Keywords
budget light-curing units - light-curing units - battery discharge - power - irradiance
- radiant exposure
Introduction
To produce resin-based composites (RBCs) that achieve their intended mechanical, chemical,
and physical properties, the light-curing unit (LCU) must deliver sufficient energy
at the correct wavelengths to the RBC.[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10] In most countries, LCUs are classified as medical devices and should comply with
standards set by the regulatory authorities. However, some manufacturers, mainly from
China, have introduced budget LCUs claiming that their devices are similar to those
from major dental manufacturers, but they cost much less.[11]
[12] These budget LCUs are usually purchased over the Internet from websites such as
amazon.com or ebay.com[11]
[12] and may not be approved medical devices. Since these devices may not have undergone
safety tests and may not have the appropriate electrical safety certification, they
may not be safe to use on patients.[12]
[13] In addition, they are often poorly made, most do not come with understandable instructions
for use, the power and irradiance may not be stable, and may decline without any warning;
they do not dissipate heat adequately, the battery life may be very short and may
even catch on fire, the light-guide tip diameter is typically small (∼7-mm), the beam
profile is often inhomogeneous across the light-guide tip, and they are usually single-peak
emission light-emitting diode (LED) units.[11]
[12]
[13]
[14]
[15] With dental students and practitioners now purchasing these LCUs due to their low
price,[14]
[15] the question is can these budget LCUs perform as well as LCUs purchased from major
manufacturers?. Also, different units from the same manufacturer might behave differently.[16] Since research is lacking in this area, more research is warranted concerning budget
LCUs.
This study assessed the effect of battery discharge on the power, irradiance, and
radiant exposure values from different budget LCUs over one fully charged battery
discharge cycle compared to the output from an LCU from a major manufacturer. The
hypotheses are:
-
The light output will be stable for all the LCUs over one full battery discharge.
-
The power, irradiance, and radiant exposure values will be similar among different
budget LCUs and a control unit LCU from a major manufacturer.
Materials and Methods
Following the guidelines of King Abdulaziz University policy, the project was exempt
from ethics approval by the Research Ethical Committee in King Abdulaziz University
Faculty of Dentistry (Reference no. 249-06-21). Two different budget LCUs and one
LCU from a major manufacturer were tested. The budget LCUs were purchased over the
Internet; two examples (#1 and 2) of the Rainbow LED Curing light model LY-A180 (Guangdong,
China) were purchased for 26 USD each, and two examples (#1 and 2) of the LED curing
light (LED-CL) (Putian City, China) for 45 USD each. All LCUs were single-peak wavelength
lights. All the budget units had a 7-mm optical diameter light tip. The Elipar DeepCure-S
(3M, St. Paul, Minnesota, United States) was used as a control LCU, and its internal
optical light tip diameter was 9 mm. [Table 1] provides the information about the LCUs used in this study. The power, irradiance,
and radiant exposure were measured with a Managing Accurate Resin Curing-Light Collector
(MARC-LC) laboratory-grade spectrometer (BlueLight Analytics Inc., Halifax, Nova Scotia,
Canada). The position of each LCU guide tip was standardized over the MARC-LC sensor
using a fixed mechanical arm with a 0-mm distance between the light-guide tip and
the sensor.
Table 1
Light-curing units (LCUs) evaluated, assigned reference, and manufacturer
|
LCU type
|
Model
|
Assigned reference
|
Branda
|
Sellera
|
SN/Product number
|
Manufacturer city, country
|
|
Budget light (#1)
|
LY-A180
|
LY-A180 (#1)
|
Rainbow LED Curing Light
|
Aphrodite
|
X001KLMS6X/
180130621
|
Guangdong, China
|
|
LY-A180
|
LY-A180 (#2)
|
Rainbow LED Curing Light
|
NSKI
|
X001L6FWSN/ 190330087
|
Guangdong, China
|
|
Budget light (#2)
|
Not found
|
LED-CL (#1)
|
LED Curing Light
|
BoNew/Local dental store
|
Not found
|
Putian City, China
|
|
Not found
|
LED-CL (#2)
|
LED Curing Light
|
Dr. Royal
|
X001YSHNB7
|
Putian City, China
|
|
Major manufacturer
|
Elipar DeepCure-S
|
Elipar DeepCure-S
|
3M
|
3M Certified local agent
|
933123008807
|
St. Paul, Minnesota, USA
|
Abbreviation: LED-CL, LED Curing Light; LCU, Light-curing unit; LED, Light-emitting
diode.
