COMPARISON BETWEEN FREESTANDING AND TOOTH-CONNECTED PARTIALLY-STABILIZED ZIRCONIA IMPLANTS AFTER 2 YEARS FUNCTION IN MONKEYS - A CLINICAL AND HISTOLOGIC-STUDY

Statement of problem. Partially stabilized zirconia implants placed by a 1-stage procedure have been previously shown to obtain initial osse ointegration under clinically unloaded condition. However, it is unkno wn whether freestanding and tooth-connected partially stabilized zirco nia implants can maintain a long-term direct bone-implant interface. P urpose. This study examined the possibility of the long-term stability of osseointegration around partially stabilized zirconia implants wit h a 1-stage procedure with different loading designs. Material and met hods. Thirty-two partially stabilized zirconia implants were placed in to the mandibles of 8 monkeys. Three months after implant placement, 3 types of superstructure were provided in each animal to obtain differ ent concepts of support as (1) single freestanding implant support, (2 ) connected freestanding implant support, and (3) a combination of imp lant and tooth support. At 12 and 24 months after loading, clinical, h istologic, and histomorphometric evaluations of peri-implant tissues w ere performed on 28 implants. Results. No clear difference in clinical features was observed among the different types of support. Direct bo ne apposition to the implant was generally seen in all groups. Histome trically, bone contact ratio ranged between 66% and 81%, and bone area ratio varied between 49% and 78% at 24 months after loading. These va lues showed almost no difference among single freestanding, connected freestanding, and implant-tooth supports of partially stabilized zirco nia implants. Conclusion. In a primate model, partially stabilized zir conia implants placed with a 1-stage procedure achieve long-term stabi lity of osseointegration with the use of single freestanding, connecte d freestanding, and implant-tooth supports.