Bone tissue reactions at sites grafted with Bio-Oss®

Abstract

AIM: To analyze bone tissue reactions at sites grafted with a deproteinized bovine bone mineral (Bio-Oss®, Geistlich Pharma AG, Wolhusen, Switzerland). For this purpose experimental studies were conducted in dogs and one study was performed in humans.MATERIAL & METHODS: The mandibular premolars were extracted and open buccal bone defects were created in dogs. In study I, implants were placed in the compromized ridge, and compared with implants placed in a "normal" ridge. In study II, 5 months after tooth extraction, the buccal bone defect in the test animals was augmented with a graft made of Bio-Oss® and Tisseel® (Immuno AG, Vienna, Austria). After 3 months, titanium implants were inserted in the edentulous areas. Control sites consisted of implants placed in a non-augmented buccal defect. In studies I and II the animals were sacrificed 7 months after implant installation and biopsies were harvested. Ground sections were prepared for histological analysis.Cylindrical bone defects were prepared in the mandible of labrador dogs, 3 to 5 months after the extraction of the premolar teeth. The defects were either filled with Bio-Oss® alone or with Bio-Oss® mixed with Tisseel®, or covered with a collagen membrane (Bio-Gide®, Geistlich Pharma AG, Wolhusen, Switzerland). The animals were sacrificed 6 months after tooth extraction. Block biopsies were collected for histological analysis.In 21 subjects, tooth extraction was performed and bone augmentation was required at the extraction sites before fixture placement. The sockets were filled with Bio-Oss® granules or covered with a Bio-Gide® membrane. Bone biopsies were collected during implant installation and prepared for histological examination.In beagle dogs, the 4th mandibular premolars were extracted and the sockets filled with Bio-Oss®. Three months later an orthodontic device was inserted on the canine, the 3rd premolar and the 1st molar in each side of the mandible and bodily movement in a distal direction of the 3rd premolar was initiated. When the 3rd premolar had been moved into the extraction site of the 4th premolar, the animals were sacrificed and biopsies of the premolar-molar regions of the mandibles sampled. Paraffin sections were prepared and subjected to histological examination.RESULTS: Implants placed in a non-augmented compromized ridge were osseointegrated in their apical portion. At the buccal aspect of the fixture the bone defect was still present and at the lingual aspect a deep angular bone defect had formed. Sites where implants had been placed in the augmented buccal "defect" showed similar features at the buccal aspect as implants placed in the non-augmented ridge. The Bio-Oss® granules were located coronally to the bone crest and were surrounded by connective tissue.One and 3 months after grafting, cylindrical bone defects filled with a graft made of Bio-Oss® or Bio-Oss® mixed with Tisseel® showed the presence of newly formed bone in the periphery of the defect. In the central portion of the defect the graft was surrounded by connective tissue. The percentage of contact between Bio-Oss® particles and bone tissue was considerably smaller in sites grafted with Bio-Oss® mixed with Tisseel® than at sites grafted with Bio-Oss® alone.Human extraction sites covered with a Bio-Gide® membrane showed large amounts of lamellar bone and bone marrow and small proportions of woven bone. Sites grafted with Bio-Oss® were comprised of connective tissue including the graft particles and of scarce amounts of newly formed bone. Spontaneously healed sites were characterized by the presence of mineralized bone and bone marrow.It was possible to orthodontically move a tooth in bone tissue augmented with Bio-Oss®. At the pressure side of the 3rd premolar some Bio-Oss® granules were located in the periodontal ligament space. Osteoclast-like cells were occasionally observed to be in contact with the graft particles.