Effects of various periodontal ligament elastic moduli on the stress distribution of a central incisor and surrounding alveolar bone.
OBJECTIVE
Previous studies investigating the effects of core or post on the fracture strength of teeth often omitted the periodontal ligament (PDL) because its physical properties are difficult to reliably quantify. This study investigated the effects of various PDL elastic moduli on the stress distribution around a central incisor and surrounding alveolar bone using 3-dimensional finite element stress analyses.


METHODS
Four 3-dimensional finite element models of an upper central incisor and the dento-alveolar complex were established. Five models were constructed, including: no PDL, as well as a PDL with elastic moduli of 6.9 MPa, 68.9 MPa, and 1750 MPa. Two loading conditions were simulated, one with protrusive force and one with intrusive force. Protrusive loading was generated using a point force of 200 N at 45 degrees inclination to the longitudinal axis of the incisor applied on the lingual side. Intrusive loading was generated using a point force of 200 N applied perpendicular to the incisal edge.


RESULTS
The absence of a PDL had detrimental effects on the surrounding bone, because the applied stress remained concentrated at the bone crest and cervical third of the root. A PDL with a lower elastic modulus, on the other hand, helped to alleviate the magnitude of stress throughout the surrounding bone and the bone crest, in particular, by distributing the stress deeper towards the apical region. The stress distribution at the crown was unaffected by variations in the PDL elastic modulus.


CONCLUSIONS
PDL with a lower elastic modulus can help protect the alveolar bone crest from stress concentration.
Department of Biomedical Engineering, Chung Yuan Christian University, Chungli, Taiwan.
Weng-Pin
WP
Chen
Bor-Shiunn
BS
Lee
Yu-Chih
YC
Chiang
Wan-Hong
WH
Lan
Chun-Pin
CP
Lin
D000539:Alveolar Process / Q000502:physiology*; D003799:Dental Stress Analysis; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D007180:Incisor / Q000502:physiology*; D010513:Periodontal Ligament / Q000502:physiology*