軟化象牙質と再石灰化象牙質の歯ブラシによる摩耗：in situ 研究

Brushing abrasion of softened and remineralised dentin: an in situ study.

抄録

本研究の目的は，口腔内の再石灰化期間の違いが，軟化象牙質の歯ブラシ摩耗に対する感受性に及ぼす影響を評価することである．11名のボランティアに21日間装着された口腔内装置の頬側に，6個のヒト象牙質試料群（A～F）を埋没させた．試料は1日2回，酸性飲料スプライトライト（pH2.9）中で90秒間経口脱灰し，その後，異なるタイミングでブラッシングを行った．試料Aは脱灰直後，試料B〜Eは脱灰後にブラッシングした．試料B〜Eは，口腔内装置を口腔内に装着して10分，Cは20分，Dは30分，Eは60分経過後にブラッシングを行った．検体Fはブラッシングを行わなかった（コントロール）．21日後，象牙質摩耗量をプロフィルメーターで測定した．以下の値（平均値＋/-標準偏差）を記録した（μm）．a, 23.6 +/- 16.7; b, 37.9 +/- 29.7; c, 31.8 +/- 26.5; d, 18.5 +/- 10.5; e, 15.3 +/- 11.6; f, 12.6 +/- 6.7である．A、B、C群では、対照群に比べ、象牙質の損失が統計的に有意に増加した（U検定：p＜0.05）。しかし，30分および60分の口腔内時間経過後，摩耗量は未研磨の対照群に比べ有意に増加しなかった．以上のことから，象牙質表面を保護するためには，侵襲を受けた後，少なくとも30分経過してから歯ブラシを行うことが望ましいと考えられる．

The aim of the present in situ study was to evaluate the effect of different periods of intra-oral remineralisation on the susceptibility of softened dentin to toothbrushing abrasion. Groups of 6 human dentin specimens (A-F) were recessed in the buccal aspects of intra-oral appliances which were worn for 21 days by 11 volunteers. The samples were demineralised twice a day extra-orally in the acidic beverage Sprite Light (pH 2.9) for 90 s. Subsequently, the dentin specimens were brushed at different times. Specimen A was brushed immediately after demineralisation. Specimens B-E were brushed after the intra-oral appliances had been worn for various periods in the mouth: specimen B for 10 min, C for 20 min, D for 30 min and E for 60 min. Specimen F was not brushed (control). After 21 days, dentin wear was measured with a profilometer. The following values (means +/- standard deviation) were recorded (microm): A, 23.6 +/- 16.7; B, 37.9 +/- 29.7; C, 31.8 +/- 26.5; D, 18.5 +/- 10.5; E, 15.3 +/- 11.6; F, 12.6 +/- 6.7. There was a statistically significantly increased dentin loss for groups A, B and C as compared to the controls (U test: p < 0.05). However, after intra-oral periods of 30 and 60 min, wear was not significantly higher than in unbrushed controls. It is concluded that for protection of dentin surfaces at least 30 min should elapse before toothbrushing after an erosive attack.