a The brand was not listed; therefore, the name on the box and seller was listed. The
same budget LCU may be available from multiple sellers and were purchased from amazon.com
or a local dental store. All LCUs were single-peak lights. All the budget units had
a 7-mm optical light tip diameter. The internal optical tip diameter of the Elipar
DeepCure-S was 9-mm.
All the LCUs were fully charged before the power, irradiance, and radiant exposure
from each LCU was measured during every 10-second exposure cycle in the continuous
mode setting. A 30-second rest interval was used between exposures until the end of
one full battery charge and the LCU no longer emitted light. Each unit was tested
once. From the total number of irradiation cycles, representative evenly distributed
measurements were selected for analysis starting from the first exposure cycle, followed
by exposure 30 (equivalent to 5 min of using the light), 50 (equal to approximately
8 min of using the light), followed by increments of 50, and ending with the last
exposure cycle of each LCU (i.e., first cycle, 30, 50, 100, 150, 200, …, the last
exposure cycle). The power and irradiance measurements were plotted for a visual comparison.
Statistical Analysis
The power, irradiance, and radiant exposures at the selected exposure intervals from
the same unit, among LCUs, and between the same brand of LCUs were compared. In addition,
visual comparisons were performed between the power and irradiance graphs. For every
LCU tested, the mean power, irradiance, radiant exposure, and percent decrease at
each representative cycle were calculated and analyzed using STATA software version
17 (StataCorp. 2021. Stata Statistical Software: Release 17. College Station, Texas,
United States). One-way analysis of variance (ANOVA) and Bonferroni post-hoc tests
were used to detect if differences from three consecutive readings at each representative
cycle of the power, irradiance, and radiant exposure existed between the five LCUs.
To determine the agreement between the results from the two LY-A180 and the two LED-CL
LCUs, the interclass correlation coefficient was reported using equal numbers of exposure
cycles from the LCUs.
Results
[Fig. 1] shows that the positions of the LED emitters in the body of the budget units were
not all well centered in the body of the LCU compared to the control LCU. [Figs. 2] and [3] report the power and irradiance output values at representative cycles for the budget
LCUs compared to the control LCU. In general, the power, irradiance, and radiant exposure
in the budget LCUs fluctuated and decreased as their battery discharged compared to
the control LCU. When comparing the different budget LCU brands, each unit had a different
pattern and different brands and units from the same brand did not produce similar
exposure patterns or the same total number of exposure cycles. Also, the light outputs
were not the same among the different budget LCUs from the same brand. In some cycles,
both LY-A180 units ([Figs. 1] and [2A] and [B]), and the LY-A180 (#1) LCU did not complete the 10-second exposure cycle. Instead,
they abruptly turned off mid-cycle. In cycle 300, LY-A180 (#1) the exposure stopped
at 6 seconds instead of 10 seconds, and some cycles extended inconsistently beyond
the 10 seconds between 11 and 12 seconds compared to LY-A180 (#2). The power and irradiance
values continued to drop at a faster rate for LY-A180 (#2) and exposure cycles were
more consistent at approximately 11 seconds compared to LY-A180 (1). The LED-CL (#1)
delivered very low light outputs for the first second. This then increased as if in
a soft start mode, even though a soft start mode is not a setting for this LCU. In
contrast, the LED-CL (#2) showed a different light output. In addition, LED-CL (#1)
exposure stopped in several cycles between 9 and 12 seconds instead of 10-s. For the
LED-CL (#2), the light exposure for most cycles ranged between 6.5 and 10 seconds
([Figs. 1] and [2C] and [D]). When comparing the budget LCUs to the control ([Figs. 1] and [2E]), the control LCU showed consistent and stable power and irradiance values and all
the cycles lasted for 10 seconds. [Fig. 2] showed that the unit LY-A180 (#2) delivered irradiance values less than 400 mW/cm2 starting from cycle 150 until the battery ran out, and unit LED-CL (#1) delivered
irradiance values less than 400 mW/cm2 starting from cycle 300 until the battery ran out of charge.
