Comparative assessment of mouse models for experimental orthodontic tooth movement

Christian Kirschneck,Joshua Gubernator,Agnes Schröder,Maria Bauer,Peter Proff

doi:10.1038/s41598-020-69030-x

Abstract

Animal experiments are essential for the elucidation of biological-cellular mechanisms in the context of orthodontic tooth movement (OTM). So far, however, no studies comparatively assess available mouse models regarding their suitability. OTM of first upper molars was induced in C57BL/6 mice either via an elastic band or a NiTi coil spring for three, seven or 12 days. We assessed appliance survival rate, OTM and periodontal bone loss (µCT), root resorptions, osteoclastogenesis (TRAP+ area) and local expression of OTM-related genes (RT-qPCR). Seven days after the elastic bands were inserted, 87% were still in situ, but only 27% after 12 days. Survival rate for the NiTi coil springs was 100% throughout, but 8.9% of the animals did not survive. Both methods induced significant OTM, which was highest after 12 (NiTi spring) and 7 days (band), with a corresponding increase in local gene expression of OTM-related genes and osteoclastogenesis. Periodontal bone loss and root resorptions were not induced at a relevant extent by neither of the two procedures within the experimental periods. To induce reliable OTM in mice beyond 7 days, a NiTi coil spring is the method of choice. The elastic band method is recommended only for short-term yes/no-questions regarding OTM.

Highlights

The mouse model has the advantage over the rat model that there are a large number of genetically modified mice available, which makes it possible to investigate genetic influences on orthodontic tooth movement (OTM)
Due to the renewed expansion of the compressed elastic band, there is a considerable force acting on the adjacent teeth, which causes them to diverge in a reciprocal manner and leads to an experimental tooth movement of the first upper molar in anterior direction
Our results show that variability of the OTM induced is much higher with the elastic band method than with the NiTi coil spring method, which is probably related to the increased loss of the elastic bands within the experimental periods of seven and 12 days

Summary

Introduction

The mouse model has the advantage over the rat model that there are a large number of genetically modified mice available, which makes it possible to investigate genetic influences on OTM. The second method uses an elastic band placed in the interdental space between the first and second upper molar as described by Waldo and R othblatt[13]. There are no studies that examined these two methods in comparison regarding their suitability and validity for inducing experimental orthodontic tooth movement as well as appropriate time intervals. For this reason, this study deals with the establishment, validation and comparative assessment of these two regularly used methods and associated time intervals for inducing OTM in mice

Methods

Results

Discussion

Conclusion