Relationship between magnitude of immediate loading and peri-implant osteogenesis in dogs

Objectives: The purpose of this study was to investigate the influence of the magnitude of immediate loading on peri-implant bone in an animal model of dental implantation. Material and methods: Eight weeks after the extraction of maxillary and mandibular premolars, three implants were inserted bilaterally in the mandibles of six Beagle dogs. One implant was unloaded (UL) as a control, and two implants were loaded immediately with 10 N (mild loading: ML) or 50 N (excessive loading: EL) laterally using a cyclic loading device twice a week for 3 weeks. Fluorescent bone markers were injected to examine bone formation around the implants. The animals were sacrificed 3 weeks after implantation. Peri-implant osteogenesis was assessed by histomorphometric procedures, i.e., measuring bone-implant contact (BIC) and bone density (BD). Results: The UL and ML groups had no peri-implant infection, and newly formed bone was observed over a wide area from the implant neck toward the tip, and in direct contact with the implant surface. In contrast, in the EL group, newly formed bone was rarely observed around the implant neck and there were signs of infection. Both BIC and BD in the ML group were significantly greater than those in the other groups. BIC and BD in the EL group were significantly lower than those in the other groups. Conclusion: A suitable magnitude of load applied immediately after dental implantation promotes peri-implant osteogenesis.