A porous, resorbable and flexible dental surgical membrane (16) is made from chitosan having a viscosity average molecular weight of about 400,000 daltons up to about 2,000,000 daltons and has a thickness of from about 100 microns to about 0.5 mm. The membrane is easily insertable over a bone graft material site to confine the bone graft material (14) while allowing access to the bone graft material of blood and oxygen and applied medicaments through the membrane. The high molecular weight of the chitosan may be chosen so that the membrane will not dissolve or resorb in a human mouth for a protracted period, e.g., from about 12 to about 16 weeks. The membrane is made by dissolving medical grade chitosan in aqueous acetic acid, dispersing fine silica particles into the solution to form a slurry, depositing a film of the slurry on a support surface, evaporating liquid from the slurry sufficiently to form a coherent chitosan membrane having silica particles dispersed therein, and then dissolving the silica particles with a sodium hydroxide solution followed by a water wash to form the porous chitosan membrane.
