ABSTRACT
A tooth is secured to the alveolar bone by fibrous connective tissue that is called the periodontal ligament (PDL). The PDL not only strongly binds the tooth root to the supporting alveolar bone but also absorbs occlusal loads and distributes the resulting stress over the alveolar bone. The mechanical properties of the PDL are, therefore, essential parameters for understanding the mechanical behaviour of a tooth root and that of surrounding tissues. The PDL also plays an important role in the mechanical adaptation of the dentition, based on alveolar bone remodelling induced by a change in mechanical stress or strain around a tooth root. This adaptability is important for the maintenance of optimal occlusion at a proper vertical dimension and is also utilised for orthodontic treatment in which an optimal orthodontic force is applied so as to induce maximum cellular activities, resulting in the most efficient tooth movement.
