Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA.
Dent Mater. 2012 Aug;28(8):853-62. doi: 10.1016/j.dental.2012.04.024. Epub 2012 May 10.
Half of dental restorations fail in 10 years, with secondary caries as the main reason. Calcium phosphate composites could remineralize tooth lesions. The objectives of this study were to: (1) impart antibacterial activity to a composite with nanoparticles of amorphous calcium phosphate (NACP); and (2) investigate the effect of quaternary ammonium dimethacrylate (QADM) on mechanical and dental plaque microcosm biofilm properties for the first time.
The NACP and glass particles were filled into a dental resin that contained bis(2-methacryloyloxy-ethyl) dimethyl-ammonium bromide, the QADM. NACP nanocomposites containing 0%, 7%, 14%, and 17.5% of QADM by mass, respectively, were photo-cured. A commercial composite with no antibacterial activity was used as control. Mechanical properties were measured in three-point flexure. A human saliva microcosm model was used to grow biofilms on composites. Live/dead assay, metabolic activity, colony-forming unit (CFU) counts, and lactic acid production of biofilms on the composites were measured.
Increasing QADM mass fraction monotonically reduced the biofilm viability, CFU and lactic acid. Biofilms on NACP nanocomposite with 17.5% QADM had metabolic activity that was 30% that on a commercial composite control (p<0.05). Total microorganisms, total streptococci, and mutans streptococci CFU counts (mean ± sd; n = 6) on composite control was 6-fold those on NACP +17.5% QADM nanocomposite. Composite control had long strings of bacterial cells with normal short-rod shapes, while some cells on NACP-QADM nanocomposites disintegrated into pieces. Adding QADM to NACP did not decrease the composite strength and elastic modulus, which matched (p>0.1) those of a commercial composite without Ca-PO(4) or antibacterial activity.
A dental plaque microcosm model was used to evaluate the novel NACP-QADM nanocomposite. The nanocomposite greatly reduced the biofilm viability, metabolic activity and lactic acid, while its mechanical properties matched those of a commercial composite. NACP-QADM nanocomposite with calcium phosphate fillers, good mechanical properties and a strong antibacterial activity may have potential for anti-biofilm and anti-caries restorations.
半数的牙修复体在 10 年内失败，继发龋是主要原因。磷酸钙复合材料可使牙体病变再矿化。本研究的目的是：（1）用无定形磷酸钙纳米颗粒（NACP）赋予复合材料抗菌活性；（2）首次研究季铵基二甲基丙烯酰胺（QADM）对机械性能和牙菌斑微生物膜的影响。
将 NACP 和玻璃颗粒填充到含有双（2-甲基丙烯酰氧乙基）二甲基溴化铵的牙科树脂中，即 QADM。用光固化分别含有 0%、7%、14%和 17.5%（质量分数）QADM 的 NACP 纳米复合材料。使用不含抗菌活性的商业复合材料作为对照。在三点弯曲试验中测量力学性能。用人唾液微宇宙模型在复合材料上生长生物膜。测量生物膜在复合材料上的活/死测定、代谢活性、菌落形成单位（CFU）计数和乳酸产量。
随着 QADM 质量分数的增加，生物膜的活力、CFU 和乳酸逐渐降低。含 17.5%QADM 的 NACP 纳米复合材料上的生物膜代谢活性仅为商业复合材料对照的 30%（p<0.05）。复合对照组的总微生物、总链球菌和变异链球菌 CFU 计数（平均值±标准差；n=6）是 NACP+17.5%QADM 纳米复合材料的 6 倍。复合对照组的细菌细胞呈长串状，具有正常的短杆状，而 NACP-QADM 纳米复合材料上的一些细胞则分解成碎片。向 NACP 中添加 QADM 不会降低复合材料的强度和弹性模量，这与不含 Ca-PO（4）或抗菌活性的商业复合材料的强度和弹性模量相匹配（p>0.1）。
使用牙菌斑微宇宙模型评估新型 NACP-QADM 纳米复合材料。该纳米复合材料极大地降低了生物膜的活力、代谢活性和乳酸，而其力学性能与商业复合材料相匹配。具有磷酸钙填料、良好力学性能和较强抗菌活性的 NACP-QADM 纳米复合材料可能具有抗生物膜和抗龋修复的潜力。
