American Journal of Orthodontics and Dentofacial Orthopedics
Original ArticleNonlinear stress-strain behavior of periodontal ligament under orthodontic loading*,**,*,**,*,**
Section snippets
Material and methods
Tooth specimens were harvested from 4 frozen human cadavers obtained through the University of Alabama at Birmingham's Willed Body Program. All procedures were approved by the University's Institutional Review Board (E990513003). The young donors were white men, 24 and 27 years old, and the elderly donors were white men, 78 and 79 years old. The causes of death were gunshot wound, asphyxia, cardiac arrest, and emphysema, respectively.
After thawing, each mandible was isolated, and external soft
Results
Of the 56 specimens tested, data from the 22 young specimens and the 8 elderly specimens were included in the analyses presented. Data from the remaining specimens were excluded because of PDL failure during testing. The coefficients of determination, r2, illustrate goodness of fit of the linear regressions to the experimental data.
Distinct linear and toe regions were observed for all specimens in both loading directions (Figs 4, 5, and 6).
Discussion
The current study offers unique information about the nonlinear elasticity of the PDL in the range of orthodontic forces for intrusive and extrusive loading of young and elderly samples. Although limited in sample size, the data from cadaveric testing show complex elastic behavior of the PDL from which 4 generalizations can be made.
The linear modulus was higher in intrusion than extrusion, indicating that less force was required to achieve an orthodontic level of stress in intrusion than
Conclusions
In this study, cadaveric specimens of mandibular premolars from 2 young adult and 2 elderly donors were tested to determine stress-strain behavior of the PDL over an orthodontic force range. The following conclusions could be made:
- 1.
Stress-strain curves for both intrusion and extrusion had distinct toe and linear regions, demonstrating the nonlinear mechanical behavior of the PDL.
- 2.
The average linear shear modulus was higher for intrusion than extrusion, suggesting anisotropic material properties
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Cited by (0)
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aDepartment of Biomedical Engineering.
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bDepartment of Orthodontics.
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cDepartment of Orthopedic Research.
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dDepartment of Biostatistics.
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This research was supported by NIDCR Grant K16DE00279.
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Reprint requests to: Alan W. Eberhardt, PhD, HOEHN Room 370, 1075 13th St South, Birmingham, AL 35294-4440; e-mail, [email protected].