PERIODONTAL-LIGAMENT STRESSES IN THE INITIATION OF OCCLUSAL TRAUMATISM

Mechanical stresses in the periodontal ligament [PDL] which helps initiate the lesion of occlusal trauma have been difficult to evaluate. A mathematical system (finite element analysis) was used to calculate principal PDL stresses in primary and secondary occlusal trauma. Maximally central incisors were modeled in peridontal tissues representing 4 levels of bone support. Models were partitioned and subjected to 3 simulated functional loads. Stresses were calculated at multiple nodes in the PDL adjacent to root and bone. Results showed areas of greatest compressive stress near the alveolar crest and in the apical 1/2 of the root for all loads at all bone levels. Stess curves correlated well and with 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 PDL stress until 6 mm (60%) of bone support had been lost. Finite element analysis provides a convenient model for the study of the mechanical component of occlusal traumatism.