Article_5_4_4

RESTORATIVE DENTISTRY
LIGHT CURING MATTERS: FACTS OFTEN OVERSEEN BY DENTISTS
Review Article
Dayane Carvalho Ramos Salles de Oliveira1,2a* , Mateus Garcia Rocha1,2b , Jean-François Roulet1c

1
Department of Restorative Dental Sciences, College of Dentistry, University of Florida, 1395 Center Dr, 32610, Gainesville, FL, USA
2
Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Avenida Limeira, 901, 13414-903, Piracicaba, SP, Brazil
a
DDS, MSc, PhD, Post-Doctoral Researcher
b
DDS, MSc, PhD, Researcher
c
Dr med dent, Dr hc, Professor, Director of Center for Dental Biomaterials

ABSTRACT DOI: 10.25241/stomaeduj.2018.5(4).art.4
OPEN ACCESS This is an Open Access article under the CC
BY-NC 4.0 license.
Aim: To make dentists aware on the importance of correctly used light cure Peer-Reviewed Article
resin composites. Citation: de Oliveira DCRS, Rocha MG, Roulet J-F. Light curing matters:
Method: Highlighting important facts about light curing: Use of high Facts often overseen by dentists. Stoma Edu J. 2018;5(4):236-242.
quality light curing unit, use of the resin composite specific appropriate Academic Editor: Nicoleta Ilie, Dipl-Eng, PhD, Professor, Ludwig-
radiant exposure to adequately cure a resin composite, and highlighting Maximilians-Universität München, München, Germany
important facts that may alter the radiant exposure received clinically by Received: November 27, 2018
a resin composite restoration. Revised: December 03, 2018
Accepted: December 17, 2018
Results: Application of this knowledge should change the behavior of Published: December 18, 2018
dentists when it comes to light curing.
*Corresponding author:
Conclusions: The facts described should help educational institutes Dr. Dayane C. R. S. de Oliveira, DDS, MSc, PhD, Researcher
and professors to reinforce proper light curing techniques and associate Department of Restorative Dental Sciences, College of Dentistry, University
of Florida
training sessions within educational courses in order to improve 1395 Center Dr, 32610, Gainesville, FL, USA
teaching and learning. Tel: +1 352 273 5850;
Fax: +1 352 846 1643,
Keywords: light curing, composites, teaching. e-mail: dayoli87@gmail.com

1. Introduction is worth, considering that the use of a deficient LCU
When placing a restoration, dentists are mainly may result in a poorly polymerized resin composite
performing a manufacturing process. This restoration, while the materials used will not perform
presumes good equipment, materials and process as intended by the manufacturer.
techniques. This short article will focus on the latter. Generally, manufacturers clearly indicate the radiant
A prerequisite for a proper functionality of a resin exposure necessary to adequately polymerize
composite restoration in the oral cavity [1] is to their materials (e.g. 20 seconds at 800 mW/cm2).
receive sufficient radiant exposure (= irradiance of However, a fact that is often forgotten by dentists
the light curing unit x exposure time). is to take into account the incremental thickness
In advertisements, light curing units (LCU) are usually of the applied resin composites. Resin composites
characterized by their irradiance, which is expressed absorb, reflect and scatter the light they receive
in mW/cm2. This parameter alone is, however, by during polymerization. This means that if the
far insufficient to assess the quality of light curing. maximum recommended incremental thickness is
It should be mentioned that currently, the range of exceeded, the polymerization of the material may
prices for dental LCUs varies among $18.59 (best- be insufficient, with the consequences described
selling offer on e-bay on December 3rd 2018) and above. The incremental thickness recommended for
even more than $1000. While the irradiance of low- most regular resin composites is 2 mm, while for bulk
cost and expensive LCUs may be comparable, the fil resin composites it may be extended to 4-5 mm. It
price difference is reflected in the homogeneity should be emphasized that darker shades and less
of the light beam, the diameter of the light exiting translucent resin composites will absorb more light
window, the collimation of the light beam, the and show a reduced depth of cure (= incremental
battery management to deliver a constant radiant thickness that is adequately cured) [2].
exposure over time (Fig. 1). Saving on the cost of Besides the above-mentioned reasons, the success
a light curing unit is saving on the wrong side. It of resin composite restorations depends on further
should be emphasized here that, related to the total factors [3], while the less known and most neglected
costs of a resin composite restoration, the use of an factor is the light curing process [4-6]. Resin composite
expensive LCU does not exceed 1%. This investment restorations increasingly fail due to marginal failures

