Dental study models are made of Gypsum (Plaster), and should not be disposed of with any other non-gypsum waste. See
www.environment-agency.gov.uk/static/doc...sum_rev_Jan_2011.pdf
for a bit of guidance.
As plaster suppliers, we now provide a waste plaster collection and disposal service, but it's currently limited in area. If you'd like more info, please shout!