Method for making a numerical three-dimensional model of a chewing system of a living body and the parts surrounding the chewing system, comprising soft parts such as gums and hard parts such as teeth and bones, wherein at least the soft parts have an outer surface, comprising: - making at least two sections of the chewing system located at a mutual distance by means of penetrating radiation and numerically representing the absorption for the radiation; - storing in a memory the sections numerically representing the absorption; and - constructing a numerical three-dimensional model of the chewing system on the basis of the sections stored in the memory, - wherein a contrast agent with an absorption coefficient for the radiation differing substantially from that of the soft parts is applied to a carrier manufactured from material with a low absorption coefficient for the penetrating radiation, of which the contour forms an approximation of the contour of the outer wall of the soft parts of the chewing system, - wherein the carrier is then placed on the outer wall of the soft parts of the chewing system prior to making the sections, characterized in - that the contrast agent is arranged in a thin layer on the side of the carrier directed toward the soft parts of the chewing system, - that the thickness of the layer is such that the degree of radiation absorption of the layer is in the order of magnitude of the degree of radiation absorption of the soft parts of the chewing system by radiation beams propagated straight through the layer of contrast agent and - that during making of the sections at least a part of the outer surface of the soft parts of the chewing system is provided with the layer of contrast agent. - making at least two sections of the chewing system located at a mutual distance by means of penetrating radiation and numerically representing the absorption for the radiation; - storing in a memory the sections numerically representing the absorption; and - constructing a numerical three-dimensional model of the chewing system on the basis of the sections stored in the memory, - wherein a contrast agent with an absorption coefficient for the radiation differing substantially from that of the soft parts is applied to a carrier manufactured from material with a low absorption coefficient for the penetrating radiation, of which the contour forms an approximation of the contour of the outer wall of the soft parts of the chewing system, - wherein the carrier is then placed on the outer wall of the soft parts of the chewing system prior to making the sections, characterized in - that the contrast agent is arranged in a thin layer on the side of the carrier directed toward the soft parts of the chewing system, - that the thickness of the layer is such that the degree of radiation absorption of the layer is in the order of magnitude of the degree of radiation absorption of the soft parts of the chewing system by radiation beams propagated straight through the layer of contrast agent and - that during making of the sections at least a part of the outer surface of the soft parts of the chewing system is provided with the layer of contrast agent.