Background: Given the increasing use of photo-activated resins in dentistry, dentists and researchers need a user-friendly dental radiometer to measure the power output from dental light-curing units (LCUs). Objective: Our goal was to measure the accuracy of two brands of dental radiometers in reporting the power (mW) from twelve brands of contemporary LCUs compared to a 'gold standard' (GS) reference value obtained from an integrating sphere attached to a fiberoptic spectroradiometer. Methods: The power output was measured from two units of 12 brands of LCUs, five times on the "GS" system, five times on two Bluephase Meter II dental radiometers, and five times on two Mini Gig hand-held spectroradiometers. The emission spectrum was also recorded using the 'GS' integrating sphere. The power values reported by each meter were subjected to t-tests to compare the two examples of each LCU, and 3-way ANOVA followed by Bonferroni's post-hoc tests. Regression analyses were also performed to determine the relationship between the data from the hand-held radiometers and the 'GS' integrating sphere. Results: There was a large difference in the power values (mW) and the emission spectra from the 12 brands of LCUs on their standard-settings (p<0.001). Except for one LCU (Dental Spark @ 15.1%), the differences between the two LCUs of the same brand were less than 5.3% when measured using the 'GS' integrating sphere. Regression analyses showed a highly significant agreement between the power values reported from the two brands of radiometers and the 'GS' integrating sphere (R2 > 98%). Conclusion: We concluded that the power values reported from both brands of dental radiometers we tested were accurate, provided that the light source did not emit wavelengths of light that were beyond the radiometer's detection limit.
After diabetes and cardiovascular diseases, the treatment of oral disease now accounts for the third-highest expenditure among non-communicable diseases in European Union [[
Research on the properties of dental resins, the effects of different photo-activation protocols, and on factors affecting the adhesion between the resin, tooth and restorative materials has become prolific [[
Most clinicians will choose their LCU based on the price and radiant exitance (tip irradiance) value in the belief that a light that delivers a high irradiance value is better and more powerful than one that delivers a lower value. This may not be correct. To determine the radiant exitance from the LCU, the ISO 10650 standard [[
Therefore, both dental clinicians and researchers need to easily and accurately measure the output from the LCU. Although hand-held dental radiometers are readily available, most are inaccurate [[
Thus, since the radiant flux (power) measurement forms the foundation of the ISO 10650 standard [[
Therefore, in this study, we aimed to:
- Report the power (mW) from twelve contemporary LED LCUs using two brands of radiometers and compare these values to 'gold standard' reference values obtained from a laboratory-grade integrating sphere attached to a fiberoptic spectrometer.
- Report the emission spectra from these twelve LED LCUs.
- Determine if both brands of radiometers could provide precise and accurate power values compared to the 'gold standard' system.
Our research hypotheses were:
- There would be no difference (p ≥ 0.05) in the power values and the emission spectra from the 12 brands of contemporary LCUs.
- When measured on the 'gold standard' integrating sphere system, the power values from two examples of each brand of LCU tested would be within ± 10% of each other.
- The two examples of each brand of radiometer would report power values that were within ± 10% of each other.
- The power values reported by the two brands of radiometer tested would be accurate and precise compared to the power values obtained from the 'gold standard' system.
We measured 7 brands of single peak and 5 brands of multiple peak wavelength LED LCUs (Fig 1). All the LCUs had been used for several hours in other laboratory studies, and they represented a wide range of contemporary LCUs that dentists and researchers currently use. The brand, serial number, manufacturer, output mode, tip diameter, and type of LCU (single emission peak or multiple emission peak LCU) are reported in Table 1. Four of these LCUs were purchased from online sellers on the Internet and we considered them to be 'budget' LCUs. The other eight LCUs were from six major dental manufacturers. Two lower-priced and two higher-priced hand-held radiometers (Fig 2 and Table 2) that could both report the power in mW were tested.
Graph: Fig 1 Units #1 and #2 of each brand of light-curing unit used in the study.
