Implant micromotion is related to peak insertion torque and bone density

Objectives: Measuring peak insertion torque in relation to different bone densities, the
present study seeks to determine whether micromotion at the interface is related to
primary stability achieved by increasing insertion torque.
Material and methods: A total of 120 Ti-Bone implants were placed in fresh bovine bone
samples representing three density categories: hard, normal and soft (HNS). Five groups of
peak insertion torque (20, 35,45, 70 and 100 N'cm) were evaluated in the three bone
density categories noted. Customized electronic equipment connected to a PCwas used to
register the peak and other insertion torque data. A loading device, consisting of a digital
force gauge and a digital micrometer, was used to measure the micromovements of the
implant during the application of 20,25 and 30 N lateral forces. The data were analyzed for
statistical significance by ANOVA and Spearman's rank correlation coefficient tests.
Results: A statistically significant difference between implant micromobility placed with
different levels of torque and in different bone densities was demonstrated by ANOVA.
Spearman's rank correlation coefficient showed a high dependency between the peak
insertion torque and the observed micromovement. Particularly, in soft bone, it was not
possible to achieve more than 35 N'cm of peak insertion torque.
Conclusions: Results showed that increasing the peak insertion torque reduces the level of
implant micromotion. In addition, micromotion in soft bone was found to be consistently
high, which could lead to the failure of osseointegration. Thus, immediate functional
loading of implants in soft bone should be considered with caution.