Enhancement of Maturation Using Low-intensity Pulsed Ultrasound on Bone Formation Induced by rhGDF-5

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In our previous study, we were able to induce bone formation by using rhGDF-5. However, the results of that study showed that even though bone formation occurred, the resulting bone growth was immature. This study assessed the efficacy of the low-intensity pulsed ultrasound stimulation (LIPUs)to enhance the bone maturation that was induced by the recombinant human growth differentiation factor 5 (rhGDF-5). This study used adult beagle dogs that weighed about 12 kg. The composite of β-TCP matrix with rhGDF-5 is made of rhGDF-5 which contained 500 micro-gram per gram of β-TCP particles. A Ti-6A1-4V dental implant with a 3.7 mm diameter and an 8 mm length was used in this study. The LIPUs had an intensity of 100mW/cm^2, a wave length of 3.0 MHz, a pulse width of 1.0 msec, a pulse cycle of 10.0 msec. Exposure of the frontal sinus was carried out bilaterally and received 2 grams of the rhGDF-5 composite. After 4, 8 and 12 weeks postsurgery, the implants were placed in the sinus graft regions. For 1 week, one sinus was stimulated by LIPUs for 10 or 20 minutes a day as the experimental group and the other sinus was not stimulated as the control group. The frontal sinuses were excised 8 weeks after dental implants placement. The bone maturation in response to LIPUs was evaluated histologically and bone contact ratio around the dental implant surface was measured. It seemed that the promoting of new bone formation was observed in the experimental groups. It was shown that the bone contact ratio of 4 weeks groups was higher the experimental groups than the control group, however there were no significant differences of bone contact ratio among three groups.