Thermally disrupting biofilm, disinfecting, or sealing tooth

A method of heat treating a root canal or other target portion of a tooth, the method comprising:

• inserting a distal end working portion of a heat treatment device into a root canal or a cavity in a tooth, the heat treatment device including a conformal polymer heat-generating substrate, sized and shaped and flexible enough to be inserted into the root canal or cavity in the tooth, and the heat treatment device including an electromagnetic-to-heat heating transducer, carried by the substrate;
• applying in situ localized heating from within the root canal or the cavity in the tooth, the heating being from the heating device and generated within the substrate while located within the root canal or the cavity in the tooth to treat a target region associated with the tooth;
• and
• applying the heating to the target region for a duration and at a temperature selected to seal the target region associated with the tooth, wherein the sealing includes heat-softening an active polymer substrate in which heat is generated by the heating device carried within the substrate in response to an AC electrical input signal applied to an electrically conductive trace formed on the substrate to adhere to and seal the target region of the tooth using the heat-softened substrate.