Solid-state NMR investigation on the mineral structure in de- and remineralized dentin. Solid-state NMR investigation to provide evidence of fluoride-effect for caries prevention

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K09972
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 57030:Conservative dentistry-related
• Research Institution: Tokyo Medical and Dental University
• Principal Investigator: Hiraishi Noriko 東京医科歯科大学, 大学院医歯学総合研究科, 講師 (20567747)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: フッ化物 / フルオロアパタイト / 固体核磁気共鳴装置 / エナメル質 / 象牙質 / フッ化カルシウム / X線回折装置

Outline of Final Research Achievements

Various fluorides were applied to bovine and human enamel and dentin and the effect of fluoride treatment was assessed by solid-state NMR. Bovine tooth bioapatite was used in preliminary experiments and its crystallinity was investigated to compare with human tooth. Enamel was found to be a highly crystalline mineral. Rietveld analysis of X-ray diffraction confirmed smaller crystal sizes and greater microstrain in dentin. 19F NMR analysis of fluoride showed that it was highly reactive in dentin, producing fluoroapatite (FAp) and calcium fluoride (CaF2). Acid fluoride is reactive, but the by-product CaF2 is mainly formed. The formation of CaF2 was found by silver diammine fluoride as well as FAp. Solid-state NMR and XRD analysis allowed the action of fluoride on dentine apatite and the identification of its products, suggesting that the reactivity varies with the acidity and concentration of fluoride, providing new insights into its caries-preventive effect.

Free Research Field

保存修復

Academic Significance and Societal Importance of the Research Achievements

う蝕予防のためのフッ化物の応用については、エナメル質初期う蝕予防並みならず、成人期以降に見られる歯根面う蝕の予防においても、フッ化物の応用効果が期待される。前者には1450ppm以上のフッ化物、後者にはフッ化ジアンミン銀塗布が広く使用されるが、どのような生成物が生じるかを、固体NMRの高度分析技術を駆使して、分子、原子レベルでの的確な分析を行った。結果、酸性フッ化物は反応性が高いが、高濃度の場合、フルオロアパタイト以外にフッ化カルシウムが多く生成される傾向があった。エナメル質と象牙質で、フッ化物の反応性が違うため、臨床での使用にその特徴に合わせた使用方法が望ましいと考えた。