A comparison of the mechanical behavior of posterior teeth with amalgam and composite MOD restorations

Objective: To compare the mechanical behavior, and infer differences in fra cture resistance, of mandibular molars with amalgam and composite MOD resto rations to that of an unrestored molar. Method: Finite element models were developed for an unrestored molar and mo lars with MOD amalgam and composite restorations. The location and magnitud e of maximum principal stress resulting from simultaneous mechanical and th ermal loads were determined for each molar using a series of designed exper iments. An analysis of variance was conducted with the components of stress to distinguish the relative influence of oral parameters and restoration o n the stress distribution in each molar. Results: The maximum principal stress in the unrestored molar was the large st of all three molars examined and occurred within the dentin along the pu lpal wall. Maximum principal stresses in the molars with amalgam and compos ite restorations both occurred along the cavosurface margin. Maximum princi pal stresses in the molar with amalgam restoration occurred at the pulpal f loor and lingual wall junction and resulted from large occlusal loads. Alth ough occlusal loading had minimal effects on the stress distribution within the molar with composite restoration, low oral temperatures were responsib le for the maximum principal stresses, which were found at the lingual marg in and occlusal surface junction. Conclusion: There was no significant difference in the magnitude of maximum stress that occurred in the molars with amalgam and light curing composite restorations. However, the location and orientation of maximum stress in t he restored molars were largely dependent on the restorative material. Alth ough clinical studies report that tooth fracture occurs predominately to re stored molars, the unrestored molar experienced the highest stress in this investigation. Therefore, the reduction in fracture resistance of restored posterior teeth appears to result from changes in the location of maximum s tress resulting from mastication and temperature changes. (C) 2001 Elsevier Science Ltd. All rights reserved.