Objectives: Rehabilitation of the posterior edentulous maxilla using a dental implant is challenging when bone volume is limited. The literature supports the use of sinus lift procedures for increasing bone volume by filling the sinus cavity with autogenous bone and/or bone graft substitutes. This study reports on a patient with clinical, tomographic, microtomographic and histomorphometric evaluation of the resorption of Bio-Oss[tm] after maxillary sinus floor augmentation.
Methods: A 55-year-old, non-smoking woman presented with limited bone volume on both sides of the posterior edentulous maxilla that required rehabilitation. She had no systemic problems that might affect the surgical procedures. Preoperative cone-beam CT revealed significant maxillary sinus pneumatisation. Sinus lift procedures were performed on both sides of the maxilla, using a lateral surgical approach, and the maxillary sinuses were filled with a bovine bone graft substitute (BioOss[tm] small particles). A 25x25-mm collagen membrane (BioGide[TM]) was placed over the graft and the surgical flaps were sutured to entirely cover the membranes. Postoperative medications were amoxicyillin 500mg, clavulanic acid 125mg, ibuprofen 200mg and PerioGard[TM] rinse. Sutures were removed 14 days after surgery. Healing was uneventful, with no membrane exposure or other complications. After 12 months, further cone-beam CT showed significant gains in bone volume in both maxillary sinus areas, supporting the installation of osseointegrated implants. The patient postponed implant placement surgery; the left side was reopened 12 months after sinus lifting and the right side after 20 months. Before placing an implant, a bone biopsy was collected with a 2-mm trephine bur from both sides and samples were prepared for microtomographic and histological analysis.
Results: Four months after implant installation, the healing abutments were connected and cone-beam CT was performed to evaluate the implants. Provisional prostheses were then installed and remained in function for 3 months, allowing functional analysis of the prosthetic rehabilitation. Definitive ceramic crowns were then installed. Microtomography showed newly formed bone (27%) and residual biomaterial (39%). Biopsy samples at 20 months post-operatively contained [ok?] 52% newly formed bone and 16% residual biomaterial. These results revealed the process of particle resorption and replacement by new bone tissue between 12 and 20 months. Histological analysis demonstrated remnants of biomaterial particles surrounded by newly formed bone without connective tissue. There were no signs of inflammation and there was no gap between the bone and Bio-Oss[tm] particles. The biopsy collected at 20 months showed noticeably fewer particles of residual biomaterial than that collected at 12 months.
Conclusion: This report showed that an inorganic bovine bone graft associated with collagen membrane can be used successfully in this sinus lift procedure for the subsequent installation of dental implants. There was slow resorption of particles and continuous replacement by newly formed bone, which are desirable for to maintaining grafted bone volume for a longer period. It is important to emphasize that this report is not intended to change the protocol for installation of implants after sinus lifting using inorganic bovine bone and collagen membrane. The extended implant placement times (12 and 20 months) described here related to the patient's situation and are not necessary or desirable in clinical practice.

Description of baseline situation; Exposure of underlying bone; Insertion of four implants; Impression-taking; Bar construction; Welding the individual components, Correction of tension; Finishing the bar; Adjusting the prosthesis; Implant placement.