title: Influence of polymerization time and depth of cure of resin composites determined by Vickers hardness.
abstract: BACKGROUND
  Adequate polymerization of resin composites could be considered as a crucial factor in obtaining good clinical performance, particularly in stress-bearing areas. An insufficient curing degree affects the resin composite's chemical properties The current in vitro study evaluated the influence of polymerization time and depth of cure of six commercial resin composites by Vickers microhardness (VK).
  
  
  METHODS
  SIX RESIN COMPOSITES WERE SELECTED: Three microhybrid (Esthet.X HD, Amaris, Filtek Silorane), two nanohybrid (Grandio, Ceram.X mono), and one nanofilled (Filtek Supreme XT). The VK of the surface was determined by a microhardness tester using a Vickers diamond indenter and a 200 g load applied for 15 s. The bottom to top mean VK ratio was calculated using the formula: Hardness ratio = VK of bottom surface/VK of top surface. Vickers hardness values of test materials during exposure time of 20 and 40 s and depths of cure of 2 and 3 mm were determined and compared. Data were analyzed using analysis of variance (ANOVA) test.
  
  
  RESULTS
  For all the tested materials and with all the exposure time periods, hardness ratio was higher than the minimum value indicated in literature (0.8). Exposure time and depth of cure did not affect hardness ratio values for Filtek Silorane, Grandio, and Filtek Supreme XT.
  
  
  CONCLUSIONS
  Among the materials tested, the nanofilled and the nanohybrid resin composites were rather insensible to thickness variations. Miicrohybrid composites, instead, had features different from one another.
authors.affiliation: Department of Operative Dentistry, University of Pavia, Policlinico "San Matteo", Piazzale Golgi, Pavia, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Lombardini
authors.forename: Marco
authors.initials: M
authors.lastname: Chiesa
authors.forename: Andrea
authors.initials: A
authors.lastname: Scribante
authors.forename: Marco
authors.initials: M
authors.lastname: Colombo
authors.forename: Claudio
authors.initials: C
authors.lastname: Poggio
keywords: Depth of cure; Vickers hardness; hardness ratio; polymerization time
references.citation: Oper Dent. 2001 Sep-Oct;26(5):460-6
references.pmid: 11551010
references.citation: J Oral Rehabil. 2004 Mar;31(3):258-64
references.pmid: 15025659
references.citation: J Oral Rehabil. 2002 Dec;29(12):1165-73
references.pmid: 12472853
references.citation: Dent Mater. 2006 Nov;22(11):988-94
references.pmid: 16469373
references.citation: J Oral Rehabil. 2010 Apr;37(4):278-82
references.pmid: 20050987
references.citation: Dent Mater. 1985 Feb;1(1):11-4
references.pmid: 3160625
references.citation: J Dent. 2007 Jun;35(6):513-20
references.pmid: 17383067
references.citation: Scand J Dent Res. 1982 Dec;90(6):484-9
references.pmid: 6218603
references.citation: Acta Odontol Scand. 1982;40(3):179-92
references.pmid: 6957140
references.citation: Oper Dent. 2002 Jan-Feb;27(1):44-9
references.pmid: 11822365
references.citation: J Mater Sci Mater Med. 2008 Mar;19(3):1027-32
references.pmid: 17665098
references.citation: Dent Mater. 1987 Feb;3(1):19-25
references.pmid: 3471605
references.citation: Quintessence Int. 1993 Jul;24(7):517-21
references.pmid: 8210323
references.citation: Dent Mater. 1992 Sep;8(5):299-304
references.pmid: 1303371
references.citation: Oper Dent. 2009 Jan-Feb;34(1):65-71
references.pmid: 19192839
references.citation: Oper Dent. 2004 Nov-Dec;29(6):698-704
references.pmid: 15646227
references.citation: Dent Mater J. 2012;31(4):656-61
references.pmid: 22864221
references.citation: Int J Prosthodont. 1993 Jul-Aug;6(4):364-70
references.pmid: 8240647
references.citation: J Mater Sci Mater Med. 1997 Jul;8(7):413-6
references.pmid: 15348723
references.citation: J Biomed Mater Res. 1986 Jan;20(1):121-31
references.pmid: 3949822
references.citation: J Oral Rehabil. 2010 May 1;37(5):364-76
references.pmid: 20202096
references.citation: Dent Mater. 1994 Jul;10(4):282-6
references.pmid: 7664999
references.citation: Oper Dent. 2009 Sep-Oct;34(5):551-7
references.pmid: 19830969
references.citation: Braz Dent J. 2004;15(3):199-203
references.pmid: 15798823
references.citation: Oper Dent. 2008 May-Jun;33(3):287-93
references.pmid: 18505219
references.citation: Oper Dent. 2007 Nov-Dec;32(6):571-8
references.pmid: 18051007
references.citation: J Oral Rehabil. 2005 Feb;32(2):134-40
references.pmid: 15641980
references.citation: Oper Dent. 2008 Jul-Aug;33(4):408-12
references.pmid: 18666498