Effect of combined oral contraceptives on orthodontic tooth movement in a female rat model

Jinghong Yu,Tao Zhang,Fiona Firth,Xiaomei Xu,Jialing Lv,Li Mei,Xian Zhao,Yifei Zhou

doi:10.21307/aoj-2020-041

Abstract

Abstract Background To investigate the effect of combined oral contraceptives (COC) on orthodontic tooth movement (OTM) and periodontal remodelling in a female rat model. Methods A total of 80 three-month-old female, Sprague-Dawley rats were randomly divided into experimental and control groups. The maxillary first molars were moved mesially using nickel-titanium coil springs (50 g force). The experimental group (N = 40) ingested 1.5 ml COC (Marvelon, 0.12 mg/d, N.V. Organon, Oss, The Netherlands) daily. The control group (N = 40) ingested 1.5 ml saline (0.9% sodium chloride) daily. After 7, 14, 21 and 28 days of force application, 10 rats in each group were euthanased and a vernier calliper was used to measure the orthodontic movement of the first molar. Root resorption at pressure areas was assessed by H and E staining. Micro-CT was used to detect alveolar bone mineral density. Results and conclusion The amount of OTM in the experimental group (0.46 ± 0.16 mm) was significantly less than in the control group (0.85 ± 0.25 mm; p = 0.003) during the 28 days of observation. There were significantly smaller (p = 0.002) root resorption lacunae in the experimental group (111710 ± 4037 pixels) compared with the control group (204962 ± 21318 pixels) after 28 days. There was no statistically significant difference in the bone mineral density between the experimental and control groups throughout the study period (p > 0.05 at each time point). The short-term administration of COC may retard tooth movement and reduce the level of root resorption during OTM in female rats.

Highlights

Orthodontic tooth movement (OTM), a result of tissue remodelling within the periodontium and alveolar bone, is mediated by a localised inflammatory response.[1]
There were significantly smaller (p = 0.002) root resorption lacunae in the experimental group (111710 ± 4037 pixels) compared with the control group (204962 ± 21318 pixels) after 28 days
The distance of OTM in both groups increased with time during the study, but the amount of OTM in the experimental group was approximately half of that in the control group at each of the assessed time points (0.04 ± 0.04 mm vs. 0.09 ± 0.04 mm on the 7th day, 0.11 ± 0.03 mm vs. 0.20 ± 0.07 mm on the 14th day, 0.32 ± 0.13 mm vs. 0.60 ±0.16 mm on the 21st day; p < 0.05 at each time point; Table I)

Summary

Introduction

Orthodontic tooth movement (OTM), a result of tissue remodelling within the periodontium and alveolar bone, is mediated by a localised inflammatory response.[1] The process of alveolar bone remodelling usually involves resorption of existing bone by osteoclasts in the pressure zone, and bone formation. Sex hormones, such as oestrogen, androgen and progesterone, have been confirmed to have important physiological roles in OTM through their effects on Australasian Orthodontic Journal Volume 35 No 2 November 2019. The short-term administration of COC may retard tooth movement and reduce the level of root resorption during OTM in female rats. (Aust Orthod J 2019; 35: 127-133)

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