Dentition three-dimensional data and jaw-bone three-dimensional data are collected from a patient and they are combined. According to the combined data, dental crown data for making up for data on a lost tooth and occlusion data on a dental crown represented by the dental crown data are created. When an occlusion force according to the occlusion data is exerted on the occlusion face of a dental crown, a mechanical evaluation factor is produced in a jaw bone. The mechanical evaluation factor produced near the place where an artificial tooth root supporting a dental crown is to be implanted is calculated. The implantation place is determined so that the mechanical evaluation factor may be smaller and the mechanical load on the jaw bone from the opposed tooth during mastication may be lighter.