Secondary stability of microthickness hydroxyapatite-coated dental implants installed without primary stability in dogs

OBJECTIVES: The objective of this study was to evaluate the secondary stability of microthickness hydroxyapatite (HA)-coated implants placed without primary stability in dogs. MATERIALS AND METHODS: A total of 48 implants were placed in six dogs. The groups were divided according to the absence or presence of primary stability and healing periods (4 and 8 weeks). Two implants for histological analysis and removal torque test in experimental group were placed without primary stability, showing rotational movement. The other two implants in control group were placed with primary stability. Mechanical test values and histometric measurements were analyzed. RESULTS: The experimental group showed significant increase in a time-dependent manner, while the mean values of the control group were constant in the mechanical tests. The HA layer remained intact, and substantial bone fragments were attached on the surface of the retrieved implant. All implants appeared to be in intimate contact with the host bone and without any inflammation after both 4 and 8 weeks of healing in histology. CONCLUSION: The HA-coated implants exhibited mechanically and histometrically comparable osseointegration after 4 weeks of healing, regardless of primary stability, and the HA-coating layer demonstrated high resistance to exfoliation.ope