• Users Online: 77
  • Home
  • Print this page
  • Email this page
Home About us Editorial board Ahead of print Current issue Search Archives Submit article Instructions Subscribe Contacts Login 

 Table of Contents  
Year : 2017  |  Volume : 2  |  Issue : 2  |  Page : 37-39

Light cure devices

Department of Prosthodontics, Saveetha Dental College, Chennai, Tamil Nadu, India

Date of Web Publication1-Feb-2018

Correspondence Address:
M Namrata
Department of Prosthodontics, Saveetha Dental College, Chennai, Tamil Nadu
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijofr.ijofr_17_17

Rights and Permissions

With the invention of light-cured resin materials used in bonding and restorations, the use of light cure units has become an integral part of dentistry. There is a vast change in the curing devices over the last 30 years. At present, the following types of light-curing devices are available – Quartz-tungsten-halogen, light-emitting diode, plasma arc curing, and Argon laser. This review is primarily focused on discussing the types and limitation of each type of light cure units and also maintenance of light cure units to optimize their use.

Keywords: Curing units, eye protection, light emitting diode, Quartz-tungsten halogen unit

How to cite this article:
Namrata M, Ganapathy D. Light cure devices. Int J Orofac Res 2017;2:37-9

How to cite this URL:
Namrata M, Ganapathy D. Light cure devices. Int J Orofac Res [serial online] 2017 [cited 2023 Dec 4];2:37-9. Available from: https://www.ijofr.org/text.asp?2017/2/2/37/224499

  Introduction Top

In this era of esthetic dentistry light-activated resin cement, bonded direct, and indirect restorations have become the material of choice and light cure units an integral part of the procedure. The materials which require photopolymerization include pit and fissure sealants, direct and indirect resin composite restorations, resin-modified glass ionomer, etc.[1] At present, 4 types of curing lights are available; conventional Quartz-tungsten halogen (QTH) unit, light-emitting diodes (LEDs), plasma arc curing (PAC), and argon laser curing. The success of restoration depends on the effectiveness of curing as inadequate polymerization may lead to tooth sensitivity, microleakage of components of restoration, fractures, or complete debonding of restorations.

  Quartz-Tungsten-Halogen Lamp Top

Dentists have been using QTH polymerization unit to polymerize composite resin for nearly 30 years.[2] Conventionally, a QTH source, filtered to provide blue light has wavelengths starting around 380–400 nm and ending around 500-51 nm.[3] Since they have such a wide spectrum they are capable of curing short wavelength photoinitiators as well as camphorquinone (CQ).[3] The standard intensity of the QTH sources has been approximately found to be 600 mW/cm 2.[4] This intensity can adequately cure most dental composites to a depth of 2 mm in approximately 40 s.[5] They produce light by passing a current through a tungsten filament housed in a quartz bulb filled with halogen gas. As the current passes through the filament, most of the energy generated is changed into heat, but a small portion is given off as light, and a filter allows only blue light to pass.[6] This explains excessive heat generation by QTH units which in turn leads to damage of bulb components and decreases lifespan of the curing unit to 100 h.[7],[8],[9],[10] Another drawback of QTH-curing units is that only a small portion of the halogen emission spectrum actually is used to active the photoinitiator molecules when the CQ absorption spectrum is compared with emission characteristics of halogen lights.[6]

  Argon Laser-Curing Units Top

A lot of research has been done on the use of argon laser for photopolymerization of composite resin restorative materials since 1980 and this interest has arisen because the wavelength (488 nm) of light emitted by the argon laser is optimal for the initiation of polymerization of composite resins [11],[12] The argon laser units do not employ the use of filters unlike QTH-curing units but instead, it generates one wavelength of blue light (monochromatic light) having a bandwidth of only 400–450 nm [12],[13] Advantages of argon laser include reduced curing time, improved depth of cure, and reduced heat generation but the most important one being that argon laser radiation alters the surface chemistry of both enamel and surface dentin reducing the risk of recurrent carries [14],[15],[16],[17],[18] They are especially useful in class 2 restoration as it provides easy access to the interproximal box because of the small fiber size but in case of large restoration it becomes a drawback.[1] The drawbacks include bulkiness, heat generation, and nonaffordability [19] also there is a 30-s time lag between turning the unit on and actual light emission.[20] The dentist must determine the risk to surrounding tissues when laser is used since when laser light hits the target, it may be absorbed, transmitted, scattered, or reflected.[21]

