RESEARCH ARTICLE

Effect of Curing Light Barriers and Light Types on Radiant Exposure and Composite Conversion RHODA JOYNER SWORD, DMD*, UYEN NGOC DO, DMD†, JONATHAN HU CHANG, DMD‡, FREDERICK ALLEN RUEGGEBERG, DDS, MS§

ABSTRACT Purpose: Previous research investigated the effects of curing tip barriers on light output and composite properties, but no study has measured the effect of a wide variety of barriers and curing light types on delivered radiant exposure and the resulting composite cure 2 mm below the radiated surface. Materials and Methods: Six barrier materials and six curing light types were tested. Spectroradiometry was used to measure irradiance with and without barriers for each light type, and radiant exposure values were determined for a commercial camphorquinone-based dental composite material. Composite monomer conversion was measured at 10 minutes following exposure for each light type/barrier condition (N = 5) using infrared spectroscopy. Results were subjected to one-way analyses of variance for radiant exposure and conversion among barrier types within a given curing light: preset alpha 0.05. Results: All barriers significantly reduced radiant exposure compared with the uncovered tip, but the use of the two polywave LEDs covered with a latex-based barrier demonstrated significantly lower conversion values. Conclusions: Although light-curing barriers reduce radiant exposure to a restorative material over a recommended exposure, this reduction is not sufficient to cause significant reduction in composite cure, except when using a latex-based barrier and a polywave LED curing light.

CLINICAL SIGNIFICANCE Clinicians need to be aware of the possible interaction between curing light barriers and curing light type in order to optimally photocure restorative materials. Esthet Restor Restor Dent Dent ••:••–••, 28:29^42, 2015) 2016) (J(J Esthet

INTRODUCTION Current Center for Disease Control (CDC) guidelines state that instruments in contact with mucous membranes or nonintact skin are considered “semi-critical items” and should have high-level disinfection.1 Contemporary light-curing units (LCUs) belong to this category, leaving several clinical options related to their cleaning between patients. The units could be sprayed with a

surface disinfectant, which is not ideal for electrical equipment, and surface wipe disinfection may leave crevices untreated.2 Cold sterilization of removable tips or disposable light-curing tips is also a consideration. However, these methods have several negative side effects, including reduced light transmission and the need for tip polishing.3,4 Thus, the previously mentioned techniques may not be the most efficient. The CDC guideline further states that cleaning or disinfection of

*Assistant Professor, Department of Oral Rehabilitation, Georgia Regents University, Augusta, GA, USA † Private Practitioner, Kennesaw, GA, USA ‡ Private Practitioner, Atlanta, GA, USA § Professor, Section Director, Dental Materials, Department of Oral Rehabilitation, Georgia Regents University, Augusta, GA, USA

C 2015 V © 2015Wiley WileyPeriodicals, Periodicals,Inc. Inc. DOI DOI10.1111 10.1111/jerd.12173 /jerd.12173

Journal of of Esthetic andand Restorative Dentistry •• •28No •• 1•••–•• Journal Esthetic Restorative DentistryVol Vol  No 29^42 • 2015 2016

1 29

EFFECT OF CURING LIGHT BARRIERS BARRIERS AND AND LIGHT LIGHTTYPES TYPES Sword Swordetetalal

certain noncritical, patient care items can be difficult, or may even damage surfaces. Therefore, the use of disposable barrier protection of these surfaces might be a preferred alternative.1 Several barrier methods have been used with curing lights, since their inception, including adhesive touch and splash surface barriers, dissection gloves, steri-shields, and even finger cots.5 A customfitting LCU plastic film barrier was patented in 1998,6 and LCU-specific barriers were commercialized after that time. Contemporary barriers are much more brandspecific, with many created to fit only one model of LCU. Barriers are made of various materials, including latex-free polyurethane, low-density polyethylene, and polyvinyl chloride (Table 1). After infection control became a consideration with LCUs, several of the above-mentioned methods of disinfection were explored. Because the potential for polymerization in the depths of composite is already decreased by light attenuation within the material,7 any further reduction of light striking the restorative material caused by a barrier film has the potential to even further reduce composite curing with depth. Curing light tips were autoclaved, but it was found that, although autoclaving diminishes the ability of tips to transmit light, the effects can be minimized by tip polishing at frequent intervals, which may be fairly time-intensive.3 A subsequent study found that, although some cold sterilization solutions did not affect light output compared with a water-immersed control, other solutions significantly decreased the emitted light

