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VOLUME 8 , ISSUE 2 ( February, 2007 ) > List of Articles


The Knoop Hardness of a Composite Resin Polymerized with Different Curing Lights and Different Modes

A. Rüya Yazici, Gerard Kugel, Gülsün Gül

Citation Information : Yazici AR, Kugel G, Gül G. The Knoop Hardness of a Composite Resin Polymerized with Different Curing Lights and Different Modes. J Contemp Dent Pract 2007; 8 (2):52-59.

DOI: 10.5005/jcdp-8-2-52

License: CC BY-NC 3.0

Published Online: 01-02-2007

Copyright Statement:  Copyright © 2007; Jaypee Brothers Medical Publishers (P) Ltd.



The purpose of this study was to compare the surface hardness of a hybrid composite resin polymerized with different curing lights.

Methods and Materials

Two 3.0 mm thick composite resin discs were polymerized in a prepared natural tooth mold using: (1) a conventional quartz-tungsten halogen light (QTH- Spectrum 800); (2) a high-intensity halogen light, Elipar Trilight (TL) - standard/exponential mode; (3) a high-intensity halogen light, Elipar Highlight (HL) - standard/soft-start mode; (4) a light-emitting diode, Elipar Freelight (LED); and (5) a plasma-arc curing light, Virtuoso (PAC). Exposure times were 40 seconds for the halogen and LED lights, and three and five seconds for the PAC light. Following polymerization, the Knoop hardness was measured at the bottom and the top surfaces of the discs.


Significant differences were found between top and bottom Knoop Hardness number (KHN) values for all lights. The hardness of the top and bottom surfaces of both specimens cured by the PAC light was significantly lower than the other lights. No significant hardness differences were observed between the remaining curing units at the top of the 2.0 mm specimens. Significant differences were found between the LED and two modes of HL on the bottom surfaces. For the 3.0 mm thick samples, while significant differences were noted between LED and TL standard mode and between the two TL curing modes on the top, significant differences were only observed between QTH and the standard modes of TL and HL at the bottom.


Yazici AR, Kugel G, Gül G. The Knoop Hardness of a Composite Resin Polymerized with Different Curing Lights and Different Modes. J Contemp Dent Pract 2007 February;(8)2:052-059.

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  1. Does an incremental filling technique reduce the polymerization shrinkage stresses? J Dent Res 1996;75(3):871-878.
  2. Effect of irradiation type (LED or QTH) on photo-activated composite shrinkage strain kinetics, temperature rise, and hardness. Eur J Oral Sci 2002;110(6):471-479.
  3. Comparison study of visible curing lights and hardness of light-cured restorative materials. J Prosthet Dent 1984;52(4):504-506.
  4. Factors affecting cure at depths within light-activated resin composites. Am J Dent 1993;6(2):91-5.
  5. Tooth-colored restoratives. Principles and techniques. London: BC Decker Inc; 2002:90-93.
  6. Dental composite depth of cure with halogen and blue light emitting diyote technology. Br Dent J 1999;186(8):388-391.
  7. Microhardness of resin composites polymerized by plasma arc or conventional visible light curing. Oper Dent 2002;27(1):30-37.
  8. Characteristics of visible-light-activated composite systems. Br Dent J 1984;156(6):209-215.
  9. Post-irradiation polymerization of different anterior and posterior visible lightactivated resin composites. Dent Mater 1992;8(5):299-304.
  10. Effect of light intensity and exposure duration on cure of resin composite. Oper Dent 1994;19(1):26-32.
  11. Effectiveness of polymerization in composite restorative claiming bulk placement: Impact of cavity depth and exposure time. Oper Dent 2000;25(2):113-120.
  12. Update on dental composite restorations. J Am Dent Assoc 1994;125(6):687-701.
  13. Effects of curing tip distance on light intensity and composite resin hardness. Quintessence Int 1993;24(7):517-521.
  14. Visible-light curing units: correlation between depth of cure and distance between exit window and resin surface. Acta Odontol Scand 1997;55(3):162-6.
  15. Effects of curing tip distance on light intensity and composite resin microhardness. Quintessence Int 1993;24(7):517-521.
  16. Influence of polymerization technique on microleakage and microhardness of resin composite restorations. Oper Dent 2003;28(2):200-206.
  17. Succesful photocuring. Don't restore without it. Oper Dent 1999;24(2):109-114.
  18. Effectiveness of composite cure with pulse activation and soft-start polymerization. Oper Dent 2002;27(1):44-9.
  19. Comparison between a plasma arc light source and conventional halogen curing units regarding flexural strength, modulus and hardness of photoactivated resin composites. Clin Oral Invest 2000;4(3):140-147.
  20. Surface hardness of light-activated resin composites cured by two different visible light sources: An in vitro study. Quintessence Int 2001;32(5):401-405.
  21. Comparative efficiency of plasma and halogen light sources on composite micro-hardness in different curing conditions. Dent Mater 2003;19(6):493-500.
  22. Effect of light source and specimen thickness on the surface hardness of resin composite. Am J Dent 2002;15(1):47-53.
  23. Comparison of PAC and QTH light sources on polymerization of resin composites. Am J Dent 2004;17(2):113-117.
  24. A comparison of polymerization by light - emitting diode and halogen based light curing units. J Am Dent Assoc 2002;133(3):335-341.
  25. Effect of high intensity vs. soft-start halogen irradiation on light-cured resin-based composites. PartII: hardness and solubility. Am J Dent 2004;17(1):38-42.
  26. Polymerization efficiency of LED curing lights. J Esthet Rest Dent 2002;14(5):286-295.
  27. Thermal emission and curing efficiency of LED and halogen curing lights. Oper Dent 2005;30(2):257-264.
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