IADR Abstract Archives
Strain-Guided Biomineralization within the Bone-PDL-Cementum Complex
Strain-Guided Biomineralization within the Bone-PDL-Cementum Complex
Objective: Pullout forces at the PDL-bone and PDL-cementum interfaces can be amplified by applying a unidirectional force to the bone-periodontal ligament-cementum complex. We investigated physicochemical properties of biomineral at the strained PDL-bone and PDL-cementum attachment sites.
Methods: A unidirectional force of 0.6 N acting mesially was applied on rat molars for two months using an in vivo model (N=5-experimental; N=5-control). Harvested hemimaxillae were investigated using X-ray microscopy, and Raman spectroscopy. Dynamic histomorphometry by injecting fluorescent dyes into a separate set of rats was performed.
Results: Histomorphometry illustrated a reversed effect in naturally occurring mesial-bone formation and distal-bone resorption patterns normally observed in controls. Dynamic histomorphometry was positively correlated to TRAP-positive osteoclast localization in experimental groups at the mesial-69%, distal-14%, and apical-17% regions, and were significantly different (Student's t-test, P < 0.05) compared to mesial-7%, distal-91%, and apical-2% within controls. Mineral growth along the strained PDL-fibers was identified as bone-fingers (figure), but a heterogeneous mineral density compared to primary bone was observed using an X-ray microscope. An increase in organic to inorganic ratio in bone-fingers was illustrated using Raman microspectroscopy. Phosphate-PO43--960cm-1 peak was relatively higher compared to carbonate-CO32--1070cm-1 peak in older bone. Although the relative intensity between these peaks varied, the carbonate peak was higher in bone fingers. It is plausible that bone fingers are less mineralized and that the chemical composition is yet to reach that of mature hydroxyapatite.
Conclusion: Unique to this study is the use of an in vivo model to investigate the quality of strain-guided biomineral. We propose that “strain-guided biomineralization” along the stretched PDL fibers at the interfaces is the underlying mechanism in the advancement of mineralization fronts within the complex. However, the response of cementum to mechanical strain and within the context of organ function is yet to be understood.