intensity to a level that could not be reversed, even when using conventional tip-polishing methods.4 Once barriers were commonly being used to cover all or parts of LCUs, more studies investigated the effects of using various LCU and barrier combinations. A single brand of quartz-tungsten-halogen (QTH) LCU and four types of nonspecific barriers (cellophane, plastic dissection gloves, steri-shields, and finger cots) were tested, and a statistical difference was found in light output among the groups, compared with a noncovered control. The level of attenuation, however, was not found to significantly affect composite Knoop hardness, even at 2.5-mm depth of one composite.5 In another study, when using four brands of QTH lights and four types of nonspecific barriers (sani-shield, Protectop, all-purpose adhesive covering, and prophy wrap), light output was shown to be affected differently with respect to barrier type and light manufacturer combinations.6 However, this work did not involve using the lights with or without barriers to expose any composite material, and thus did not assess the curing potential of their findings. Later, a study involving one type of QTH LCU and three specific barrier materials (Cure Sleeve, Curelastic, and Saran Cling Plus) showed that irradiance was significantly less than the uncovered control, but the effect was small. Although not studied in detail, this report showed no overt shift in spectral output, compared with the uncovered control tip, when evaluating a range of wavelengths. In addition, only a QTH source was evaluated. The authors reported that

TABLE 1. Barriers used Classification

Brand name

Composition (from manufacturer)

Cure Sleeve

Low-density polyethylene

Curelastic

Polyurethane

Latex type

Finger cots

Latex

Food wrap

FoodService Film

Polyvinyl chloride

Bluephase 20i

Polyethylene

Pinnacle Complete Curing Light Sleeve

Low-density polyethylene

VALO

Polyethylene

Item # 4511

Manufacturer information Kerr, Metrex Research Corp, Romulus, MI, USA

Tip only

Dedicated

2 30

•• • No No1•• • ••–•• • 2015 Journal of Esthetic Restorative Dentistry Vol 28  29^42  2016 Journal of Esthetic and and Restorative Dentistry

088-065 20501 914 608554 CLS-250

5932

Steri-shield, Santa Barbara, CA, USA Sultan Chemists, Inc, Englewood NJ, USA Reynolds Food Packaging, LLC, Mount Vernon, KY, USA Ivoclar Vivadent AG, Schaan Liechtenstein Kerr, Metrex Research Corp, Romulus, MI, USA

Ultradent, South Jordan, UT, USA

C 2015 V DOI 10.1111/jerd.12173 Wiley Periodicals, Periodicals, Inc. DOI 10.1111/jerd.12173 © 2015 Wiley

EFFECT EFFECTOF OFCURING CURINGLIGHT LIGHTBARRIERS BARRIERSAND AND LIGHT LIGHT TYPES Sword Sword et et al

there would likely be no clinical significance to their findings, but the properties of exposed composite material were not evaluated to substantiate these assumptions.8 The results of the two additional studies indicated that the use of barriers did not significantly affect depth of cure, in up to 2.0-mm thick increments.9,10 Various methods have been used to assess the effect of composite curing.11,12 Direct measurement of the extent of the polymerization process using monomer conversion is a method of achieving a more realistic idea of how well a composite polymerizes. This technique monitors the amount of available carbon-to-carbon double bonds prior to and subsequent to the polymerization reaction. Thus, this type testing provides a direct indication of localized extent of composite cure, does not require extensive surface preparation, and minimizes property alteration as would preparation for microhardness testing. In addition, composite conversion values have been directly correlated with important physical parameters (wear, marginal breakdown, fracture toughness) of the resulting material.13,14 Most previous work on examining the effect of barriers on LCUs includes only QTH LCUs, which are only one of the several types of lights currently being used clinically. Blue LED, polywave LED, and plasma arc (PAC) LCUs are also in common contemporary use. Previous studies have not shown the effects of barriers on all of these different categories of lights. The barrier material composition could filter light at specific wavelengths emitted by these units, and possibly affect composite cure. If it is shown that these light types, in combination with specific contemporary barriers, have an effect on composite light-curing, the clinician could better choose the most appropriate barrier–LCU combination for their specific operating conditions. The purpose of this study was to examine the effect of a wide variety of light-curing tip barrier films on their ability to affect transmitted, radiant exposure from representative dental LCU types. The LCUs used provided a variety of contemporary, commercially available devices, including broad-banded emission

