Purpose: Application of function-restoring individual implants for the bridging of defects in mandibles with continuity separation requires a stable fixation with special use of the cortical bone stumps. Materials and Methods: Five section planes each of 100 computed tomographies of poly-traumatized patients jaws were used for measuring the thickness of the cortical layer and the bone density of the mandible. The CT scans of 28 female and 72 male candidates aged between 12 and 86 years with different dentition of the mandible were available. Results: The computed tomographic evaluations of human mandibles regarding the layer thickness of the cortical bone showed that the edge of the mandible in the area of the horizontal branch possesses the biggest layer thickness of the whole of the lower jaws. The highest medians of the cortical bone layer thickness were found in the area of the molars and premolars at the lower edge of the lower jaws in 6-oclock position, in the area of the molars in the vestibular cranial 10-oclock position and in the chin region lingual-caudal in the 4-oclock position. The measurement of the bone density showed the highest values in the 8-oclock position (vestibular-caudal) in the molar region in both males and females. Conclusion: The average values available of the bone density and the layer thickness of the cortical bone in the various regions of the lower jaw, taking into consideration age, gender and dentition, are an important aid in practice for determining a safe fixation point for implants in the area of the surface layer of the mandible by means of screws or similar fixation elements.