A Study On C-type Natriuretic Peptide Express During The Replacement Of Primary And Permanent Teeth

The replacement of primary and permanent teeth is an important physiological phase that belongs to the growth and development of teeth and maxillofacial region. A lot of changes have taken place in the correlated tissues including the primary teeth roots, alveolar bone, periodontal ligament and the successional permanent teeth germs during this procedure while osteoclast play key role. Now many cytokines are refined stimulating osteoclast to proliferation, differentiation , activation and bone resorption ,such as 1,25 (OH) 2D3, IL, M-CSF, PTH, PGE2. As a multinucleate large cell, osteoclasts were believed derived from marrow and spleen hematopoietic lineage cell. At present to culture osteoclast in vitro is difficult and its lower purity (<10%) brings obstacle for studying its biological character.Since 1992, the third natriuretic peptide family member CNP are found, many study about CNP concentrate in neurosecretory system. Recently CNP has been found related with osteoporosis, so we can presume CNP involved in osteoclast formation, but CNP is never seen in replacement of primary and permanent teeth. We observe CNP expression and action in deciduous teeth roots, periodontal ligament, alveolar bone and permanent teeth germs under three statesof the dogs' teeth (primary dentition roots stability, primary dentitionroots resorption permanent dentition) by immunohistochemistry, in situ hybridization method and cell culture. The main content and results of our researches are below:Part One: Immunohistochemical technique and in situ hybridization method were used in this study to observe the CNP expression under three states of the dogs' teeth: primary dentition roots stability, primary dentition roots resorption, permanent dentition.1.dogs' primary dentition roots stability stage: The deciduous teeth roots were not absorbed biologically. The permanent teeth germs were developing and dentin and enamel matrix started to form. In the immunohistochemical and in situ hybridization experiment, CNP positive signals were seen in the multinucleated osteoclasts localized in the absorbed lacunae of the alveolar bone near the germs, as well as ameloblasts, odontoblasts of the permanent teeth germs. These results indicated that CNP involved in the development of dogs' permanent teeth germs and the alveolar bones' moulding during the stages of the primary dentition roots stability.2.dogs' primary dentition roots resorption stage: Dogs' deciduous teeth roots were undergoing absorbed biologically and there were a lot of absorbed lacunae on the roots in which multinucleate odontoclast were located. Around dental sac and alveolar bone lacuna multinucleate osteoclast were also found. Dentin and enamel of the permanent teeth germs went on forming and calcifying. Ameloblasts and odontoblasts appeared to tall posts and the nuclears were away from the membranes, polarity -inverted clearly. CNP-positive cells were identified as osteoclasts in the alveolar bone and odontoclasts in the in situ...