フッ化物徐放性修復材料の象牙質再石灰化能 : 経時的再石灰化能と耐酸性能  [in Japanese] Time-course Study of Fluoride-releasing Restorative Materials on Dentin Remineralization and Following Acid Resistance in vitro  [in Japanese]

本研究では,フッ化物が拡散しやすいような環境における,フッ化物徐放性修復材料の周囲象牙質に対する経時的再石灰化効果をin vitroにおいて検討した.修復材料には,フッ化物徐放性修復材料として,光重合型コンポジットレジンであるBeautifil(BF),Reactomer(RE),光重合型フロアブルレジンのBeautifil Flow(BFF),従来型グラスアイオノマーセメントのGlasionomer-F(GI),また,コントロールとして,フッ化物非徐放性修復材料のLite-Fil II A(LF)を使用した.ウシ歯根部象牙質より作製した象牙質シングルセクションを,脱灰溶液10m/l(l.5 mmol/l Ca, 0.9mmol/l PO_4, 0.1mol/l酢酸,0.5ppm F,pH 5.0)に3日間浸漬後,プラスチック製の人工窩洞(直径4mm,深さ2mm)に各材料を充填,圧接,研磨し,1mm離れた溝にシングルセクションを挿入した.その後,再石灰化溶液(1.5mmol/l Ca,0.9mmol/l PO_4,130 mmol/l KCl,20mmol/l Hepes, pH7.0)に1,2,4,6週間浸漬し再石灰化試料を作製した.さらに,再石灰化部位の耐酸性を検討する目的で再石灰化期間終了後,脱灰溶液(1.5mmol/l Ca,0.9mmol/l PO_4,0.1mol/l酢酸,pH 5.0)に3日間浸漬した.各再石灰化期間および耐酸性試験終了後,顕微エックス線装置(PW3830)にてTransversal Microradiography撮影(管電圧25kV,管電流15mA,照射時間20分)を行った.すべての材料で再石灰化が認められ,その量は再石灰化期間を通してグループ間で有意差を認めなかった.しかしながら,LFとGIのミネラルプロファイルの比較では,LFでは表層,病巣体部ともにゆるやかに再石灰化が生じているのに対し,GI,BFでは表層に比較的強い再石灰化が生じ,病巣体部の再石灰化はやや遅れて生じていた.また,6週間の再石灰化期間終了後の耐酸性試験では,GIに有意な脱灰抑制能が認められた.以上の結果から,充填物周囲に初期根面齲蝕が残存していても,口腔内のプラークコントロールが良好で,唾液量が多く,再石灰化条件が整った環境であれば,フッ化物徐放性材料と非徐放性材料では再石灰化量に差はないと推察されるが,いったん脱灰優位な環境に変化した場合,特にグラスアイオノマーが脱灰抑制能を発揮するものと示唆された.

This study evaluated the time-course remineralization effect of fluoride-releasing materials on dentin in vitro. Restorative materials used in this study were Beautifil (BF) and Reactomer (RE) as fluoride-releasing light-cured composites, Beautifil Flow (BFF) as fluoride-releasing flowable resin composite, Glasionomer-F (GI) as a conventional glass ionomer, and Lite-Fil IIA (LF) as a non-fluoride releasing composite. Root dentin single-sections were demineralized with 10 ml of acetic acid solution (0.1 mol/l acetic acid, 1.5 mmol/l CaCl_2, 0.9 mmol/l KH_2PO_4, 0.5 ppm F, pH 5.0) for 3 days. Each material was filled in a cylindrical cavity in a perspex block and a demineralized root dentin single-section was inserted into the groove at a distance of 1 mm from the material. The block was immersed in 10 ml of remineralization solution (1.5 mmol/l CaCl_2, 0.9 mmol/l KH_2PO_4, 130 mmol/l KCl, 20 mmol/l HEPES, pH 7.0) for 1, 2, 4 and 6 weeks, at 37℃. After the 6 weeks of remineralization period, an acid resistance test was performed for 3 days with fluoride-free acid demineralization solution (pH 5.0). After each period of remineralization and acid resistance test, the sections were subjected to transverse microradiography (TMR) analysis. Remineralization was found in all groups, however, significant differences were not recognized among all the groups throughout the remineralization periods. On the other hand, characteristics of remineralization profiles were found between the LF and the GI. The mineral profile of LF showed that the surface layer and body of lesion were slowly remineralized, however, GI and BF showed a steep increase in the surface layer, but the body of the lesion was left. As a result of the acid resistance test, GI had a significantly lower mineral loss than the other materials. It is concluded that the remineralization characteristics of fluoride-releasing materials and non-fluoride-releasing materials were different, however, the total amounts of remineralization were not significantly different throughout the experimental period under the conditions of this study which simulated an oral environment with predominant saliva flow and diminished plaque accumulation. Glass ionomer may exhibit beneficial acid resistance characteristics when the demineralization environment is advanced.