OBJECTIVE To evaluate the protease activity in dentin matrices subjected to lactic acid (LA) in comparison to polyacrylic acid (PAA) challenge model at cathepsin K (CT-K) optimum pH 5.5 to assess effectiveness of inhibitors in dentin collagen degradation. METHODS Dentin disks measuring 0.5mm prepared from human molars were completely demineralized in 10% H3PO4. Demineralized dentin disks were challenged with 0.1M LA, 1.1mM PAA, artificial saliva (AS), or deionized water (C) for 24h or 7-days. Dentin collagen properties were tested by measurement of %dry mass change, and ultimate tensile strength (UTS). Degradation of dentin type I collagen was measured by telopeptide assays measuring the sub-product release of C-terminal cross-linked telopeptides (ICTP) and C-terminal peptide (CTX) in the incubation media in relation to total protein concentration, which correlates with matrix metalloproteinases (MMPs) and CT-K activities. RESULTS Gravimetric analysis showed statistically significant difference between C and other groups (p<0.04) at 24h. LA specimens showed significantly higher weight loss from 24h to 7-days (p=0.02). UTS revealed statistically significant difference between AS and LA at 24h and 7-days. UTS at 24h and 7-days for C and AS had significantly higher mean values compared to LA and PAA. Telopeptide assays reported that CTXtp results showed that LA at 24h had significantly higher mean values compared to C and AS. SIGNIFICANCE LA has the ability to activate endogenous CT-K in dentin as measured by the release of CTX (CT-K specific telopeptide). This LA based model has the potential application for further investigations on the activity and possible inhibitors of CT-K in human dentin.

中文翻译：

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人牙本质中组织蛋白酶K激活的替代模型。

目的比较在组织蛋白酶K（CT-K）最佳pH 5.5下与聚丙烯酸酯（PAA）攻击模型相比，乳酸（LA）对牙本质基质的蛋白酶活性，以评估抑制剂在牙本质胶原降解中的有效性。方法用人类臼齿制备的直径为0.5mm的牙本质牙盘在10％的H3PO4中完全脱盐。用0.1M LA，1.1mM PAA，人工唾液（AS）或去离子水（C）刺激去矿质的牙本质牙盘24小时或7天。通过测量％干质量变化和极限抗张强度（UTS）来测试牙本质胶原蛋白的性质。牙本质I型胶原蛋白的降解通过端肽测定法进行测量，该测定法测量孵育介质中C端交联端肽（ICTP）和C端肽（CTX）的副产物释放与总蛋白浓度的关系，该总蛋白浓度与基质金属蛋白酶（MMP）和CT-K活性。结果重量分析显示C组与其他组在24h时有统计学差异（p <0.04）。从24小时到7天，洛杉矶的标本显示出明显更高的体重减轻（p = 0.02）。UTS在24小时和7天显示AS和LA之间存在统计学上的显着差异。与LA和PAA相比，C和AS在24小时和7天的UTS平均值明显更高。端肽测定报告，CTXtp结果显示，与C和AS相比，LA在24h的平均值明显更高。意义LA具有激活牙本质中内源性CT-K的能力（通过CTX（CT-K特异性端肽）的释放来衡量）。该基于LA的模型具有潜在用途，可用于进一步研究人牙本质中CT-K的活性和可能的​​抑制剂。