ABSTRACT
<p><b>OBJECTIVE</b>To study the expression of MMP-8 in human and rat tooth development.</p><p><b>METHODS</b>Immunohistochemistry was used to detect the localization of MMP-8 protein while in situ hybridization was used to examine the expression of MMP-8 mRNA.</p><p><b>RESULTS</b>The expression of MMP-8 protein was localized in odontoblast and dentin matrix at the later bell stage in human tooth germ. The dentin was denser close to the pulp cavity. The expression of MMP-8 mRNA was found in very few polarized odontoblast at the early bell stage and all polarized odontoblast at the later bell stage in rat tooth germ.</p><p><b>CONCLUSION</b>The results suggested that MMP-8 involved in dentin matrix rebuilding in the process of dentin formation in human and rat dental development.</p>
Subject(s)
Animals , Rats , Animals, Newborn , Dentin , Embryo, Mammalian , In Situ Hybridization , Matrix Metalloproteinase 8 , Genetics , Maxilla , Odontogenesis , RNA, Messenger , Genetics , Rats, Sprague-Dawley , Tooth Germ , EmbryologyABSTRACT
<p><b>OBJECTIVE</b>To study the effects of excessive fluoride on type I collagen in rat developmental dentine.</p><p><b>METHODS</b>Eighty SD rats, 5 days old, were divided into experimental and control groups, 40 in each group. The experimental group received subcutaneous injection of 0.2% NaF every 4 days (the dose was 2 mg NaF per kg body wt). The same volume of 0.9% NaCl was used in the control. Twenty rats in each group were killed 4 days after the second and the seventh injection respectively. The expression of type I collagen was assayed with immunohistochemical technique.</p><p><b>RESULTS</b>4 out of 20 rats after two injections showed abnormal distribution of type I collagen (dense stain of collagen in the odontoblast, aggregation of collagen in the dentine and disordered arrangement of collagen in the predentine; All 20 rats after seven injections showed abnormal distribution of type I collagen.</p><p><b>CONCLUSION</b>Excessive fluoride may affect the metabolism of type I collagen in rat developmental dentine.</p>