This invention relates to a tissue expander for use in medical, veterinary and dental applications. The tissue expander comprises a self-inflating polymer network and a biodegradable polymer having a non-degraded state and a degraded state which in the non-degraded state constrains the inflation of the self-inflating polymer network and in the degraded state allows inflation of the self-inflating polymer network. In a preferred embodiment, the self-inflating polymer network and the biodegradable polymer form an interpenetrating polymer network or a semi-interpenetrating polymer network. Alternatively or in addition, the self-inflating polymer network forms a core and the biodegradable polymer forms coating which partially or fully surrounds the core.
