoporosis.[11,12] Astronauts, without skeletal loading, exhibit more than a 10% decrease in bone mineral density and suffer a higher risk of osteoporosis.[13,14] In vivo studies have suggested that skeletal unloading in mice, by tail suspension, Australasian Orthodontic Journal Volume 36 No 2 November 2020

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