Comparison of bone reactions adjacent to titanium implants under barious loading conditions : an animal study in dog

Abstract

Mostly, implant success depends on deciding the time and the method of loading. This experiment was designed to investigate bone reactions adjacent to titanium implants in various loading conditions through the loading device, designed for applying controlled loading to the implants. Twenty-four implants in Six Beagle dogs were used for the study. Loading devices were fabricated by cast metal bars and orthodontic mini screw welded by laser. After extraction of all premolars, two implants were placed in each side of mandibles of Beagles. After two weeks, the loading device was inserted. In delayed loading (DL) group, 3-unit loading was applied after eight weeks of loading device placement; in early loading (EL) group, 3-unit loading was applied simultaneously after loading device placement, in periodic loading (PL) group, each 1-unit loading was applied after 2, 4 and 8 weeks after loading device placement. To simulate implant with low initial stability, periodic loading with rotation mobile implant (Pm) group was added. Twelve weeks after loading device placement, all the animals were sacrificed, and the results from the histological, histomorphometric, radiographic, and resonance frequency analyses were as below.1. Four implants from 24 implants became loss of osseointegration. All failed implant were excluded from the results, and the implants adjacent to the failed implants were referred to non-loaded negative control group.2. All the implants, except 4 failed, showed successful osseointegration, new bone formation was observed inside of implant threads. 3. Implant stability quotient (ISQ) values were increased by time in all groups.4. Bone to implant contact (BIC), Bone density from histological specimen (h-BD), Bone density (BD) and Bone volume (BV) from MicroCT images showed increased values in all the loaded groups, compared with negative control group. But significant difference were observed between PL and negative control in BIC (P=0.029), between DL and negative control in BD (P=0.029).5. Bone mineral apposition rate (BMAR) were similar in all groups, but BMAR-1 was higher than BMAR-2 and BMAR-3 (P=0.000, P=0.029, respectively).Within the limitations in this study, there are no differences in new bone formation, bone remodeling and bone mineral apposition rate among the various loading methods after initial healing. Loading applied to the implant may stimulate new bone formation around the implant and increase bone density by bone remodeling. Periodic gradual loading may increase new bone formation and bone remodeling, compared with submerged implant, though, marginal bone loss may also be increased.