Page 169 - Clinical relevance of current materials for cranial implants

Leachables from materials used for cranioplasties
Differences in the composition of PMMA-based materials result in different quantities and release patterns of residual monomers present within the polymerized material. These differences may originate from subtle differences in the concentration and type of activator, catalyst, or filler particles which may have an impact on the degree of conversion and consequently the amount of residual monomers. Palacos R+G likely contains less activator than DePuy CMW-37 which should result in a final PMMA product with longer polymer chains and more crosslinks, and thus a higher molecular weight. Due to this structure it should be more difficult for residual monomers in Palacos R+G to release into water, resulting in a slower release pattern and a lower cumulative concentration of leached monomers. Different crosslinking agents may influence the hydrophobicity of the final product. This may enable, or hinder, leaching of residual monomers into surrounding water-based fluids.
Adverse reactions to PMMA bone cements are reported. Cardiovascular dysfunction,
fat-embolic events, and hypotension are described in patients who underwent a
PMMA cemented knee or hip implant in orthopedics1,18. Dentistry patients with
dentures based on PMMA can experience a burning sensation, redness, swelling, and
pain at the palate, tongue, and oral mucosa2. Symptoms of neurological dysfunction
are described after PMMA craniofacial reconstruction19,20. During preparation of
PMMA, respiratory problems such as irritation of the airways and shortness of breath
are reported in literature21,22. Residual monomers may leach into water, saliva, or other 8 bodily fluids and can be toxic to the human body7,8,12. PMMA-based materials used for
dental applications release MMA into saliva for up to one week after insertion, with a three times higher concentration near the surface of the implant23. The release of MMA into protein-rich solutions (native saliva) was significantly lower than the release into protein-free solutions (protein-free saliva or water)24. This likely reduces potentially toxic effects of leached MMA in physiological situations. Plasma concentrations of MMA during arthroplasty peaked shortly after cement implantation (30 seconds25 to 2 minutes26), and were cleared quickly, more than half of the MMA was cleared during the transpulmonary passage26.
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