Fig. 1 The location of the light-emitting diode (LED) chips within the body of the different
light-curing units.
Fig. 2 The power (mW) of representative measurements of the different light-curing units
from the first to the last cycle. (A) LY-A180 (#1) unit. (B) LY-A180 (#2) unit. (C) LED-CL (#1) unit. (D) LED-CL (#2) unit. (E) Elipar DeepCure-S unit.
Fig. 3 The irradiance (mW/cm2) at representative exposures from the different light-curing units from the first
to the last cycle. (A) LY-A180 (#1) unit. (B) LY-A180 (#2) unit. (C) LED-CL (#1) unit. (D) LED-CL (#2) unit. (E) Elipar DeepCure-S unit.
[Table 2] reports the number of cycles, mean power, irradiance, and radiant exposure values
at representative cycles and the percent decrease. Units from the same brand did not
have similar patterns of light output nor the same total number of exposure cycles.
The percent decrease in the mean power, mean irradiance, and radiant exposure among
the cycles between the first and last light exposure cycle from each LCU varied. The
output measurements from the LY-A180 (#1) decreased by 48.4% in power and irradiance
and by 50.6% in radiant exposure due to the fluctuations in the exposure time. The
LY-A180 (#2) had an 81.1% decrease in power and an 81.2% decrease in irradiance and
radiant exposure. The power, irradiance, and radiant exposure output from the LED-CL
(#1) decreased by 70.5% and by 24% from the LED-CL (#2). In sharp contrast, the power
and irradiance from the Elipar DeepCure-S LCU decreased by only 4.9%, and there was
no change in the radiant exposure.
Table 2
Number of cycles, mean power (W), irradiance (mW/cm2), radiant exposure (J/cm2) values, and percent decrease in values for representative cycles from the first
to the last cycle for the different budget LCU and control
|
LCU
|
Cycle no.
|
Power (mW)
|
Irradiance (mW/cm2)
|
Radiant exposure (J/cm2)
|
% Decrease (power)
|
% Decrease (irradiance)
|
% Decrease (radiant exposure)
|
|
LY-A180 (#1)
|
1
|
341.0
|
885.0
|
9.7
|
13.2
|
13.0
|
6.0
|
|
30
|
296.0
|
770.0
|
9.1
|
1.0
|
1.2
|
2.6
|
|
50
|
293.0
|
761.0
|
8.9
|
−3.1
|
−3.2
|
1.8
|
|
100
|
302.0
|
785.0
|
8.7