Graph: Fig 2 The two examples of the Bluephase Meter II and the Mini Gig radiometer used in the study.
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Table 1 Light curing units (LCUs) and information provided by the manufacturers.
Light Curing Unit Code Manufacturer Serial Number Single Peak/Multi-Peak Emission Tip diameter (mm) Wavelength range (nm) Irradiance (mW/cm2) Tolerance (±%) SmartLite Pro #1 a#1 Dentsply Sirona, Charlotte, NC, USA H00045 Single Peak 10 450–480 1,200 SmartLite Pro #2 a#2 H00466 DeepCure #1 b#1 3M Oral Care, St. Paul, MN, USA 939112012777 Single Peak 10 430–480 1,470 (10%/+20%) DeepCure #2 b#2 933112003463 Dental Spark #1 c#1 Foshan Keyuan Medical Equipment Foshan City, Guangdong, China SK13L0201324 Single Peak 8 430–485 1,400 Dental Spark #2 c#2 SK13L0301315 Denjoy #1 d#1 Denjoy Dental Co, Changsha, China DYD21302089 Single Peak 8 450–470 1,000 1,400 Denjoy #2 d#2 DYD21302064 Woodpecker LED.D #1 e#1 Guilin Woodpecker Medical Instrument Co., Guilin, Guangxi, China D12020417A Single Peak 8 420–480 1,000–1,200 Woodpecker LED.D #1 e#1 D12020417A Woodpecker LED.B #1 f#1 L12B0572B Single Peak 8 420–480 850–1,000 Woodpecker LED.B #2 f#2 L1340459B SDI radii plus #1 g#1 SDI, Bayswater Victoria, Australia Nothing visible Single Peak 8 440–480 1,500 SDI radii plus #2 g#2 Nothing visible Valo Grand #1 h#1 Ultradent, South Jordan, UT, USA T10172 Multi-Peak 12 385–515 900 (±10%) Valo Grand #2 h#2 S01264 Bluephase G4 #1 i#1 Ivoclar Vivadent, Schaan, Liechtenstein 1404001370 Multi-Peak 10 385–515 1,200 (±10%) Bluephase G4 #2 i#2 1400002115 Valo Cordless #1 j#1 Ultradent, South Jordan, UT, USA C43122 Multi-Peak 10 385–515 900 (±10%) Valo Cordless #2 j#2 C11296 Bluephase PowerCure #1 k#1 Ivoclar Vivadent, Schaan, Liechtenstein 1428005297 Multi-Peak 9 385–515 1,200 (±10%) Bluephase PowerCure #2 k#2 1428007901 PinkWave #1 l#1 Vista Dental Products, Racine, WI, USA 00107C Multi-Peak 12 395–900 > 1,515 PinkWave #2 l#2 00225C
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Table 2 Information provided by the manufacturers about their radiometers.
Radiometer Serial Number Manufacturer Spectral Range (nm) Sensor Window Aperture (mm) Claimed Accuracy Bluephase 1300011617 Ivoclar Vivadent, Schaan, Liechtenstein 380–550 15 ±10% Meter II #1 Bluephase 1300011631 Meter II #2 Mini Gig #1 45047 Gigahertz Optik, Türkenfeld, Germany 360–830 15 ±4% Mini Gig # 2 34845
To ensure that a representative example of each brand was measured, the light outputs from two units of each brand of LCU were measured in their standard output mode for 10 seconds. These LCUs were not new, but they were in good condition and showed no visible signs of damage (Fig 1). The power output from each LCU was measured five times using two new units of the Bluephase Meter II and five times using two examples of the Mini Gig spectroradiometer (Fig 2 and Table 2). The LCUs were recharged after every 5 exposures to ensure that their batteries were always adequately charged. The LCUs and meters were used in random order and at room temperature (20°C±1).
