OBJECTIVETo analyze the stress distribution in the abutment periodontal ligament of posterior cantilever bridge under transient dynamic loads using a three-dimensional finite element(FE) model.

METHODSA cantilever bridge using 5, 6 as abutments to restore missing 7 was designed, and its FE model was established and loaded with dynamic loads. The loads were set as 250 N occlusal forces loaded at different positions on the cantilever, and in different directions to simulate the masticatory cycle. FE analysis was conducted on the ANSYS to analyze stress distributions in abutment periodontal ligament under dynamic loads. Stress-time curves were traced to understand the biomechanical behavior of abutment periodontal ligament.

RESULTSWith loading and unloading time accumulated, the stress value in the abutment periodontal ligament increased gradually. Loads in lateral direction induced peak value stress in a masticatory cycle. There was little residual stress in the end of unloading phase. The maximum stress concentrated in abutment periodontal ligament adjacent to the missing tooth. Without restoration abutment periodontal ligament was mainly under compressive stress. However, when 7 was restored with a cantilever bridge, tensile stress was shown in the mesial cervical area of 5, Three masticatory cycles were simulated, and stress values in abutment periodontal ligaments increased with the number of masticatory cycles. But the differences of the stress between different masticatory cycles were not significant.

CONCLUSIONSIn the mastication movement, lateral loads induce maximum stress in abutment periodontal ligament. Cantilever fixed bridge design is more demanding for the periodontal condition of the abutment adjacent to the missing tooth than for the other abutment. When loaded with continuous masticatory force, the stress concentration does not increase significantly. Therefore, cantilever bridge is one of the feasible choices to restore missing lower second molar.