Page 163 - Clinical relevance of current materials for cranial implants
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                                Leachables from materials used for cranioplasties
INTRODUCTION
Poly(methyl methacrylate) (PMMA) has been widely used in different fields of healthcare, as a bone cement in orthopedics, as dentures or orthodontic applications in dentistry, and in craniofacial reconstructions in maxillofacial surgery and neurosurgery 1–4. PMMA is formed through the polymerization of methyl methacrylate (MMA) using PMMA powder as a filler to minimize shrinkage. The conversion is not complete and some unpolymerized MMA, so-called ‘residual monomers’, remains in the final PMMA product5. MMA is known to cause various skin irritations and has toxic effects on neuronal cells and the respiratory system1. However, there is inadequate indication for alleged carcinogenicity according to the International Agency for Research of Cancer of MMA in humans1,6.
The amount of residual monomers typically varies between 2% and 6%7 and may
depend on: the initial polymer to monomer ratio8, the method of polymerization8–10,
the processing method11, and the use of a water-bath after preparation12. Auto-, heat- ,
and photopolymerization are well-known techniques for the preparation of PMMA.
Curing under pressure decreases porosity and increases the degree of conversion,
reducing the amount of residual monomers13. Additionally, due to the increased
temperature and chain mobility, the degree of conversion may further increase,
resulting in an even lower amount of residual monomers. If a water bath is used during 8 the polymerization the amount of residual monomers decreases10. Furthermore, the
amount of residual monomers decreased post-polymerization following 10 minutes incubation in a water bath at 37.0 ± 1.0 °C 14. Residual monomers influence the material properties of PMMA, i.e. water resorption, biocompatibility, hardness and dimensional stability5.
The aim of this study is to evaluate the release of residual monomers from PMMA- based materials in water at 37.0 ± 1.0 °C using different compositions and fabrication methods of PMMA.
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