Ability of mini-implant-facilitated micro-osteoperforations to accelerate tooth movement in rats

Abstract

Introduction: Although current techniques for accelerated tooth movement often involve invasive surgical procedures, micro-osteoperforations (MOPs) using mini-implants may facilitate orthodontic tooth movement without raising flaps, reduce surgical risks, and increase patient acceptance. In this study, we evaluated the effectiveness of mini-implant-facilitated MOPs in inducing accelerated tooth movement and investigated the potential risks for root resorption.

Methods: Five MOPs were placed on the left side around the maxillary first molars in 6 rats using an automated mini-implant driver, whereas the right side received no MOPs as the control. Closed-coiled springs were secured from incisors to first molars for orthodontic tooth movement. Tooth movement was measured, and samples underwent radiologic and histologic analyses.

Results: The MOP side exhibited a 1.86-fold increase in the rate of tooth movement with decreased bone density and bone volume around the first molars compared with the control side. Hematoxylin and eosin and tartrate-resistant acid phosphatase analyses showed increased numbers of osteoclasts as well as new bone formation. Three-dimensional volumetric analysis of all 5 roots of the maxillary first molars demonstrated no statistically significant difference in root volumes.

Conclusions: Mini-implant-facilitated MOPs accelerated tooth movement without increased risk for root resorption and therefore may become a readily available and efficient treatment option to shorten orthodontic treatment time with improved patient acceptance.

Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Figures

Fig 1. Illustration of the orthodontic tooth movement animal model

The orthodontic appliance protracts the first maxillary molar using the maxillary incisor as an anchor on both sides, while micro-osteoperforations (red dots) are placed around the first maxillary molar only left side using commercially available orthodontic mini-implants. A closed coil spring provides consistent orthodontic force (red arrows). A) Palatal view. B) Lingual view

Fig 2. Comparison of the rate of tooth movement

Tooth movement was significantly greater on the micro-osteoperforation side compared to the control side. MOP, micro-osteoperforation; **p

Fig 3. MicroCT analysis of bone quality comparison

Axial A) and Coronal B) of images of microCT scan showed osteopenia with decreased bone volume and bone density around the maxillary first molar on the micro-osteoperforation side compared to the control side in all animals. C) Quantification of bone fraction (BV/TV) D) Quantification of bone mineral density (BMD). MOP, micro-osteoperforation;.**p<0.05.

Fig 4. Evaluation of root resorption and bone loss

A) Histomorphometric analysis with H&E showed more bone loss (yellow box A) and root resorption (yellow box B) in the micro-osteoperforation side compared to the control side. Increased number of osteoclasts (white arrow) were detected on the micro-osteoperforation side. B) MicroCT volumetric analysis of all five roots of maxillary first molar showed no significant difference in root volume between the two groups. MOP, micro-osteoperforation.

Fig 5. Evaluation of TRAP+ osteoclasts

Greater numbers of osteoclasts were found on the micro-osteoperforation pressure side: A) TRAP staining of the mesial root apex showed osteoclasts on the pressure side, where catabolic activity was taking place. B) The mean number of osteoclasts for the micro-osteoperforation and control side was obtained for each rat. MOP, micro-osteoperforation.

Fig 6. Evaluation of new bone formation

More new bone formation on the micro-osteoperforation side bone: A) Mature and organized lamella bone predominated in the control side. Dark blue lines (black arrows) in the micro-osteoperforation side represent new or woven bone, indicative of increased bone metabolic activity. B) Quantification of new bone formation showed more bone formation in the micro-osteoperforation side. MOP, micro-osteoperforation. **p<0.05