Objective

Proteolytic and demineralizing agents have a profound influence on the dentin ultrastructure, which plays a key role in the mechanical integrity of the tooth and integrity of dentin-biomaterial interfaces. In-depth characterization of dentin treated with a novel root canal irrigation protocol comprising sodium hypochlorite (NaOCl) and etidronate (HEDP) is lacking. This study comprehensively characterized and compared the effects of the continuous chelation (NaOCl/HEDP) and sequential chelation (NaOCl/EDTA) protocols on dentin.

Methods

Dentin blocks, dentin powder and root canals of mandibular premolars were distributed into Group 1, Saline (control); Group 2, NaOCl/EDTA; and Group 3, NaOCl/HEDP. Ultrastructural characteristics of the treated dentin were investigated using electron microscopy and light microscopy, while the surface roughness was analyzed using atomic force microscopy. Chemical compositional changes were characterized using Fourier transform infrared spectroscopy (FTIR) and energy-dispersive-X-ray spectroscopy (EDS), while collagen degradation was determined using ninhydrin assay. Data were statistically analyzed using multiple-factor one-way ANOVA and Tukey HSD tests (P = 0.05).

Results

NaOCl/HEDP resulted in partially degraded, yet mineralized collagen fibers, with minimal alteration to the subsurface matrix. Conversely, NaOCl/EDTA dissolved the hydroxyapaptite encapsulation, exposing collagen fibre bundles. There was no significant difference in the surface roughness between the two protocols (P > 0.05). NaOCl/HEDP resulted in homogenous distribution of organic and inorganic components on the treated surface.

Significance

This study highlighted that continuous chelation (NaOCl/HEDP) resulted in a frail surface collagen layer while sequential chelation (NaOCl/EDTA) exposed bare collagen fibres. These surface and sub-surface effects potentially contribute to structural failures of dentin and/or dentin-biomaterial interfacial failures.

中文翻译：

---

连续和连续螯合对牙本质的影响

目的

蛋白水解和脱矿物质剂对牙本质的超微结构有深远的影响，这在牙齿的机械完整性和牙本质-生物材料界面的完整性中起着关键作用。缺乏对用含有次氯酸钠（NaOCl）和依替膦酸钠（HEDP）的新型根管冲洗方案治疗的牙本质的深入表征。这项研究全面表征并比较了连续螯合（NaOCl / HEDP）和顺序螯合（NaOCl / EDTA）方案对牙本质的影响。

方法

将下颌前磨牙的牙本质块，牙本质粉和根管分配到第1组，盐水（对照组）中；第2组，NaOCl / EDTA；和第3组，NaOCl / HEDP。使用电子显微镜和光学显微镜研究处理过的牙本质的超微结构特征，同时使用原子力显微镜分析表面粗糙度。使用傅里叶变换红外光谱（FTIR）和能量色散X射线光谱（EDS）表征化学成分的变化，同时使用茚三酮测定法测定胶原蛋白的降解。使用多因素单向方差分析和Tukey HSD测试对数据进行统计学分析（P = 0.05）。

结果

NaOCl / HEDP导致部分降解但矿化的胶原纤维，对地下基质的影响极小。相反，NaOCl / EDTA溶解了羟基磷灰石包封物，露出胶原纤维束。两种方案之间的表面粗糙度没有显着差异（P> 0.05）。NaOCl / HEDP导致处理过的表面上有机和无机成分均匀分布。

意义

这项研究强调，连续螯合（NaOCl / HEDP）会导致脆弱的表面胶原蛋白层，而连续螯合（NaOCl / EDTA）会暴露裸露的胶原纤维。这些表面和亚表面效应可能导致牙本质的结构破坏和/或牙本质-生物材料界面破坏。