Title of Thesis:
Comparison of the effects of micro-osteoperforations and corticision on the rate of orthodontic tooth movement in rats
Author: Teng-Kai Yang
Thesis directed by: Chi-Yang Tsai, DDS, PhD (Graduate Institute of Oral Science, College of Oral Medicine, Taipei Medical University)
:
In contemporary orthodontic treatment, it takes an average of two years for adult patients to complete. It has been shown that prolonged treatment time raises some risks due to difficulties in maintaining periodontal health. Result in higher caries risk, gingival recession, and more root resorption. In addition to the above mentioned risks, prolonged treatment may be more likely to decrease satisfaction of patients. Therefore, there is a goal to accelerate orthodontic tooth movement in clinical orthodontic practices.
In recent years, accelerated orthodontic tooth movement caused by “regional acceleratory phenomenon (RAP)” after surgical trauma has become a popular issue. It has been suggested there is regional accelerated tooth movement after micro-osteoperforation and corticision.
We aim to compare the two different less invasive approaches in tooth movement acceleration by using movement distance, density changes of alveolar bone, and numbers of osteoclasts as the criteria.
:
In this study, 45 male adult Sprague-Dawley rats were enrolled at 8 weeks of age. On first day, upper left first molars were pulled forward by orthodontic appliance from upper incisor as anchorage in all groups. Surgical interventions were conducted in Group I and II.
The rats were randomly divided into 3 groups: I, II and III
Group I: micro-osteoperforation + orthodontic force
Group II: corticision + orthodontic force
Group III (control): orthodontic force only
The experimental duration was 6 weeks, and distance of tooth movement was observed every week. Half of the rats in all groups were sacrificed on week 3, while the others were sacrificed on week 6. Alveolar bone density and the quantity of osteoclasts were evaluated using microcomputed tomography and histological examination, respectively.
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The distances of tooth movement of the both experiment groups were significantly greater than the control side at T2 (p=0.04). At the final phase of the experiment T6, the total tooth movement was 3.18±0.92mm in MOP + F, and it was 3.11±0.40mm in C + F, while it was 2.80±0.56mm in the control group F. There were no significant differences in weekly tooth movement between MOP + F and C + F within 6 weeks.
The bone density of BV/TV decreased in the MOP + F (55.52±15.52%) and C + F (58.07±4.92%) at T3, but the differences were not statistically significant when compared with the controls (60.56±11.45%). In the changes of BMD, we found significant decrease (P<0.05) between the both experiment groups and the control F group at both T3 and T6.
The quantity of osteoclasts in the MOP + F group was 14.80±1.64 on average, and it was 16.00±4.42 in C + F, but only 5.40±3.05 in the F group at T3. At T6, the statistics showed no difference. Both the two experiment groups showed that osteoclasts decreased to 11.17±6.18 and 11.25±2.22, while the F group increased to 6.0±2.19.
:
The two flapless minor surgeries increased bone remodeling, osteoclast activity, and faster orthodontic tooth movement in at lease 2 weeks in rats.
Surgical interventions decreased the severity of root resorption.
There were no obvious differences between flapless micro osteo-perforation and corticision in rats.
: micro-osteoperforation, corticision, acceleratory orthodontic tooth movement.