Article_5_3_1
DENTAL MATERIALS
LIGHT TRANSMISSION THROUGH RESIN COMPOSITES
Original Article
Nicoleta Ilie1a* , Eva-Maria Plenk2b
1
Department of Operative Dentistry and Periodontology, University Hospital, Ludwig-Maximilians-Universität München, Goethestr. 70, D-80336 Munich,
Germany
2
Privat clinic, Bahnhofsweg 6, D-82008 Unterhaching, Germany
a
Prof. Dr. Dipl. Eng.
b
DDS, Dr.
ABSTRACT DOI: 10.25241/stomaeduj.2018.5(3).art.1
Introduction: The study aimed to quantify the amount of light that passes through different
OPEN ACCESS This is an Open
resin-based composite (RBC) types and to assess if a clinically used polymerization procedure in Access article under the CC BY-NC
curing incrementally filled deep cavities is justified. 4.0 license.
Methodology: Light transmission through 2-mm thick specimens made of three regular RBCs - a Peer-Reviewed Article
nano, a flowable nano and a microhybrid – of the same shade A3, was analyzed under 24 different Citation: Ilie N, Plenk E-M. Light transmis-
curing conditions, that resulted by varying the curing mode, exposure distance and exposure time sion through resin composites. Stoma Edu J.
2018;5(3):148-154
when using a violet-blue LED light curing unit. Incident and transmitted irradiances were assessed
Academic Editor: Jean-François Roulet,
in real-time on a spectrophotometer and radiant exposure, transmittance (T) and absorbance (A) DDS, PhD, Prof hc, Professor, University of
were calculated. A multivariate analysis assessed the effects of various parameters on T and A. Florida, Gainesville, FL, USA
Results: Incident irradiance varied among 656.4 (8.1) mW/cm² (Standard mode, exposure Received: June 29, 2018
distance = 7 mm) and 3361.5 (33.6) mW/cm² (Plasma Emulation mode, 0 mm). The filler amount Revised: July 02, 2018
Acccepted: July 7, 2018
(weight and volume %) exerted a significant effect on transmitted irradiance (p < 0.001; partial Published: August 01, 2018
eta squared ηP² = 0.400 and 0.362, respectively) while the effect of exposure distance was low (p *Corresponding author: Prof. Dr. Dipl.
< 0.001, ηP² = 0.141). Light transmittance was material-dependent and very low. The significant Eng. Nicoleta Ilie, Department of Operative
lowest absorbance was identified in Filtek Supreme XTE flow (1.11 ± 0.09), followed by Filtek Dentistry and Periodontology, University
Hospital, Ludwig-Maximilians-Universität
Silorane (1.21 ± 0.03) and Filtek Supreme XTE (1.62 ± 0.13). Incident and transmitted radiant München, Goethestr. 70, D-80336 Munich,
Germany,
exposure correlated exceptionally well in each RBC (Pearson correlations coefficient > 0.99). Phone: +49-89-44005-9412, Fax: +49-
Conclusion: When restoring a deep cavity with regular RBCs, each increment needs to be cured 89-44005-9302
e-mail: nilie@dent.med.uni-muenchen.de
adequately, since final curing to compensate for deficits in polymerisation is insufficient.
Keywords: resin-based composites, light curing unit, irradiance, radiant exposure, transmittance, Copyright: © 2018 the Editorial Council
for the Stomatology Edu Journal.
absorbance.
1. Introduction reinforcing particles and polymer matrix is minimized
The optical properties of light cured resin-based when the mismatch in refractive index between
composites (RBC) are essential material characteristics each material is reduced [14]. It is thus a function of
that are relevant for both the esthetical appearance the chemical composition of both constituents and
of a restoration [1,2] and the quality of curing in differs accordingly within individual RBCs. In addition
depth [3]. The latter is fundamentally related to the to the refractive index, also the filler dimension exerts
translucency of the material and thus to the amount a significant effect on light scattering, that was shown
of light (photons) that is allowed to pass through to be highest when the filler diameter approaches
the RBC during polymerization. While the surface approximately one-half the wavelength of incident
of an RBC filling is prevalently sufficiently cured, the light, i.e. ~0.2–0.3 µm [3]. It must also be noted that
polymerization of deeper increments is decisively large variation in light transmission was observed also
influenced by the light transmitted through the within resin composite of similar shade [15]. Moreover,
material [4]. Yet, an insufficient polymerization may light transmittance varied during polymerization,
not be immediately noticeable. It is evidenced later while increasing or decreasing during curing as a
in the reduced mechanical properties [5], low degree function of the RBC type and composition [16].
