Abstract
It has been generally considered that the susceptibility of enamel to caries is higher in a newly erupted tooth, and one of the reasons for this susceptibility is associated with the grade of enamel maturation. The present study was carried out to investigate the maturation of enamel associated with caries susceptibility and the affect of saliva on the maturation.
For this purpose, incisors of Wister rats,11,18,20,30 and 53 days after birth, were used in the experiment and the enamel was categorized as follows,
A. the enamel of the erupting region
B. the enamel adjacent to the epithelial attachment
C. the enamel adjacent to the bone and examined with the aid of a Scanning Electron Microscope, Microradiography, Electron Probe X-ray Microanalyzer and X-ray Diffraction for enamel maturation in each region, and the affect investigated when the ducts of major salivaly gland were ligated, and when the immature enamel was exposed to the oral enviornment.
The results obtained from the present study were as follows;
1) Finding with SEM disclosed that there were a number of pits on the enamel surface adjacent to the epithelial attachment of young rat.
2) It was noticed that the distinct hypomineralized areas still existed in the enamel adjacent to the epithelial attachment of 11 day old rats compared with 18-53day old rats.
3) Even after the ligation of the salivaly gland ducts, no remarkable changes of the enamel of erupted region was noticed.
4) The enamel apatite in the hypomineralized areas showed a low crystallinity in the a-axis direction.
5) When the hypomineralized enamel areas were exposed to the oral enviormnent after gingival excision, mineralization would occure and the crystallinity of it was improved in the a-axis. These changes were more reinforced by the topical application of APF gel. These results suggested that immature enamel should be protected immeidately after eruption, in a cases when the unerupted tooth is surgically exposed.
