title: Cuspal flexure of teeth with composite restorations subjected to occlusal loading.
abstract: OBJECTIVE
  To measure in vitro the cuspal deflection produced by polymerization shrinkage and occlusal loading in mesio-occlusal (MO) and mesio-occlusal-distal (MOD) bonded composite restorations.
  
  
  METHODS
  Twenty first premolars were studied, attaching a small crystal ball to each cusp vertex as a reference point for intercuspal distance measurements. MO cavities were made in ten premolars and MOD cavities in the other ten. Cavities were then restored with Syntac Single adhesive and Tetric Ceram composite in two increments. A precision micrometer was used to measure intercuspal distances in unaltered teeth (baseline distance), unaltered teeth under 150 N load, restored teeth at 5 min after restoration completion, and restored teeth under 150 N load.
  
  
  RESULTS
  In the two study groups, both polymerization shrinkage and application of 150 N load produced a statistically significant change in intercuspal distance compared with baseline measurement. The cuspal deflection produced by 150 N load was statistically similar between unaltered and restored teeth, although polymerization shrinkage acted as a preload in the latter case (starting point was not baseline condition). The cuspal deflection produced by polymerization shrinkage and occlusal load was significantly greater in MOD than in MO restorations.
  
  
  CONCLUSIONS
  The cuspal deflection produced by composite polymerization shrinkage and occlusal loading is significantly greater in MOD vs MO composite restorations.
authors: Faculty of Dentistry, Department of Pathology and Dental Therapeutics, School of Dentistry, University of Granada, Campus de Cartuja, Granada, Spain. sglopez@ugr.es
authors: Santiago
authors: S
authors: González-López
authors: Miguel Angel
authors: MA
authors: Vilchez Díaz
authors: Francisco
authors: F
authors: de Haro-Gasquet
authors: Laura
authors: L
authors: Ceballos
authors: Cristina
authors: C
authors: de Haro-Muñoz
mesh_terms: D001641:Bicuspid / Q000503:physiopathology; D001732:Bite Force; D003188:Composite Resins / Q000737:chemistry*; D003737:Dental Cavity Preparation / Q000145:classification; D003743:Dental Enamel / Q000503:physiopathology*; D003793:Dental Restoration, Permanent / Q000145:classification; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006801:Humans; D009811:Odontometry; D018583:Pliability; D011108:Polymers / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D019228:Tooth Crown / Q000503:physiopathology*
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; D011108:Polymers; D019279:Resin Cements; C078484:Syntac dentine adhesive; C121818:Tetric ceram