of conversion [6], elution of unreacted monomers [6], In clinical dentistry, many of the aspects described
increased toxicity [7] and potential hypersensitivities. above are not sufficiently considered when making
The transmitted light through a material sums the recommendations on restoration techniques. It is, for
remaining light, after the incident light, striking instance, occasionally acclaimed to only “pre-cure”
the surface of the RBC, was reflected, absorbed and the first, lowest increment for 2-3 seconds, when
scattered. Light absorption occurs when atoms restoring incrementally a deep cavity with an RBC.
or molecules of the RBC’s constituents, such as This proceeding is justified by the additional amount
monomers [8], filler particles [9,10], photo-initiator of light that would pass through the filling when the
molecules [11], dyes and pigments [8,12,13] take up upper RBC increments are exposed to light or, as usual
the energy of a photon of light. In contrast, scattering clinically, when the entire filling is exposed again to
take place on reinforcing particles or porosity voids light at the end of the restoration.
[9]. The extent of scattering at the interfaces between Therefore it was the aim of the present study to
148 Stoma Edu J. 2018;5(3): 148-154. http://www.stomaeduj.com
LIGHT TRANSMISSION THROUGH RESIN COMPOSITES
Original Article
Table 1. Resin composite brand, type, chemical composition of matrix and filler as well as filler content by weight (wt.) and volume (vol.) %. All materials
are manufactured by 3M ESPE.
Filler wt%/
RBCs RBC-Type Batch Shade Resin Matrix Filler
vol%
FiltekTM A3 Bis-GMA, Bis-EMA, UDMA, TEGDMA, ZrO2, SiO2
Nano N229448 78.5/63.3
Supreme XTE Dentin PEGDMA ZrO2/SiO2
FiltekTM
ZrO2, SiO2
Supreme XTE flowable Nano N236527 A3 Bis-GMA, Bis-EMA, TEGDMA, PEGDMA 65/55
ZrO2/SiO2
flow
3,4-Epoxycyclo-hexylethylcyclopolym
FiltekTM ethylsiloxane
Microhybrid N225426 A3 SiO2, YF3 76/55
Silorane Bis-3,4-epoxycyclo-hexylethylphenyl-
methylsilane
simulate and quantify the amount of light that would (6 mm diameter, increment thickness 2 mm, n = 5),
pass through 2 mm thick increments of different RBC and cured by applying the aforementioned curing
types - a nano, a flowable nano and a microhybrid – unit directly, perpendicularly and centered on the
as it would be received from a lower layer in a resin surface of the sample using a mechanic arm. While
composite filling. To simulate clinically relevant curing the specimens were cured, the spectrophotometer
conditions, 24 different radiant exposures were measured in real-time the irradiance at the bottom
considered for each material, that were obtained of the specimens. The cylindrical Teflon molds
by varying the curing mode of a modern, high- containing the material were aligned centered on
performance LED light-curing unit (LCU), the exposure the round detector of the spectrometer, which had a
distance and the exposure time. diameter of 3.9 mm. Consequently, the irradiance and
The null hypotheses assume: a) similar light radiant exposure reaching this area were considered.
transmittance (= ratio of transmitted to incident The miniature fiber optic USB4000 Spectrometer
radiant power) through all material types; b) within employs a 3648-element Toshiba linear Charge-
one material, similar transmittance for all curing coupled Device (CCD) array detector and high-
modes of the LCU; c) similar absorbance in all speed electronics (Ocean optic, Largo, FL, USA). The
materials. spectrometer was calibrated using an Ocean Optics’
NIST-traceable light source (300–1050 nm). The
system uses a CC3-UV Cosine Corrector (Ocean optic,
2. Materials and Methods Largo, FL, USA) to collect radiation over a 180° field of
Light transmission through three regular RBCs (Table view, thus mitigating the effects of optical interference
1) was analyzed under different curing conditions at associated with light collection sampling geometry.
