Journal of implantology and applied sciences ISSN:2765-7833(Print) 2765-7841(Online) 대한구강악안면임플란트학회지

Once the implant is integrated to living bone tissue, biomechanical bond between them is too strong to separate without fracturing the bone or the implant. If an excessive rotational force acting as a removal torque is applied to the osseointegrated implant in a second-stage surgery for abutment connection, its direct bone anchorage can be destroyed. The purpose of this study is to examine the time-dependent healing process of bone tissue around the implant with destroyed osseointegration and to evaluate the change in bone implant bond strength with time by means of measuring removal torques. Screw-shaped commerciaily pure (CP) titanium implants were inserted in the tibial metaphyses of 10 rabbits. 8 weeks later the removal torques necessary for destruction of osseointegration were measured with a torque gauge by turning each implant to the removal direction and the implants were placed in situ without loading. At the same time new implants were inserted in the contralateral area as controls. At 1, 2, 3, 4 and 6 weeks after implant insertion and destruction of the osseointegration, the removal torques were re-measured, respectively. The specimens taken from both groups were decalcified and stained with hematoxylin-eosin for histologic study. The results obtained were as follows : 1. The removal torque after implant insertion increased with time and the mean for the osseointegrated implants at 8 weeks was 5.13 kfgㆍ㎝ with a range of 3.6 to 7.2 kfgㆍ㎝. 2. The bone tissue around the implant of destroyed osseointegration was well-recovered and showed time-dependent increase in removal torques. At 3 weeks of healing time its interfacial strength was greater than that of the osseointe grated implants at 8 weeks. 3. Histologically new bone was formed around the implant at 2 weeks after insertion and wellorganized, more mature bone similar to the old bone could be observed at 4 weeks with further condensation. In both groups there were some bony cracks near bone-implant interface. The present study demonstrates that if unloaded and not contaminated, bone tissue around the implants with destroyed osseointegration can be healed in a shorter period than normal osseointegration time. In addition, it suggests that stronger osseointegration require more heaiing time without loading since biomechanical bond strength between bone and the implant increases with time.