Impairment of rat tooth eruption in pups born to mothers exposed to chronic stress during pregnancy

Abstract

Objective: Tooth eruption is a multifactorial process in which bone tissue plays a prevailing<br />role. In this study we evaluated the bone overlying the developing tooth germ and the degree<br />of tooth eruption of the first mandibular molar in pups born to mothers subjected to<br />constant light during pregnancy.<br />Design: Pregnant rats were divided into two groups: mothers chronically exposed to a 12:12<br />light/light cycle (LL) from day 10 to 20 of pregnancy and controls (C) maintained on a 12:12 h<br />light/dark cycle. Pups from each group were euthanized at the age 3 or 15 days.<br />Buccolingually oriented sections of mandibles were stained with haematoxylin?eosin or<br />for histochemical detection of tartrate resistant acid phosphatase (TRAP). The histomorphometric<br />parameters evaluated were bone volume, number of osteoclasts, TRAP+ bone<br />surface, number of TRAP+ and TRAP osteoclasts per mm2 and degree of tooth eruption<br />(mm).<br />Results: It was found an increase in bone volume (LL: 58.14 4.24 vs. C: 32.31 2.16; p &lt; 0.01)<br />and a decrease in the number of osteoclasts (LL: 3.5 0.65 vs. C: 8.03 1.31; p &lt; 0.01) and<br />TRAP+ cells (LL: 0.84 0.53 vs. C: 8.59 1.26; p &lt; 0.01) in 3-day-old pups born to LL-exposed<br />mothers. These observations are consistent with the decrease in the degree of tooth eruption<br />observed in 15-day-old experimental pups (LL: 0.605 0.05 vs. C: 0.342 0.02; p &lt; 0.0001).<br />Conclusion: Our results suggest that chronic constant light applied as a pre-natal stressor<br />impairs the resorptive capacity of osteoclasts involved in the formation of the eruption<br />pathway and consequently the degree of tooth eruption.