a specimen thickness of 2 mm. Therefore the violet- Irradiance and radiant exposure at a wavelength
blue LED LCU VALO (Ultradent, South Jordan, USA, range of 360–540 nm were individually collected
serial number VO 7710) was applied in three different at a rate of 16 records/s. The sensor was triggered
exposure modes (Standard, High Power and Plasma at 20 mW. The radiant exposure was calculated by
Emulation), at various exposure times (5 s, 10 s, 15 s, integrating the irradiance versus the wavelength at
20 s and 40 s in the Standard mode; 1 s, 2 s, 3 s, 4 s the used exposure time.
and 12 s in the High Power mode and 3s and 6s in the
Plasma Emulation mode) and exposure distances (0 2.2. Transmittance and absorbance
mm and 7 mm). This resulted in 24 different curing Transmittance (T) is defined as the ratio of transmitted
conditions. irradiance (radiant power) to incident irradiance: T =
It/I0, where It is the irradiance after the beam of light
2.1. Spectrophotometry: measurement of the passes through the specimen and I0 is the irradiance
Incident irradiance and Light Transmittance of the incident light.
Incident irradiance and light transmittance through Transmittance is related to absorbance by the
the analyzed RBCs were assessed on a laboratory- expression: Absorbance (A) = − log(T) = −log(It/Io),
grade National Institute of Standards and Technology where absorbance stands for the amount of photons
(NIST)-referenced USB4000 Spectrometer (MARC that are absorbed.
(Managing Accurate Resin Curing) System, Blue light Being defined as ratios of irradiance values,
Analytics Inc., Halifax, NS, Canada). The incident transmittance and absorbance are dimensionless.
irradiance (the irradiance reaching the specimen’s
surface) was determined on five occasions, by 2.3. Statistical Analysis
applying the curing unit directly to the sensor. A Shapiro–Wilk test verified the normal distribution
With each program (standard, high power, plasma of the data. A multivariate analysis (general linear
emulation) and material (Table 1) the maximum model) assessed the effects of various parameters
irradiance reaching the sensor was measured in a as well as their interaction terms on the transmitted
random order. The exposure distance was set at 0 mm irradiance and absorbance. The partial eta-squared
and 7 mm. statistic reports the practical significance of each
Specimens were prepared in cylindrical Teflon molds term, based on the ratio of the variation accounted
Stomatology Edu Journal 149
LIGHT TRANSMISSION THROUGH RESIN COMPOSITES
for by the effect. Larger values of partial eta-squared
Original Article indicate a greater amount of variation accounted for
by the model effect, to a maximum of 1. Correlation
among incident and the transmitted radiant exposure
was assessed by a Pearson correlation analysis. In all
statistical tests, p-values < 0.05 were considered
statistically significant when using SPSS Inc. (Version
24.0, Chicago, IL, USA).
3. Results
The irradiance of the analyzed LED LCU at an exposure
distance of 0 mm amounted to 1174.1 (12.4) mW/
cm² in the Standard mode, 1760.3 (9.8) mW/cm² in
the High Power mode and 3361.5 (33.6) mW/cm² in
Figure 1. Incident irradiance as a function of the curing mode and
the Plasma Emulation mode. The incident irradiance
exposure distance.
decreased at an exposure distance of 7 mm to 656.4
(8.1) mW/cm², 986.3 (10.6) mW/cm² and 1917.8 (31.6) Table 2. Absorbance as a function of RBC, curing mode and exposure
mW/cm², respectively (Fig. 1). distance as well as loss in transmitted irradiance (Δ I, %) at an exposure
The effect of the parameter filler amount (weight distance of 7 mm related to 0 mm within each RBC and curing mode.
and volume %) was proved to be significant on the Curing Exposure
transmitted irradiance (p < 0.001; partial eta squared RBC Absorbance ΔI
mode distance
ηP² = 0.400 for weight % and 0.362 for volume %),
FiltekTM 0mm 1.58 (0.2)
while the effect of exposure distance was low (p < 43.3 %
Supreme XTE 7mm 1.57 (0.21)
0.001, ηP² = 0.141).