C 2015 V © 2015Wiley WileyPeriodicals, Periodicals,Inc. Inc. DOI DOI10.1111 10.1111/jerd.12173 /jerd.12173

units (a QTH and a PAC light), conventional blue-only LEDs, and polywave LEDs. The barriers used represented commercial, generic products to be used universally on lights, barriers dedicated for use on specific LCUs, as well as clear food wrap. Radiant exposure from each LCU during a manufacturer-recommended exposure was calculated with and without the barriers present. In addition, the effect of the barriers on monomer conversion was examined using infrared spectroscopy. Monomer conversion was measured at the bottom surface of a 2-mm thick composite specimen, when irradiated using the variety of LCUs mentioned above with and without a barrier film present. The following research hypotheses were tested: Regardless of curing light type, there will be no significant difference in radiant energy transmission among the different barriers, when compared with the nonbarrier-covered tip end. Within a given LCU, there would be a significant difference in emitted energy levels among the barrier materials. The distribution of spectral light transmission through each barrier will be linear across the emitted spectrum, indicating that the barrier material itself is not acting as a wavelength-dependent light filter. Within a given barrier material, the type of curing light will have no significant influence on monomer conversion at 2-mm composite depth, when conversion values are compared using the barrier with those without the same barrier present.

MATERIALS AND METHODS A list of all barrier products used is provided in Table 1. These items were selected to represent a wide variety of commercially available materials known to be used clinically for the purpose of providing a protective, barrier film for both the light-curing tip as well, in some cases, providing full protection for the tip and curing light body. Because a Curelastic product was not available to fit the FLASHlite Magna, a latex-based finger cot was used instead. In addition to commercial barrier products, the use of a single or triple layer of

Journal of of Esthetic andand Restorative Dentistry •• •28No •• 1•••–•• Journal Esthetic Restorative DentistryVol Vol  No 29^42 • 2015 2016

3 31

EFFECT OF CURING LIGHT BARRIERS BARRIERS AND AND LIGHT LIGHTTYPES TYPES Sword Swordetetalal

clear, plastic food wrapping film was also tested because many offices use such material, due to its low cost, ease of adaptability to fit any configuration of curing light form factor, and the ability to purchase in bulk. The use of a triple layer was to simulate a more typical placement of the food wrap that would leave the barrier wrinkled or potentially overlapping in various areas.

Light Output Characterization The LCUs used for this study are listed in Table 2. These lights represent the range of commercially available products thought to still be in clinical practice. The spectral power of each light unit was measured using a laboratory grade, 6″ integrating sphere containing an National Institutes of Science and Technology (NIST)-traceable source (Model CTSM-LMS-60-SF, Labsphere, Inc., N. Sutton, NH, USA). The system was calibrated for spectral power (350 nm–700 nm), and the sphere output was directed to a spectroradiometer (USB 2000, Ocean Optics, Dunedin, FL, USA). Data from the spectrometer were analyzed using software (SpectraSuite, Ocean Optics). The lights were tested with no barrier present, as well as with each type of barrier material fully in place. Five replications were made for each light and test condition. The distal end of the curing light was directed into the sphere opening. The total radiant power was summed between 350 and 550 nm, and was divided by the emitting area of the fiber optic light guide (or lens) area and was reported in units of milliWatts/cm2 (irradiance) within the tip end area. Then, radiant exposure (J/cm2) was determined by multiplying the irradiance values by the exposure

duration. The order of the barrier testing within each LCU was totally randomized.