236 Stoma Edu J. 2018;5(4): 236-242 http://www.stomaeduj.com
LIGHT CURING MATTERS:
FACTS OFTEN OVERSEEN BY DENTISTS

Review Article
Figure 1. Homogeneity differences in light beam profile of mono- (Radii, SDI) and multi-wave (VALO Cordless, Ultradent) LED curing lights.

Figure 2. Marginal breakdowns due to inadequate light curing.
(Source: H. Strassler on youtube: https://www.youtube.com/watch?v=48XZgR37djY)

[7,8], as evidenced especially in Cass II restorations,
which might be found in periodical x-rays (Fig. 2).
What the majority of dentists do not know is that
the most common reason for this kind of marginal
breakdown is inadequate light curing [9].
It is nowadays well-documented that there is a
large variation between operators in delivering the
radiant exposure during the light curing process of
a resin composite restoration. The use of an efficient Figure 3. Light curing skills tested before and after training.
LCU is therefore not a guarantor for an adequate
polymerization [5,9-11]. Fortunately, education 2.1. Blue-blocking filters
associated with proper training was proved to be The right way to properly cure a restoration is
efficient to improve light curing skills (Fig. 3) [9-11]. positioning the light tip as close as possible and
parallel to the restoration and stabilize and maintain
it throughout the exposure [15]. In order to do so,
2. Clinical aspects some kind of blue-blocking shield is extremally
The first important factor that can lead to improper needful. Different kinds of orange filters are available
light curing is not paying attention [9-11]. Modern in the market to provide protection to the eyes
curing lights emit irradiances above 1000 mW/cm2 during the light curing process (Fig. 4). These filters
[12], thus looking into the light during polymerization are able to block at least 97% of the light emitted
is not recommended due to potential risk for ocular from dental curing lights [16]. As can be observed
hazards [13-15]. In response to that, most dentists in Fig. 5, the radiant emittance from the curing light
avoid looking to the patient’s mouth during the light is 1000 mW/cm2, however, after interposing a blue-
curing process. block filter in between the curing light emission and
the sensor, the irradiance emittance from the curing

Stomatology Edu Journal 237
LIGHT CURING MATTERS:
FACTS OFTEN OVERSEEN BY DENTISTS

Review Article

Figure 4. Blue-blocking filters:
a) hand-held light filter,
b) blue-blocking protective glasses,
c) flip-up shield,
d) clip-on shield,
e) ease-in removable shield.

Figure 5. Effect of blocking blue-light irradiance from a multi-wave light curing unit during light exposure.

Figure 6. Irradiance increase as a result of using magnification loupes.

light is totally blocked. It is worthwhile mentioning Another aspect that cannot be neglected is that
that while using magnification loupes, the irradiance different curing lights have different light tip sizes.
received at the pupil can be increased by up to The light tip diameter of the curing lights in the
8 times greater than when no loupes are used market are between 7 and 12 mm [19,20]. Usually
(Fig. 6) [13]. Despite almost no publicity even from fiber optic guides vary from 7 to 9 mm in diameter
the own brands, blue-blocking filters specially made [19], while quartz lenses such as used in the VALO
for loupes are available in the market, as previously Cordless and VALO Grand (Ultradent, South Jordan,
illustrated in Fig. 3. UT, USA) are 10 and 12 mm in diameter, respectively
[19,20]. Usually pre-molar are about 7 mm wide, but
2.2. Positioning average molars are about 10 mm wide (Fig. 8) [21].
The ideal case scenario is to light cure positioning Thus, special attention in positioning the curing light
the light tip as close as possible and parallel to is encouraged when light curing proximal boxes
the restoration during light curing [15]. However, in Class II restorations, as well as two light curing
different clinical situations can make this difficult or procedures in each end (mesial and distal) while
almost impossible, such as the restauration location using bulk fill composites in Class II restorations (Fig.
and the light tip angulation versus patient mouth 9) [4,6,15].
aperture (Fig. 7) [17,18]. When the light tip is not positioned properly,