The Plasma Emulation mode induced the highest FiltekTM 0mm 1.08 (0.14)
transmitted irradiances in each analyzed RBC, while Supreme XTE 47.1 %
flow 7mm 1.10 (0.14)
the lowest values were identified when the LCU was Standard
run in the Standard mode. Increasing the exposure 0mm 1.1 (0.15)
FiltekTM Silorane 43.1 %
distance from 0 mm to 7 mm lowered the transmitted 7mm 1.10 (0.143)
irradiance by 43 % to 49 % (Table 2), while the incident 0mm -
irradiance was lowered by 42.9% to 44.1%. air 44.1 %
7mm -
Within each curing mode and exposure distance,
the significant highest transmitted irradiances were FiltekTM 0mm 1.63 (0.03)
46.6 %
identified in the Filtek Supreme XTE flow, followed by Supreme XTE 7mm 1.65 (0.006)
the Filtek Silorane, while the significant lowest values FiltekTM 0mm 1.1 (0.0001)
were identified in the Filtek Supreme XTE (p < 0.001). Supreme XTE 49.3 %
Within the analyzed incident irradiances, which varied High flow 7mm 1.14 (0.003)
in the range 656.4 (8.1) mW/cm² (Standard mode, 7 mm Power 0mm 1.13 (0.0001)
exposure distance) to 3361.5 (33.6) mW/cm² (Plasma FiltekTM Silorane 42.9 %
7mm 1.13 (0.013)
mode, 0 mm exposure distance), the transmitted
irradiance was reduced within the range 16.5 (1.3) 0mm -
air 44.0 %
mW/cm² to 71.7 (4.9) mW/cm² in Filtek Supreme XTE, 7mm -
49.5 (2.3) mW/cm² to 217.9 (13.0) mW/cm² in Filtek 0mm 1.66 (0.01)
FiltekTM
Silorane and 49.7 (2.4) mW/cm² to 249.1 (16.3) mW/ 45.1 %
Supreme XTE 7mm 1.69 (0.008)
cm² Filtek Supreme XTE flow (Fig 2). This means that
within the above-mentioned intervals the percentage of FiltekTM 0mm 1.13 (0.006)
Supreme XTE 48.5 %
transmitted irradiance relative to the incident irradiance 7mm 1.17 (0.006)
flow
amounted 1.4% to 2.1% in the Filtek Supreme XTE, 4.2% Plasma E.
0mm 1.14 (0.2)
to 6.5% in the Filtek Silorane and 4.2% to 7.4% in the FiltekTM Silorane 47.0 %
Filtek Supreme XTE flow. Within these limits, by trend, 7mm 1.22 (0.02)
the lower the incident irradiance, the higher the % 0mm -
transmitted light related to the initial irradiance. air 42.9 %
7mm -
The significant lowest absorbance was identified in
the Filtek Supreme XTE flow (1.11±0.09), followed exposure distance of 0 mm, the highest incident
by the Filtek Silorane (1.21±0.03) while the highest radiant exposure was identified when the LCU was
absorbance was measured in the Filtek Supreme XTE run in the Standard mode and an exposure time of
(1.62±0.13). A strong influence on absorbance was 40s (46.96 J/cm²), followed by the 20s exposure in the
identified in the parameter RBC (p < 0.001; partial same curing mode (23.48 J/cm²), the 12 s exposure
eta squared ηP² = 0.744), followed by the parameter in the High Power mode (21.12 J/cm²), and the 6s
curing mode (p < 0.001; ηP² = 0.364) while the exposure time in the Plasma Emulation mode (20.17
exposure distance exerted only a low influence (p < J/cm²). The lowest radiant exposure resulted at an
0.001; ηP² = 0.117) (Table 2). exposure time of 1s in the High Power mode (1.76 J/
Within the 12 analyzed curing conditions at an cm²) (Fig. 3). For an exposure distance of 7 mm, the
150 Stoma Edu J. 2018;5(3): 148-154. http://www.stomaeduj.com
LIGHT TRANSMISSION THROUGH RESIN COMPOSITES
Original Article
Figure 2. Transmitted irradiance through 2 mm thick specimens of the (a)
analysed RBCs as a function of curing mode and exposure distance.
