Skrtic D, Antonucci J M, Eanes E D
National Institute of Dental Research, Research Associate Program, Maryland, USA.
Dent Mater. 1996 Sep;12(5):295-301. doi: 10.1016/s0109-5641(96)80037-6.
The rationale for this study was based on the hypothesis that the mechanical strength of methacrylate composites containing the bioactive filler, amorphous calcium phosphate, can be enhanced by synthesizing this filler in the presence of glass-forming agents. Specifically, this study was conducted to prepare composites with zirconia- and silica-modified amorphous calcium phosphate fillers, and to determine whether the remineralization potential from the release of calcium and phosphate ions and the mechanical properties of the corresponding methacrylate composites were enhanced.
The modified amorphous calcium phosphates were synthesized at pH 10.5 by mixing 800 mmol/L Ca(NO3)2 solutions and either 250 mmol/L zirconylchloride (ZrOCl2) or 4.4 mol/L tetraethoxysilane (TEOS) solutions with solutions containing 525 mmol/L Na2HPO4 and 11 mmol/L Na4P2O7. After washing and drying, the amorphous calcium phosphates were mixed with visible light-activated resins and photopolymerized to form composite disks that were then examined for their ability to release Ca2+ and total ionic phosphate (PO4(3-) + HPO4(2-) + H2PO4-, hereafter indicated as PO4) by immersion in HEPES-buffered (pH 7.4) saline at 37 degrees C. Solution ion concentrations were compared at regular intervals up to 265 h. Biaxial flexural strengths of the composites before and after immersion were compared, and significant differences were established by Student's test (p < 0.05).
Both ZrOCl2- and TEOS-modified amorphous calcium phosphate composite disks released Ca2+ and PO4 ions at sustained levels requisite for remineralization to occur. The transformation of amorphous calcium phosphate into hydroxyapatite within the composites was also retarded, particularly in the case of amorphous calcium phosphate modified with ZrOCl2. Biaxial flexure strength values of composite disks showed that TEOS- and ZrOCl2-amorphous calcium phosphate-filled composites increased in strength by 33% and 21% before immersion and by 25% and 27% after immersion, respectively, compared to unmodified amorphous calcium phosphate composites (controls). All strength increases except TEOS after immersion were significant (p < 0.05).
Properly modified amorphous calcium phosphate fillers can be used to prepare bioactive composites with enhanced mechanical properties for more demanding dental applications without compromising their remineralizing potential.
本研究的理论依据基于这样一个假设，即通过在玻璃形成剂存在的情况下合成含生物活性填料无定形磷酸钙的甲基丙烯酸酯复合材料，可以提高其机械强度。具体而言，本研究旨在制备含有氧化锆和二氧化硅改性无定形磷酸钙填料的复合材料，并确定钙离子和磷酸根离子释放所带来的再矿化潜力以及相应甲基丙烯酸酯复合材料的机械性能是否得到增强。
在pH 10.5条件下，将800 mmol/L硝酸钙溶液与250 mmol/L氧氯化锆（ZrOCl₂）或4.4 mol/L四乙氧基硅烷（TEOS）溶液，与含有525 mmol/L磷酸氢二钠和11 mmol/L焦磷酸钠的溶液混合，合成改性无定形磷酸钙。洗涤并干燥后，将无定形磷酸钙与可见光固化树脂混合并光聚合，形成复合盘，然后通过将其浸泡在37℃的HEPES缓冲（pH 7.4）盐水中，检测其释放Ca²⁺和总离子磷酸盐（PO₄³⁻ + HPO₄²⁻ + H₂PO₄⁻，以下简称PO₄）的能力。在长达265小时的时间内定期比较溶液中的离子浓度。比较浸泡前后复合材料的双轴弯曲强度，并通过学生检验确定显著差异（p < 0.05）。
ZrOCl₂和TEOS改性的无定形磷酸钙复合盘均以再矿化所需的持续水平释放Ca²⁺和PO₄离子。复合材料中无定形磷酸钙向羟基磷灰石的转化也受到抑制，特别是在ZrOCl₂改性的无定形磷酸钙的情况下。复合盘的双轴弯曲强度值表明，与未改性的无定形磷酸钙复合材料（对照）相比，TEOS和ZrOCl₂无定形磷酸钙填充的复合材料在浸泡前强度分别提高了33%和21%，浸泡后分别提高了25%和27%。除浸泡后TEOS外，所有强度增加均具有显著性（p < 0.05）。
适当改性的无定形磷酸钙填料可用于制备具有增强机械性能的生物活性复合材料，以满足更苛刻的牙科应用需求，同时不影响其再矿化潜力。