238 Stoma Edu J. 2018;5(4): 236-242 http://www.stomaeduj.com
LIGHT CURING MATTERS:
FACTS OFTEN OVERSEEN BY DENTISTS

Review Article
Figure 7. LCU tip angulation and ideal positioning, at same mouth aperture situation: A) VALO Cordless (Ultradent), B) Radii Plus (SDI), C) Bluephase
Style (Ivoclar Vivadent), D) Bluephase G2 (Ivoclar Vivadent), E) Elipar S10 (3M ESPE), F) G-light (GC).

Figure 8. Overlapping ofa 10 mm wide molar with different light guides sizes

either because of limitations due to its size (Fig. 2.3. Cleaning and maintaining
8) or because of angulations caused by mouth Finally, leaning and maintaining should not be
aperture (Fig. 10), not enough light will reach the forgotten. It is already known that broken and dirty
resin material and polymerization can be affected light curing tips can affect the polymerization of
[15], especially in depth, possible causing marginal the material [15]. Usually, when the light tip gets in
breakdowns such as exemplified in Fig. 1. direct contact with the resin composite or adhesive

Stomatology Edu Journal 239
LIGHT CURING MATTERS:
FACTS OFTEN OVERSEEN BY DENTISTS

Review Article

Figure 9. Instructions on light curing a 10 mm wide molar using different light tip sizes.

Figure 10. Instructions on positioning the curing light properly.

Figure 11. Irradiance emittance drop from a curing light with dirty tip and use of barrier sleeve.
during polymerization, part of this material adheres material is transferred to the light tip, but the next
to the light tip. The problem is that not only does increment of resin will not receive the same radiant
the restoration lose shape because part of the resin exposure than the first one. Light curing sleeves are

240 Stoma Edu J. 2018;5(4): 236-242 http://www.stomaeduj.com
LIGHT CURING MATTERS:
FACTS OFTEN OVERSEEN BY DENTISTS

not only able to protect from cross-contamination, 5. Samaha S, Bhatt S, Finkelman M, et al. Effect of instruction,

