Evaluation of standardized porcine bone models to test primary stability of dental implants, using biomechanical tests and Micro-CT. An in vitro pilot study

Aim This study evaluated a new porcine bone model to test the primary stability of different implants, analyzing Micro-CT, insertion torque, and pull-out strength.

Materials and methods Bone cylinders were prepared from porcine bone and separated into 2 groups: 10 high density bone cylinders (HDB), and 10 low density bone cylinders (LDB). Then, 3D pre-implant analyses were performed, evaluating tridimensional bone density (ratio of trabecular bone volume and total tomographic volume, BV/TV), trabecular separation; percentage of closed pores; percentage of open pores; percentage of total porosity, in 3 bone levels (L1 bone volume corresponding to the internal part of the threads; L2 corresponding to the area between 0 to 0.5 mm from the end of threads; L3 corresponding to the area between 0.5 to 1.5 mm from the end of threads). Twenty implants of two different macrostructures were inserted in the bone cylinders, and divided into 4 groups (5 implants each): Group 1, e-Fix HE implant placed in HDB cylinder; Group 2, e-Fix HE implant in LDB cylinder; Group 3, e-Fix HE Silver implant placed in HDB cylinder; Group 4, e-Fix HE Silver implant in LDB cylinder. The insertion torque was recorded and bone cylinders were re-evaluated by Micro-CT (post-implant analysis). Then a pull-out strength test was performed.

Results 3D analysis showed that pre- and post-implants intra-groups evaluation had statistically significant differences in Group 3 and 4, for all  tomographic parameters assessed. Group 3 showed the best values for biomechanical tests (Friedman Test, p<0.05).

Conclusion This methodology can produce standardized bone cylinders of high and low bone density, in which different implant designs are able to promote different effects, evidenced by biomechanical and image analysis.