Elastic Modulus and Hardness of Cortical and Cancellous Bone Measured by Nanoindentation in Maxilla and Mandible

Advances in our ability to predict implant success and evaluate new therapies depend on our understanding of anatomically specific measures of local tissue mechanical properties near and surrounding the implant. Bone mass, structural and material properties constitute mechanical competence of bone, which is integral to a load-bearing implant/bone union. Objective: To quantify the elastic properties of maxillary and mandibular bone at the lamellar level and compare these properties among varying sites. Methods: Moderately resorbed edentulous maxilla and mandible from a human cadaver were analyzed. 4 mm thick buccal-lingual cross-sections from anterior maxilla(Amx) and mandible(AMn), and posterior maxilla(PMx) were embedded in resin and highly polished before testing. The load-displacement sensing nanoindentation instrument (TriboIndenter, Hysitron Inc., Minneapolis, MN) was used for modulus of elasticity and hardness measurements. The tests on the cortical and cancellous bone samples consisted of multiple indents with a maximum load of 5000µN. Data were analyzed using one-way ANOVA. Results: The mean overall elastic moduli were 14. 76 ± 3.19 GPa for cortical bone and 15.37 ± 2.03 Gpa for cancellous bone without yielding statistical significance. The modulus for cortical bone among sites showed significant variation between AMn (17.01±2.94) and PMx (13.47±2.72) (p<.05), but not in relation to AMx (14.01±2.60). The variation was significant (p<.05) in cancellous bone modulus between AMx (17.12±1.76) and PMx (14.46±1.60), however not significant with AMn (14.74 ±1.69). Hardness values were similar in cortical (0.43±0.13 GPa) and cancellous (0.46±0.08 GPa) bones. Conclusion: The overall values for modulus of elasticity and hardness varied mildly with the possibility of site-specific differences. This preliminary study suggests that the understanding of mechanical competence of cortical and trabecular bone of different sites might reveal further information about bone loss and implant failure. Supported by UCLA School of Dentistry and Hysitron, Inc.