Characterization of porous polymethylmethacrylate space maintainers for craniofacial reconstruction

Porous polymethylmethacrylate (PMMA) has been used as an alloplastic bone substitute in the craniofacial complex, showing integration with the surrounding soft and hard tissue. This study investigated the physicochemical properties of curing and cured mixtures of a PMMA-based bone cement and a carboxymethylcellulose (CMC) gel porogen. Four formulations yielding porous PMMA of varied porosity were examined; specifically, two groups containing 30% (w/w) CMC gel in the mixture using a 7% (w/v) or 9% (w/v) stock CMC gel (30-7 and 30-9, respectively) and two groups containing 40% (w/w) CMC gel (40-7 and 40-9). An additional group comprising solid PMMA without CMC was investigated. The incorporation of the CMC gel into the PMMA bone cement during polymerization decreased the setting time from 608 ± 12 s for the solid PMMA to 427 ± 10 s for the 40-9 group, and decreased the maximum temperature from 81 ± 4°C for the solid PMMA to 38 ± 2°C for the 40-9 group. The porous PMMA groups exhibited reduced compressive strength and bending modulus and strength relative to the solid PMMA. All the porous PMMA formulations released more unconverted methylmethacrylate (MMA) monomer and N,N-dimethyl-p-toluidine (DMT) from cured specimens and less MMA and DMT from curing specimens than the solid PMMA. The data suggest that the physicochemical properties of the porous PMMA formulations are appropriate for their application in craniofacial space maintenance.