Removal torque for dental implants placed in early regenerate bone

Objectives: Mandibular reconstruction using distraction osteogenesis has shown promising results. The purpose of this study was to reconstruct mandibular bone defects using bone transport distraction osteogenesis, and test the effect of dental implant placement in regenerate bone after six weeks of consolidation. Methods: In five dogs, a 30mm mandibular defect was created and bone transport distraction started after 7 days and continued for 4 weeks at 1 mm/day. Half way through the distraction period molars were extracted on the contralateral control side, creating a 3cm edentulous ridge. After distraction was completed, the regenerate was allowed to consolidate for 6 weeks before placement of dental implants in both the experimental and control sides. After a healing period of 6 weeks animals were sacrificed, the mandibles harvested and immediately CT scanned. Thereafter, removal torque tests were done on the most posteriorly placed dental implant in the control and regenerate sides, to test the degree of osteointegration in control and regenerate bone. Results: Radiographic analysis showed three implants with partial placement in host bone. Removal torque of implants was significantly (p<0.044) lower in regenerate than control bone. There was a significant (p<0.02) linear relationship (corr=0.94) between increasing torque values and increasing contact with host bone. Conclusions: Implants placed in 6-week regenerate and allowed to integrate for 6 weeks have low removal torque compared to implants in control bone. When some contact with host bone is present, removal torque is higher than with no host bone contact. Supported by R41 and R42 DE015437 and R43 DE017259 from NIDCR and generous donation of implants from Straumann.