dos Santos Luís Alberto, Carrodeguas Raúl García, Boschi Anselmo Ortega, de Arruda Antônio Celso
Faculdade de Engenharia Mecânica, Universidade Estadual de Campinas, Campinas, SP, Brazil.
Artif Organs. 2003 May;27(5):412-8. doi: 10.1046/j.1525-1594.2003.07248.x.
alpha-Tricalcium phosphate bone cement, as formerly designed and developed by Driessens et al., consists of a powder composed by alpha-tricalcium phosphate (alpha-TCP) and hydroxyapatite (HA) seeds, and an aqueous solution of Na2HPO4 as mixing liquid. After mixing powder and liquid, alpha-TCP dissolves into the liquid and calcium deficient hydroxyapatite (CDHA), more insoluble than the former, precipitates as an entanglement of crystals, which causes the setting and hardening of the cement. alpha-TCP bone cement offers several advantages in comparison to calcium phosphate bioceramics and acrylic bone cements as bone graft and repairing material, like perfect adaptability to the defect size and shape, osteotransductibility, and absence of thermal effect during setting. The main handicap is its low mechanical strength. Therefore, approaching its mechanical strength to that of human bone could considerably extend its applications. In the present work, an in situ polymerization system based on acrylamide (AA) and ammonium polyacrylate (PA) as liquid reducer was added to alpha-TCP cement to increase its mechanical strength. The results showed that the addition of 20 wt% of acrylamide and 1 wt% AP to the liquid increased the compressive and tensile strength of alpha-TCP bone cement by 149 and 69% (55 and 21 MPa), respectively. The improvement in mechanical strength seems to be caused by a decrease of porosity and the reinforcing effect of a polyacrylamide network coexisting with the entanglement of CDHA crystals. The studied additives do not affect the nature of the final product of the setting reaction, CDHA, but promote the reduction of its crystal size.
α-磷酸三钙骨水泥，如Driessens等人之前设计和开发的，由一种粉末和一种混合液体组成。粉末由α-磷酸三钙（α-TCP）和羟基磷灰石（HA）晶种组成，混合液体是Na2HPO4的水溶液。将粉末和液体混合后，α-TCP溶解到液体中，而比前者更难溶解的缺钙羟基磷灰石（CDHA）以晶体缠结的形式沉淀出来，这导致了骨水泥的凝固和硬化。与磷酸钙生物陶瓷和丙烯酸骨水泥相比，α-TCP骨水泥作为骨移植和修复材料具有几个优点，如对缺损大小和形状的完美适应性、骨传导性以及凝固过程中无热效应。其主要缺点是机械强度低。因此，使其机械强度接近人体骨骼的强度可以显著扩展其应用范围。在本工作中，将基于丙烯酰胺（AA）和聚丙烯酸铵（PA）作为液体减水剂的原位聚合体系添加到α-TCP骨水泥中以提高其机械强度。结果表明，向液体中添加20 wt%的丙烯酰胺和1 wt%的AP分别使α-TCP骨水泥的抗压强度和抗拉强度提高了149%和69%（分别为55和21 MPa）。机械强度的提高似乎是由于孔隙率的降低以及与CDHA晶体缠结共存的聚丙烯酰胺网络的增强作用。所研究的添加剂不影响凝固反应最终产物CDHA的性质，但促进了其晶体尺寸的减小。