|
6.3
|
6.4
|
3.3
|
|
150
|
283.0
|
735.0
|
8.4
|
3.2
|
3.0
|
6.9
|
|
200
|
274.0
|
713.0
|
7.9
|
4.4
|
4.5
|
1.3
|
|
250
|
262.0
|
681.0
|
7.8
|
1.9
|
1.9
|
−0.9
|
|
300
|
257.0
|
668.0
|
7.8
|
5.4
|
5.4
|
7.7
|
|
350
|
243.0
|
632.0
|
7.2
|
9.9
|
9.8
|
13.8
|
|
400
|
219.0
|
570.0
|
6.2
|
6.4
|
6.7
|
10.0
|
|
450
|
205.0
|
532.0
|
5.6
|
14.1
|
14.1
|
14.4
|
|
493 (last cycle)
|
176.0
|
457.0
|
4.8
|
48.4
|
48.4
|
50.6
|
|
LY-A180 (#2)
|
1
|
307.7
|
799.3
|
8.0
|
24.4
|
24.4
|
24.4
|
|
30
|
232.7
|
604.0
|
6.0
|
8.7
|
8.6
|
8.6
|
|
50
|
212.3
|
552.0
|
5.5
|
20.3
|
20.4
|
20.4
|
|
100
|
169.3
|
439.7
|
4.4
|
19.5
|
19.4
|
19.4
|
|
150
|
136.3
|
354.3
|
3.5
|
13.4
|
13.5
|
13.5
|
|
200
|
118.0
|
306.7
|
3.1
|
16.4
|
16.3
|
16.3
|
|
251
|
98.7
|
256.7
|
2.6
|
18.9
|
19.0
|
19.0
|
|
300
|
80.0
|
208.0
|
2.1
|
27.5
|
27.7
|
27.7
|
|
326 (last cycle)
|
58.0
|
150.3
|
1.5
|
81.1
|
81.2
|
81.2
|
|
LED-CL (#1)
|
1
|
205.3
|
533.7
|
5.3
|
−1.6
|
−1.6
|
−1.6
|
|
30
|
208.7
|
542.0
|
5.4
|
2.6
|
2.5
|
2.5
|
|
50
|
203.3
|
528.3
|
5.3
|
4.4
|
4.5
|
4.5
|
|
100
|
194.3
|
504.7
|
5.0
|
3.1
|
3.1
|
3.1
|
|
150
|
188.3
|
489.0
|
4.9
|
7.8
|
7.7
|
7.7
|
|
200
|
173.7
|
451.3
|
4.5
|
7.9
|
8.0
|
8.0
|
|
250
|
160.0
|
415.3
|
4.2
|
7.5
|
7.4
|
7.4
|
|
300
|
148.0
|
384.7
|
3.8
|
7.4
|
7.4
|
7.4
|
|
350
|
137.0
|
356.3
|
3.6
|
12.7
|
12.6
|
12.6
|
|
400
|
119.7
|
311.3
|
3.1
|
2.5
|
2.8
|
2.8
|
|
450
|
116.7
|
302.7
|
3.0
|
8.9
|
8.6
|
8.6
|
|
500
|
106.3
|
276.7
|
2.8
|
5.6
|
5.9
|
5.9
|
|
550
|
100.3
|
260.3
|
2.6
|
10.6
|
10.4
|
10.4
|
|
600
|
89.7
|
233.3
|
2.3
|
13.0
|
13.0
|
13.0
|
|
650
|
78.0
|
203.0
|
2.0
|
8.5
|
8.5
|
8.5
|
|
700
|
71.3
|
185.7
|
1.9
|
15.0
|
15.3
|
15.3
|
|
751 (last cycle)
|
60.7
|
157.3
|
1.6
|
70.5
|
70.5
|
70.5
|
|
LED-CL (#2)
|
1
|
444.0
|
1154.0
|
11.5
|
3.3
|
3.3
|
3.3
|
|
30
|
429.5
|
1116.0
|
11.2
|
0.3
|
0.3
|
0.3
|
|
50
|
428.0
|
1113.0
|
11.1
|
1.6
|
1.8
|
1.8
|
|
100
|
421.0
|
1093.5
|
10.9
|
−1.4
|
−1.4
|
−1.4
|
|
150
|
427.0
|
1109.0
|
11.1
|
1.2
|
1.1
|
1.1
|
|
200
|
422.0
|
1097.0
|
11.0
|
1.1
|
1.1
|
1.1
|
|
250
|
417.5
|
1085.0
|
10.9
|
−1.1
|
−1.1
|
−1.1
|
|
300
|
422.0
|
1097.0
|
