Influence of barrier occlusiveness on guided bone augmentation. An experimental study in the rat.

The present study was designed to test perforated and non-perforated barriers for their ability to promote augmentation of bone tissue. More specifically, 1 totally occlusive barrier and 6 barriers with perforation sizes of about 10, 25, 50, 75, 100, and 300 microns and 1 group with no barriers placed (open test chambers) were used to test the effect of a barrier's occlusiveness on the amount and composition of augmented tissue over time. The skull of the rat was used as the experimental area. Prefabricated, flexible silicone frames with an inferior flange for peripheral sealing to the bone surface and a central vertical through hole with a diameter of 3.6 mm and a height of 2 mm were used as test chambers. The barriers were inserted to cover the superior opening of the through hole. The healing periods were 4, 8, and 12 weeks. All test chambers exhibited newly formed skull bone which was augmented over time. The placement of totally occlusive barriers resulted in the slowest rate of bone tissue augmentation but in a highly predictable manner, i.e., there were only small individual variations. Placement of barriers with perforations exceeding 10 microns, on the other hand, resulted in a faster rate of bone augmentation with larger individual variations and a totally different augmentation pattern. A pronounced augmentation of calvarial soft tissue from the sagittal suture of the skull as well as ingrowth of suprabony connective tissue through the barriers were also observed. After 12 weeks of healing, no differences in the amount of augmented mineralized bone related to perforation sizes > 10 microns were found. The open test chambers also showed bone augmentation, although most of their volume was occupied by suprabony connective tissue.