(b)
Figure 4. Radiant exposure as recorded at the bottom of 2-mm thick
Figure 3. Radiant exposure received by the top-surface of the analysed specimens of the analysed RBCs, as a function of exposure time and
specimens as a function of exposure time, distance and curing mode. curing mode at an exposure distance of a) 0 mm and b) 7 mm.
radiant exposure varies in the same sequence at lower more reasons against exposure to high irradiance, as
values, which varied from 26.26 J/cm² (40s, standard curing fast at high irradiances leave no room to relieve
mode) to 0.99 J/cm² (1s, High Power mode). internal stresses accumulated during shrinkage [17].
An excellent correlation was found in each RBC To address light transmittance also from the perspective
between the incident and the transmitted radiant of a different chemical composition of the organic matrix,
exposure (Fig. 4 a, b) (Pearson correlations coefficient the silorane based material Filtek Silorane was additionally
= 0.997 for Filtek Supreme XTE, 0.999 for Filtek selected. It must be noted that this material is no longer on
Supreme XTE flow and 0.925 for Filtek Silorane). the market. The reasons therefore were not motivated in
the physical properties or curing behavior of Filtek Silorane,
since there were comparable to regular methacrylate-
4. Discussion based RBCs [18,19]. The siloran monomer was obtained
The present study quantifies the attenuation of from the reaction of oxirane and siloxane molecules, thus
light when traveling through different types of resin combining the two key advantages of the individual
composite specimens of a predetermined thickness components: low polymerization shrinkage due to the ring-
of 2 mm. This thickness was chosen owing to the fact opening oxirane monomer and increased hydrophobicity
that all three analyzed materials are regular RBCs that due to the presence of the siloxane species [20]. It is a four-
need to be placed incrementally, while the thickness branched monomer (methacylate monomers are only
of an increment should not exceed 2 mm. The selected two-branched) which suggest a high crosslinking density
materials belong to different RBC types - nano, flowable of the final polymer and, as a result, good chemical stability.
nano and microhybrid. Two of the analyzed RBCs - Filtek A further particularity of this system is the cationic initiated
Supreme XTE flow and Filtek Supreme XTE – have a quite polymerization which is less sensitive to oxygen compared
similar chemical composition of all their constituents and to the radical polymerization of the methacylate-based
primarily differ with respect to the filler amount (Table 1). RBCs. The cationic polymerization initiation system
Both are methacrylate-based RBCs. The difference in filler consists of camphorquinone, an iodonium salt, and an
amount resulted in significantly lower light transmittance electron donor. In the redox process, the electron donor
and a ca. 50% higher absorbance in the higher filled decomposes the iodonium salt to an acidic cation which
material. Although light transmittance was higher in the then starts the ring-opening polymerization process [20].
Filtek Supreme XTE flow, it amounted to less than 250 The transmittance and absorbance characteristics
mW/cm² also at the highest analyzed incident irradiance measured in the present study for Filtek Silorane were
(3361.5 ± 33.6 mW/cm², Plasma Emulation). Considering rather comparable to the flowable then to the nano RBC
that the polymerization at such high irradiances should Filtek Supreme XTE. Apart from differences in the refractive
not exceed a few seconds, due to the increased risk index and filler size that influence light scattering and thus
to over-heat the pulp, the amount of light available to light transmittance [3,14] as mentioned above, the results
potentially complete the curing of an underneath pre- may be explained by the similar volumetric filler amount of
cured increment might be by far insufficient. There are both materials (Table 1).
