次亜塩素酸ナトリウム水溶液による表面処理が象牙質接着強度に及ぼす影響

[Influence of surface treatment with sodium hypochlorite solution on dentin bond strength].

• Y Wang
• Y H Liang

抄録

目的:

根管治療中に使用した次亜塩素酸ナトリウム（NaOCl）溶液が象牙質結合強度に及ぼす影響を評価する。

OBJECTIVE: To evaluate the influence of sodium hypochlorite (NaOCl) solution used during root canal therapy on dentin bond strength.

方法:

本研究では、完全歯冠、カリエス、充填物なしの抜歯したてのヒト第三大臼歯15本を選択した。咬合エナメル質を歯の長軸に対して垂直に除去し、健全な象牙質の中間平坦面を露出させた。次に、咬合象牙質表面を600グリットのシリコンペーパーで1分間研磨し、脱イオン水で1分間洗浄した。A群（陰性対照群）では、サンプルを脱イオン水に20分間浸漬し、B群では、象牙質表面を2.50%NaOCl溶液に20分間浸漬し、5分ごとに溶液を更新し、C群では、象牙質表面を5.25%NaOCl溶液に20分間浸漬し、5分ごとに溶液を更新した。すべての処理された象牙質表面は、高さ5mmのレジンコンポジット（AP-X）を用いたセルフエッチング接着システム（SEボンド）を用いて接着された。37℃の脱イオン水中で24時間保存した後，接着剤サンプルを縦断して1.0mm×1.0mmのスティック試験片(n=45)を作製し，微小引張接着強度(MPa)試験を行った．実体顕微鏡を用いて，象牙質と樹脂の界面における破壊モード（接着破壊，凝集破壊，混合破壊）を観察した．3群間の微小引張接着強さデータを一方向ANOVAで解析した後，ポストホック検定(LSD)を用いてペアワイズ比較を行った．また，カイ二乗検定を用いて，各グループ間の故障モードの分布を解析した。

METHODS: In the study, 15 freshly extracted human third molars with complete dental crowns, caries and filling-free were selected. The occlusal enamel was removed perpendicular to the long axis of the tooth to expose middle flat surfaces of sound dentin. The occlusal dentin surfaces were then polished using 600-grit silicon papers for 1 min and rinsed with deionized water for 1 min. The teeth were randomly divided into three groups according to the treatment received: group A (negative control group), the samples were immersed in deionized water for 20 min; group B, the dentin surfaces were immersed in 2.50% NaOCl solution for 20 min, with the solution being renewed every 5 min; group C, the dentin surfaces were immersed in 5.25% NaOCl solution for 20 min, with the solution being renewed every 5 min. All the treated dentin surfaces were bonded using a self-etching adhesive system (SE bond) with a 5 mm in height resin composite (AP-X). After storage in deionized water at 37 °C for 24 h, the adhesive samples were sectioned longitudinally to produce 1.0 mm×1.0 mm stick specimens(n=45) for micro-tensile bond strength testing (MPa). Failure modes (adhesive failure, cohesive failure or mixed failure) at the dentin-resin interface were observed using a stereomicroscope. The micro-tensile bond strength data among the three groups were analyzed by a one-way ANOVA, then the Post-hoc test(LSD) was employed for pairwise comparison. The distribution of failure modes among the groups were analyzed by chi-square test.

結果:

2.50%NaOCl処理群(26.04±5.74)MPa，5.25%NaOCl処理群(24.46±3.77)MPaでは，ネガティブコントロール群(48.71±7.77)MPa，P=0.000と比較して有意な接着強度の低下が認められた。陰性対照群と比較して、2.50%NaOCl処理群では46.5%低下、5.25%NaOCl処理群では50.2%低下した。しかし，2つのNaOCl処理群間では接着強さに有意な差は見られなかった(P=0.214)。故障モードの分布は3群とも有意差を示した(2=56.324, P=0.000)。その結果、ネガティブコントロール群では混合破壊(68.9%)が最も多く、次いで接着破壊(24.4%)、凝集破壊(6.7%)が最も少なかった。接着破壊モードの割合は、NaOCl処理群の方が陰性対照群よりも高かった(P=0.000)。2.50%NaOCl処理群と5.25%NaOCl処理群との間では，故障モードの分布に有意な差はなく(P=0.197)，両群では凝集故障モードは検出されなかった．

RESULTS: Significant decreased bond strength values were found for the 2.50% NaOCl-treated group (26.04±5.74) MPa and 5.25% NaOCl-treated group (24.46±3.77) MPa when compared with the strength of negative control group (48.71±7.77) MPa,P=0.000. Compared with the negative control group, themicro-tensile bond strength of the 2.50% NaOCl-treated group and 5.25% NaOCl-treated grouphad dropped by 46.5% and 50.2%. However, there was no significant difference of bond strength between the 2 NaOCl-treated groups (P=0.214). The distribution of failure modes showed significant difference in all the three groups (2=56.324, P=0.000). The mixed failure (68.9%) was the most mode of fracture in the negative control group, followed by adhesive failure(24.4%), and the cohesive failure was least(6.7%). The proportion of adhesive failure mode was higher in NaOCl-treated groups than in negative control group (P=0.000). There was no significant difference of the distribution of failure modes between the 2.50% NaOCl-treated group and 5.25% NaOCl-treated group(P=0.197), and there was no cohesive failure mode detected in the two groups.

結論:

歯質とコンポジットレジンの微小引張接着強さは，NaOCl水溶液に曝露すると低下することがわかった．

CONCLUSION: The micro-tensile bond strength of dentin to composite resin was lower after exposure to NaOCl solution.