Enlargement of edentulous ridges by bone regeneration: an histological and ultrastructural study of 20 clinical cases

Aim of the study

To determine the nature of regenerated bone and the physiological processes which take place after the enlargement of an edentulous ridge by the mobilisation of a portion of vestibular bone, until a trench of 4-6,5 mm has been obtained.

Materials and methods

Twenty patients who had 2 to 4 implants and ridge augmentation were selected for bone biopsies. They were taken 40, 90, 120, 150 and 480 days after surgery and the last ones 360 days after the implants were brought into function.

Results

After 40 days, optical microscopy revealed actively proliferating young bone with many cells. There was a layer of osteoid on trabecular bone, in contact with osteoblasts and fibroblasts. Biopsies taken at later stages showed the maturation of the mineralised bone. Electron microscopy showed a dark layer separating the very well mineralised matrix from that which was less well calcified. After the implants had been brought into function, there was a change in the orientation of the fibre bundles and the primary trabeculae were replaced by mature spongy bone. After 480 days, there was mature bone with Haversian systems. There were no differences between smokers and non-smokers.

Conclusion

This technique induced bone formation and the osseointegration of implants with a success rate of 97 %. Two essential requirements are : flaps of at least 1-1,5 mm thickness in order to carry sufficient nutrients to the site and sufficient vascularity to induce new blood vessel formation. The bone formed is the membranous type with spongy bone containing large bundles of intersecting fibres. The loading of the implants is necessary for bone maturation.

Commentary

This study has the merit of being the first prospective multicentre study of partially edentulous cases (mostly posterior) over 10 years. It makes a good case to practitioners and to patients alike for the predictability of Brånemark implant systems in partially edentulous cases.