OBJECTIVETo investigate the effects of tooth apical stress changes caused by different types of occlusion on the TMJ stresses.

METHODSThe apical stresses measured from photo-elastic experiments (2 Kg centric vertical loading to seven types of occlusions separately) were applied to the established 3D finite elemental model. The stress distributions on condyle, superfacial cartilage of condyle and TMJ disc were compared.

RESULTS(1) The stress on both anterior surface of condyle and its superfacial cartilage and on the intermediate band of disc were mainly compressive, while the stress on both posterior surface of condyle and its superficial cartilage and on the posterior band of disc were mainly tensile (P < 0.01). (2) The values of TMJ stresses of models with flat surface occlusion, distal occlusion, unilateral partial molar teeth cross bite, and occlusion with right second and third molar tooth missing were different to some extent from that with normal occlusion, among which the TMJ stress from the flat surface occlusion differed most significantly (P < 0.01). The TMJ stresses of models with unilateral upper third molar hyper-eruption occlusion and unilateral lower third molar hyper-eruption occlusion did not significantly differ from that with normal occlusion.

CONCLUSIONSChanges of apical principle stress resulted from different types of occlusions during centric biting have effects to some extent on TMJ stress quantitatively but not qualitatively.