  Plasma Arc Curing Lamps Top

To save irradiation time as an economic factor PAC lamps emitting visible light at higher intensities were introduced.[22] PAC-curing lamps polymerize composite in the least amount of time by producing a power density of 100 mw/cm 2.[23] PAC lamps apply a high-voltage current across two closely placed electrodes, resulting in a light arc between the electrodes [24],[25] PAC-curing lamps have a 5 mm spot size and a bandwidth of 380–500 nm.[1] The manufacturers of this lamp, due to its tremendous energy output claim that 3 s irradiation with PAC lamp gave same material properties as with 40 s curing with QTH lamp.[26] However, of late this claim has been proved wrong [26],[27],[28],[29],[30] The drawbacks include that the source requires a wait time (minimum 10 s) after each use to allow the unit to recover since it gives tremendously powerful light energy.[31] In a study done by Hoffman hybrid composite cured by PAC produced inferior mechanical properties as it contains CQ and other short wavelength absorbing photoinitiators (370–450 nm), thus giving a conclusion that the suitability of plasma unit depends on the photoinitiators the resin composite contains.[32] The efficiency of PAC lights for curing in deep preparations or thick composite layers has been questioned.[8] According to the results from a study by Cavalcante, there is significant gap formation when PAC units are used which is more than that in argon laser but lesser than QTH units, also hardness is comparatively less especially in the bottom region.[33]

  Led-Curing Units Top

To overcome the disadvantage of halogen polymerization light, in 1995, Mills et al. proposed using solid-state LED technology.[34] Several generations of LED light-curing units have been introduced over the last few years:[35] 1st-generation LED lights generally were low in intensity and did not cure materials completely as the diodes were designed to activate only CQ, 2nd-generation LED light-curing units have a single, high-powered diode with multiple emission areas, and these units have a large surface area of emission and high-energy output; and 3rd-generation LED light-curing units have two or more diode frequencies and emit light in different ranges to activate CQ and alternative photoinitiators. When subjected to an electric current, electrons, and holes recombine at the LEDs p-n junction of a semiconductors material such as gallium nitride, leading to the emission of blue light.[36] The emission spectrum falls between 450 and 500 nm.[3] They are battery operated, portable with little heat emission.[35] LED units do not require fillers as they have a narrow band that falls in absorption spectrum of CQ [34],[37] According to a study conducted by Mousavinasab, the hardness values and depth of cure obtained by LED units was greater than with the QTH light and also the thermal changes on using QTH light for 3 s were same as using LED light for 40 s.[38] LEDs are resistant to shock and vibration, consume little power on operation and have a shelf life of 10,000 h.[1]

  Maintanance Top

Checking of a number of features of the light cure unit is necessary to ensure that it works to the optimum. Resin contamination on the curing tip tends to scatter the light, thus reducing the effective output.[39] Hence, the tip requires to be cleaned using an appropriate rubber wheel and slow handpiece. According to the study by Friedman, the polymerization units used in dental practices have lost 45%–89% of their initial intensity due to lack of maintenance.[40]

  Occular Hazards and Eye Protection Top

The blue light emitted from various light-curing devices is reportedly harmful for human vision.[41] It has been demonstrated that the blue light in the process of producing free radicals in composite to cure also produces free radicals in the eye.[42] These free radicals react with the water content of the cells to produce peroxides which are highly reactive and denaturate the delicate photoreceptors called retinitis.[43] Hence, effective eye protection against blue light is mandatory. Best method would be to avoid looking at the blue light completely or to cover the curing area with reflective side of mouth mirror.[1] A number of colored plastic glasses and hand-held shields are also available.[44]

