Analytically determined mechanical properties of, and models for the periodontal ligament: critical review of literature.

OBJECTIVE: This review is intended to highlight and discuss discrepancies in the literature of the periodontal ligament's (PDL) mechanical properties and the various analytical models, approaches and assumptions used in simulating its behaviour. The present study then offers to propose a model development that allows for a better phenomenological description of PDL behaviour under static, near clinical, orthodontic loading conditions.
METHODOLOGY: Searches were performed on biomechanical and orthodontic publications (in databases: Compendex, EMBASE, MEDLINE, PubMed, ScienceDirect and Scopus).
RESULTS: The review revealed that significant variations exist, some on the order of six orders of magnitude, in the PDL's elastic constants and mechanical properties. Possible explanations may be attributable to different modelling approaches and behavioural assumptions. SIGNIFICANCE: The discrepancies highlight the need for further research into determining what the key factors that contribute to tooth movement are, their correlations and their degree of impact. Despite the PDL's definitive role in orthodontic tooth movement, proposed models of the PDL's mechanical behaviour thus far have been unsatisfactorily inadequate. Hence, there is a need to develop a robust PDL model that more accurately simulates the PDL's biomechanical response to orthodontic loads. Better understanding of the PDL's biomechanical behaviour under physiologic and traumatic loading conditions might enhance the understanding of the PDL's biologic reaction in health and disease. Providing a greater insight into the response of the PDL would be instrumental to orthodontists and engineers for designing more predictable, and therefore more efficacious, orthodontic appliances.