11.0
|
0.8
|
0.9
|
0.9
|
|
350
|
418.5
|
1087.0
|
10.9
|
1.8
|
1.7
|
1.7
|
|
400
|
411.0
|
1068.0
|
10.7
|
1.6
|
1.6
|
1.6
|
|
450
|
404.5
|
1051.0
|
10.5
|
−3.2
|
−3.3
|
−3.3
|
|
500
|
417.5
|
1085.5
|
10.9
|
5.6
|
5.7
|
5.7
|
|
550
|
394.0
|
1024.0
|
10.2
|
5.2
|
5.3
|
5.3
|
|
600
|
373.5
|
970.0
|
9.7
|
4.6
|
4.5
|
4.5
|
|
650
|
356.5
|
926.5
|
9.3
|
1.7
|
1.7
|
1.7
|
|
700
|
350.5
|
911.0
|
9.1
|
4.0
|
4.0
|
4.0
|
|
750
|
336.5
|
875.0
|
8.8
|
-0.3
|
-0.2
|
-0.2
|
|
764 (last cycle)
|
337.5
|
876.5
|
8.8
|
24.0
|
24.0
|
24.0
|
|
Elipar DeepCure-S
|
1
|
906.3
|
1427.9
|
14.3
|
1.6
|
1.6
|
1.6
|
|
30
|
892.1
|
1404.6
|
14.0
|
−1.0
|
−1.0
|
−1.0
|
|
50
|
901.1
|
1418.8
|
14.2
|
0.2
|
0.2
|
0.2
|
|
100
|
898.9
|
1415.8
|
14.2
|
0.5
|
0.5
|
0.5
|
|
150
|
894.2
|
1408.8
|
14.1
|
0.1
|
0.1
|
0.1
|
|
200
|
893.2
|
1406.7
|
14.1
|
0.1
|
0.0
|
0.0
|
|
250
|
892.6
|
1406.3
|
14.1
|
0.5
|
0.5
|
0.5
|
|
300
|
888.4
|
1399.2
|
14.0
|
−0.7
|
−0.7
|
−0.7
|
|
350
|
894.7
|
1408.8
|
14.1
|
−0.8
|
−0.8
|
−0.8
|
|
400
|
901.6
|
1420.0
|
14.2
|
−0.8
|
−0.7
|
−0.7
|
|
450
|
908.4
|
1430.4
|
14.3
|
0.8
|
0.8
|
0.8
|
|
500
|
901.1
|
1418.8
|
14.2
|
0.1
|
0.1
|
0.1
|
|
550
|
900.0
|
1417.5
|
14.2
|
−0.1
|
−0.1
|
−0.1
|
|
600
|
901.1
|
1419.6
|
14.2
|
0.0
|
0.1
|
0.1
|
|
650
|
901.1
|
1418.8
|
14.2
|
0.1
|
0.0
|
0.0
|
|
700
|
900.5
|
1418.8
|
14.2
|
0.1
|
0.1
|
0.1
|
|
750
|
899.5
|
1416.7
|
14.2
|
−0.4
|
−0.4
|
−0.4
|
|
800
|
902.6
|
1422.1
|
14.2
|
0.7
|
0.7
|
0.7
|
|
850
|
896.3
|
1412.1
|
14.1
|
−0.9
|
−0.9
|
−0.9
|
|
900
|
904.2
|
1424.2
|
14.2
|
−6.3
|
−6.3
|
−6.3
|
|
950
|
961.6
|
1514.6
|
15.1
|
1.1
|
1.1
|
1.1
|
|
959 (last cycle)
|
951.1
|
1498.3
|
15.0
|
−4.9
|
−4.9
|
0.0
|
Abbreviations: LCU, light-curing unit; LED, light-emitting diode; LED-CL, LED Curing
Light.
[Table 3] reports the mean, standard deviation, median, and interquartile range of the outputs
from the LCUs. One-way ANOVA and Bonferroni post-hoc test showed that the power, irradiance,
and radiant exposure values for all budget units were significantly different from
the control, and LY-A180 (#1) and LED-CL (#2) LCU were significantly different from
each other.
