The exquisite sensitivity of the skeleton to mechanical force underlies the adaptive response of bone to exercise, implant integration and space travel. Increases in bone mass by exercise and bone loss during prolonged space flight are examples of the adaptive response of bone to mechanical loading. The mechanisms that comprise this adaptation to applied force are not entirely understood. Dynamic (intermittent) force applied to the skeleton has been shown to be anabolic, while constant load does not elicit this favorable response. The goal of this project is to elucidate the specific responses to dynamic localized loading in the alveolar process (bone surrounding a tooth) by measuring remodeling (turnover) rate, mineral content and elastic modulus, a physical property, which reflects bone quality. We hypothesize that one of the mechanisms by which bone responds to higher levels of localized mechanical loading is by elevating its remodeling rate. This higher remodeling results in a lower mineral content and a lower elastic modulus.
The specific aims of this proposal are to identify: 1) determinants of mineral content and elastic modulus and 2) the role of localized loading on the mineral and mechanical property adaptations in the alveolar process. We will quantitatively define the interplay between tissue level remodeling, mineral content and elastic modulus. Skeletally mature beagle dogs will be given one pair of IV bone labels over a period of 2 weeks to mark sites of mineralization in vivo. Post-sacrifice, the maxillary and mandibular second premolars (non-occluding teeth) and maxillary fourth premolar and mandibular first molar (occluding teeth) will be sectioned. Until recently, it was not possible to quantitatively measure mineral and mechanical properties of small volumes of bone tissue. We propose three integrated biologic and engineering methods to test our specific aims: A) Elastic modulus of bone in the alveolar process of occluding and non-occluding teeth will be measured by nanoindentation, B) Specimens used for nanoindentation will be subjected to quantitative backscattered imaging to measure mineral content at sites of indentations, and C) Bone remodeling rates in the alveolar process will be measured using histomorphometric techniques. Statistical analyses will be used to investigate the relationships between elastic modulus, mineral content and remodeling. Also, regional differences in the material properties of bone in the alveolar process will be statistically evaluated. Future interventional studies will examine the mechanisms for the initial and the long-term adaptive response in material properties of bone.
| Huja, Sarandeep S; Rummel, Andrew M; Beck, Frank M (2008) Changes in mechanical properties of bone within the mandibular condyle with age. J Morphol 269:138-43 |
| Huja, S S; Fernandez, S A; Hill, K J et al. (2007) Indentation modulus of the alveolar process in dogs. J Dent Res 86:237-41 |
| Huja, Sarandeep S; Fernandez, Soledad A; Hill, Kara J et al. (2006) Remodeling dynamics in the alveolar process in skeletally mature dogs. Anat Rec A Discov Mol Cell Evol Biol 288:1243-9 |
