ABSTRACT. This study assessed the effects of pregnancy and lactation on the morphology of the dentine tubules and external enamel surface of rat incisor teeth using a scanning electron microscope (SEM) equipped with an energy dispersive x-ray (EDX) system. Twentyfour female Wistar rats were divided into three groups; group A rats were at the end of pregnancy, group B rats were in the post-lactation period and group C rats, the control group, were unmated. The outer enamel surface and openings of the dentine tubules at the neck regions of the incisors were observed under the SEM and photographed. Examination of the incisor teeth of pregnant and post-lactation rats revealed scratches on the enamel surface. There were few eroded areas and slight changes and the dentine tubules of the pregnant group were fully or partially occluded on the entire surface of the enamel in the lactating rats. Almost all dentine tubules of the rats in this group were open. During the study, EDX analysis of calcium, phosphate and magnesium was also performed at 20 kV and 0 degree tilt. The results of EDX analyses of magnesium were significantly lower in the pregnant group compared with the lactation and control groups for the dentine in the neck region (p<0.05). The calcium values increased in the lactation group compared with those of the rats in the other two groups (p<0.05). These results might indicate that changes during pregnancy and lactation affect the content and morphology of mineralized dental hard tissue.KEY WORDS: dentine, enamel, lactation, pregnancy, SEM.J. Vet. Med. Sci. 71(10): 1273-1277, 2009 The tooth is a convenient model for studying basic biological phenomena such as cell generation, cell differentiation and interaction, synthesis, secretion and organization and mineralization of extracellular matrices. Rat incisor teeth grow continuously and can exhibit all stages of tooth formation at any time. This characteristic makes them ideal models for enamel formation [4]. In addition, in dentine, dentinal tubules play an important role in transferring stimuli and irritants to the pulp. By way of this route and through diffusion in the liquid filling the tubules, various therapeutic agents applied locally to exposed dentin may also reach the pulp [1]. Zeni et al. [16] examined bone mass changes in the total, axial and appendicular skeleton as well as in the different subareas of the femur and tibia in rats kept on a diet including normal amounts of calcium. Their experimental study using dual energy absorptiometry in vivo to visualize changes in BMD during the reproductive cycle of the rat showed that normal pregnancy in the rat appears to have little influence on bone, whereas lactation induces significant bone loss, mainly in areas with predominant trabecular bone [16]. Moreover, Miller et al. [5] demonstrated that significant changes occur in the rates of dentin apposition in the continuously erupting incisors of rats during pregnancy and lactation. The rate of dentin apposition in the rat is known to be sensitive to e...