Many types of artificial bone filling material are used for the treatment of osteoanagenesis. b-tricalcium phosphate (b-TCP) is a bio-ceramic that has been used as an artificial bone replacement material in the fields of orthopedics and dental implant treatment. Despite many studies of β-TCP involving histological evaluation, there has been no study of continuous ossification in the living body, because the animals used for experiments are slaughtered at the time of assessment. Therefore, we tried to analyze the ossification of b-TCP diachronically and noninvasively by CT using a bone mass phantom and dental film with an aluminum step at the time of assessment. Two beagle dogs were used, and their second and third front mandibular molars were extracted. After curing, buccolingual bone defects measuring 10 mm×5 mm were produced at two locations on the right and left in the beagle lower jaw, respectively, to give a total of four places. We transplanted a piece of autologous bone, b-TCP granules and a b-TCP block (OSferion, Olympus Biomaterial Co, Ltd). In addition, we defined the bone defect and the circumferential bone as contrasts. We defined the transplant day as 0 week, and conducted measurements after 2, 4, 6, and 12 weeks. We analyzed dental films with an aluminum step (Nihon Atom Industry Co., Ltd. Al 99.98%) and CT scans with a bone mass phantom (B-MAS, Kyoto Science Co., Ltd.) on each occasion. We performed image analysis of dental films input to a PC using Adobe Photoshop Ver.7 (Adobe Co., Ltd.) and evaluated changes in density on the film as the brightness level on a monitor using Scion Image (Scion Co., Ltd.). Using Scion Image, we measured the density of each thickness of the aluminum step and a region of interest (ROI). From the measured density of the aluminum step, a regression line was obtained and used to calculate the thickness of aluminum equivalency of ROI from the density of the ROI. The software used was SimPlant Ver.10 (Yokokawa Materialise Co., Ltd.), from which we measured the CT value of five CaCO3 combination rods in a bone mass phantom, and found a regression line. We measured the CT value of the ROI from three directions and found the average. We then found a regression line, and determined the CaCO3 equivalency of the ROI from the CT value. 1At 12 weeks, in terms of aluminum equivalency, comparison of circumferential bone density gave values of 29.75% for the bone defect, 61.60% for b-TCP granules, 58.68% for the b-TCP block, and 73.35% for autologous bone. In addition, in terms of CaCO3 equivalency, the corresponding values were 10.02% for the bone defect, 58.87% for the b-TCP granules, 64.67% for the b-TCP block, and 78.21% for autologous bone.2The autologous bone showed the best ossification, and b-TCP granules tended to show ossification resembling that of autologous bone.3The bone defect showed a tendency to differ in aluminum chemical equivalency from CaCO3 equivalency. Sequential and noninvasive analysis of b-TCP ossification is possible using CT with a bone mass phantom and dental film with an aluminum step.