title: Effect of prewarming and/or delayed light activation on resin-modified glass ionomer bond strength to tooth structures.
abstract: BACKGROUND
  Recent research shows that the acid-base reaction and light-activated polymerization in resin-modified glass ionomers (RMGI) compete with and inhibit one another. In addition, extrinsic energy would improve some properties of RMGI. This in vitro study evaluated the effect of prewarming and/or delayed light activation on bond strength of RMGI to tooth structure.
  
  
  METHODS
  Ninety-six flat enamel and dentin surfaces of human molars were ground with sequentially finer abrasives to 600-grit silicon carbide paper. Each surface was treated with a cavity conditioner for 10 seconds, rinsed, and gently air-dried (n=12). RMGI was applied to tooth substrates according to the following protocols: group 1) according to manufacturer's instructions; group 2) a delay of two minutes in light activation; group 3) prewarming of the encapsulated material (90 seconds, 40°C); group 4) prewarming plus a delay of two minutes in light activation. After 24 hours of storage at 37°C and 500 rounds of thermocycling, the samples were tested for shear bond strength and analyzed using two-way analysis of variance and Tukey HSD test (α=0.05).
  
  
  RESULTS
  Significant differences were observed between study groups (p<0.05). The highest enamel bond strength was recorded in group 2. Regarding dentin groups, the highest bond strength was recorded in group 1.
  
  
  CONCLUSIONS
  Within the limitations of the present study, delaying light activation might improve bond strength of RMGI to enamel; however, the standard procedure recommended by the manufacturer is the best procedure for bonding of RMGI to dentin. More investigations are necessary.
authors.affiliation: Department of Operative Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran. khoroushi@dnt.mui.ac.ir
authors.forename: M
authors.initials: M
authors.lastname: Khoroushi
authors.forename: T M
authors.initials: TM
authors.lastname: Karvandi
authors.forename: R
authors.initials: R
authors.lastname: Sadeghi
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000268:Adhesiveness; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D055117:Curing Lights, Dental; D001840:Dental Bonding; D003743:Dental Enamel / Q000648:ultrastructure*; D003804:Dentin / Q000648:ultrastructure*; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006358:Hot Temperature; D006801:Humans; D008027:Light; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008964:Molar, Third / Q000648:ultrastructure; D019279:Resin Cements / Q000737:chemistry*; D012117:Resins, Synthetic / Q000737:chemistry; D033081:Shear Strength; D017655:Silicon Compounds / Q000737:chemistry; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors
chemical_list: D000180:Acrylic Resins; D017554:Carbon Compounds, Inorganic; C431351:Fuji II LC cement improved; D005899:Glass Ionomer Cements; D019279:Resin Cements; D012117:Resins, Synthetic; D017655:Silicon Compounds; C006903:carbopol 940; C022088:silicon carbide