Potential use of one-phase (methyl methacrylate) in dental implants.

Three techniques were studied to control the porosity and the pore size of the one-phase PMMA matrix, namely light sintering and the use of hydroxyapatite- or NaCl-filler. These techniques alleviate the problems of residual monomer inherent in the two-phase PMMA system. A two-step light sintering technique with a solid polymer core and porous outer layer showed improvement in the overall mechanical properties and good potential for anatomical implants. The NaCl-filled PMMA was found to give the best overall mechanical properties and control of porosity. The mechanical properties of the filled, water-equilibrated composites were close to literature values of dry PMMA systems except for a noticeable drop in their modulus. In the instance of hydroxyapatite, the 20 wt %-filled PMMA composites with 35-mesh particle size suffered a substantial loss in their mechanical properties and physical integrity after soaking for one week in water. Polymer-filler particle size ratio should be taken into consideration in compounding in order to obtain the desired filler distribution (either random or network).