  Conclusion Top

Appropriately polymerized material shows good physical and mechanical properties in turn promote success of restoration. Thus, an ideal light cure unit having maximum diameter of curing, minimal heat generation, ease of use, durability, portability, and cost-effectiveness should be used. Periodical evaluation and maintenance of the curing unit should be done for optimal use.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Singh TK, Ataide I, Fernandes M, Lambor RT. Light curing devices a clinical review. J Orofac Res 2011;1:111, 5-19.  Back to cited text no. 1
Bassiouny MA, Grant AA. A visible light-cured composite restorative. Clinical open assessment. Br Dent J 1978;145:327-30.  Back to cited text no. 2
Ontiveros C.J.C., Paravina Rade D. Light-emitting diode polymerization: A review of performance, Part I. Acta Stomatol Naissi 2006;22:601-10.  Back to cited text no. 3
Kanca J 3rd. High-energy illumination of the truth, or the serial endorser? J Esthet Restor Dent 2001;13:147-9.  Back to cited text no. 4
Caughman WF, Rueggeberg FA, Curtis JW Jr. Clinical guidelines for photocuring restorative resins. J Am Dent Assoc 1995;126:1280-2, 1284, 1286.  Back to cited text no. 5
Althoff O, Artung MH. Advances in light curing. Am J Dent 2000;13:77-81.  Back to cited text no. 6
Barghi N, Berry T, Hatton C. Evaluating intensity output of curing lights in private dental offices. J Am Dent Assoc 1994;125:992-6.  Back to cited text no. 7
Martin FE. A survey of the efficiency of visible light curing units. J Dent 1998;26:239-43.  Back to cited text no. 8
Miyazaki M, Hattori T, Ichiishi Y, Kondo M, Onose H, Moore BK, et al. Evaluation of curing units used in private dental offices. Oper Dent 1998;23:50-4.  Back to cited text no. 9
Leonard DL, Charlton DG, Hilton TJ. Effect of curing-tip diameter on the accuracy of dental radiometers. Oper Dent 1999;24:31-7.  Back to cited text no. 10
Blankenau R, Kelsey WP, Kutsch VK. Clinical applications of argon laser in restorative dentistry. In: Miserendino LJ, Pick RM, editors. Lasers in Dentistry. Chicago: Quintessence Publishing; 1995. p. 217-30.  Back to cited text no. 11
Kelsey WP 3rd, Blankenau RJ, Powell GL, Barkmeier WW, Cavel WT, Whisenant BK, et al. Enhancement of physical properties of resin restorative materials by laser polymerization. Lasers Surg Med 1989;9:623-7.  Back to cited text no. 12
Harris DM, Pick RM. Laser physics. In: Miserendino LJ, Pick RM, editors. Lasers in Dentistry. Chicago: Quintessence Publishing Company Inc.; 1995. p. 27-38.  Back to cited text no. 13
Walsh LJ. The current status of laser applications in dentistry. Aust Dent J 2003;48:146-55.  Back to cited text no. 14
Anić I, Pavelić B, Perić B, Matsumoto K.In vitro pulp chamber temperature rises associated with the argon laser polymerization of composite resin. Lasers Surg Med 1996;19:438-44.  Back to cited text no. 15
Cobb DS, Dederich DN, Gardner TV.In vitro temperature change at the dentin/pulpal interface by using conventional visible light versus argon laser. Lasers Surg Med 2000;26:386-97.  Back to cited text no. 16
Hicks MJ, Flaitz CM, Westerman GH, Blankenau RJ, Powell GL, Berg JH, et al. Caries-like lesion initiation and progression around laser-cured sealants. Am J Dent 1993;6:176-80.  Back to cited text no. 17
Westerman G, Hicks J, Flaitz C. Argon laser curing of fluoride-releasing pit and fissure sealant:In vitro caries development. ASDC J Dent Child 2000;67:385-90, 374.  Back to cited text no. 18
Fleming MG, Maillet WA. Photopolymerization of composite resin using the argon laser. J Can Dent Assoc 1999;65:447-50.  Back to cited text no. 19
Subject: Intraoral Resin Curing Lights. Clinical Research Associates Newsletter. Vol. 1. 1996. p. 1-2.  Back to cited text no. 20
Dederich DN. Laser/tissue interaction: What happens to laser light when it strikes tissue? J Am Dent Assoc 1993;124:57-61.  Back to cited text no. 21
Rueggeberg F. Contemporary issues in photocuring. Compend Contin Educ Dent Suppl 1999;8:S4-15.  Back to cited text no. 22
