The bioengineering aspect of this research originates from Wolff's law which explains bone adaptation due to mechanical loads at an organ-level. At a tissue- and a cell-level, local strains trigger mechanobiological events and are responsible for maintaining a uniform functional PDL-space. However, a uniform PDL-space can shift toward a nonuniform PDL-space due to aberrations in strains at the PDL-bone and PDL-cementum interfaces as a result of altered mechanobiology. We wil test cell- and tissue-level responses that could cause an increase or decrease in PDL-space and the accompanying gradients that result from a change in function. We will investigate:
Aim 1) that in situ the surfaces of bone and tooth are originally conforming and with application of mechanical load can induce localized compressive and tensile strains within the bone-tooth complex. Changes in PDL-space and resulting strains will be evaluated using a loading device coupled to a Micro X-ray computed tomography (?-XCT) followed by digital image correlation (DIC) of virtual sections taken at no load and loaded conditions;
Aim 2) that in vivo the mechanobiologically active compression and tension sites promote biochemical changes through expression of genes and matrix proteins, causing resorption and formation of bone and cementum resulting in a widened or a narrowed PDL-space. The spatiotemporal outcomes of mechanosensitive genes and protein expressions promoting mineral formation at the tension sites, resorption at the compression sites, and responsible for maintaining tissue and interface integrity will be mapped by using fluorescence based immunohistochemistry;
Aim 3) that biochemically altered regions identified in Aim 2 cause measurable changes in structure, chemical composition and mechanical properties of bone, cementum, PDL (e.g. tensile strains induce bone formation).
This aim i ncludes mapping the shifts in gradients of the PDL-bone and PDL-cementum interfaces. Spatiotemporal changes in local structure, chemical composition and mechanical properties of wet PDL-bone, PDL-cementum, cementum, bone, and PDL using state-of-the-art high resolution microscopy and spectroscopy equipment will be mapped;
Aim 4). the functionally adapted systems in situ have an altered response to mechanical loads. Load-displacement curves and correlating strains fields in adapted complexes of 2nd molar from freshly harvested experimental groups and controls (as in Aim 1) will be evaluated and compared. Studies will use in situ loading, ?-XCT, and DIC as in Aim 1.
The proposed translational research is based on our incomplete understanding of how PDL-space adapts to functional loads. Local functional adaptations can be unfavorable outcomes with an increased or a decreased range of tooth motion due to root and/or bone resorption or formation resulting in a widened (tooth loosening) or narrowed PDL-space (ankylosis). Such adapted sites could act as the local stress points inducing positive feedback when the complex is subjected to implants and/or periodontitis, normal or therapeutic loads (orthodontic braces) subsequently impairing function.
Teeth are suspended in a bony socket via a soft ligament, and this bone-ligament-tooth complex adapts to functional demands. The proposed systematic research strategy provides insights into physical and biological mechanisms of load-mediated adaptation using in vivo models. From a clinical perspective, this research is a prerequisite to develop optimum guidelines for effective treatments and can be extended to orthopedic applications in bone-ligament and bone-tendon dynamic and common injury sites in the human musculoskeletal system.
|Lin, Jeremy D; Lee, Jihyun; Ozcoban, Huseyin et al. (2014) Biomechanical adaptation of the bone-periodontal ligament (PDL)-tooth fibrous joint as a consequence of disease. J Biomech 47:2102-14|
|Jang, Andrew T; Lin, Jeremy D; Choi, Ryan M et al. (2014) Adaptive properties of human cementum and cementum dentin junction with age. J Mech Behav Biomed Mater 39:184-96|
|Grandfield, Kathryn; Chattah, Netta Lev-Tov; Djomehri, Sabra et al. (2014) The narwhal (Monodon monoceros) cementum-dentin junction: a functionally graded biointerphase. Proc Inst Mech Eng H 228:754-67|
|Jang, Andrew T; Lin, Jeremy D; Seo, Youngho et al. (2014) In situ compressive loading and correlative noninvasive imaging of the bone-periodontal ligament-tooth fibrous joint. J Vis Exp :|
|Lee, Ji-Hyun; Lin, Jeremy D; Fong, Justine I et al. (2013) The adaptive nature of the bone-periodontal ligament-cementum complex in a ligature-induced periodontitis rat model. Biomed Res Int 2013:876316|
|Lin, Jeremy D; Ozcoban, Huseyin; Greene, Janelle P et al. (2013) Biomechanics of a bone-periodontal ligament-tooth fibrous joint. J Biomech 46:443-9|
|Ho, Sunita P; Kurylo, Michael P; Grandfield, Kathryn et al. (2013) The plastic nature of the human bone-periodontal ligament-tooth fibrous joint. Bone 57:455-67|
|Lin, J D; Aloni, S; Altoe, V et al. (2013) Elastic discontinuity due to ectopic calcification in a human fibrous joint. Acta Biomater 9:4787-95|