Periodontal ligament stresses in the initiation of occlusal traumatism.

Mechanical stresses in the periodontal ligament which help initiate the lesion of occlusal trauma have been difficult to evaluate. The purpose of this study was to use a mathematical system (finite element analysis) to calculate principal periodontal ligament stresses in primary and secondary occlusal trauma. Maxillary central incisors were modeled in periodontal tissues representing four levels of bone support. Models were partitioned and subjected to three simulated functional loads. Stresses were calculated at multiple nodes in the periodontal ligament adjacent to root and bone. Results showed areas of greatest compressive stress near the alveolar crest and in the apical one-half of the root for all loads at all bone levels. Stress curves correlated well with the histologic lesion of occlusal trauma. Centric contact loads (P3) consistently produced less ligament stress than protrusive contact (P1). Reduction of alveolar bone height had little effect on the degree of periodontal ligament stress until six millimeters (60%) of bone support had been lost. Finite element analysis provides a convenient model for the study of the mechanical component of occlusal traumatism.