Evaluation of titanium dental implant osseointegration in posterior edentulous areas of micro swine.

This study investigated the micro swine (Sus scrofa) as an animal model for research in osseointegrated implant systems. As the first in a series of investigations based on this model, the study focused on the histological evaluation of the bone-implant interface of Brånemark implants. Ten titanium implants were placed in posterior edentulous areas of the swine for longitudinal evaluation of healing and osseointegration. Six-week and 18-week post-operative specimens were removed en bloc at the time of death. The samples were fixed in glutaraldehyde, embedded in acrylic, and sectioned with a diamond wafering saw. The specimens were viewed under SEM and photographed. The percentage of bone that was in direct contact with the coronal, middle, and apical segments of the implant, referred to as the contact length fraction (CLF), was determined by use of a digitizing analyzer. All implant fixtures became exposed through the soft tissue within one week of placement. Of the ten titanium fixtures placed, three failed--one by post-surgical day 14 due to food impaction into the surgical site, and the other two because of failure to osseo-integrate. Bone contact with the successfully integrated implant surfaces ranged from 19.2 to 58.5%, with a mean of approximately 34%. Osseointegration did not appear to increase over the experimental time period, since there was no difference in the percentage of bone contact between the 18-week and the six-week specimens. The lack of soft-tissue coverage over the implants caused bone loss, but did not significantly affect osseointegration in the coronal third. The micro swine appears to be a suitable animal model for use in implant research in posterior edentulous regions.