An oral appliance having a base member with a generally U shaped body formed from a thermoplastic elastomer material that is not mouldable at temperatures below about 100° C., the base member having an outer wall portion that defines the outer wall of the appliance and a base extending inwardly from the outer wall that defines a non-mouldable section of the web, the web portion having at least one void formed therein； an inner wall member having a generally U shaped body formed from a material that softens and is mouldable at a temperature below 100° C., that is compatible with the thermoplastic elastomer of the base member, the inner wall member being joined to the base member by chemical adhesion and includes an inner wall portion that defines the inner wall of the appliance and a web portion that projects outwards from the inner wall portion so as to define a user mouldable tooth receiving surface of the web, the web having at least one projection that is complimentary to and received by the at least one void in the base member； and a frame member having a generally U shaped body formed from a thermoplastic material that is rigid and non-mouldable at temperatures below about 100° C. that is encased within the body.
