title: Initial fracture resistance and curing temperature rise of ten contemporary resin-based composites with increasing radiant exposure.
abstract: OBJECTIVE
  The principal objective of this study was to determine whether the bulk fracture resistance of ten light activated composites varied over a clinically realistic range of radiant exposures between 5 and 40 J/cm(2).
  
  
  METHODS
  Ten operators were tested for clinically simulated radiant exposure delivery from a Bluephase(®) (Ivoclar Vivadent, Schaan, Liechtenstein) LED light to an occlusal cavity floor in tooth 27 in a mannequin head using a MARC(®)-Patient Simulator (Bluelight Analytics Inc., Halifax, NS) device. Notch disc test samples were prepared to determine the torque resistance to fracture (T) of the composites. Samples were irradiated with the same monowave Bluephase(®) light for 10s, 20s or 40s at distances of 0mm or 7 mm. After 24h, storage samples were fractured in a universal testing machine and torque to failure was derived.
  
  
  RESULTS
  Radiant exposure delivered in the clinical simulation ranged from 14.3% to 69.4% of maximum mean radiant exposure deliverable at 0mm in a MARC(®)-Resin Calibrator (Bluelight Analytics Inc., Halifax, NS) test device. Mean torque to failure increased significantly (P<0.05) with radiant exposure for 8 out of 10 products. The micro-fine hybrid composite Gradia Direct anterior (GC) had the lowest mean (S.D.) T between 10.3 (1.8)N/mm and 13.7 (2.2)N/mm over the tested radiant exposure range. Three heavily filled materials Majesty Posterior, Clearfil APX and Clearfil Photo-Posterior (Kuraray) had mean T values in excess of 25 N/mm following 40 J/cm(2) radiant exposure. Mean T for Z100 (3MESPE) and Esthet-X (Dentsply) increased by 10% and 91% respectively over the tested range of radiant exposures.
  
  
  CONCLUSIONS
  Individual products require different levels of radiant exposure to optimize their fracture resistance. Light activated composites vary in the rate at which they attain optimal fracture resistance.
  
  
  CONCLUSIONS
  Unless the clinician accurately controls all the variables associated with energy delivery, there is no way of predicting that acceptable fracture resistance will be achieved intra-orally.
authors: The University of Birmingham, The Dental School, Biomaterials Unit, St. Chad's Queensway, Birmingham B4 6NN, England, United Kingdom. a.c.c.shortall@bham.ac.uk
authors: A
authors: A
authors: Shortall
authors: W
authors: W
authors: El-Mahy
authors: D
authors: D
authors: Stewardson
authors: O
authors: O
authors: Addison
authors: W
authors: W
authors: Palin
mesh_terms: D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D055117:Curing Lights, Dental / Q000145:classification; D003764:Dental Materials / Q000737:chemistry / Q000528:radiation effects*; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D011829:Radiation Dosage; D012822:Silicon Dioxide / Q000737:chemistry / Q000528:radiation effects; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D019415:Torque; D015040:Zirconium / Q000737:chemistry / Q000528:radiation effects
chemical_list: C112828:Clearfil AP-X; D003188:Composite Resins; D003764:Dental Materials; C466112:Esthet-X; C474035:Filtek Supreme; C500649:Filtek Supreme Translucent; C444701:Filtek Z250; C470230:Gradia; D008689:Methacrylates; C083568:Z100 composite resin; C541508:clearfil majesty; C092420:Clearfil Photo Posterior; D012822:Silicon Dioxide; D015040:Zirconium