Analysis of Bone Mineral Density and Area of Newly Formed Bone Around Implants Using Micro-CT After Pull-Out Tests

New bone formation around implants has been evaluated two-dimensionally by the histopathological examination of sections. However, micro-computed tomography (micro-CT) allows the three-dimensional observation of bone structure. The purpose of this study is to compare bone mineral density and area of newly formed bone around implants with two types of surface treatment. We evaluated the influence of differences in surface treatment using micro-CT. The Ti-6Al-4V alloy implants (3.1 mm in diameter and 30.0 mm in length) underwent mechanical polishing (‘machined”) as a control or shot-blast surface treatment (‘blasted’) and their average surface roughness was≤0.70. The implants were inserted into the femurs of New Zealand White rabbits (16 weeks old). After 4, 8, 12, 24, and 48 weeks, pull-out tests were performed and the rabbit femurs were studied after the tests. The bone mineral density of newly formed bone was slightly higher for the blasted implants than for the machined implants from 4 to 48 weeks. Blasted implants showed a significantly greater area of newly formed bone around them after each observation period than did machined implants. These results suggested that surface treatment of implants is a factor affecting the bone mineral density and bone area. These micro-CT measurement results revealed that blasted surface was a factor for increasing the bone mineral density and bone area with time, in contrast to machined surface. Furthermore, micro-CT is a valuable analytical tool for assessing the implant-bone interface and the effect of implant surfaces on the quality and structure of newly formed bone.