Stresses in the periodontal ligament

Measurements have been made of the root areas of forty five extracted teeth. These have been used to calculate the theoretical pressures that may occur in the region of the alveolar crest and their increase with progressive loss of alveolar bone when a lateral force is applied to the crown of the tooth. Pressures generated in the periodontal ligament as a result of axial loadings have also been calculated and compared with those due to lateral loadings. The results suggest that a very rapid increase in pressures in the periodontal ligament would occur with bone losses in excess of 55 per cent in the case of lateral loadings and over 80 per cent in the case of axial loading. The implications for clinical practice are discussed.