The furnace (1) has a housing (3), a heating device (9) such as inductive heater or microwave heater, and an optical temperature determining element (6) for determining temperature in a combustion chamber (4). A dental combustion object (2) is supported on and/or in and/or below and/or beside cuboid shaped combustion aids (7) that are provided in the combustion chamber. The optical temperature determining element determines temperature of the combustion aids and/or the combustion object, and is formed by a pyrometer. An independent claim is also included for a method for thermal treatment i.e. sintering, of a dental combustion object.
