CRESTAL BONE CHANGES AROUND TITANIUM IMPLANTS - A RADIOGRAPHIC EVALUATION OF UNLOADED NONSUBMERGED AND SUBMERGED IMPLANTS IN THE CANINE MANDIBLE

CURRENT IMPLANT PLACEMENT UTILIZES both nonsubmerged and submerged tec hniques. However, the implications of the location of a rough/smooth i mplant interface as well as the location of a microgap between implant and abutment on crestal bone changes are not well understood. The pur pose of this study was to radiographically evaluate crestal bone chang es around unloaded nonsubmerged and submerged titanium implants in a s ide-by-side comparison. Fifty-nine (59) Implants were placed at differ ent levels to the alveolar crest in 5 foxhounds. Standardized radiogra phs were taken at baseline and at monthly intervals until sacrifice at 6 months. Radiographic assessment was carried out by measuring the di stance between the top of the implant/abutment and the most coronal bo ne-to-implant contact (DIB), and by evaluation of bone density changes using computer-assisted densitometric image analysis (CADIA). DIB mea surements revealed that in 1-part, nonsubmerged implants, the most cor onal bone-to-implant contact followed at all time points the rough/smo oth implant interface. In all 2-part implants, nonsubmerged and submer ged, the most coronal bone-to-implant contact was consistently located approximately 2 mm below the microgap. In addition, CADIA values for all 2-part implants were decreased in the most coronal area-of-interes t (AOI). All bone changes were statistically significant and detectabl e 1 month after implant placement in nonsubmerged implants or 1 month after abutment connection in submerged implants. Neither implant posit ion nor individual dog effects were statistically significant, These r esults demonstrate that the rough/smooth implant interface as well as the location of the microgap have a significant effect on marginal bon e formation as evaluated by standardized longitudinal radiography. Bon e remodeling occurs rapidly during the early healing phase after impla nt placement for nonsubmerged implants and after abutment connection f or submerged implants.