The effects of pregnancy and fluoride on orthodontic tooth movements in rats

Abstract

The present investigation was undertaken in order to study the velocity of orthodontic tooth movement in rats and the effect of the hormonal changes that occur during pregnancy or with fluoride, which is one of several trace elements that affect hard tissue metabolism. Adult, female Sprague-Dawley rats were separated into three groups: non-pregnant, pregnant, and non-pregnant NaF-supplied. All rats were treated with a fixed orthodontic appliance which moved the upper first molars in a buccal direction during 21 days. The appliances delivered an initial force of 150 mN. Repeated intra-oral, standardized radiographs were taken during the experimental period, and at the end of the experiment the maxillae were examined histologically. The velocity of tooth movement was calculated after measurement of the radiographs. The first molars were moved in a buccal direction in all groups. The mean value of the expansion from day 0 to 21 was significantly higher among the pregnant rats (0.64 mm) compared to the non-pregnant, control animals (0.46 mm) while the NaF-supplied rats had a significantly lower expansion (0.22 mm) compared to the control animals. In the histological examination of the pressure sides of the PDL of the upper first molars, the mean value of osteoclasts per microns x 10(-3) increased non-significantly in the group of pregnant rats and decreased significantly among the NaF-supplied animals compared to the non-pregnant control rats. The present experiment in rats indicated that the velocity of orthodontic tooth movement is influenced by hormones as well as trace elements.

Factors related to the rate of orthodontically induced tooth movement

“…Furthermore, the velocity of tooth movement can be influenced by the hormonal changes during pregnancy: a 3-week period of experimental tooth movement in rats showed that the mean value of expansion was significantly greater among the pregnant rats compared with the nonpregnant rats. 25 In addition to the above conditions related to hormonal changes, other systemic conditions have been identified that can modulate the pattern and the velocity of tooth movement: eg, diabetes, allergies, and cancer. 10 The therapeutic intake of bisphosphonates has been associated with the inhibition of tooth movement, 26 and the systemic administration of leptin, a central hormone, with the inhibition of bone formation.…”

Effect of fluoride on root resorption following heavy and light orthodontic force application for 4 weeks and 12 weeks of retention

“…4 It has been shown that fluoride reduced the number of the osteoclasts in bone. 24 Additionally, it has been demonstrated that fluoride decreases the number of resorption lacunae made by individual clast cells, 25 the resorbed area per clastic cells, 16,19,25 and the depth of the clastic cell demineralization pit. 16,19,26 In the present study, high fluoride groups exhibited a decreased amount of root resorption after the application of light and heavy forces for 4 weeks.…”

Drugs influencing orthodontic tooth movement: An overall review

“…Even a very active caries treatment with sodium fluoride during orthodontic treatment may delay orthodontic tooth movement and increase the time of orthodontic treatment. [9] Sodium fluoride has been shown to inhibit the osteoclastic activity and reduce the number of active osteoclasts.…”