The power values obtained from each radiometer were compared to a 'GS' reference value obtained from a laboratory-grade spectroradiometer attached to an integrating sphere. Using previously described methods [[
The power values of the tested LCUs were subjected to normality and homoscedasticity tests using Shapiro-Wilk and Levene tests, respectively. After they had passed these tests, the data were subjected to a 3-way ANOVA followed by Bonferroni's post hoc test using the SPSS v20 statistical program (SPSS Inc, IBM Company, Armonk, NY, USA) and the results are reported in Tables 3 and 4. Finally, regression analyses (Origin Pro, Northampton, MA, USA) were used to evaluate the relationship between power values from the hand-held radiometers and those from the 'GS' integrating sphere. For a dental LCU, the Pinkwave LCU has an unusually broad emission spectrum that ranged from 390 to 870 nm and the Bluephase Meter II is not designed to measure light outside of the 380 to 550 nm range. Therefore, since the power values reported for the Pinkwave using the Bluephase Meter II were obviously incorrect, the data from this LCU was removed from the regression analyses.
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Table 3 Mean power (mW) ± standard deviation (SD) and coefficient of variation (CV) values recorded using the 'gold standard' or using the two examples (#1 and #2) of each brand of hand-held radiometer when measuring unit #1 of each brand of LCU.
LCU #1 Gold Standard Bluephase #1 Bluephase #2 Mini Gig #1 Mini Gig #2 Mean Power (mW) SD (mW) CV Sig. Equivalent Groups Mean Power (mW) SD (mW) CV Sig. Equivalent Groups Mean Power (mW) SD (mW) CV Sig. Equivalent Groups Mean Power (mW) SD (mW) CV Sig. Equivalent Groups Mean Power (mW) SD (mW) CV Sig. Equivalent Groups Valo Grand 918 8.8 1.0 Ac 903 5.9 0.7 Bc 953 6.0 0.6 Bb 946 5.2 0.6 Ab 994 5.2 0.5 Aa PinkWave 913 2.9 0.3 Ac 1389 13.7 1.0 Ab 1427 14.9 1.1 Aa 914 16.0 1.8 Bc 915 25.5 2.8 Cc SmartLite Pro 896 13.8 1.5 Ac 813 4.2 0.5 Ce 841 1.9 0.2 Cd 937 10.3 1.1 Ab 967 7.0 0.7 Ba DeepCure 754 2.9 0.4 Bb 727 4.5 0.6 Dc 756 4.9 0.7 Dab 731 1.4 0.2 Cc 770 2.4 0.3 Da Bluephase G4 715 10.5 1.5 Cb 679 2.2 0.3 Ec 719 3.7 0.5 Eb 709 3.8 0.5 Db 735 4.6 0.6 Ea Valo Cordless 661 11.7 1.8 Bc 638 7.8 1.2 Fd 665 7.8 1.2 Fc 687 2.5 0.4 Eb 713 2.8 0.4 Fa PowerCure 581 8.4 1.4 Eab 528 5.1 1.0 Gd 556 3.7 0.7 Gc 568 3.2 0.6 Fbc 592 2.3 0.4 Ga Dental Spark 466 30.4 6.5 Fa 384 3.5 0.9 Ic 399 5.6 1.4 Ic 425 2.5 0.6 Hb 439 6.2 1.4 Ib Denjoy 465 6.8 1.5 Fab 417 6.0 1.5 Hc 432 12.3 2.8 Hc 463 3.3 0.7 Gb 480 2.4 0.5 Ha Woodpecker LED.D 382 3.7 1.0 Ga 353 6.2 1.8 Jb 361 8.3 2.3 Jb 379 2.5 0.7 Ia 390 3.6 0.9 Ja Woodpecker LED.B 359 5.6 1.6 Hab 321 4.8 1.5 Kd 337 4.8 1.4 Kcd 347 6.1 1.8 Jbc 364 3.5 1.0 Ka SDR Radii Plus 288 31.9 11.1 Ia 251 6.1 2.4 Lc 255 7.2 2.8 Lc 271 9.4 3.5 Kb 272 13.1 4.8 Lb
1 (N = 5 repeated measurements using each meter).
