<https://data.doctorgenius.com/definition/polyurethane-resin.rdf>
<http://schema.org/sameAs>
<https://www.wisegeek.com/what-is-polyurethane-resin.htm>
<https://www.dentalexcellencegroupnj.com/dumont-nj/which-is-better-invisalign-or-braces/>