Istvan Urban - Vertical 2 - The Next Level of Hard and Soft Tissue Augmentation

Fig 1-21 Note the excellent cortical bone formation.

The use of a membrane in GBR has been evaluated successfully for decades in multiple clinical and preclinical investigations. The role of the membrane has been determined to exclude competing cells such as fibroblasts. The clinical experience demonstrated that an important role of the membrane is to stabilize the bone graft. This has been well demonstrated in the Sausage technique using a collagen membrane and titanium pins for immobilization. In the author’s experience, the Sausage technique has resulted in the best bone quality and is usually faster and better than PTFE membranes. The native collagen membrane allows transvascularization and a possible accumulation of osseoinductive stimuli from the periosteum. In addition, the fast resorption of the collagen may also play a part in the maturation of the graft, since the periosteum holds vessels as well as mesenchymal cells that can turn into bone-forming cells. Therefore, a perforated membrane might help in bone formation. The goal is to develop ‘sausage-like’ bone quality faster.

One idea was to perforate PTFE membranes to allow faster bone maturation. In several preclinical investigations, different aspects of this idea were investigated, as is shown in the following subsections.

The osseoinductive action of BMP-2 depends on the presence of mesenchymal cells. The question is: How important are these types of cells in the periosteum versus the bone surface and the blood clot?

Dense versus perforated membrane was compared in a chronic vertical defect ( Figs 1-22 to 1-24 ). The results demonstrated significantly more bone fill when using the perforated membrane. The non-perforated membrane usually demonstrated appositional bone formation from the host bone with a lack of bone formation under the membrane ( Figs 1-25 to 1-27 ). These results demonstrated that the communication with the periosteum might be important when a graft containing BMP-2 is being used, such as autogenous particles.

This experiment focused on the vascularization and bone formation activity of the newly formed bone. A xenogenic bone graft was used without any growth factors or autogenous bone. The perforated membrane was used with and without a collagen membrane covering the non-perforated membrane ( Figs 1-28 to 1-31 ). Each group demonstrated a similar amount of bone formation as well as soft tissue invagination ( Figs 1-32 to 1-34 ). However, when the vascularized area of the regenerated ridge was examined, the perforated group demonstrated a tendency toward better vascularization ( Fig 1-35 and Table 1-1).

Fig 1-22 Labial view of a dense membrane fixated around a chronic vertical defect.

Fig 1-23 Labial view of a perforated membrane fixated around a chronic vertical defect.

Fig 1-24 Bone morphogenetic protein-2 (BMP-2) is bound into a collagen carrier. No other graft is used.

Figs 1-25 and 1-26 Cross-sectional views showing bone formation in both groups just below the periosteum and above the membrane.

Fig 1-27 Graph showing bone growth of the perforated and non-perforated sites. The perforated membranes demonstrated significantly more bone growth.

Fig 1-28 Labial view of a xenograft placed on a chronic vertical defect.

Fig 1-29 Labial view of a fixated dense membrane.

Fig 1-30 Labial view of a perforated membrane.

Fig 1-31 Labial view of a perforated membrane covered with a collagen membrane.

The tendency of having less pseudoperiosteum formation has been seen in well-adapted sites, even in cases of perforated membranes ( Figs 1-36and 1-37). Since membrane adaptation seems to be important, a hybrid design PTFE mesh/membrane was tested clinically ( Fig 1-38).

Figs 1-32 and 1-33 Cross-sectional views of the histologies of the regenerated bone after vertical ridge augmentation in this study.

Fig 1-34 Graph showing the bone formation of the three groups. No statistically significant differences were found.

Fig 1-35a and b The perforated group demonstrated a tendency toward better vascularization.

Table 1-1 Table showing the tendency toward a better vascularized surface of the perforated group.