2 Mean power (mW) values followed by the same letters (upper case letters within the column; lower case letters within the row) are not significantly different (3-way ANOVA p≥0.05)
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Table 4 Mean power (mW) ± standard deviation (SD) and coefficient of variation (CV) values recorded using the 'gold standard' or using the two examples (#1 and #2) of each brand of hand-held radiometer when measuring unit #2 of each brand of LCU.
LCU #2 Gold Standard Bluephase #1 Bluephase #2 Mini Gig #1 Mini Gig #2 MeanPower (mW) SD (mW) CV Sig. Equivalent Groups Mean Power (mW)) SD (mW) CV (mW) Sig. Equivalent Groups Mean Power (mW)) SD (mW) CV Sig. Equivalent Groups Mean Power (mW) SD (mW) CV Sig. Equivalent Groups Mean Power (mW)) SD (mW) CV Sig. Equivalent Groups SmartLite Pro 929 12.6 1.4 Ac 851 4.4 0.5 Ce 876 7.6 0.9 Cd 974 24.0 2.5 Ab 1005 12.3 1.2 Aa PinkWave 905 8.6 1.0 Bd 1362 11.3 0.8 Ab 1420 9.2 0.7 Aa 889 14.9 1.7 Ce 921 13.7 1.5 Ccd Valo Grand 882 1.7 0.2 Cc 886 4.1 0.5 Bc 924 6.0 0.7 Bb 929 2.7 0.3 Bb 978 1.8 0.2 Ba DeepCure 765 3.3 0.4 Dab 753 1.6 0.2 Dbc 777 5.5 0.7 Da 742 0.6 0.1 Dc 778 5.3 0.7 Da Bluephase G4 709 1.9 0.3 Eb 655 9.9 1.5 Ec 701 8.1 1.2 Eb 710 2.5 0.4 Eb 735 4.2 0.6 Ea Valo Cordless 698 1.4 0.2 Eb 661 3.7 0.6 Ec 692 8.9 1.3 Eb 698 3.6 0.5 Eb 720 3.7 0.5 Ea PowerCure 601 10.9 1.8 Fab 554 4.1 0.7 Fd 586 3.4 0.6 Fbc 580 1.2 0.2 Fc 603 2.1 0.4 Fa Dental Spark 549 25.0 4.6 Ga 464 3.6 0.8 Gc 495 6.0 1.2 Gb 468 2.4 0.5 Gc 485 5.6 1.2 Gb Denjoy 459 10.1 2.2 Ha 411 6.6 1.6 Hc 415 8.9 2.1 Hc 440 3.4 0.8 Hb 460 1.9 0.4 Ha Woodpecker LED.D 372 11.0 3.0 Ia 329 7.4 2.2 Ib 341 4.4 1.3 Ib 364 1.8 0.5 Ia 378 1.6 0.4 Ia Woodpecker LED.B 344 3.1 0.9 Ja 298 5.5 1.9 Jb 313 2.9 0.9 Jb 332 3.5 1.1 Ja 345 3.9 1.1 Ja SDR Radii Plus 304 18.8 6.2 Ka 257 5.0 1.9 Kc 255 7.9 3.1 Kc 273 11.0 4.0 Kb 276 10.2 3.7 Kb
- 3 (N = 5 repeated measurements using each meter)
- 4 Mean power (mW) values followed by the same letters (upper case letters within the column; lower case letters within the row) are not significantly different (3-way ANOVA p≥0.05)
Representative real-time radiant power outputs and emission spectra of the 12 brands of LCU measured using the 'GS' integrating sphere system over the 10-s exposures are reported in Figs 3 and 4, respectively. Fig 3 shows that the power output from the 12 LCUs was stable (flat) when the LCUs were turned on. Of note, in Fig 3, the Pinkwave LCU would remain on for 20-s and the Radii Plus for 60-s, but only the output in the first 15-s is reported.
