フッ化物徐放性修復材料の象牙質再石灰化誘導能 : 再石灰化環境のpH,粘性が及ぼす影響  [in Japanese] Remineralizing Effect of Fluoride-releasing Materials on Dentin in vitro : Influences of pH and Viscosity as Remineralization Conditions  [in Japanese]

一般的に,フッ化物徐放性修復材料は,非徐放性修復材料に比較し歯質周囲の脱灰抑制のみならず,窩洞形成時に取り残した脱灰部位の再石灰化も促すといわれている.しかし,再石灰化が歯面を取り巻く環境によってどのように誘導されるかということは知られていない.この研究の目的は,in vitroにおいて,pHと粧性の異なる口腔の条件をシミュレートした液相でこの物性を評価することである.Baselineを作製するため,ウシ象牙質のシングルセクションを,37℃,pH 5.0の酢酸ゲルシステム中に5日間浸漬した.グラスアイオノマーセメント(GIC)およびコンポジットレジン(CR)をアクリルブロックの人工窩洞内に填塞し,脱灰された象牙質のシングルセクションを材料から1mm離れた溝に挿入した.これらのブロックは,以下の4つの再石灰化環境中に37℃で4週間保管された.Group 1:pH 7.0溶液群(Ca/PO_4:1.5/0.9),Group 2:pH 7.0 2層法群(ゲルとpH 7.0の溶液),Group 3:pH 6.5 2層法群(ゲルとpH 6.5の溶液),Group 4:pH 6.0 2層法群(ゲルとpH6.0の溶液).また,Transversal Microradiographyは再石灰化の前後で撮影し,平均的なミネラル喪失量(ΔZ)の差はΔZaとして算出した.収集したデータは,one-way ANOVA とDuncan's multiple range test を用いて統計学的分析を行った.Group 1:再石灰化はGICとCRともに示したが,ΔZaの有意差は認められなかった.Group 2:再石灰化はGICとCRともに示されたが,CRはGICほど著明ではなかった.Group 3:CR と比較して,GICは"過石灰化"を伴う顕著な再石灰化を示し,ΔZaはCRより有意に高かった(p<0.05).Group 4:ΔZaは両材料とも,脱灰を示すマイナスの値になったが,GICはCRより小さかった(p<0.05).結論として,この研究からpHと粘性のわずかな差は再石灰化に影響すること,また,pH 6.5ゲルすなわち,歯の表面状態のプラーク蓄積によるわずかに酸性状態をシミュレートしたような状態では,代表的なフッ化物徐放性填塞材であるGICは,辺縁の表層下病巣に顕著な再石灰化を誘導することが示された.

It is unknown whether the ability to induce remineralization occurs in any tooth surface condition. The aim of this study was to evaluate this property in solutions simulating different oral conditions of pH and viscosity in vitro. Bovine dentin single-sections were immersed in an acetic acid gel system to make baseline lesions at pH 5.0 for 5 days at 37℃. Glass-ionomer cement (GIC) or resin composite (CR) was placed in artificial cavities in perspex blocks and a demineralized dentin single-section was put into the groove leaving 1 mm from the material. These combinations were subjected to one of four remineralization conditions (4 weeks, 37℃). Group 1: pH 7.0 solution group (Ca/PO_4: 1.5/0.9), Group 2: pH 7.0 Gel group (8% MC gel covered with pH 7.0 solution), Group 3: pH 6.5 Gel group (8% MC gel covered with pH 6.5 solution), Group 4: pH 6.0 Gel group (8% MC gel covered with pH 6.0 solution). Transversal Microradiography were taken before and after the remineralization. The difference between integrated mineral loss values (ΔZ) was calculated as ΔZa. The collected data were analyzed statistically using one-way ANOVA and Duncan's multiple range test as the post-hoc test. In Group 1, remineralization was shown for both GIC and CR, however, ΔZa was not significantly different. Group 2: Remineralization was shown for both GIC and CR, however, CR was not markedly different from GIC. Group 3: In comparison with CR, GIC induced prominent remineralization accompanying "hyper remineralization" and ΔZa was significantly higher than CR(p<0.05). Group 4: ΔZa shifted to a negative value as demineralization in both materials, however, it was lower in GIC (p<0.05). In conclusion, in this study, small differences of pH and viscosity affected remineralization, and in the pH 6.5 gel condition, which may simulate a slightly acidic condition on the tooth surface with plaque accumulation, GIC as a representative fluoride-releasing filling material will induce prominent remineralization on marginal subsurface lesions.