OBJECTIVETo investigate the effects of lead exposure at different levels in utero on the teeth eruption and enamel development of rat offsprings.

METHODS27 pregnant SD rats were divided into three groups randomly: high level lead group (HLG), low level lead group (LLG) and control group with nine rats in each group. The three groups from the gestation day to the end of the gestation were given either deionized water in control group or deionized water containing 200 mg/L Pb2+ as lead acetate through drinking method in high level lead experimental group and 50 mg/L Pb2+ as lead acetate through drinking method in low level lead experimental group. The incisors of newborn rats were marked at the level of the gingival papilla on the 26th day after birth. On the 36th day, the incisors of newborn rats were marked again at the same level. Then the rat offsprings were killed and their blood was collected for lead analysis. The mandible incisors of rat offspring were separated and the content of Pb in incisors was determined by using a graphite furnace atomic absorption spectrometric method. The teeth of rat offspring were observed and the distance between two marks were measured by means of stereomicroscope. The ratio of calcium to phosphate of enamel of rat offspring was compared by electron probe microanalyses.

RESULTSThe level of blood lead in 200 mg/L, 50 mg/L treated rat offspring groups was higher than that in control group. The tooth lead of 200 mg/L, 50 mg/L treated rat offspring groups [(77.3 +/- 6.3), (27.8 +/- 4.5) microg/g] were higher than the control [(6.6 +/- 0.8) microg/g, P < 0.01]. Compared with the control group, the teeth of lead exposure experimental groups were smaller and severity of attrition was obvious and pulpal perforations were often observed. These appearances was more distinct in rats of high level lead experimental group. The incisors of lead-treated rat offspring erupted [(0.25 +/- 0.08), (0.30 +/- 0.09) mm/d] more slowly than control ones [(0.39 +/- 0.09) mm/d, P < 0.01]. The ratio of calcium to phosphate (Ca/P) decreased with the increase of lead exposure. It was found that Ca/P in lead exposure experimental groups (1.68 +/- 0.54), (1.37 +/- 0.47) was significantly lower than that in the control group (2.14 +/- 0.33).

CONCLUSIONLead exposure in utero affects the normal eruption of teeth and enamel formation and the degree was related with the lead exposure level.