To analyze the temporomandibular joint (TMJ) loading affected by the fulcrum in different positions on the occlusal surface of 36.

Through the chilled skull model reconstructed in preliminary study, which was for the TMJ loading analysis, we defined the conditionⅠ, Ⅱ, Ⅲ and Ⅳ when there were no occlusal fulcrum and when occlusal fulcrums were located on the Mesial buccal cusp, central fossa and distal lingual cusp of 36′s occlusal surface. Then we recorded and analyzed comprehensive force center, pressure concentration area, pressure peak value and pressure contact area of the joint surface of bilateral TMJ after loading by the mechanical testing machine. All the data were analyzed by the variance analysis in the SPSS.

(1) In the different working conditions, the comprehensive force center of bilateral TMJ shifted to lower interface of the right side, the working condition Ⅲ is the most obvious; the pressure concentration area of articular surfaces in the left side was displacement inordinately, while the right side was stable. (2) Compared with conditionⅠ, in the working condition Ⅱ, Ⅲ and Ⅳ, all the interface peak pressure of TMJ of left side tended to decrease (F_upper = 4.49, P_upper = 0.63; F_lower = 7.11, P_lower = 0.01) , but no significant difference shown in the right side (F_upper = 0.60, P_upper = 0.04; F_lower = 1.13, P_lower = 0.39) . (3) Compared with conditionⅠ, in the working condition Ⅱ, Ⅲ and Ⅳ, all the contact area of the TMJ articular surfaces have no significant difference (P>0.05) .

The occlusal fulcrum on different positions of the 36 occlusal surfaces would affect the force forms of TMJ joint surface and changed the stress environment of the TMJ.