Biomechanics of a bone-periodontal ligament-tooth fibrous joint

This study investigates bone-tooth association under compression to identify strain amplified sites within the bone-periodontal ligament (PDL)-tooth fibrous joint. Our results indicate that the biomechanical response of the joint is due to a combinatorial response of the constitutive properties of organic, inorganic, and fluid components. Second maxillary molars within intact maxillae (N=8) of 5-month-old rats were loaded with a μ-XCT-compatible in situ loading device at various permutations of displacement rates (0.2, 0.5, 1.0, 1.5, 2.0mm/min) and peak reactionary load responses (5, 10, 15, 20N). Results indicated a nonlinear biomechanical response of the joint, in which the observed reactionary load rates were directly proportional to displacement rates (velocities). No significant differences in peak reactionary load rates at a displacement rate of 0.2mm/min were observed. However, for displacement rates greater than 0.2mm/min, an increasing trend in reactionary rate was observed for every peak reactionary load with significant increases at 2.0mm/min. Regardless of displacement rates, two distinct behaviors were identified with stiffness (S) and reactionary load rate (LR) values at a peak load of 5N (S5N=290-523N/mm) being significantly lower than those at 10N (LR5N=1-10N/s) and higher (S10N-20N=380-684N/mm; LR10N-20N=1-19N/s). Digital image correlation revealed the possibility of a screw-like motion of the tooth into the PDL-space, i.e., predominant vertical displacement of 35μm at 5N, followed by a slight increase to 40μm at 10N and 50μm at 20N of the tooth and potential tooth rotation at loads above 10N. Narrowed and widened PDL spaces as a result of tooth displacement indicated areas of increased apparent strains within the complex. We propose that such highly strained regions are "hot spots" that can potentiate local tissue adaptation under physiological loading and adverse tissue adaptation under pathological loading conditions. © 2012.

Subjects

Biomechanics

Bone-PDL-tooth fibrous joint

Periodontal ligament

Rat

Stiffness

DDC Class

570: Biowissenschaften, Biologie

610: Medizin

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Biomechanics of a bone-periodontal ligament-tooth fibrous joint