An evaluation of the ability of materials used as adjuvants with the placement of implants to cause the release of bone induction factors

Aim of the study

The ability of materials to stimulate an adequate release of osseo-inductive cytokines such as morphogenic proteins (BMP) is a major factor of their success. This study, involving monkeys, evaluates 3 types of rhBMP-2 media (balls of poly [methylethyl methacrylate] [HTR^®], Bio-Oss^® and BioCoral^®), inserted into peri-implant surgical defects.

Materials and methods

Twenty-four sites were created in 6 monkeys. The three media, with or without rhBMP-2, were inserted into each of 4 sites. Two implants and each of the materials were placed in the defects. At the end of 5 months, abutments were fitted and the implants brought into function. Histology was undertaken after a further 5 months. Tetracycline was used as a vital marker to assess the process of remodelling during healing.

Conclusion

Three histomorphometric parameters were used assess the quality of support produced ; the amount of osseointegration, the density, volume and quality of newly formed bone. Even though the three media allowed good osseointegration of the implants, it seems that Bio-Oss^® offers the best prospects for the restoration of surgical defects. HTR^® gave good results but did not resorbed completely, whereas BioCoral^® resorbed too rapidly, only allowing knife-edged ridges to be obtained.

Commentary

This well managed study, with a fascinating discussion, observes the very different results obtained from the three media. Bio-Oss^® induces the greatest volume of newly formed bone when it is impregnated with rhBMP-2 but equally an excellent bony contour without rhBMP-2. It seems to me that it is the rate of resorption of the supporting medium that is the key to new bone formation.