title: A comparison of the mechanical behavior of posterior teeth with amalgam and composite MOD restorations.
abstract: OBJECTIVE
  To compare the mechanical behavior, and infer differences in fracture resistance, of mandibular molars with amalgam and composite MOD restorations to that of an unrestored molar.
  
  
  METHODS
  Finite element models were developed for an unrestored molar and molars with MOD amalgam and composite restorations. The location and magnitude of maximum principal stress resulting from simultaneous mechanical and thermal loads were determined for each molar using a series of designed experiments. An analysis of variance was conducted with the components of stress to distinguish the relative influence of oral parameters and restoration on the stress distribution in each molar.
  
  
  RESULTS
  The maximum principal stress in the unrestored molar was the largest of all three molars examined and occurred within the dentin along the pulpal wall. Maximum principal stresses in the molars with amalgam and composite restorations both occurred along the cavosurface margin. Maximum principal stresses in the molar with amalgam restoration occurred at the pulpal floor and lingual wall junction and resulted from large occlusal loads. Although occlusal loading had minimal effects on the stress distribution within the molar with composite restoration, low oral temperatures were responsible for the maximum principal stresses, which were found at the lingual margin and occlusal surface junction.
  
  
  CONCLUSIONS
  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 the restored molars were largely dependent on the restorative material. Although clinical studies report that tooth fracture occurs predominately to restored 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 stress resulting from mastication and temperature changes.
authors.affiliation: Department of Mechanical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA. darola@engr.umbc.edu
authors.forename: D
authors.initials: D
authors.lastname: Arola
authors.forename: L A
authors.initials: LA
authors.lastname: Galles
authors.forename: M F
authors.initials: MF
authors.lastname: Sarubin
mesh_terms: D000704:Analysis of Variance; D001732:Bite Force; D001831:Body Temperature; D003188:Composite Resins; D019245:Compressive Strength; D003198:Computer Simulation; D003723:Dental Amalgam; D003743:Dental Enamel / Q000502:physiology; D003782:Dental Pulp / Q000502:physiology; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000009:adverse effects*; D003799:Dental Stress Analysis / Q000379:methods; D003804:Dentin / Q000502:physiology; D020342:Finite Element Analysis; D006801:Humans; D008954:Models, Biological; D003765:Models, Dental; D008963:Molar / Q000293:injuries / Q000502:physiology* / Q000503:physiopathology; D013314:Stress, Mechanical; D013718:Tensile Strength; D019228:Tooth Crown / Q000293:injuries / Q000502:physiology / Q000503:physiopathology; D014082:Tooth Fractures / Q000209:etiology* / Q000503:physiopathology
chemical_list: D003188:Composite Resins; D003723:Dental Amalgam