Biomechanical adaptation of the bone-periodontal ligament (PDL)-tooth fibrous joint as a consequence of disease

In this study, an in vivo ligature-induced periodontitis rat model was used to investigate temporal changes to the solid and fluid phases of the joint by correlating shifts in joint biomechanics to adaptive changes in soft and hard tissue morphology and functional space. After 6 and 12 weeks of ligation, coronal regions showed a significant decrease in alveolar crest height, increased expression of TNF-α, and degradation of attachment fibers as indicated by decreased collagen birefringence. Cyclical compression to peak loads of 5-15. N at speeds of 0.2-2.0. mm/min followed by load relaxation tests showed decreased stiffness and reactionary load rate values, load relaxation, and load recoverability, of ligated joints. Shifts in joint stiffness and reactionary load rate increased with time while shifts in joint relaxation and recoverability decreased between control and ligated groups, complementing measurements of increased tooth displacement as evaluated through digital image correlation. Shifts in functional space between control and ligated joints were significantly increased at the interradicular (δ10-25. μm) and distal coronal (δ20-45. μm) regions. Histology revealed time-dependent increases in nuclei elongation within PDL cells and collagen fiber alignment, uncrimping, and directionality, in 12-week ligated joints compared to random orientation in 6-week ligated joints and to controls. We propose that altered strains from tooth hypermobility could cause varying degrees of solid-to-fluid compaction, alter dampening characteristics of the joint, and potentiate increased adaptation at the risk of joint failure. © 2013.

Subjects

Biomechanical adaptation

Biomechanics

Bone-PDL-tooth fibrous joint

Periodontal ligament

Periodontitis

Stiffness

DDC Class

540: Chemie

570: Biowissenschaften, Biologie

610: Medizin

More Funding Information

The authors also thank the Biomaterials and Bioengineering Micro-CT Imaging Facility at UCSF for the use of the Micro-XCT unit and the in situ loading device. Support was provided by NIH/NIDCR R00DE018212 (SPH), NIH/NIDCR R01DE022032(SPH), NIH/NIDCR T32DE07306-16(JDL), NIH/NCRR S10RR026645(SPH), and the Department of Preventive and Restorative Dental Sciences, UCSF, and the Department of Orofacial Sciences, UCSF.

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Biomechanical adaptation of the bone-periodontal ligament (PDL)-tooth fibrous joint as a consequence of disease