Vertical ridge augmentation: what is the limit?

The aim of this study is to show the possibility of achieving more than a 4-mm new vertical bone apposition on partially edentulous ridges. Six healthy, partially edentulous patients were treated from July 1993 to September 1993. After accurate radiographic investigation, all of the patients were treated using the Branemark System. After insertion, 14 fixtures were left circumferentially exposed for 37 mm. Autogenous bone graft harvested from a bone filter was placed around the exposed threads and completely covered with titanium-reinforced Gore-Tex augmentation membranes (TR-GTAM). Flaps were coronally displaced to passively cover the regenerative materials. Only one of the six membranes was exposed and it was removed immediately. After a 12-month healing period, the membranes were removed in conjunction with the second-stage surgical procedure. In the five cases where the membranes were kept covered, all of the available space underneath the TR-GTAM was filled with regenerative tissue. In all of the cases a histologic biopsy was performed. In one case all the space was filled with more than 7 mm of bone. In three cases all the space was filled with more than 5 mm of bone. In one case the most coronal part (approximately 1 mm) of the regenerative tissue was represented by connective tissue; the remaining tissue was represented by bone. The measurements demonstrated an average of vertical ridge augmentation of 4.95 mm. In the only case where the membrane underwent exposure and was then removed there was no regenerative tissue present.