Healing around implants placed in bone defects treated with Bio-Oss. An experimental study in the dog

The aim of the present experiment was to (i) study the healing after 3 and 7 months of bone defects filled with cancellous bovine bone mineral and (ii) compare the healing around implants placed in normal bone and in defects filled with bovine bone mineral. 5 beagle dogs, about 1-year-old, were used. At baseline, extractions of all mandibular left and right premolars were performed. Bone defects were prepared in the left mandibular quadrant. The defect was immediately filled with natural bovine cancellous bone mineral particles (Bio-Oss, Geistlich Sons Ltd. Wolhusen, Switzerland). No resective surgery was performed in the right jaw quadrant. In both quadrants the flaps were adjusted to allow full coverage of the edentulous ridge and sutured. 3 months later, 2 dogs (group I) were euthanized and biopsies from the premolar regions obtained and prepared for histologic analysis. The 3 remaining dogs (group II) were at this time interval (3 months) subjected to implant installation in the premolar region of both the right and left mandibular jaw quadrants. 2 fixtures of the ITI Dental Implant System (Straumann, Waldenburg, Switzerland; solid-screw; 8 x 3.3 mm) were installed in each side. The fixtures in the test side were placed within the previously grafted defect area, while the fixtures in the control side were placed in normally healed extraction sites. A 4 month period of plaque control was initiated. At the end of this period, a clinical examination including assessment of plaque and soft tissue inflammation was performed and radiographs obtained from the implant sites. Biopsies were harvested and 4 tissue samples were yielded per dog, each including the implant and the surrounding soft and hard peri-implant tissues. The biopsies were processed for ground sectioning or "fracture technique" and the sections produced were subjected to histological examination. The volume of the hard tissue that was occupied by clearly identified Bio-Oss particles was reduced between the 3- and 7-month intervals. This indicates that with time, Bio-Oss becomes integrated and subsequently replaced by newly formed bone. In other words, this xenograft fulfils the criteria of an osteoconductive material. It was also observed that 4 months after implant installation, the titanium/hard tissue interface at test and control sites exhibited, from both a quantitative and qualitative aspect, a similar degree of "osseointegration".