Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, P.R. China.
Department of Endodontics, The Dental College of Georgia, Augusta University, Augusta, GA, USA.
J Dent Res. 2022 Nov;101(12):1490-1498. doi: 10.1177/00220345221103137. Epub 2022 Jun 16.
The concept of extrafibrillar demineralization involves selective removal of apatite crystallites from the extrafibrillar spaces of mineralized dentin without disturbing the intrafibrillar minerals within collagen. This helps avoiding activation of endogenous proteases and enables air-drying of partially demineralized dentin without causing collapse of completely demineralized collagen matrix that adversely affects resin infiltration. The objective of the present study was to evaluate the potential of quaternized carboxymethyl chitosan (QCMC)-based extrafibrillar demineralization in improving resin-dentin bond durability. Isothermal titration calorimetry indicated that QCMC synthesized by quaternization of -carboxymethyl chitosan had moderate affinity for Ca (binding constant: 8.9 × 10 M). Wet and dry bonding with the QCMC-based demineralization produced tensile bond strengths equivalent to the phosphoric acid (HPO)-based etch-and-rinse technique. Those bond strengths were maintained after thermocycling. Amide I and PO mappings of QCMC-conditioned dentin were performed with atomic force microscope-infrared spectroscopy (AFM-IR). Whereas HPO-etched dentin exhibited an extensive reduction in PO signals corresponding to apatite depletion, QCMC-conditioned dentin showed scattered dark areas and bright PO streak signals. The latter were consistent with areas identified as collagen fibrils in the amide I mapping and were suggestive of the presence of intrafibrillar minerals in QCMC-conditioned dentin. Young's modulus mapping of QCMC-demineralized dentin obtained by AFM-based amplitude modulation-frequency modulation recorded moduli that were the same order of magnitude as those in mineralized dentin and at least 1 order higher than HPO-etched dentin. In situ zymography of the gelatinolytic activity within hybrid layers created with QCMC conditioning revealed extremely low signals before and after thermocycling, compared with HPO-etched dentin for both wet and dry bonding. Confocal laser scanning microscopy identified the antibacterial potential of QCMC against and biofilms. Taken together, the QCMC-based demineralization retains intrafibrillar minerals, preserves the elastic modulus of collagen fibrils, reduces endogenous proteolytic activity, and inhibits bacteria biofilms to extend dentin bond durability.
纤维外脱矿的概念涉及到在不破坏胶原纤维内的矿物质的情况下，从矿化牙本质的纤维外空间中选择性地去除磷灰石晶体。这有助于避免内源性蛋白酶的激活，并使部分脱矿牙本质在空气干燥时不会塌陷，而完全脱矿的胶原基质的塌陷会对树脂渗透产生不利影响。本研究的目的是评估基于季铵化羧甲基壳聚糖 (QCMC) 的纤维外脱矿在提高树脂-牙本质粘结耐久性方面的潜力。等温滴定微量热法表明，通过 -羧甲基壳聚糖季铵化合成的 QCMC 对 Ca 具有中等亲和力（结合常数：8.9×10 M）。使用 QCMC 基脱矿剂进行湿粘结和干粘结，其拉伸粘结强度与磷酸（HPO）基蚀刻-冲洗技术相当。这些粘结强度在热循环后仍能保持。使用原子力显微镜-红外光谱（AFM-IR）对 QCMC 处理牙本质进行酰胺 I 和 PO 映射。虽然 HPO 蚀刻牙本质显示出与磷灰石消耗相对应的 PO 信号的广泛减少，但 QCMC 处理牙本质显示出分散的暗区和明亮的 PO 条纹信号。后者与酰胺 I 映射中鉴定为胶原纤维的区域一致，并表明 QCMC 处理牙本质中存在纤维内矿物质。通过基于 AFM 的振幅调制-频率调制获得的 QCMC 脱矿牙本质的杨氏模量映射记录的模量与矿化牙本质相同数量级，至少比 HPO 蚀刻牙本质高 1 个数量级。与 HPO 蚀刻牙本质相比，QCMC 处理后形成的混合层中明胶酶活性的原位酶谱法在热循环前后均显示出极低的信号，无论是湿粘结还是干粘结。共聚焦激光扫描显微镜鉴定了 QCMC 对 和 生物膜的抗菌潜力。综上所述，基于 QCMC 的脱矿作用保留了纤维内矿物质，保持了胶原纤维的弹性模量，降低了内源性蛋白水解活性，并抑制了细菌生物膜，从而延长了牙本质粘结耐久性。
