Objective: : To investigate the effects of flapless micro-osteoperforation and corticision on the rate of orthodontic tooth movement in rats. Materials and Methods: : Forty-five 8-week-old male Sprague-Dawley rats were divided into the following groups: micro-osteoperforation and orthodontic force (MOP + F), corticision and orthodontic force (C + F), and orthodontic force only (F, control). The left maxillary first molars were pulled forward with a force of 50 g. Flapless surgical interventions were conducted in the MOP + F and C + F groups. The total duration of the experiment was 6 weeks. Alveolar bone density and the number of osteoclasts were evaluated using microcomputed tomography and histologic examination, respectively. Results: : The tooth movement distance was significantly higher in both experimental groups than in the control group. Bone density and bone mineral density decreased in the MOP + F and C + F groups. The number of osteoclasts in the MOP + F and C + F groups was significantly higher than in the control group F. Conclusion: : The two minimally invasive flapless surgical interventions increased bone remodeling and osteoclast activity and induced faster orthodontic tooth movement for at least 2 weeks in rats. No differences were observed between the outcome of flapless micro-osteoperforation and corticision in the rats.

In this study, botulinum neurotoxin type A (BoTx/A) was injected into the temporalis and masseter muscles of growing rats to induce masticatory hypoactivity. Sixty, 30-day-old, male Long-Evans rats were randomly divided into four groups. BoTx/A was bilaterally injected in the masseter muscles in group I, in the temporalis muscles in group II, and into both the masseter and the temporalis muscles in group III. Group IV served as the control in which saline was bilaterally injected into both muscles. Forty-five days after the injections, the rats were sacrificed. Observation of cortical bone thickness from bone biopsies of the right halves of the mandibles, evaluation of the volume of masseter and temporalis muscles with a plethysmometer, and scanning of bone mineral density (BMD) of the skull and mandibular bone structure with dual-energy X-ray absorptiometry were performed. One-way analysis of variance was employed to analyse measurements of muscle volume, BMD, and cortical bone thickness among the groups. The least square difference was then used to determine significance. Reduced cortical bone thickness and BMD of the skull and mandibular bone structure were observed. The volumes of the temporalis and masseter muscles injected with BoTx/A were smaller. Masticatory hypofunction affects bone structure during development.