Weir Michael D, Ruan Jianping, Zhang Ning, Chow Laurence C, Zhang Ke, Chang Xiaofeng, Bai Yuxing, Xu Hockin H K
Department of Endodontics, Periodontics and Prosthodontics, University of Maryland School of Dentistry, Baltimore, MD 21201, USA.
School of Stomatology, Xi'an Jiaotong University, Xi'an, Shaanxi, China.
Dent Mater. 2017 Sep;33(9):1033-1044. doi: 10.1016/j.dental.2017.06.015. Epub 2017 Jul 19.
Secondary caries is a primary reason for dental restoration failures. The objective of this study was to investigate the remineralization of human dentin lesions in vitro via restorations using nanocomposites containing nanoparticles of amorphous calcium phosphate (NACP) or NACP and tetracalcium phosphate (TTCP) for the first time.
NACP was synthesized by a spray-drying technique and incorporated into a resin consisting of ethoxylated bisphenol A dimethacrylate (EBPADMA) and pyromellitic glycerol dimethacrylate (PMGDM). After restoring the dentin lesions with nanocomposites as well as a non-releasing commercial composite control, the specimens were treated with cyclic demineralization (pH 4, 1h per day) and remineralization (pH 7, 23h per day) for 4 or 8 weeks. Calcium (Ca) and phosphate (P) ion releases from composites were measured. Dentin lesion remineralization was measured at 4 and 8 weeks by transverse microradiography (TMR).
Lowering the pH increased ion release of NACP and NACP-TTCP composites. At 56 days, the released Ca concentration in mmol/L (mean±SD; n=3) was (13.39±0.72) at pH 4, much higher than (1.19±0.06) at pH 7 (p<0.05). At 56 days, P ion concentration was (5.59±0.28) at pH 4, much higher than (0.26±0.01) at pH 7 (p<0.05). Quantitative microradiography showed typical subsurface dentin lesions prior to the cyclic demineralization/remineralization treatment, and dentin remineralization via NACP and NACP-TTCP composites after 4 and 8 weeks of treatment. At 8 weeks, NACP nanocomposite achieved dentin lesion remineralization (mean±SD; n=15) of (48.2±11.0)%, much higher than (5.0±7.2)% for dentin in commercial composite group after the same cyclic demineralization/remineralization regimen (p<0.05).
Novel NACP-based nanocomposites were demonstrated to achieve dentin lesion remineralization for the first time. These results, coupled with acid-neutralization and good mechanical properties shown previously, indicate that the NACP-based nanocomposites are promising for restorations to inhibit caries and protect tooth structures.
继发龋是牙齿修复失败的主要原因。本研究的目的是首次通过使用含无定形磷酸钙（NACP）纳米颗粒或NACP与磷酸四钙（TTCP）的纳米复合材料进行修复，体外研究人牙本质病变的再矿化情况。
通过喷雾干燥技术合成NACP，并将其掺入由乙氧基化双酚A二甲基丙烯酸酯（EBPADMA）和均苯四甲酸甘油二甲基丙烯酸酯（PMGDM）组成的树脂中。在用纳米复合材料以及一种不释放离子的市售复合树脂对照修复牙本质病变后，将标本进行循环脱矿（pH 4，每天1小时）和再矿化（pH 7，每天23小时）处理4周或8周。测量复合材料中钙（Ca）和磷（P）离子的释放量。在4周和8周时通过横向显微放射照相术（TMR）测量牙本质病变的再矿化情况。
降低pH值会增加NACP和NACP-TTCP复合材料的离子释放量。在56天时，pH 4时释放的Ca浓度以mmol/L计（平均值±标准差；n = 3）为（13.39±0.72），远高于pH 7时的（1.19±0.06）（p<0.05）。在56天时，pH 4时P离子浓度为（5.59±0.28），远高于pH 7时的（0.26±0.01）（p<0.05）。定量显微放射照相显示在循环脱矿/再矿化处理前有典型的牙本质表层下病变，以及在处理4周和8周后通过NACP和NACP-TTCP复合材料实现的牙本质再矿化。在8周时，NACP纳米复合材料实现的牙本质病变再矿化（平均值±标准差；n = 15）为（48.2±11.0）%，远高于在相同循环脱矿/再矿化方案后市售复合树脂组牙本质的（5.0±7.2）%（p<0.05）。
首次证明新型基于NACP的纳米复合材料可实现牙本质病变的再矿化。这些结果，再加上先前显示的酸中和能力和良好的机械性能，表明基于NACP的纳米复合材料在用于抑制龋齿和保护牙齿结构的修复方面具有前景。
