HEALING AROUND IMPLANTS PLACED IN BONE DEFECTS TREATED WITH BIO-OSS(R) - 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 miner al 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 natur al bovine cancellous bone mineral particles (Bio-Oss(R), Geistlich Son s Ltd. Wolhusen, Switzerland). No resective surgery was performed in t he right jaw quadrant. In both quadrants the flaps were adjusted to al low full coverage of the edentulous ridge and sutured. 3 months later, 2 dogs (group I) were euthanized and biopsies from the premolar regio ns 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 mandib ular jaw quadrants. 2 fixtures of the ITI Dental Implant System (Strau mann, Waldenburg, Switzerland; solid-screw; 8 x 3.3 mm) were installed in each side. The fixtures in the test side were placed within the pr eviously grafted defect area, while the fixtures in the control side w ere placed in normally healed extraction sites. A 4 month period of pl aque control was initiated. At the end of this period, a clinical exam ination including assessment of plaque and soft tissue inflammation wa s performed and radiographs obtained from the implant sites. Biopsies were harvested and 4 tissue samples were yielded per dog, each includi ng the implant and the surrounding soft and hard peri-implant tissues. The biopsies were processed for ground sectioning or ''fracture techn ique'' and the sections produced were subjected to histological examin ation. The volume of the hard tissue that was occupied by clearly iden tified Bio-Oss(R) particles was reduced between the 3- and 7-month int ervals. This indicates that with time, Bio-Oss(R) becomes integrated a nd subsequently replaced by newly formed bone. In other words, this xe nograft fulfils the criteria of an osteoconductive material. It was al so observed that 4 months after implant installation, the titanium/har d tissue interface at test and control sites exhibited, from both a qu antitative and qualitative aspect, a similar degree of ''osseointegrat ion''.