26 illustrated in fig1 the height of the muffle used can also vary such that the muffle material to be heated can for instance vary by the factor of 4 from one pressing cycle to the next according to the invention a thermal detection device which is formed as a thermal imaging camera 30 is attached to the dental furnace 10 namely on the outside of the dental furnace preferably to the furnace bottom 14 the field of vision of the thermal imaging camera is directed to an area slightly above the firing chamber floor 16 i e where the muffle 26 u2014 or the dental restoration part in the case of a firing furnace u2014 is placed the thermal imaging camera 30 is adjusted such that it detects a slightly larger area in the horizontal and vertical direction than the size of the largest muffle 26 used this can also be seen schematically from fig2 if necessary the thermal imaging camera can also be provided with a lens system at its front in order to adjust the size and thus the resolution of the detection range as required for protection reasons the thermal imaging camera 30 is received within a frame 32 which remains intact even if the muffle 26 is bumped inadvertently furthermore it is preferably attached laterally at the rear of the furnace bottom 14 instead of laterally at the front as a consequence it does not get in the way on the one hand and it is directed towards clear space on the other hand in which typically no other heat sources are disposed preferably the orientation is selected such that the optical axis of the thermal imaging camera.