Nanomechanical Evaluation of Bone Around Non-Loaded and Loaded Endosseous Implants

Objective:

According to Wolff’s theory, bone is expected to remodel as needed to achieve appropriate biomechanical competence. To test this prediction, we compared the hardness and toughness of bone surrounding functional and non-functional dental implants in a canine mandible model.

Method:

The right third and fourth premolars and the first molar of three adult Doberman dogs were extracted and the sockets were allowed to heal for a period of six months. Four standard implants^TM (Nobel Biocare, Gothenburg, Sweden) of 10mm length and 3.75mm diameter were placed in one side of the mandible after a mucoperiosteal flap elevation. The mesial implant received a cover screw and remained unloaded as the control. The remaining three implants received multi-unit abutments, titanium cylinders (Nobel Biocare, Gothenburg, Sweden) and Ti c.p. cast fixed prostheses within 48 hours after surgery and remained loaded throughout the course of the study (two years). Following sacrifice, the implants were non-decalcified processed for testing, and for each implant, nano-indentations were performed within regions of cortical and trabecular bone in order to collect measures of modulus and hardness. Following rank transformation of the data, a mixed model ANOVA was used to determine differences between loaded and non-loaded implants at 95% level of significance.

Result:

Modulus and hardness were both about 50% better for bone adjacent to functional implants than for bone adjacent to non-nonfunctional implants (p < .05). Differences were more pronounced in regions of cortical than trabecular bone.

Conclusion:

Compared to unloaded implants, functional loading of dental implants results in greater remodeling and improved mechanical properties of surrounding bone.