Birth Control and Braces: Taking It Slow

It’s probably a safe assumption that most young women who wear braces don’t want to get pregnant any time soon. Thorny orthodontics might put a damper on first-base kisses, ¬but hey, home runs can still happen. And that’s why many tinsel-toothed tarts take birth control.

Inquisitive researchers in Iran wanted to know if taking contraceptives could affect orthodontic tooth movement. But why investigate the connection between such seemingly unrelated factors? The answer might surprise you - brace yourself!

Braces do not simply push and pull teeth around your mouth as if they are rearranging furniture in your living room. Instead, they rely on biologic responses to the mechanical force they apply, actually remodeling the alveolar bone in which your teeth sit. Osteoclasts, the cells responsible for bone resorption, remove bone on the side of the tooth that experiences positive pressure; while osteoblasts, the cells responsible for bone formation, create new bone on the side of the tooth that experiences negative pressure.

The activities of osteoclasts and osteoblasts are sensitive to many hormones, including ethinyl estradiol and norgestrel, synthetic versions of estrogen found in many contraceptive pill formulations. Previous studies have shown that these hormones actually reduce bone turnover, a consequence which might lessen the efficacy of orthodontics.

To test the effect these synthetic estrogens have on tooth movement, the researchers divided a colony of rats into an experimental group and a control group. The experimental group was fed the aforementioned hormones, and the control group was fed saline. One week later, while the rats continued to take their prescribed hormones or placebo, a spring exerting a specific amount of force was wedged between the two front teeth of each rat.

Can you guess which group of rats looked more like Madonna, Flea, and Anna Paquin after 14 days? If you’re thinking the control group, you’re correct! The synthetic estrogen significantly reduced the number of osteoclasts in the experimental group, slowing the rate at which the rats could remodel their alveolar bone to accommodate tooth movement. So, at the end of two weeks, the control group had experienced faster tooth movement and had bigger gaps to show for it.

These results have serious implications for young women who are in a hurry to flash gorgeous smiles without the unsightliness and discomfort of train-track braces. Female patients should be advised that taking birth control might increase the length of orthodontic treatment, a good thing to know while they are trying to balance their priorities. Thanks science!

References:
[1] Olyaee P, Mirzakouchaki B, Ghajar K, Seyyedi SA, Shalchi M, Garjani A, Dadgar E. “The effect of oral contraceptives on orthodontic tooth movement in rat.” Med Oral Patol Oral Cir Bucal. 2013 Jan 1;18(1):e146-50.