Graph: Fig 3 Representative 'gold standard' power (mW) emitted by the 12 LCUs evaluated: Single Peak LCUs a) SmartLite Pro; b) DeepCure; c) Dental Spark; d) Denjoy; e) Woodpecker LED D; f) Woodpecker LED B; g) SDI Radii Plus; and Multi-peak LCUs h) Valo Grand; I) Bluephase G4; j) Valo; k) Bluephase Powercure; and l) Pinkwave.
Graph: Fig 4 Spectral Radiant Powers (mW/nm) emitted by the 12 LCUs with the emission peaks identified: Single Peak LCUs a) SmartLite Pro; b) DeepCure; c) Dental Spark; d) Denjoy; e) Woodpecker LED D; f) Woodpecker LED B; g) SDI Radii Plus; and Multi-peak LCUs h) Valo Grand; I) Bluephase G4; j) Valo; k) Bluephase Powercure; and l) Pinkwave.
Fig 4 shows that 7 (a to g) of the LCUs (SmartLite Pro, DeepCure S, Dental Spark, Denjoy, Woodpecker LED B and D, and Radii Plus) were single emission peak LCUs. The remaining 5 LCUs (h to l) were broader spectrum multi-emission peak LCUs. The Pinkwave LCU (l) emitted 4 distinct wavelength peaks (λ1 = 411 nm, λ2 = 472 nm, λ3 = 633 nm, and λ4 = 857 nm) and was noticeably different from the other LCUs. Fig 5 illustrates the power values from the 24 LCUs when measured with the 'GS' and using the other 4 radiometers. Apart from the Pinkwave LCU when it was measured using both examples of the Bluephase Meter II, Fig 5 shows that all the measurement methods produced similar power values from the LCUs. However, statistically, there were significant differences in the power values reported from the various radiometers when measuring each LCU (p<0.05). Fig 6 compares the 12 brands of LCUs as a percentage of the maximum power (929 mW) that was measured using the 'GS' system. This maximum value was measured from the SmartLite Pro unit, but the Valo Grand and Pinkwave both delivered similar power values (918 and 905 mW, respectively). However, 5 LCUs (Dental Spark, Denjoy, Woodpecker LED.D, Woodpecker LED.B, and the SDI Radii Plus) delivered only 59%, 50%, 41%, 39% and 33% respectively of the power from the SmartLite Pro.
Graph: Fig 5 Mean power output(mW) from the LCUs recorded using the gold standard (GS), and the two examples of the Bluephase Meter II (BM#1 and #2) and the Mini Gig (MG#1 and #2) radiometers.Note the range in power values from the LCUs and the overall similarity in the radiometer power values for each LCU, apart from the inability of both Bluephase meters to accurately measure the Pinkwave.
Graph: Fig 6 Comparison of the power output of the 12 LCUs described as a percentage of the most powerful LCU (SmartLite Pro) recorded using the 'gold standard' system.
The mean power values, standard deviation (SD), and coefficient of variation (CV) of LCU units #1 and 2 measured using the 'GS' system and using the four different dental radiometers are reported in Tables 3 and 4. The comparisons between the power values reported by the two examples of each brand of meter showed some significant differences for some LCUs. However, Table 5 shows that the average ± standard deviation % difference in these power values from the two examples of each meter was only 3.8 ± 1.5% for the Bluephase Meter II and 3.4 ± 1.3% for the Mini Gig radiometer.
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Table 5 Percentage differences between the power values from each LCU (units #1 and #2) recorded using the two Bluephase Meter II and Mini Gig radiometers.