Table 3
Mean (SD), median, interquartile range, and p-values of the different budget LCU and control
|
LCU
|
Mean
|
SD
|
Median
|
IQR
|
p-Value
|
|
Power
|
|
LY-A180 (#1)
|
262.7c
|
45.02
|
296.5d
|
230.5–296.5
|
<0.0001
|
|
LY-A180 (#2)
|
155.5d
|
76.2
|
136c
|
98–213
|
|
LED-CL (#1)
|
138.1b
|
49.76
|
135b,c
|
96–189
|
|
LED-CL (#2)
|
400.28b
|
33.3
|
417.5b
|
374.5–423
|
|
Elipar DeepCure-S
|
906.5a
|
19.7
|
900.5a
|
896.8–904.2
|
|
Irradiance
|
|
LY-A180 (#1)
|
682.8c
|
116.9
|
693d
|
599.5–771
|
<0.0001
|
|
LY-A180 (#2)
|
404.5d
|
198.3
|
354c
|
254–555
|
|
LED-CL (#1)
|
359.6b
|
129.2
|
352b,c
|
250–492
|
|
LED-CL (#2)
|
1040.2b
|
86.6
|
1085.25b
|
973–1098.5
|
|
Elipar DeepCure-S
|
1427.7a
|
31
|
1418.3a
|
1412.5–1424.2
|
|
Radiant exposure
|
|
LY-A180 (#1)
|
7.6c
|
1.4
|
7.8c
|
6.7–8.7
|
<0.0001
|
|
LY-A180 (#2)
|
4.04d
|
1.98
|
3.54d
|
2.54–5.55
|
|
LED-CL (#1)
|
3.6b
|
1.3
|
3.52b
|
2.5–4.92
|
|
LED-CL (#2)
|
10.4b
|
0.87
|
10.85b
|
9.73–10.99
|
|
Elipar DeepCure-S
|
14.3a
|
0.31
|
14.2a
|
14.125–14.24
|
Abbreviations: IQR, interquartile range; LCU, Light-curing unit; LED, light-emitting
diode; LED-CL, LED Curing Light; SD, standard deviation.
Superscript letters represent significant differences among the units within each
variable.
One-way ANOVA followed by Bonferroni post-hoc test comparisons among the LCU cycles
showed significant differences in most exposure cycles (comparison data not shown).
However, the nonsignificant cycles were minimal and did not follow any specific pattern.
The reliability test between the two LY-A180, and the two LED-CL LCUs, showed poor
reliability in the interclass correlation coefficient between the two LCUs from the
same brand.
Discussion
The unstable light output and the decrease in power, irradiance, and radiant exposure
values as the battery discharged in the budget LCUs indicate that the electronic circuitry
used in the budget LCUs could not compensate for the battery discharge and thus could
not maintain a stable light output. In addition, these budget LCUs showed an inconsistent
battery performance. The battery discharged rapidly, at different rates, and the LCUs
stopped for no reason during some exposure cycles. In contrast, the control LCU delivered
a stable light output as the battery discharged. Thus, the first hypothesis was rejected
(p < 0.01). In addition, the approximate 50 to 81% decrease in power, irradiance, and
radiant exposure from the LY-A180 (units #1 and #2), and LED-CL (#1) confirms the
inability of these units to compensate for the battery discharge. Therefore, progressively
worse photocuring may occur as the battery discharges.[17]
The power, irradiance, and radiant exposure values were all different among the LCUs
and the Elipar DeepCure-S consistently delivered the highest values ([Tables 2] and [3]). Therefore, the second hypothesis was also rejected (p < 0.01). Browsing the Internet and looking at different budget LCUs to purchase,
it was clear that other sellers of the budget lights had similar models, but with
different brand names or they were even unbranded with only the seller's name. This
could indicate that a third party manufactures the LCUs for these sellers without
disclosing their company name. Unlike the Elipar DeepCure-S light from 3M, no contact
information was provided for the budget LCUs and there was no website for the company.
