Reduced mechanical load decreases the density, stiffness, and strength of cancellous bone of the mandibular condyle

Abstract

Objective. To investigate the influence of decreased mechanical loading on the density and mechanical properties of the cancellous bone of the human mandibular condyle. Design. Destructive compressive mechanical tests were performed on cancellous bone specimens. Background. Reduced masticatory function in edentate people leads to a reduction of forces acting on the mandible. As bone reacts to its mechanical environment a change in its material properties can be expected. Methods. Cylindrical bone specimens were obtained from dentate and edentate embalmed cadavers. Mechanical parameters were determined in the axial and in the transverse directions. Subsequently, density parameters were determined according to a method based on Archimedes’ principle. Results. The apparent density and volume fraction of the bone were about 18% lower in the edentate group; no age-related effect on density was found. The decrease of bone in the edentate group was associated with a lower stiffness and strength (about 22% and 28%, respectively). The ultimate strain, however, did not differ between the two groups. Both groups had similar mechanical anisotropy; in axial loading the bone was stiffer and stronger than in transverse loading. Conclusions. Reduced mechanical load had affected the density and herewith the mechanical properties of condylar cancellous bone, but not its anisotropy. Relevance The change in material properties of the cancellous bone after loss of teeth indicate that the mandibular condyle is sensitive for changes in its mechanical environment. Therefore, changes in mechanical loading of the condyle have to be accounted for in surgical procedures of the mandible.