Acrylic cements with different compositions were prepared by mixing the solid part (composed of poly(methyl methacrylate), PMMA, and benzoyl peroxide, BPO) and the liquid part (composed of methyl methacrylate, MMA, and N,N-dimethyl-p-toluidine, DMPT), modified by addition of hydroxyapatite (HA) and ammonium nitrate (AN) and characterized by measuring thermal and mechanical properties. Three sets of samples were prepared. For B-group, the total amount of solid including HA was constant but the PMMA to HA ratio was varied. For C-group, polymer/monomer ratio was constant and varying amounts of HA was added. For D-group, polymer/monomer ratio was kept constant and AN was added in varying amounts. Effects of these composition changes on the properties of the cement such as setting time, curing temperature, tensile and compression strength, and deformation were examined. For B-group samples, no linear change was observed in thermal (curing temperatures were all quite high) and mechanical (between 27 and 19 MPa for tensile, and 98 and 116 MPa for compression strength) properties upon change of HA content with change in solid/liquid ratio. For C and D-group samples, a continuous decrease in curing temperature from 114 to 101 degrees C and from 94 to 73 degrees C was observed upon increasing HA and AN contents, respectively. Also, a linear relation was observed in compression strength (from 98 to 111 MPa) and in tensile strength (from 27 to 21 MPa) upon HA addition, and in the compression strength (from 103 to 85 MPa) and in the tensile strength (from 22 to 17 MPa) with NA addition. (c) 2006 Wiley Periodicals, Inc.