Impact of Cortical Perforations of Contiguous Donor Bone in a Guided Bone Augmentation Procedure: An Experimental Study in the Rabbit Skull

BACKGROUND: It has been shown that bone can be augmented beyond the original skeletal envelope by using space-making barriers. Further, it has been suggested that perforation of the contiguous donor bone enhances bone formation in guided bone augmentation procedures. PURPOSE: The goal of the present investigation was to evaluate whether perforations into the donor bone marrow through the cortical plate, located contiguous to an extracalvarial experimental space, influence bone generation into this space with regard to augmented bone tissue volume and bone density 3 months postoperatively. MATERIALS AND METHODS: Two titanium cylinders, each with a titanium lid, were subcutaneously placed with their open ends facing the parietal bones of eight rabbits and secured with miniscrews. The cortical bone plate on the test side was perforated with seven evenly distributed holes, each with a diameter of 1.2 mm, using carbon-steel burs. Together, these perforations corresponded to about one-third of the total experimental bone area. The bone on the control side was left intact, and no bleeding occurred during the placement of the titanium lid. The perforation procedure (test side) resulted in various degrees of blood fill. After 3 months, the animals were sacrificed to obtain ground sections for histology and histomorphometry. RESULTS: The cylinders were found to be partly filled with tissue containing slender bone trabeculae and marrow spaces in abundance. The bone consistently reached a higher level at the inner wall compared with the central part of the cylinders (p = .001). Hollow connections between the experimental space and the skull bone marrow were found in the contiguous outer cortical plate in four of the seven control sites. No statistically significant differences could be demonstrated between the perforated test sites and the control sites regarding augmented tissue volume (64.4 +/- 18.9% vs. 64.9 +/- 22.2%) or bone density, although there was a tendency toward denser bone in the test sites (21.5 +/- 11.1%) versus control sites (14.7 +/- 5.4%). There was no statistical difference regarding relative bone-to-titanium wall contact (27.4 +/- 14.7% for test; 38.6 +/- 25.9% for control). Thickness (height) and density of the skull bone vault were measured in the area beneath and lateral to the cylinders. No significant differences could be observed regarding these parameters between the test and control side. There were no correlations between thickness (height) or density of donor bone versus amount or density of augmented bone. The degree of immediate blood fill could not be shown to correlate with augmented tissue volume or augmented bone density. CONCLUSIONS: In the present model, as observed 3 months postoperatively, cortical perforations of contiguous donor bone or degree of immediate blood fill of an extracalvarial experimental space were not found to enhance augmented tissue volume beyond the skeletal envelope. Although there was a much higher mean value for bone density of augmented bone in the test sites, the large variations failed to show significant intergroup differences.

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