title: Bi-axial flexural strength of dual-polymerizing agents cemented to human dentin after photo-activation with different light-curing systems.
abstract: OBJECTIVE
  This study aimed to assess the bi-axial flexural strength of two dual-polymerizing resin luting agents cemented to human dentin when photo-activated with different light-curing units.
  
  
  METHODS
  Two dual-cured resin cements: choice (CH) and Variolink II (VL) were tested. Hybrid composite resin (Z-250) discs (12 × 1.5 mm) were fabricated. Three types of light-curing units were used halogen-curing unit (QTH), light-emitting diode (LED) and plasma arc (PAC). Sixty dentin discs of 0.5 mm thickness were prepared from extracted human teeth. A circular mold (2.5 mm in height and 12 mm diameter) was utilized to create supporting structure for dentin, resin cement complex. The resin luting cement (0.5 mm) was placed on the previously prepared dentin discs and covered with the prefabricated composite discs. Photo-activation of cements was performed for 40 s with QTH and LED units and for 3 s with PAC. The specimens were divided into 12 groups (20 specimens for each light source). Six groups were kept in distilled water for 24 h and the rest were stored for 6 weeks. Bi-axial flexural strength was determined using Instron machine. The data was analyzed using two-way ANOVA and Tukey test for comparison.
  
  
  RESULTS
  The findings indicated that the bi-axial flexural strength values for both cements CH and VL were higher for 24 h over 6 weeks but not statistically significant when cured with QTH. Meanwhile, when LED light was used for photo-activation the cements, the flexural strength values reported were statistically higher of 24 h over 6 weeks storage at P = 0.4(E-6) However, PAC light did not record any statistically significant difference between two duration for the CH cement although when used for polymerization of VL the reported value for 6 weeks were statistically significantly higher value than 24 h duration at P = 0.002.
  
  
  CONCLUSIONS
  When high immediate flexural strength is preferred in clinical situation photo-activation the cements with LED reported the greatest value.
authors: Division of Operative Dentistry, Department of Restorative Dental Sciences, College of Dentistry, King Saud University, P.O. Box 5967, Riyadh 11432, Saudi Arabia.
authors: Nadia Malek A
authors: NM
authors: Taher
keywords: Bi-axial flexural strength; Dual curing cement; Light-curing unit; Resin cement
references: Compend Contin Educ Dent Suppl. 1999;(25):S4-15; quiz S73
references: 11908395
references: Compend Contin Educ Dent. 2000 Sep;21(9):740-2, 744
references: 11199648
references: J Dent Res. 1990 Dec;69(12):1791-9
references: 2250083
references: J Contemp Dent Pract. 2008 Feb 01;9(2):57-64
references: 18264526
references: J Orthod. 2001 Sep;28(3):237-44
references: 11504902
references: Oper Dent. 2005 Mar-Apr;30(2):257-64
references: 15853113
references: J Prosthodont. 2007 Jan-Feb;16(1):18-24
references: 17244303
references: J Biomater Appl. 2000 Jan;14(3):296-315
references: 10656545
references: Scand J Dent Res. 1991 Oct;99(5):440-4
references: 1836644
references: Int J Prosthodont. 1993 Jul-Aug;6(4):364-70
references: 8240647
references: Am J Dent. 2000 Nov;13(Spec No):60D-76D
references: 11763920
references: J Prosthet Dent. 2006 Aug;96(2):115-21
references: 16911888
references: J Prosthet Dent. 1992 Feb;67(2):156-61
references: 1538320
references: Minerva Stomatol. 2003 May;52(5):193-200
references: 12874538
references: J Dent. 1998 Sep;26(7):599-602
references: 9754749
references: Dent Mater. 1996 Nov;12(6):328-32
references: 9171002
references: J Biomed Mater Res. 1998 Dec 5;42(3):465-72
references: 9788511
references: J Oral Rehabil. 1993 Mar;20(2):133-46
references: 8468625
references: J Dent. 1995 Jun;23(3):183-9
references: 7782531
references: Dent Mater. 2002 Dec;18(8):609-21
references: 12385903
references: Dent Mater. 1994 Nov;10(6):353-62
references: 7498599
references: J Prosthodont. 2008 Jul;17(5):415-9
references: 18482364
references: J Prosthet Dent. 2007 Feb;97(2):99-106
references: 17341378
references: Oper Dent. 2007 Jan-Feb;32(1):37-44
references: 17288327
references: Oper Dent. 2004 May-Jun;29(3):287-94
references: 15195729
references: J Dent. 2003 Nov;31(8):549-57
references: 14554072
references: Br Dent J. 2002 Oct 26;193(8):459-63; discussion 455
references: 12516671