Tarle Z, Meniga A, Knezević A, Sutalo J, Ristić M, Pichler G, et al. Composite conversion and temperature rise using a conventional, plasma arc, and an experimental blue LED curing unit. J Oral Rehabil 2002;29:662-7.  Back to cited text no. 23
Yearn JA. Factors affecting cure of visible light activated composites. Int Dent J 1985;35:218-25.  Back to cited text no. 24
Musanje L, Darvell BW. Polymerization of resin composite restorative materials: Exposure reciprocity. Dent Mater 2003;19:531-41.  Back to cited text no. 25
Peutzfeldt A, Sahafi A, Asmussen E. Characterization of resin composites polymerized with plasma arc curing units. Dent Mater 2000;16:330-6.  Back to cited text no. 26
Burgess JO, Walker RS, Porche CJ, Rappold AJ. Light curing – An update. Compend Contin Educ Dent 2002;23:889-92, 894, 896.  Back to cited text no. 27
Danish G, Davids H, Reinhardt KJ, Ott K, Schafer E. Polymerisation characteristics of resin composites polymerized with different curing lights. J Dent 2004;32:479-88.  Back to cited text no. 28
Deb S, Sehmi H. A comparative study of the properties of dental resin composites polymerized with plasma and halogen light. Dent Mater 2003;19:517-22.  Back to cited text no. 29
Hofmann N, Denner W, Hugo B, Klaiber B. The influence of plasma arc vs. halogen standard or soft-start irradiation on polymerization shrinkage kinetics of polymer matrix composites. J Dent 2003;31:383-93.  Back to cited text no. 30
Albers HF. Tooth Colored Restoratives Principles and Techniques. 9th ed. Hamilton, Ontario, Lewiston, NY: BC Decker; 2002.  Back to cited text no. 31
Hofmann N, Hugo B, Schubert K, Klaiber B. Comparison between a plasma arc light source and conventional halogen curing units regarding flexural strength, modulus, and hardness of photoactivated resin composites. Clin Oral Investig 2000;4:140-7.  Back to cited text no. 32
Cavalcante LM, Peris AR, Silikas N, Pimenta LA. Effect of light curing units on marginal adaptation and hardness of Class II composite resin restorations. J Contemp Dent Pract 2007;8:38-45.  Back to cited text no. 33
Mills RW. Blue light emitting diodes-another method of light curing? Br Dent J 1995;178:169.  Back to cited text no. 34
The Dental Advisor JCDA 2005;71:710-2.  Back to cited text no. 35
Duke ES. Light-emitting diodes in composite resin photopolymerization. Compend Contin Educ Dent 2001;22:722-5.  Back to cited text no. 36
Mills RW, Jandt KD, Ashworth SH. Dental composite depth of cure with halogen and blue light emitting diode technology. Br Dent J 1999;186:388-91.  Back to cited text no. 37
Mousavinasab SM, Meyers I. Comparison of depth of cure, hardness and heat generation of LED and high intensity QTH light sources. Eur J Dent 2011;5:299-304.  Back to cited text no. 38
Friedman J. Variability of lamp characteristics in dental curing lights. J Esthet Dent 1989;1:189-90.  Back to cited text no. 39
Friedman J. Care and maintenance of dental curing lights. Dent Today 1991;10:40-1.  Back to cited text no. 40
Ham WT Jr., Ruffolo JJ Jr., Mueller HA, Guerry D 3rd. The nature of retinal radiation damage: Dependence on wavelength, power level and exposure time. Vision Res 1980;20:1105-11.  Back to cited text no. 41
Ham WT Jr., Mueller HA, Ruffolo JJ Jr., Millen JE, Cleary SF, Guerry RK, et al. Basic mechanisms underlying the production of photochemical lesions in the mammalian retina. Curr Eye Res 1984;3:165-74.  Back to cited text no. 42
Ham WT Jr., Mueller HA, Ruffolo JJ Jr., Guerry D 3rd, Guerry RK. Action spectrum for retinal injury from near-ultraviolet radiation in the aphakic monkey. Am J Ophthalmol 1982;93:299-306.  Back to cited text no. 43
Berry EA, Pitts DG, Francisco PR, von der Lehr WN. An evaluation of lenses designated to block light emitted by light curing units. J Am Dent Assoc 1986;112:70-2.  Back to cited text no. 44


Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

  In this article
Argon Laser-Curi...
Plasma Arc Curin...
Led-Curing Units
Occular Hazards ...

 Article Access Statistics
    PDF Downloaded732    
    Comments [Add]    

Recommend this journal