Thus, it is it impossible to contact the manufacturer if a patient is harmed, or the
equipment requires maintenance.
Previous studies have also reported that different brands of budget LCUs failed to
achieve and maintain high power and irradiance outputs compared to LCUs from major
manufacturers.[14]
[18] They have also reported that the light output from different units of the same brand
of budget LCU was unpredictable and unreliable. In addition, the failure to center
the LED chips in the budget LCU could negatively affect their irradiance beam profile
and curing ability compared to LCUs from major dental manufacturers. Therefore, the
difference in the stability of the light output from the budget LCU compared to the
control LCU most likely indicates a difference in the quality of manufacturing of
the budget LCUs. Hence their low price.
The drop in the irradiance below 400 mW/cm2 starting after cycle 150 for LY-A180 (#2) and cycle 300 for LED-CL (#1) also confirms
that these units are unreliable because they cannot maintain the minimum irradiance
values of 400 mW/cm2 that is required according to the ISO 10650 standard.[19]
[20] When choosing which LCU to purchase, dental professionals tend to buy LCUs that
deliver an irradiance of at least 1000 mW/cm2, but other aspects such as the spectral emission, beam profile, ergonomics, medical
device approval, and patient safety should be taken into consideration when purchasing
the LCU.[13]
[21] One of these many aspects is the radiant exposure that can be delivered in the exposure
time that the clinician wishes to use.[2]
[12]
[21] The minimum radiant exposure ranges from 6 to 24 J/cm2 for every 2 mm increment of RBC,[22]
[23] with an average of 16 J/cm2.[24] In this study, LED-CL (#1) could not deliver 6 J/cm2 when used for 10s. The LY-A180 (#1) delivered a radiant exposure of less than 6 J/cm2 by the last cycle, and LY-A180 (#2) and LED-CL (#1) delivered less than 2 J/cm2 at the last exposure cycle. These low radiant exposures would likely produce an inadequately
photocured restoration. It is important to note that the units were tested under ideal
conditions. The light was fixed using a mechanical arm and the light tip was at 0 mm
from sensor. Such ideal conditions rarely occur in the mouth.
When choosing the LCU, clinicians need to consider how often the battery must be replaced
or even can it be replaced. The LCU should be monitored using a dental radiometer;
preferably, each reading should be logged from the day of purchase so that its output
can be monitored.[21] Furthermore, the light-curing technique can be optimized using the MARC-PS simulator
(BlueLight Analytics Inc., Halifax, Nova Scotia, Canada) to ensure that the user learns
how to deliver the maximum amount of light from their LCU.[21] Also, routine maintenance that includes an examination of the light guide tip before
and after light curing for any damage or debris can help prevent loss of light output.[1]
[2]
This study supports that using a budget light that has not been approved for use could
negatively affect the polymerization of light-curable resin-based materials and adversely
affect the treatment outcome and longevity of the restoration.[25] Depending on where the user practices dentistry, using a budget light may not meet
the standard of care since most countries classify LCUs as medical devices.[12]
[15] Also, since most of the budget lights have small guide tips, they require multiple
overlapping curing cycles when photo-curing large restorations. This increases the
time required to photocure the restoration.[13]
Although online marketplaces can offer cheaper products, this study shows that some
medical devices purchased online may not be as good as approved and tested products.
Further studies would be valuable on the effects on the properties of different RBCs
when other brands and other units of the same brand of LCU are used at different distances
from the light tip. However, the intra-brand variability of the budget lights means
that the conclusions of such a study may be difficult to interpret.
Conclusion
The light output from the budget LCUs tested from the same and from different manufacturers
was inconsistent. The budget lights tested could not maintain their power, irradiance,
and radiant exposure output values as their batteries discharged. In contrast, the
control LCU delivered a stable light output as the battery discharged. Therefore,
it is recommended that clinicians not use budget LCUs in their clinical practice.
Clinicians should be aware that the LCUs are classified as medical devices in most
countries, and unapproved medical devices should not be used on patients.
