Monomer elution from a dental composite

Recently, I started a series of studies on monomer elution from composites with colleagues from University of Belgrade School of Dentistry and Faculty of Technology and Metallurgy. One of these experiments was presented a month ago at an international material science and engineering conference YUCOMAT.

The nano-hybrid composite Filtek Z250 (3M ESPE) was used to study elution kinetics of monomers UDMA and HEMA over 28 days post-immersion in either distilled water or 75% ethanol. Kinetic models were proposed and it was shown that monomer elution followed the first order law for both UDMA and HEMA irrespective of the medium. However, there were some differences in that UDMA eluted more rapidly during the first 24 h and then much more slowly over the 28-day period. This indicates that during the first 24 h elution from the sample surface occurred whereas the slow phase corresponds to monomer elution from inside the polymer. On the other hand, HEMA did not start to elute immediately, but only after 24 h and the eluted concentrations increased over the 28 days. Though HEMA is not a genuine ingredient of the studied composite, its slow elution and small eluted amounts seem to support a previous statement by other authors that HEMA could elute as a product of degradation of UDMA. (We are currently investigating this hypothesis.)