title: An investigation of cuspal deformation and delayed recovery after occlusal loading.
abstract: OBJECTIVE
  The purpose of this study was to investigate the extent of progressive cuspal displacement during prolonged occlusal loading (either continuous or cyclic) and delayed cuspal recovery following removal of the load.
  
  
  METHODS
  Extracted maxillary premolars with extensive MOD cavity plus endodontic access were subjected to an occlusal load applied to both cusps, followed by a recovery period. Two types of loading were applied: (a) continuous load of 100, 200 and 300 N for 0.1--1000 s; (b) cyclic loading of 300 N at 0.83 Hz for 1--1000 cycles. Cuspal displacement during loading and subsequent recovery were measured with an extensometer attached to both cusps.
  
  
  RESULTS
  Continuous loading led to progressive cuspal displacement that was both time- and load-dependent. After removal of the load, complete recovery from cuspal deformation was prolonged up to 20 min, also in a time- and load-dependent manner. Cyclic loading resulted in a cumulative increase in cusp displacement but to only a very small extent (approximately 1 microm after 1000 cycles).
  
  
  CONCLUSIONS
  Progressive cuspal displacement and delayed recovery occur with prolonged continuous or cyclic occlusal loading. Continuous loading (e.g. as in clenching) is potentially more damaging than cyclic loading (as in chewing).
authors.affiliation: School of Dental Science, The University of Melbourne, 711 Elizabeth Street, Melbourne, Vic 3000, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Jantarat
authors.forename: J E
authors.initials: JE
authors.lastname: Palamara
authors.forename: H H
authors.initials: HH
authors.lastname: Messer
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid; D019245:Compressive Strength; D003766:Dental Occlusion; D003799:Dental Stress Analysis; D004548:Elasticity; D006801:Humans; D008409:Mastication; D008437:Maxilla; D009119:Muscle Contraction; D012044:Regression Analysis; D019228:Tooth Crown / Q000293:injuries / Q000502:physiology*; D016474:Weight-Bearing