Effects of lithium chloride and nitric oxide inhibitor on orthodontic tooth movement in the rat

Abstract

Orthodontic tooth movement in a rodent model is reduced by lithium chloride (LiCl), a mood-stabilizing agent with antithyroid effects. Considering the established inhibitory effect of N(omega)-nitro-L-arginine methyl ester (L-NAME) on orthodontic tooth movement and the possible role of nitric oxide synthase in LiCl mechanism of action, the question arises if these two mechanisms are synergistic. To answer this question, 70 male Sprague Dawley rats were randomly divided into seven groups: untreated group without any interventions (i), and the orthodontic tooth movement groups receiving daily saline injection (ii), 300 (iii), and 600 mg/kg (iv) of LiCl per os, 10 mg/kg of L-NAME (v) and the combinations of 300 (vi) and 600 mg/kg LiCl (vii) with L-NAME. The first molar was moved towards the incisor with 60 g of mesial tipping force applied by an activated fixed coil spring for two weeks. The resulted distance between the first and the second molar was measured using a feeler gauge. The serum parameters were also determined. We report here that both concentrations of LiCl significantly decreased tooth movement. Even though L-NAME was capable of reducing orthodontic tooth movement, no synergistic effects with LiCl were observed. Moreover, L-NAME had no impact on the robust and significant increase of thyroid-stimulating hormone (TSH) and decrease of triiodothyronine (T3) and thyroxine (T4) in the LiCl treated rats. These findings suggest LiCl significantly decreases the orthodontic tooth movement in rats; however, this ability seems not to be principally mediated through nitric oxide synthase.