Review Article
light curing unit, and location in the mouth on the
but the light tip from resin material adhesion when energy delivered to simulated restorations. Am J Dent.
accidental contact is made with the restoration 2017;30(6):343-349.
during the light curing process. It is known that using [Full text links] [PubMed] Google Scholar(0) Scopus(0)
6. Lima RBW, Troconis CCM, Moreno MBP, et al. Depth of cure of
light curing sleeves can cause a small reduction in bulkfill resin composites: a systematic review. J Esthet Restor
the irradiance emittance from the curing light, but it Dent. 2018;29 [epub ahead of print].
is already proven not to influence on polymerization [Full text links] [PubMed] Google Scholar(0)
7. Demarco FF, Correa MB, Cenci MS, et al. Longevity of
[22]. Fig. 11 illustrates an exemplification of the drop posterior restorations: not only a matter of materials. Dent
in the irradiance emittance from a curing light when Mater. 2012;28(1):87-101.
[Full text links] [PubMed] Google Scholar(530) Scopus(307)
no barrier sleeve is used and the light tip is clean, 8. Demarco FF, Collares K, Correa MB, et al. Should my
when the light tip is dirty and when a barrier sleeve composite restorations last forever? Why are they failing?
is used. Of course, using a barrier sleeve is extremally Braz Oral Res. 2017;31(1):e56.
[Full text links][PubMed] Google Scholar(10) Scopus(5)
important to protect the light tip, and guarantee 9. Price RB, Felix CM, Whalen JM. Factors affecting the energy
proper polymerization. delivered to simulated Class I and Class V preparations. J Can
Dent Assoc. 2010;76:a94.
[Full text links][PubMed] Google Scholar(52) Scopus(32)
10. Price RB, Strassler HR, Price HL, et al. The effectiveness of
3. Conclusions using a patient simulator to teach light-curing skills. J Am
Dent Assoc. 2014;145(1):32-43.
To conclude this topic, it is worthwhile mentioning [Full text links] [PubMed] Google Scholar(18) Scopus(16)
that several studies have demonstrated that the 11. Mutluay MM, Rueggeberg FA, Price RB. Effect of using proper
education provided to dentists and dental students light-cuing techniques on energy delivered to a Class 1
restoration. Quintessence Int. 2014;45(7):549-556.
seems to be insufficient to teach them how to [Full text links] [PubMed] Google Scholar(17) Scopus(14)
deliver the proper amount of radiant exposure from 12. Soares CJ, Rodrigues MP, Oliveira LRS, et al. An evaluation of
a curing light to the restoration [9-11]. On the other the light output from 22 contemporary light curing units.
Braz Dent J. 2017;28(3):362-371.
hand, education associated with proper training was [Full text links] [PubMed] Google Scholar(2) Scopus(2)
proved to be efficient to improve light curing skills, 13. Price RB, Labrie D, Bruzell EM, et al. The dental curing light: a
potential health risk. J Occup Environ Hyg. 2016;13(8):639-646.
even in short training sessions [9-11]. Educational [Full text links] [PubMed] Google Scholar(12) Scopus(8)
institutes and professors shall reinforce proper light 14. Labrie D, Moe J, Price RB, et al. Evaluation of ocular hazards
curing techniques and associate training sessions from 4 types of curing lights. J Can Dent Assoc. 2011;77:b116.
[Full text links] [PubMed] Google Scholar(21) Scopus(13)
within educational courses in order to improve 15. Price RB. Light curing guidelines for practitioners: a
teaching and learning. consensus statement from the 2014 symposium on light
curing in dentistry, Dalhousie University, Halifax, Canada. J
Can Dent Assoc. 2014;80:e61.
[Full text links] [PubMed] Google Scholar(6) Scopus(6)
Author Contributions 16. Soares CJ, Rodrigues MP, Vilela ABF, et al. Evaluation of
eye protection filters used with broad-spectrum and
DO: written and proofread the manuscript. conventional LED curing lights. Braz Dent J. 2017;28(1):9-15.
MR: written and proofread the manuscript. [Full text links] [PubMed] Google Scholar(5) Scopus(4)
JFR: written and proofread the manuscript. 17. Andre CB, Nima G, Sebold M, et al. Stability of the light
output, oral cavity tip accessibility in posterior region
and emission spectrum of light-curing units. Oper Dent.
2018;43(4):398-407.
Acknowledgments [Full text links] [PubMed] Google Scholar(0) Scopus(0)
18. Bhatt S, Ayer CD, Price RB, Perry R. Effect of light and
DO is a Post-Doctoral Researcher at São Paulo restoration location on energy delivered. Compend Contin
Research Foundation - FAPESP (grant #2016/05823- Educ Dent. 2015;36(3):208-210.
[Full text links] [PubMed] Google Scholar(7) Scopus(4)
3 and #2017/22161-7). MR is a PhD candidate at 19. Shortall AC, Felix CJ, Watts D. Robust spectrometer-based
São Paulo Research Foundation - FAPESP (grant methods for characterizing radiant exitance of dental LED
#2016/06019-3 and #2017/22195-9). light curing units. Dent Mater. 2015;31(4):339-350.
[Full text links] [PubMed] Google Scholar(13) Scopus(10)
20. Shimokawa CAK, Turbino ML, Giannini M, et al. Effect of light
curing units on the polymerization of bulk fill resin-based
composites. Dent Mater. 2018;34(8):1211-1221.
References [Full text links][PubMed] Google Scholar(0) Scopus(0)
1. Strassler H, Oxman J, Rueggeberg F. Light Curing - Tips on 21. Babu SS, Nair SS, Gopakumar D, et al. Linear odontometric
choosing your next curing light. CDA Essentials 2016;3:30-33. analysis of permanent dentition as a forensic aid: a
[Full text links] retrospective study. J Clin Diagn Res. 2016;10(5):C24-C28.
2. Ilie N, Plenk E-M. Light transmission through resin [Full text links] [Free PMC Article] [PubMed] Google
composites. Stoma Edu J. 2018;5(3):148-154. Scholar(3) Scopus(1)
[Full text links] 22. Scott BA, Felix CA, Price RBT. Effect of disposable infection
3. Moraschini V, Fai CK, Alto RM, Dos Santos GO. Amalgam control barriers on light output from dental curing lights. J
and resin composite longevity of posterior restorations: a Can Dent Assoc. 2004;70(2):105-110.
systematic review and meta-analysis. J Dent. 2015;43(9):1043- [Full text links] [PubMed] Google Scholar(42) Scopus(18)
1050.
[Full text links] [PubMed] Google Scholar(64) Scopus(33)
4. Rueggeberg FA, Giannini M, Arrais CAG, Price RBT. Light
curing in dentistry and clinical implications: a literature
review. Braz Oral Res. 2017;31(1):e61.
[Full text links] [PubMed] Google Scholar(10) Scopus(4)