LCU and # Difference between 2 Bluephase II meters Difference between 2 Mini Gig meters % % SmartLite Pro #1 3.4 3.1 SmartLite Pro #2 2.9 3.1 DeepCure #1 3.7 5.0 DeepCure #2 3.2 4.6 DentalSpark K.Y. #1 3.6 3.3 DentalSpark K.Y. #2 6.2 3.5 Denjoy #1 3.4 3.5 Denjoy #2 1.0 4.3 Woodpecker LED D #1 2.2 2.9 Woodpecker LED D #2 3.7 3.8 Woodpecker LED B #1 4.7 4.6 Woodpecker LED B #2 4.7 3.8 SDR Radii Plus #1 1.5 0.1 SDR Radii Plus #2 0.8 1.2 Valo Grand #1 5.2 4.8 Valo Grand #2 4.1 5.0 Bluephase G4 #1 5.5 3.5 Bluephase G4 #2 6.5 3.4 Valo Cordless #1 4.1 3.7 Valo Cordless #2 4.4 3.1 Bluephase PowerCure #1 5.0 4.1 Bluephase PowerCure #2 5.5 3.7 PinkWave #1 2.7 0.1 PinkWave #2 4.0 3.5 Mean Difference ±SD 3.8 ± 1.5 3.4 ± 1.3
Table 6 shows that the mean power values from unit #1 and #2 of each brand of LCU when measured using the 'GS' were between 0.9% and 5.3% different, with the Dental Spark (C) an outlier at 15.3%. Figs 7 and 8 illustrate the percentage differences of LCU # 1 and #2 on each radiometer compared to the 'GS' power measurement. The highest percentage difference (+51 to 57%) was for the Pinkwave when using the Bluephase Meter II, and these values were obviously incorrect. Otherwise, both meters reported power values that were both slightly above and below the 'GS' value. For the Mini Gig meter #1, the greatest difference from the 'GS' result was -15%. For the Mini Gig meter #2, the greatest difference from the 'GS' power value was -12% (Fig 8). The maximum differences in the power values recorded by the Bluephase Meter II compared to the GS was -18%. All these large % differences were measured from light (C), which we classified as a 'budget LCU', whose standard deviations and coefficient of variation in the 'GS' power values were also large, suggesting that the output from this LCU was unstable.
Graph: Fig 7 Percentage difference in the power values between radiometer units #1 and #2 compared to the 'GS' integrating sphere power values measured from unit #1 of each brand of LCU.Single Peak LCUs A) SmartLite Pro; B) DeepCure; C) Dental Spark; D) Denjoy; E) Woodpecker LED D; F) Woodpecker LED B; G) SDI Radii Plus; and Multi-peak LCUs H) Valo Grand; I) Bluephase G4; J) Valo; K) Bluephase Powercure; and L) Pinkwave.
Graph: Fig 8 Percentage difference in the power values between radiometer units #1 and #2 of both radiometers compared to the 'GS' integrating sphere power values measured from unit #2 of each brand of LCU.Single Peak LCUs A) SmartLite Pro; B) DeepCure; C) Dental Spark; D) Denjoy; E) Woodpecker LED D; F) Woodpecker LED B; G) SDI Radii Plus; and Multi-peak LCUs H) Valo Grand; I) Bluephase G4; J) Valo; K) Bluephase Powercure; and L) Pinkwave.
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Table 6 Percentage difference between the power values from units #1 and #2 of each LCU recorded using the 'gold standard' system.
