3種類の歯内療法剤の象牙細管への浸透深さの比較評価

Comparative Evaluation of the Penetration Depth into Dentinal Tubules of Three Endodontic Irrigants.

抄録

本研究では，いくつかのキレート剤の象牙細管への浸透深さを調べることを目的とした．17％EDTAと界面活性剤を含む2つの製剤（Smear Clear，Bioakt Endo）を用いた．表面張力と液体粘度は，動的接触角測定器とHaake回転式レオメーターを用いて測定した。象牙細管内への浸透深さを測定するために，ヒト永久歯を抜歯したプールから30本の上顎中切歯を選び，3つの実験グループ（各10サンプル）に割り当てた。また，機械的に成形し，5.25％NaOClで洗浄した後，最終的に設定した灌漑プロトコルに従って，各キレート剤を0.1wt％のローダミンBで標識した。試料をエポキシ樹脂に包埋した後，鋸状ミクロトームを用いて頂部から2，5，8mmの位置に厚さ200μmの横断面を得た。その後，共焦点レーザー顕微鏡（CLSM）を用いて試料を観察し，各試料の3分の1ごとに標識液の浸透量を測定した。統計解析は，Shapiro-Wilk正規性検定で評価したデータの分布に応じて，ANOVAまたはKruskal-Wallis検定を用いて行った。粘度と表面張力の試験では、BioAKT EndoはEDTAやSmear Clearと比べて最も低い値を示した。中程度の浸透深さは3つのイリゲントの間で有意な差はなかったが、すべてのグループでアピカルレベルからコロナルレベルに向かって大幅に増加した。さらに、最大浸透深さは先端部から歯冠部にかけて有意に増加したが、他の洗浄剤に比べてBioAKT Endoは先端部と中間部で最も高い値を示した。また，根全体を考慮した場合，3群間で中位および最大浸透深さに有意な差は認められなかった。界面活性剤を含む新しい刺激剤は，表面張力が低下し，1つのケース（BioAKT Endo）では粘度も低下した。表面張力の低下により，EDTA単独の場合よりも象牙細管への液体の浸透性が向上し，根管系の洗浄性が向上すると考えられる。

This study aimed to examine the penetration depth into dentinal tubules of some chelating agents. The 17% EDTA and two preparations containing surfactants (Smear Clear, Bioakt Endo) were tested. Surface tension and liquid viscosity were measured using a Dynamic Contact Angle Analyzer and a Haake rotational rheometer. To measure the penetration depth inside dentinal tubules, thirty maxillary central incisors were selected from a pool of extracted human permanent teeth and allocated to three experimental groups (10 samples each), as well as were mechanically shaped and cleansed with 5.25% NaOCl, followed by each of the chelators being labeled with 0.1 wt % Rhodamine B according to final irrigation protocol established. The samples were embedded in an epoxy resin, after which 200 μm thick transverse sections were obtained at 2, 5, and 8 mm from the apex with a saw microtome. The specimens were then observed using a confocal laser microscope (CLSM) and the penetration of the labeled solution was measured in every third of each sample. Statistical analysis was performed using ANOVA or Kruskal-Wallis tests according to the distribution of data, evaluated with the Shapiro-Wilk normality test. Viscosity and surface tension tests have shown that BioAKT Endo has the lowest values compared to EDTA and Smear Clear. The medium penetration depth did not significantly differ among the three irrigants, while it increased considerably from the apical to the coronal level in all groups. Additionally, the maximum penetration depth increased significantly from the apical to coronal level, while among groups, BioAKT Endo showed the highest values at the apical and middle level compared to the other irrigants. No significant differences were observed among the three groups in medium and maximum penetration depths when the entire root was considered. New irrigants containing surfactants show reduced surface tension and, in one case (BioAKT Endo), viscosity. The lowering of the surface tension allows for better penetration of liquids into dentinal tubules than EDTA alone, thus improving the cleaning of the root canal system.