牙本质混合层裸露胶原酶解和树脂水解是临床树脂充填失败的主要原因。课题组前期研究发现壳聚糖等高分子螯合剂可结合纤维间晶体Ca2+，实现牙本质纤维外脱矿。纤维内晶体的保留，能降低混合层酶活性，并可避免纤维网塌陷，利于干粘接条件下树脂单体渗入，减少混合层水残留。然而，壳聚糖受大分子影响，其与纤维间Ca2+配位的能力因物理空间阻碍作用而较弱。羧基的引入能提高壳聚糖的Ca2+结合能力及反应速度，我们推测对壳聚糖进行化学改性，可合成分子量合适且Ca2+配位能力强的QCMC，提高牙本质纤维外脱矿效率。因此，本课题拟分析QCMC与Ca2+的配位点及吸附动力学特征，获取Ca2+吸附性能最优的反应产物，并设计抗菌性疏水树脂粘接剂，建立QCMC纤维外脱矿的牙本质疏水性粘接体系，以原位酶谱法分析混合层内源性酶活性，从微观形态学和生物力学角度评价混合层的质量及稳定性，为该技术的转化应用、提高粘接耐久性提供理论支持。

Hydrolytic degradation of adhesive resin and enzymatic degradation of exposed collagen fibrils within the bonded interface are known as the key factors contributing to bond failure. Based on the size-exclusion characteristic of collagen fibrils, we successfully achieved extrafibrillar demineralization of dentin using polyacrylic acid sodium salt (PAAN) and chitosan respectively. However, due to their low demineralization capacity, operating time required is still impractical for clinic. Compared with chitosan, quaternized carboxymethyl chitosan(QCMC), a derivative of chitosan, possesses better calcium binding ability, due to the presence of carboxyl in chitosan. Currently, the mechanisms of dentinal extrafibrillar demineralization induced by QCMC, as well as the effect of extrafibrillar demineralization on the durability of hybrid layer, have not been clarified. In this proposal, we aim to probe into the mechanism of dentinal extrafibrillar demineralization induced by QCMC, to formulate an original hydrophobic resin adhesive containing graphite oxide，accordingly to establish a dentinal hydrophobic bonding system based on extrafibrillar demineralization. By observing the effect of extrafibrillar demineralization on the activity of endogenous collagenase within the hybrid layer through in situ zymography, analyzing the permeability of resin monomer on hybrid layer with chromatograph and electron microscope, examining the resistance capacity of the system to secondary caries, we aim to evaluate the quality and durability of the hydrophobic hybrid layer of extrafibrillar demineralized dentin induced by QCMC from molecular biology, micromorphology and biomechanics. The success of the proposed hydrophobic bonding system based on extrafibrillar demineralization would benefit clinicians by providing a means for extending the durability of resin-dentin bonds via an original demineralization protocol.