Stomatology Edu Journal 151
LIGHT TRANSMISSION THROUGH RESIN COMPOSITES
The 24 different curing conditions analyzed in the thick increments, this amounted to less than 4 J/cm² in
Original Article present study were simulated by using a violet-blue the most translucent RBCs at highest incident radiant
LED LCU that offers three different curing programs of exposure (40s, standard mode, exposure distance 0
medium and high irradiances: 1174.1 (12.4) mW/cm² in mm) and less than 2 J/cm² at an exposure distance of 7
the Standard mode, 1760.3 (9.8) mW/cm² in the High mm at similar curing conditions. A general value for the
Power mode and 3361.5 (33.6) mW/cm² in the Plasma radiant exposure that is needed to adequately cure a 2
Emulation mode. The LCU is equipped with four high- mm increment of an RBC is indicated as 16 J/cm², thus
power LED chips emitting three different wavelength the transmitted values measured in the present study
ranges (two chips with a peak at 465 nm, one chip with are far away from fulfilling this requirement (Fig 4).
a peak at 445 nm and 405 nm, respectively) and placed To transfer these data to a clinical relevant situation,
directly into the head of the LCU. we may consider the Standard mode of the LCU used
In addition to the exposure distance, the angle at which in the present study (ca. 1200 mW/cm²), which would
an LCU is placed on the restoration plays a major role for correspond to a modern and well-working LCU, as
the quality of polymerization. Particularly in posterior used by many clinicians. For this curing settings and
cavities that are difficult to access, the LCU may not be under ideal laboratory conditions (exposure distance 0
placed perpendicularly on the restoration. In this case, the mm, LCU placed perpendicularly on the RBC’s surface)
RBC may cure inhomogeneously in depth, according to significantly less than 100 mW/cm² pass through a 2 mm
the placement of the LCU, even if the surface appears to increment of a flowable RBCs (FiltekTM Supreme XTE
be well cured. This situation is a good indication for using flow), which was the most translucent material analyzed
a "pin-shaped" LCU, like the one analyzed in the present in the present study. These values are even reduced to
study. Furthermore, in a clinical situation, if the composite 87.2 (1.9) in the FiltekTM Silorane and to 29.1 (1.3) in the
surface is larger than the light exit window of the LCU, it FiltekTM Supreme XTE. Thicker composite layers, as they
must be polymerized in an overlapping manner to cover may result in a clinical situation during restoring a cavity,
the entire composite surface. It must also be taken into are even completely impermeable to light [22]. Under
account that the amount of light emitted by an LCU is not clinical relevant conditions, light transmittance may be
equal to the amount of light a restoration receives. Apart even lower, accounting for numerous factors related to
from angulation, the access to lower increments in deep the LCU or clinician. This comprises the use of LCUs with
restorations in a clinical situation may be impeded by the low irradiance, defect or contaminated waveguides,
presence of cusps. Therefore, the exposure distance was improper polymerization due to angulation and high
set in the present study either at 0-mm, to simulate the exposure distances. Thus, the present study provides
closest contact between restoration and LCU, or at 7 mm. clear arguments against the above-claimed curing
As shown in the present study the enlarged exposure techniques and reinforces the recommendation to
distance lead to a loss of almost 50% of the incident sufficiently polymerize each RBC layer. The data also
irradiance related to the closest contact, also when using suggest that a subsequent polymerization of an RBC
a modern, high-performance LCU. filling to potentially alleviate tooth sensitivity due
For economic reasons, clinicians often demand short to insufficient polymerization in depth is useless.
curing times when polymerizing RBCs. This led to the Besides, it should also be mentioned that an important
development of the concept of "exposure reciprocity". requirement for a successful polymerization is an intact
This concept considers the product of the incident and clean waveguide. This needs to be checked clinically
irradiance (mW/cm²) and exposure time (s), which is before each exposure, as residues of composite or
denominated as radiant exposure (J/cm²). It assumes adhesive, which often sticks to the waveguide, leading
that, at a given radiant exposure, the effect induced in the to a strong reduction in the irradiance of the LCU, as
RBC would be similar, irrespective if the radiant exposure the results of the present study suggest. It should also
is reached by lowering the exposure time and increasing be borne in mind, that the variation of irradiance with
the irradiance or vice versa. Even if this simple construct exposure distance is LCU-specific. What is especially fast
sounds plausible and useful in a clinical situation, it is is the reduction of the irradiance with the distance for
not universally valid. It does not apply especially if very LCUs when using a so-called "turbo" waveguide.