Curing Light % Difference between unit #1 and unit #2 of each brand of LCU DentalSpark K.Y. 15.1 Valo Cordless 5.3 SDR Radii Plus 5.2 Woodpecker LED B 4.4 Valo Grand 3.9 SmartLite Pro 3.6 Bluephase Power Cure 3.5 Woodpecker LED D 2.6 Denjoy 1.4 Deepcure-S 1.4 PinkWave 0.9 Bluephase G4 0.9
The ability of the two brands of meters to report similar power values to those obtained using the 'GS' method within each LCU also varied according to the LCU being measured (Tables 3 and 4 and Figs 7 and 8). When example #1 of each LCU was tested, the power values from three LCUs measured using the Bluephase Meter II were not significantly different from the 'GS' values. In comparison, the power values from six LCUs measured with Mini Gig matched those from the 'GS' integrating sphere. When example #2 of each LCU was measured, the values obtained from five LCUs with Bluephase Meter II were not significantly different (p>0.05) from those obtained in the 'GS' system. In comparison, the power values from eight LCUs measured with the Mini Gig radiometer were not significantly different (p>0.05) from the 'GS' values. Furthermore, Fig 7 shows that when measuring example #1 of each LCU using the Mini Gig, in 17 out of the 24 power measurements, the difference in the mean power values compared to the 'GS' values was 5% or less, and in all 24 measurements, the difference was less than 10%. Fig 8 shows that when measuring example #2 of each LCU using the Mini Gig, in 18 out of the 24 power measurements, the difference was 5% or less, and in 21 instances, the difference was 10% or less. When using the Bluephase Meter II to measure examples # 1 or 2 of each brand of LCU, Figs 7 and 8 show that the difference from the 'GS' power value was 10% or less in 17 out of the 24 instances. The power values from the Pinkwave were obviously wrong (51% to 57% greater than the 'GS' value). Figs 7 and 8 both show the power outputs from examples #1 and 2 of the Dental Spark (C), Woodpecker LED.B (F) and SDI Radii Plus (G) LCUs when measured using the Bluephase Meter II were often more than -10% different from the 'GS' power values.
When the 'GS' power values were compared with all the power values from the two Bluephase Meters II and from the two Mini Gig radiometers (omitting the Pinkwave LCU from the Bluephase Meter II readings only), the regression analyses (Fig 9) showed a highly significant positive relationship between the two brands of meters and the 'GS' measurements (R
Graph: Fig 9 Regression analysis and fitted line plots with 95% confidence and prediction intervals for mean power recordings of the 24 LCUs using the two Bluephase Meters II (units #1 and #2) and the two Mini Gig spectroradiometers (units #1 and #2).The integrating sphere was the 'gold standard (GS)' predictor variable.
The purpose of this study was not to measure the light output from brand new curing lights. Instead, we determined if two radiometers could accurately record the power from a representative sample (n = 24) of contemporary LCUs used in dental offices. To provide a broad range of lights, we chose 7 brands of single peak and 5 brands of multiple peak wavelength LCUs. Since some LCUs had only one output setting, the LCUs were all tested on their standard output settings. We found that the radiant power outputs from the LCUs tested on their standard-setting were markedly different (p<0.001), and the wavelengths of light from these LCUs were also noticeably different (Tables 3 and 4 and Figs 3–6). Five of the LCUs emitted less than 60% of the power emitted by the most powerful LCU, and one LCU emitted less than 33% of the output from the most powerful LCU tested (Fig 6). Thus, the first hypothesis that there would be no difference in the power outputs from the 12 contemporary LCUs that we tested was rejected. In addition, we noted that both meters reported power values that were slightly above and slightly below the 'GS' value (Figs 7 and 8). This supports that the 'GS' power values were accurate, and the measurement differences were based on valid 'GS' power values.
Table 6 reports that, except for the Dental Spark LCU (where the difference was 15.1%), when measured on the 'gold standard system', the differences in the mean power values from the two examples of each brand of LCU were less than 5.3%. Of note, there was less than a 0.9% difference between the two examples of the PinkWave and the two examples of the Bluephase G4 units. Thus, the second hypothesis that the power outputs from the two examples of each LCU brand measured on their standard output settings using the 'GS' system would be within ±10% was accepted for 11 out of the 12 brands of LCU. However, we rejected this hypothesis for the Dental Spark LCU.
Although there were significant differences between the power values reported by the two hand-held radiometers used in this study and the third hypothesis was rejected on statistical grounds, Table 5 shows that overall, the mean differences between the power values recorded from the 24 LCUs using the two examples of the Bluephase Meter II were only 3.8 ± 1.5% and only 3.4 ± 1.3% for the more expensive Mini Gig spectroradiometer. Even the maximum differences in the power values from any the LCUs recorded by the two examples of each meter were at most 18% for the Bluephase Meter II and at most 15% for the Mini Gig spectroradiometer. All these large % differences were measured from light (C), which we classified as a 'budget LCU', whose standard deviations and coefficient of variation in the 'GS' power values were also large, suggesting that the output from this LCU was unstable. Since most of these differences between the meters illustrated in Figs 7 and 8 were well within the ±10% tolerance, we consider the small percentage differences between the meters to be acceptable for the dental office.