Stomatology Edu Journal 241
LIGHT CURING MATTERS:
FACTS OFTEN OVERSEEN BY DENTISTS

Review Article
Dayane C. R. S. DE OLIVEIRA

DDS, MSc, PhD, Researcher
Department of Restorative Dental Sciences College of Dentistry,
University of Florida
Gainesville, FL, USA

CV
Dayane Oliveira, DDS, MS, PhD, is a post-doc fellow of the Department of Restorative Dentistry at Piracicaba Dental School,
State University of Campinas (UNICAMP), in Brazil, and visiting researcher of the Department of Restorative Dental Sciences
at the University of Florida. Dr. Oliveira is a young researcher that contributed to 6 textbook chapters, authored 7 patents and
own many awards in her area of expertise. Her areas of interest include aesthetic dentistry, color science and biomaterials
development and characterization.

Questions
1. Is the characterization of a light curing unit by its irradiance a sufficient
parameter?
qa. Absolutely yes;
qb. It tells the dentist most of the performances of the light curing unit;
qc. It only tells the user about the stability of the batteries;
qd. No, further parameters like e.g the homogeneity of the light beam should also be considered.

2. The quality of a class II resin composite restoration depends mainly on
qa. The brand of the used resin composite;
qb. Dentists’ application technique of the light curing unit;
qc. The brand of the light curing unit;
qd. The patients’ behavior.

3. The use of orange filters are needed
qa. To protect the dentist from eye damage during curing;
qb. Only to allow dentists to better see what they are doing;
qc. To prolong the working time of a light cured composite;
qd. To prevent the tooth from overheating.

4. When light curing a resin composite restoration, dentists are recommended to:
qa. Look to what they are doing, since this will improve the quality of polymerization, since the blue light of
modern LCUs represents no risk for ocular hazards;
qb. Position the light tip as close as possible and parallel to the restoration, while using blue-blocking filters;
qc. Polymerize in one-shot, irrespective of the size of the restoration and LCUs tip, to reduce shrinkage stress;
qd. Not to use light curing sleeves, since they induce a massive reduction in irradiance.

242 Stoma Edu J. 2018;5(4): 236-242 http://www.stomaeduj.com