In the current world the publications have been increased on partially biodegradable materials loaded with inorganic fillers that improve their properties for the use as bond substitutes. In this work three formulations were designed and filled previously with hydroxyapatite(HA), in which the percent of the monomeric composition (acrylic acid/methyl methacrylate, AA/MMA) was varied  and the content of the natural polymer (Chitosan, CHI), the percent of the initiator (benzoylperoxide, PBO) and the co-initiator (N,N-dimethil-p-toluidin, DMpT) were keep constant. The difference in the monomeric ratio caused an appreciable variation in the mechanical properties, not being in this way for the composites thermoanalitical parameters, which were determined by Differential Scanning Calorimeter (DSC). Also it was carried out a study to evaluate the material’s bioactivity of the composites with 15% of AA and they showed a hydroxiapatite layer on their surface, this fact was verified by SEM, EDS and FTIR.