title: Effect of different thermo-light polymerization on flexural strength of two glass ionomer cements and a glass carbomer cement.
abstract: BACKGROUND
  Whether polymerization lights can be used for heating glass ionomer cements (GICs) or glass carbomer (GCP) to improve their mechanical properties is not well established.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to assess the effect of thermo-light polymerization on the flexural strength (FS) of 2 GICs (Fuji IX GP Fast, Ketac Molar) and a GCP.
  
  
  METHODS
  Specimens (n=10) were prepared in stainless steel molds (2×2×25 mm), compressed, exposed to 3 polymerization lights (500, 1000, 1200 mW/cm2) for 2 cycles of 40 seconds on each side, and stored in petroleum jelly (37°C, 24 hours).
  
  
  RESULTS
  Significant FS differences were detected among groups after different thermo-light polymerization regimens (F=50.926, df=11, P<.001). GCP showed the highest mean FS (∼5 times, P<.001) after thermo-light polymerization with power outputs of 1000 (127.1 ±25.8 MPa) and 1200 mW/cm2(117.4 ±18.5 MPa), with no significance difference between them (P=.98), compared with 500 mW/cm2(24.1 ±1.7 MPa). For Ketac Molar, compared with autopolymerization setting (15.5 ±3.1 MPa), a significant increase in mean FS (∼2.5 times) was only observed in specimens treated with 1200 mW/cm2polymerization light (P=.03). For Fuji IX GP Fast, only the light with 1000 mW/cm2output significantly increased the FS (98.9 ±23.4 MPa, P<.001) compared with the autopolymerization setting (34.9 ±6.4 MPa).
  
  
  CONCLUSIONS
  Thermo-light polymerization accelerated the development of FS in the tested GICs, potentially protecting against saliva contamination during the first 3 to 4 minutes after mixing GIC. Thermo-light polymerization of the glass carbomer with power outputs of 1000 and 1200 mW/cm2also substantially increased FS. The clinical advantages of the findings should be validated by in vivo studies.
authors.affiliation: Assistant Professor, Department of Paediatric and Preventive Dentistry, School of Dental Medicine, University of Zagreb, Zagreb, Croatia.
authors.forename: Kristina
authors.initials: K
authors.lastname: Gorseta
authors.affiliation: Visiting Professor (Orthodontics), Department of Clinical Sciences and Translational Medicine, University of Rome Tor Vergata, Rome, Italy; and Associate Clinical Teacher, Warwick Medical School, University of Warwick, Coventry, United Kingdom. Electronic address: faraortho@yahoo.com.
authors.forename: Ali
authors.initials: A
authors.lastname: Borzabadi-Farahani
authors.affiliation: Assistant Professor, Division of Advanced Prosthodontics, UCLA School of Dentistry, Los Angeles, Calif.
authors.forename: Alireza
authors.initials: A
authors.lastname: Moshaverinia
authors.affiliation: Professor, Department of Paediatric and Preventive Dentistry, School of Dental Medicine, University of Zagreb, Zagreb, Croatia.
authors.forename: Domagoj
authors.initials: D
authors.lastname: Glavina
authors.affiliation: Professor, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
authors.forename: Edward
authors.initials: E
authors.lastname: Lynch
mesh_terms: D001031:Apatites / Q000737:chemistry* / Q000528:radiation effects*; D019245:Compressive Strength; D055117:Curing Lights, Dental; D001840:Dental Bonding; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents / Q000737:chemistry / Q000528:radiation effects; D005899:Glass Ionomer Cements / Q000737:chemistry* / Q000528:radiation effects*; D006244:Hardness; D006358:Hot Temperature; D008422:Materials Testing; D058105:Polymerization / Q000528:radiation effects*; D033081:Shear Strength; D013052:Spectrometry, X-Ray Emission; D013314:Stress, Mechanical; D013696:Temperature; D013718:Tensile Strength
chemical_list: D001031:Apatites; D017220:Dentin-Bonding Agents; C439808:Fuji IX GP Fast; D005899:Glass Ionomer Cements; C586142:glass carbomer cement; C110712:ketac-molar