Sinus Floor Elevation Using Anorganic Bovine Bone Matrix (OsteoGraf/N) With and Without Autogenous Bone: A Clinical, Histologic, Radiographic, and Histomorphometric Analysis—Part 2 of an Ongoing Prospective Study

Abstract

Sinus Floor Elevation Using Anorganic Bovine Bone Matrix (OsteoGraf/N) With and Without Autogenous Bone: A Clinical, Histologic, Radiographic, and Histomorphometric Analysis—Part 2 of an Ongoing Prospective Study S.J. Froum, D.P. Tarnow, S.S. Wallace, et al., Int J Periodontics Restorative Dent. 1998;18:528–543 Summary: This study, begun in 1993 from the New York University College of Dentistry, sought to evaluate the long-term clinical, histologic, radiographic, and histomorphometric study of sinus elevations. This study presented data collected from 113 sinus augmentations using an anorganic bovine bone matrix (Osteograft/N or OG/N), autogenous bone, or demineralized freeze-dried bone (DFDBA) as graft material. The patient pool consisted of 236 sinus lifts in 169 patients with 136 histology cores obtained. The subgroup reported in this particular study consisted of 113 sinus lifts with OG/N alone or in combination with autogenous bone and/or DFDBA. A primary parameter also consisted of: with or without the use of a nonresorbable expanded polytetrafluoraethylene (e-PTFE) membrane barrier to cover the lateral window osteotomy site along with tacks or screws for stabilization. Also, the protocol was modified to include both immediate and staged implant placement. Both protocols included biopsy cores harvested from the lateral window area. Decalcified sections were stained and magnified for grid projection or computerized image analysis for those specimens with vital bone and hydroxyapatite. Eighty percent of the specimens were processed as nondecalcified and analyzed by image analysis software. In comparing mean vital bone contact between all graft materials, the combination of OG/N+Autogen-ous+DFDBA (27.8%) was slightly greater than OG/N+Autogenous (21.1%), OG/N+DFDBA (19.7%), and OG/N alone (14.2%). Vital bone formation was enhanced when a membrane was placed, ranging from 17 to 33% with a membrane and 8.5 to 19% without a membrane. Over the 3-year period, 98.2% of the implants survived. Because of the high success rates achieved (98.2%), no correlation could be drawn between implant failure and bone-to-implant contact. Strikingly, the consistently low amount of vital bone present in the sinus after an augmentation procedure (14.2–27.8%) did not impact on the overall success of the implants. A major drawback in this study model was the short follow-up period of 3 years with histology taken at 6 to 9 months. An increased percentage of vital bone can be expected over a longer time period as the grafted bone is being continuously resorbed. 1 With further anticipated follow-up in this study, the success rates should remain high, although no additional histology is to be obtained. The choice of where the histology core was taken can be considered a flaw in this study. Because the core was taken through the lateral window, the sampled bone taken for histology is most likely not the area of where the implant is located. Also, the use of a membrane would have obvious beneficial results in increasing the amount of bone formation adjacent to the barrier, as reflected in the results. Because those areas receiving a membrane had more vital bone formation, the results of the histology cores were skewed. One of the great new paradoxes in implant dentistry is the clinical significance of bone-to-implant contact in relation to implant survivability. Nowhere in the oral cavity is the quality of bone such a concern as in the posterior maxilla. Greater implant failure rates have been reported in the maxilla without the use of bone grafts. 2 Lower success in the posterior maxilla can be attributed to the poor bone quality (types 3 and 4). 3 Even if a bone graft procedure was performed, it would seem logical that an area of initially minimal amount of alveolar bone height would have lower success than an area with greater initial bone height. This is not quite true. One hundred percent success was achieved with simultaneous lift implant placement whether 1 to 2 mm or 3 to 5 mm of initial bone height was present. 4,5 It would also seem logical that amount of quality, vital bone, as needed for increased bone-to-implant contact, would be a good predictor of successful implant integration and longevity. This report, as part of an ongoing prospective trial, disproves the clinical significance of bone-to-implant contact because, despite the low amount of vital bone, high success rates were achieved.