1992 Fiscal Year Final Research Report Summary
EXPERIMENTAL STUDY ON THE MECHANISM OF ACQUIRED ACID RESISTANCE OF HUMAN DENTAL ENAMEL BY LASER IRRADIATION
| Project/Area Number |
02454472
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
小児・社会系歯学
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
TAGOMORI Shoko KYUSHU UNIVERSITY FACULTY OF DENTISTRY ASSISTANT PROFESSOR, 歯学部, 講師 (20150469)
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| Co-Investigator(Kenkyū-buntansha) |
HORIE Junji KYUSHU UNIVERSITY FACULTY OF DENTISTRY RESEARCH ASSOCIATE, 歯学部, 助手 (60209286)
IWASE Tatsuo KYUSHU UNIVERSITY FACULTY OF DENTISTRY ASSISTANT PROFESSOR, 歯学部, 講師 (60151734)
OHO Takahiko KYUSHU UNIVERSITY FACULTY OF DENTISTRY ASSISTANT PROFESSOR, 歯学部, 講師 (50160940)
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| Project Period (FY) |
1990 – 1992
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| Keywords | HUMAN ENAMEL / LASER IRRADIATION / HEATING / BIREFRINGENCE / X-RAY DIFFRACTION / INFRARED SPECTROSCOPY / THERMAL ANALYSES |
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| Research Abstract |
A possible mechanism of acquired acid resistance of lased enamel was proposed on the basis of the investigations of optical properties, compositional and structural changes and permeability of lased and unlased human dental enamel. Lased enamel showed a high positive birefringence, suggesting the formation of 'microspaces' in enamel. No new products were found, though a decrease of lattice strain and a slight a-axis contraction were recognized in lased enamel compared with unlased enamel. The contents of water, carbonate and organic substances were reduced in lased enamel.
On the other hand, the optical properties and permeability of heated enamel and lased enamel after treatment with various solutions were investigated to elucidate the structural changes caused in dental enamel by laser irradiation. Heated enamel at 400ﾟC for 24 hours acquired the highest resistance to acid decalcification and showed a high positive birefringence which was similar to that of lased enamel. Carbolic fuchsin, acidulated phosphate fluoride (APF), and calcifying fluid did not penetrate the heated enamel, though those solutions penetrated the lased enamel well. Gradual changes of birefringence were observed in lased enamel during treatment with acid solutions, and this change was attributed to mineralization of the microspaces in lased enamel.
These results suggested that the structural changes in lased enamel are different from those of heated enamel. It appears that lased enamel has micropathways through which solutions can penetrate into the enamel, and also microspaces which could act as sites of deposition for ions released by acid decalcification.
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