Dual-setting Calcium Phosphate Cement Modified With Ammonium Polyacrylate

α-Tricalcium phosphate bone cement, as formerly designed and developed by Driessens et al., consists of a powder composed by α-tricalcium phosphate (α-TCP) and hydroxyapatite (HA) seeds, and an aqueous solution of Na2HPO4 as mixing liquid. After mixing powder and liquid, α-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, α-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 α-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 α-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.275412418Gruninger, S.E., Siew, C., Chow, L.C., Oyoung, A., Tsao, N.K., Brown, W.E., Evaluation of the biocompatibility of a new calcium phosphate setting cement (1984) J Dent Res, 63, p. 200Yu, D., Wong, J., Matsuda, Y., Fox, J.L., Higuchi, W.I., Otsuka, M., Self-setting hydroxyapatite cement: A novel skeletal drug delivery system for antibiotics (1992) J Pharm Sci, 81 (6), pp. 529-531Ginebra, M.P., Boltong, M.G., Fernández, E., Planell, J.A., Driessens, F.C.M., Effect of various additives and temperature on some properties of an apatitic calcium phosphate cement (1995) J Mater Sci Mater Med, 6, pp. 612-616Ginebra, M.P., Fernández, E., Driessens, F.C.M., Planell, J.A., The effect of Na2HPO4 addition on the setting reaction kinetics of an α-TCP cement (1998) Bioceramics, 11, pp. 243-246. , LeGeros RZ, LeGeros JP, eds., (Proceedings of the 11th International Symposium on Ceramics in Medicine), New York: World Scientific Publishing Co. Pte. LtdGinebra, M.P., Fernández, E., Driessens, F.C.M., Boltong, M.G., Muntasell, J., Font, J., Planell, J.A., The effects of temperature on the behaviour of an apatitic calcium phosphate cement (1995) J Mater Sci Mater Med, 6, pp. 857-860Santos, L.A., Oliveira, L.C., Rigo, E.C.S., Carrodéguas, R.G., Boschi, A.O., Arruda, A.C.F., Influence of polymeric additives on the mechanical properties of α-tricalcium phosphate cement (1999) Bone, 25 (2), pp. 99S-102SCarrodéguas, R.G., Oliveira, L.C., Santos, L.A., Rigo, E.C.S., Boschi, A.O., Mondéjar, S.P., Cementos de α-fosfato tricálcico de fraguado doble (1999) Revista CNIC. Serie Ciencias Químicas (Cuba), 30 (3), pp. 153-158Driessens, F.C.M., Fernández, E., Ginebra, M.P., Boltong, M.G., Planell, J.A., Calcium phosphates and ceramic bone cements vs. acrylic cements (1997) Anal Quire Int, 93, pp. S38-S43Monma, H., Goto, M., Kohmura, T., Effect of additives on hydration and hardness of tricalcium phosphate (1984) Gypsum and Lime, 188, pp. 11-16Jenkins, R., Vries, J.L., (1971) An Introduction to X-ray Powder Diffractometry, , N. V. Philips Gloeilampenfabrieken - Eindhoven HolandaGinebra, M.P., Fernández, E., De Maeyer, E.A.P., Verbeeck, R.M.H., Boltong, M.G., Ginebra, J., Driessens, F.C.M., Planell, J.A., Setting reaction and hardening of an apatitic calcium phosphate cement (1997) J Dent Res, 76 (4), pp. 905-912Fernández, E., Ginebra, M.P., Boltong, M.G., Verbeeck, R.M.H., Planell, J.A., Kinetic study of the setting reaction of a calcium phosphate bone cement (1996) J Biomed Mater Res, 32, pp. 367-374Bermúdez, O., Boltong, M.G., Driessens, F.C.M., Planell, J.Á., Development of an octacalcium phosphate cement (1994) J Mater Sci Mater Med, 5, pp. 144-146Tampieri, A., Celotti, G., Szontagh, F., Landi, E., Sintering and characterization of HA and TCP bioceramics with control of their strength and phase purity (1997) J Mater Sci Mater Med, 8, pp. 29-37Famery, R., Richard, N., Boch, P., Preparation of α- and β-tricalcium phosphate ceramics with and without magnesium addition (1994) Ceramics International, 20, pp. 327-336Chow, L.C., Hirayama, S., Takagi, S., Parry, E., Diametral tensile strength and compressive strength of a calcium phosphate cement: Effect of applied pressure (2000) J Biomed Mater Res, 53, pp. 511-517Miyamoto, Y., Ishikawa, K., Takechi, M., Toh, T., Yuasa, T., Nagayama, M., Suzuki, K., Basic properties of calcium phosphate cement containing atelocollagen in its liquid or powder phases (1998) Biomaterials, 19, pp. 707-715Miyazaki, K., Horibe, T., Antonucci, J.M., Takagi, S., Chow, L.C., Polymeric calcium phosphate cements: Analysis of reaction products and properties (1993) Dent Mater, 9, pp. 41-45Matsuya, Y., Antonucci, J.M., Matsuya, S., Takagi, S., Chow, L.C., Polymeric calcium phosphate cements derived from poly(methyl vinyl ether-maleic acid) (1996) Dent Mater, 12, pp. 2-7Cherng, A., Takagi, S., Chow, L.C., Effects of hxydroxypropyl methylcellulose and other gelling agents on the handling properties of calcium phosphate cement (1997) J Biomed Mater Res, 35, pp. 273-277Sawamura, T., Hattori, M., Calcium Phosphate Composition and a Setting Solution Therefore, , US Patent 5,980,625, November 9, 1999Sawamura, T., Hattori, M., Okuyama, M., Calcium Phosphate Cement and Calcium Phosphate Cement Composition, , US Patent 5,993,535, November 30, 1999LeGeros, R.Z., (1991) Calcium Phosphates in Oral Biology and Medicine Monography in Oral Science, 15. , Switzerland: S. KargerIshikawa, K., Asaoka, K., Estimation of ideal mechanical strength and critical porosity of calcium phosphate cement (1995) J Biomed Mater Res, 29, pp. 1537-154