title: Bond strength of resin-based restorations polymerized with different light-curing sources.
abstract: OBJECTIVE
  To evaluate the influence of different light-curing units on microtensile bond strength of resin composite restorations.
  
  
  METHODS
  Standardized Class I preparations (6.0 x 4.5 mm, 2.5 mm deep) were made in extracted human third molars after abrading the cusps. Resin was inserted in bulk using a 3M ESPE restorative system [Adper Single Bond (DBA)/ Filtek Z250 (RC)]. Both materials were polymerized using different light-curing units: QTH at 540 mW/cm(2) (XL 3000, 3M ESPE); LED at 750 mW/cm(2) (Elipar FreeLight2, 3M ESPE); PAC at 2130 mW/cm(2) (Arc Light II, Air Techniques). Nine different light combinations were developed to polymerize both DBA and RC: QTH/QTH; QTH/LED; QTH/PAC; LED/LED; LED/QTH; LED/PAC; PAC/PAC; PAC/QTH; PAC/LED. Restored teeth were stored in distilled water for 24 h at 37 degrees C and then sectioned, yielding stick-shaped specimens with a bonded area of approximately 0.9 mm(2). Specimens were assessed in a testing machine at a crosshead speed of 1 mm/min. The results were analyzed using two-way ANOVA and Tukey's test at a pre-set alpha = 0.05.
  
  
  RESULTS
  The combinations PAC/QTH and QTH/QTH presented the highest bond strength values, and LED/QTH the lowest (p < 0.05). Significantly lower values were observed in combinations when the LED light was used to polymerize DBA compared to QTH and PAC lights, irrespective of the light source used to polymerize RC (p < 0.05). Same light combinations presented similar bond strength values.
  
  
  CONCLUSIONS
  Different light sources influence restoration bond strength. Bond strength is more dependent on the light source used for DBA than for curing RC.
authors.affiliation: Department of Operative Dentistry, Endodontics and Dental Materials, Bauru Dental School, University of São Paulo, SP, Brazil.
authors.forename: Paulo H P
authors.initials: PH
authors.lastname: D'Alpino
authors.forename: Linda
authors.initials: L
authors.lastname: Wang
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Rueggeberg
authors.forename: Nádia R
authors.initials: NR
authors.lastname: Svizero
authors.forename: José C
authors.initials: JC
authors.lastname: Pereira
authors.forename: David H
authors.initials: DH
authors.lastname: Pashley
authors.forename: Ricardo M
authors.initials: RM
authors.lastname: Carvalho
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry / Q000528:radiation effects; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D001840:Dental Bonding; D003737:Dental Cavity Preparation / Q000145:classification; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis / Q000295:instrumentation; D017220:Dentin-Bonding Agents / Q000737:chemistry / Q000528:radiation effects; D004867:Equipment Design; D006801:Humans; D008029:Lighting / Q000295:instrumentation*; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; C444701:Filtek Z250; D011108:Polymers; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate