Osseointegration of titanium fixtures in onlay grafting procedures with autogenous bone and hydroxylapatite. An experimental histometric study.

The aim of the present study was to determine the degree of osseointegration of fixtures in different onlay grafting materials. Hydroxylapatite blocks of 2 different pore sizes and free monocortical bone grafts from the iliac crest were inserted in Gijttingen minipigs and fixed with 2 titanium fixtures. The extent of the bone/implant interface area on the fixture surface was determined from histological specimens by morphometric measurements and related to the total thread surface of the fixtures. Fixtures inserted into bone grafts showed the most complete degree of osseointegration, whereas the smallest bone/implant interface area was found with fixtures inserted into those HA blocks with the smaller pore size. There was a significant decrease in the degree of osseointegration between the host bone site and the augmentation material only with the fixtures inserted into the HA blocks of smaller pore size.