high or very low irradiances are used. [21]. Numerous
studies in recent years have clearly shown that efficient
polymerization, especially in depth, is achieved with LCU 5. Conclusions
of moderate irradiance (maximum 1200 mW/cm²) and All null hypotheses must be rejected. Light transmittance
exposure times of at least 20 s [5]. was shown to be material dependent and very low
The recommendation to pre-cure the lowest increment in regular RBCs, irrespective of RBC composition and
for only few seconds as justified by the additional type. It is therefore indicated to adequately cure each
amount of light supplied during the cavity restorations increment when restoring a deep cavity, and not to
must be declined. As summarized in Fig. 2, the light that relay on a final curing of a restoration to compensate for
passes through 2 mm thick layers of various RBCs after deficits in polymerisation in deeper increments.
light exposure by means of a high-performance LCU is
too low. It must be pointed out that, within the analyzed
curing conditions, the transmitted light related to Author contributions
the incident light amounted only 1.4% to 2.1% in the NI: designed the study, designed and established the
Filtek Supreme XTE, 4.2 to 6.5 in the Filtek Silorane and methods and infrastructure, analysis and interpreted
4.2% to 7.4% in the Filtek Supreme XTE flow. In terms the data, made statistics and wrote the manuscript. EP:
of radiant exposure measured at the bottom of 2-mm collected and analyzed the data.
152 Stoma Edu J. 2018;5(3): 148-154 http://www.stomaeduj.com
LIGHT TRANSMISSION THROUGH RESIN COMPOSITES
12. Haas K, Azhar G, Wood DJ, et al. The effects of different
Original Article
opacifiers on the translucency of experimental dental
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Nicoleta ILIE
Dipl. Eng, PhD, Professor
Department of Operative/Restorative Dentistry, Periodontology and Pedodontics
Faculty of Medicine, Ludwig-Maximilians University of Münich
Münich, Germany
CV
Dipl. Eng. Nicoleta Ilie attended the “Technology of silicates and high-temperature oxides” at the Traian Vuia University,
Timişoara, Romania (1989-1993). She studied material sciences with a focus on glass and ceramics at the Friedrich Alexander
University, Erlangen-Nuremberg, Germany (1994-1999). She got her doctoral degree in material sciences from the Ludwig-
Maximilians-University, Dental School, Münich, Germany (1999-2004), followed by her postdoctoral lecture qualification
(habilitation) at the same university (2004-2009). Since 1999, she has been assistant professor, associated professor (2009) and
tenured professor (2014) of biomaterials at the Dental School of the Ludwig-Maximilians-University in Münich.
Stomatology Edu Journal 153
LIGHT TRANSMISSION THROUGH RESIN COMPOSITES
Original Article
Questions
1. Which parameters do not affect light transmittance through resin composites?
qa. Reflection, absorption and scattering of the incident light;
qb. Refractive index of filler and matrix;
qc. Filler size;
qd. Type of resin composites.
2. Which type of resin composites has been analyzed in the present study?
qa. A bulk-fill resin composite;
qb. A macro-fill resin composite;
qc. A resin-modified glass-ionomer;
qd. Nano and microhybrid resin composites.
3. Light transmittance through the analyzed 2-mm thick resin composite
increments amounted:
qa. > 50% of the incident light;
qb. > 25% of the incident light;
qc. < 10% of the incident light;
qd. 0% of the incident light.
4. When restoring a deep cavity with resin composites incrementally:
qa. The lower increment needs to be cured adequately;
qb. The lower increment must only be pre-cured for few seconds since it will receive sufficient light at the
end of the restoration;
qc. At very high irradiance, curing each increment for 1-2 s is sufficient, since exposure reciprocity is a valid
concept;
qd. Curing at very high irradiance will reduce shrinkage stress.
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154 Stoma Edu J. 2018;5(3):148-154. http://www.stomaeduj.com