Crestal Bone Remodeling in Loaded and Unloaded Implants after 6 and 12 Months: an Histologic Study in the Canine Mandible

Objective: The precise mechanisms of the bone resorption around dental implants is not yet completely known. Aim of the present study was an histologic evaluation in beagle dogs of the crestal bone response to loaded and unloaded implants. Methods: Sandblasted and acid-etched implants (Bone System, Milano, Italy) were placed in the mandible of six beagle dogs. The protocol was approved by the Ethical Committee of Madrid University. The two premolars and the first molars had been extracted 3 months previously. Each dog received 12 implants in the mandible. A total of 72 implant were used in this study. Three months following implantation, second-stage surgery was performed for abutment (36 implants) or healing screws (36 implants) connection. Three dogs were killed after 6 months, and three dogs after 12 months. A total of 72 implants were retrieved. The implants were divided into four group: group I implants with healing screws after 6 months; group II implants with healing screws after 12 months; group III implants with abutments after 6 months; group IV implants with abutments after 12 months. Results: In group I the vertical bone loss was 1.24 (SD 0.32) mm; in group II the vertical bone loss was 2.09 (SD 0.42) mm; in Group III the vertical bone loss was 1.32 (SD 0.35) mm; and in group IV the vertical bone loss was 2.21 mm (SD 0.35). No statistically significant differences were found in the amount of bone loss between test and control implants both at 6 and 12 months. Statistically significant differences were found, in both groups, between the bone loss found at 6 months and that found at 12 months. Conclusion: in conclusion, our data do not appear to support a role of loading in the peri-implant bone resorption that is observed during the first year of function.