Based on our study, the Mini Gig radiometer was more precise and accurate than the Bluephase Meter II when reporting power. In view of the difference in cost and the fact that this meter meets the the ISO/IEC 17025 standard [[
In a recent study, 50% of dentists used the same light exposure technique no matter what the shade or opacity of the RBC and 13% of American dentists surveyed used the same standard approach for all light-curing conditions [[
This study also shows that measuring the output from the LCU is not easy. Even the best laboratory-grade equipment used under ideal conditions is only accurate to ± 2 to 3% [[
Ideally, researchers should use a calibrated laboratory-grade integrating sphere and a spectroradiometer to measure and report the spectral radiant power, total power, and the energy received by the specimens in experiments that use dental LCUs and resins. However, we found that the Mini Gig meter was an acceptable alternative that was an easy-to-use, self-contained laboratory-grade portable spectroradiometer that exported calibrated spectral radiant power, power, and irradiance values. If the researcher cannot afford costly optical laboratory equipment to measure the output from the LCU, then the Mini Gig spectroradiometer should be used (contact Ultradent at +1 801 553 4351 for more information). The researcher will then be able to accurately report the power, irradiance, and energy delivered as well as the emission spectrum from the LCU. This information will help the researcher from coming to incorrect and possibly misleading conclusions.
However, due to the cost and the challenges posed when using and maintaining such laboratory-grade equipment, it would be unreasonable to ask clinicians to purchase such a costly laboratory-grade radiometer. We found that the Bluephase Meter II was easy to use, and although it could not report the emission spectrum, we found that it could accurately report the power from 11 out of the 12 brands of LCU tested. Knowing the power output from the LCU will help the clinician recognize that although two LCUs may deliver the same irradiance, the actual power output may easily be 50% less from the LCU that has a smaller tip diameter. Furthermore, when the power is multiplied by the exposure time (s), the energy (in Joules) from the LCU can be calculated.
This study highlights that measuring the output from dental LCUs is not as easy as it seems. Even the best laboratory-grade equipment will only be accurate to ± 20 to 30 mW at 1000 mW [[
A limitation of this study is that the Bluephase Meter II and the Mini Gig radiometers were brand new, and how long they will remain calibrated is unknown. Also, only two examples of each meter and radiometer were measured. The LCUs were not new, but they were undamaged, in good working order, they were recharged after every five exposures. Thus, they represented what may be found in many dental offices. Finally, the LCUs were only tested on their standard power output setting. Despite these study limitations, both radiometers could accurately measure the power from a wide range of contemporary LCUs that had large differences in their power output and emission spectra.
Within the limitations of this study, we concluded that there was a large and significant (p<0.001) difference in the power values (mW) and the emission spectra emitted by 12 brands of LCUs. Five of the LCUs emitted less than 60% of the power emitted by the most powerful LCU. Except for the Dental Spark LCU, where there was a 15.1% difference, the differences between the power values from two units of the same brand of LCU were less than 5.3% when measured using the 'GS' integrating sphere system. The overall mean ± S.D. difference between the power values from the same LCU recorded by the two examples of the Bluephase Meter II was 3.8 ± 1.5% and 3.4 ± 1.3% for the more expensive Mini Gig spectroradiometer. Finally, we found that provided that the meters were not attempting to measure wavelengths beyond their design specifications, the two brands of dental radiometers tested were accurate and precise.
S1 Data.
(ZIP)
By Cristiane Maucoski; Richard B. Price; Cesar A. Arrais and Braden Sullivan
Reported by Author; Author; Author; Author