Department of Prosthetic Dentistry, Institute of Dentistry, University of Turku, Finland.
Dent Mater. 2010 Nov;26(11):1059-67. doi: 10.1016/j.dental.2010.07.006. Epub 2010 Aug 4.
The progressive degradation of resin-dentin bonds is due, in part, to the slow degradation of collagen fibrils in the hybrid layer by endogenous matrix metalloproteinases (MMPs) of the dentin matrix. In in vitro durability studies, the storage medium composition might be important because the optimum activity of MMPs requires both zinc and calcium.
This study evaluated the effect of different storage media on changes in matrix stiffness, loss of dry weight or solubilization of collagen from demineralized dentin beams incubated in vitro for up to 60 days.
Dentin beams (1mm×2mm×6mm) were completely demineralized in 10% phosphoric acid. After baseline measurements of dry mass and elastic modulus (E) (3-point bending, 15% strain) the beams were divided into 5 groups (n=11/group) and incubated at 37°C in either media containing both zinc and calcium designated as complete medium (CM), calcium-free medium, zinc-free medium, a doubled-zinc medium or water. Beams were retested at 3, 7, 14, 30, and 60 days of incubation. The incubation media was hydrolyzed with HCl for the quantitation of hydroxyproline (HOP) as an index of solubilization of collagen by MMPs. Data were analyzed using repeated measures of ANOVA.
Both the storage medium and the storage time showed significant effects on E, mass loss and HOP release (p<0.05). The incubation in CM resulted in relatively rapid and significant (p<0.05) decreases in stiffness, and increasing amounts of mass loss. The HOP content of the experimental media also increased with incubation time but was significantly lower (p<0.05) than in the control CM medium, the recommended storage medium.
The storage solutions used to age resin-dentin bonds should be buffered solutions that contain both calcium and zinc. The common use of water as an aging medium may underestimate the hydrolytic activity of endogenous dentin MMPs.
树脂-牙本质粘结的渐进性退化部分归因于混合层中胶原纤维的缓慢降解，这是牙本质基质内源性基质金属蛋白酶（MMPs）缓慢降解的结果。在体外耐久性研究中，储存介质的组成可能很重要，因为 MMPs 的最佳活性需要锌和钙。
本研究评估了不同储存介质对体外孵育长达 60 天的脱矿牙本质梁基质硬度变化、干重损失或胶原溶解的影响。
牙本质梁（1mm×2mm×6mm）用 10%磷酸完全脱矿。在干重和弹性模量（E）（三点弯曲，15%应变）的基线测量后，将梁分为 5 组（每组 n=11），并在 37°C 下在含有锌和钙的完整介质（CM）、无钙介质、无锌介质、双倍锌介质或水中孵育。在孵育 3、7、14、30 和 60 天时对梁进行重新测试。用 HCl 水解孵育培养基，以羟脯氨酸（HOP）作为 MMPs 溶解胶原的指标进行定量。使用重复测量方差分析对数据进行分析。
储存介质和储存时间对 E、质量损失和 HOP 释放均有显著影响（p<0.05）。在 CM 孵育中，硬度迅速显著降低（p<0.05），质量损失增加。实验介质中的 HOP 含量随孵育时间增加而增加，但明显低于（p<0.05）推荐储存介质 CM 中的对照介质。
用于老化树脂-牙本质粘结的储存溶液应为含有钙和锌的缓冲溶液。常用水作为老化介质可能会低估内源性牙本质 MMPs 的水解活性。
