Prati C, Chersoni S, Pashley D H
School of Dentistry, University of Bologna, Italy.
Dent Mater. 1999 Sep;15(5):323-31. doi: 10.1016/s0109-5641(99)00052-4.
The aim of this study was to evaluate the effects of NaOCl at removing the demineralized layer by examining the morphology of the hybrid layer and measuring shear bond strengths after different dentin treatments.
Dentin disks were treated with: (1) 35% phosphoric acid (PA) 20 s; (2) PA treatment followed by 1.5% NaOCl, 2 min; (3) PA treatment, followed by a 10% NaOCl immersion for 120 h. SEM was used to analyze the morphology of dentin and its interface with dentin bonding agents (DBAs), while shear bond strength tests were used to measure adhesion. All specimens were then fractured into two halves: One half was inspected under SEM; the other half was sequentially placed in 10% PA followed by 12.5% NaOCl for 70 h, to remove all dentin from the resin replica of the original bonded interface.
SEM observations showed that collagen fibrils were completely removed from the acid-etched surface by NaOCl treatment. The diameter and the size of dentinal tubules and the number of lateral branches of the tubules were increased following NaOCl treatment. NaOCl applied on dentin smear layers did not significantly modify their SEM morphology. Resin tags were larger in diameter after phosphoric acid/NaOCl treatment than after only phosphoric acid treatment. Resin-infiltrated dentin-layers were only observed after the single phosphoric acid (i.e. conventional etching) procedure, and were not observed after combined phosphoric acid/NaOCl treatment. Etched/NaOCl samples showed a lower bond strength using Scotchbond MP and 3M Single Bond, but were higher in Optibond FL and unmodified in Prime & Bond 2.0 groups when compared with acid-etched controls. Treatment of etched dentin with NaOCl for 120 h produced an unusual type of resin infiltration of mineralized dentin that could be called a "reverse hybrid layer" which may explain the mechanism of resin bonding to NaOCl treated dentin.
The use of acidic conditioners for exposure of the collagen matrix exposes a soft delicate mesh that can collapse, thereby interfering with resin infiltration. If acid-etching is followed by NaOCl treatment, high bond strengths can be achieved via "reverse hybrid layer" formation, a proposed new mechanism of micromechanical resin retention. This mechanism is not yet recommended for clinical use but demonstrates a new type of resin retention.
本研究旨在通过检查混合层的形态并测量不同牙本质处理后的剪切粘结强度，来评估次氯酸钠（NaOCl）去除脱矿层的效果。
牙本质盘分别进行以下处理：（1）35%磷酸（PA）处理20秒；（2）PA处理后用1.5% NaOCl处理2分钟；（3）PA处理后，用10% NaOCl浸泡120小时。使用扫描电子显微镜（SEM）分析牙本质及其与牙本质粘结剂（DBA）界面的形态，同时使用剪切粘结强度测试来测量粘结力。然后将所有标本切成两半：一半在SEM下检查；另一半依次置于10% PA中，然后在12.5% NaOCl中处理70小时，以从原始粘结界面的树脂复制品中去除所有牙本质。
SEM观察表明，通过NaOCl处理，胶原纤维从酸蚀表面完全去除。NaOCl处理后，牙本质小管的直径、大小以及小管侧支的数量增加。应用于牙本质玷污层的NaOCl并未显著改变其SEM形态。磷酸/NaOCl处理后的树脂突直径比仅磷酸处理后的大。仅在单一磷酸处理（即传统蚀刻）过程后观察到树脂渗入牙本质层，而在磷酸/NaOCl联合处理后未观察到。与酸蚀对照组相比，蚀刻/NaOCl样本在使用Scotchbond MP和3M单组分粘结剂时显示出较低的粘结强度，但在Optibond FL组中较高，在Prime & Bond 2.0组中无变化。用NaOCl处理蚀刻后的牙本质120小时会产生一种特殊类型的矿化牙本质树脂渗入，可称为“反向混合层”，这可能解释了树脂与NaOCl处理的牙本质粘结的机制。
使用酸性调节剂暴露胶原基质会暴露出一个柔软脆弱的网，该网可能会塌陷，从而干扰树脂渗入。如果酸蚀后进行NaOCl处理，可通过“反向混合层”形成实现高粘结强度，这是一种新提出的微机械树脂固位机制。该机制尚未推荐用于临床，但展示了一种新型的树脂固位方式。