Monomer Conversion A Camphoroquinone (CQ)-based composite was used (Premise Body, Item #32650, Lot #3450425, Shade A1, Kerr Corporation, Orange, CA, USA). This composite is a universal nanofilled, hybrid composite, with 84% wt filler, 0.4 μm glass, nanofiller, pre-polymerized composite particles.15 The uncured paste was placed into 6-mm diameter, 2-mm high brass rings, which were located on top of a diamond element in a heated, horizontal attenuated total reflectance (ATR) attachment. This attachment was located in the optical bench of a Fourier transform infrared spectrometer (FTS-40, Bio-Rad, Digilab, Cambridge, MA, USA). The ATR plate temperature was computer-controlled to 30oC, which is similar to the in vivo, prepared tooth surface temperature immediately prior to composite placement and light-curing.16 The light-curing tip was placed 2 mm from the top surface to be irradiated. Prior to light activation, the infrared spectrum of the bottom composite surface was obtained using 16 scans at a resolution of 2/cm. The LCU was activated for the prescribed exposure time according to manufacturers’ directions (Table 3). Ten minutes from the beginning of light activation, another set of infrared spectra was obtained to provide the spectrum of the specimen in the polymerized state, allowing for a significant portion of the “dark-cure” reaction to occur, prior to specimen measurement. Monomer conversion of C=C into C-C was determined using conventional methods of comparing the ratio of aliphatic C=C peak absorption

TABLE 2. Light-curing units used Category

Brand name

Manufacturer

Manufacturer location

Optilux 501

Kerr Sybron

Middleton, WI, USA

Arc IIM

Air Techniques

Hicksville, NY, USA

Elipar S10

3M ESPE

St. Paul, MN, USA

FLASHlite Magna

DenMat Holdings

Lompoc, CA, USA

Bluephase 20i

Ivoclar Vivadent

Schaan, Liechtenstein

VALO

Ultradent Products

South Jordan, UT, USA

Broad-banded

Blue-only LED

Polywave LED

4 32

•• • No No1•• • ••–•• • 2015 Journal of Esthetic Restorative Dentistry Vol 28  29^42  2016 Journal of Esthetic and and Restorative Dentistry

C 2015 V DOI 10.1111/jerd.12173 Wiley Periodicals, Periodicals, Inc. DOI 10.1111/jerd.12173 © 2015 Wiley

EFFECT EFFECTOF OFCURING CURINGLIGHT LIGHTBARRIERS BARRIERSAND AND LIGHT LIGHT TYPES Sword Sword et et al

TABLE 3. Radiant exposure (J/cm2) and 2-mm deep percent monomer conversion of various light/barrier combinations Barrier material Clear plastic tip only Class

Broadbanded

Light

Parameter

Radiant exposure (J/cm2) Optilux 501 (QTH) Conversion % at 10 minutes

Arc II (PAC)

Radiant exposure (J/cm2)

Exposure No barrier Cure Sleeve (seconds) 20

10

Conversion % at 10 minutes Radiant exposure (J/cm2)

10

Latex type Curelastic Finger cot

Food wrap 1 layer

3 layers

Light-specific full body custom barrier BP 20i

VALO

OP 501

17.4 (0.1) A

15.1 (0.3) D

11.4 (0.1) E

16.4 (0.1) B

15.2 (0.1) D

15.6 (0.1) C

49.1 (2.3) a

51.6 (1.9) a

51.4 (5.3) a

53.6 (3.4) a

52.3 (1.7) a

51.8 (2.8) a

47.2 (0.3) A

33.4 (0.6) D

16.1 (0.2) E

45.5 (0.8) B

42.8 (0.5) C

55.6 (5.1) a

48.8 (7.6) a

51.5 (3.5) a

54.4 (2.1) a

55.1 (0.4) a

14.1 (0.2) A

10.7 (0.2) C

10.3 (0.0) C 13.1 (0.5) B

12.8 (0.3) B

53.0 (1.2) a

50.7 (3.7) a

50.3 (3.3) a

52.3 (1.7) a

MAGNA Conversion % at 10 minutes

Blue-only LED

Radiant exposure (J/cm2)

10

10.7 (0.0) A

9.2 (0.0) D

8.0 (0.0) E

53.6 (3.4) a 9.9 (0.0) B

9.8 (0.0) C

Elipar S10 Conversion % at 10 minutes

Bluephase 20i

Radiant exposure (J/cm2)

10

Conversion % at 10 minutes

Polywave LED

Radiant exposure (J/cm2)

10

51.1 (2.7) a

50.3 (3.5) a

11.4 (0.0) A

10.0 (0.0) D

7.8 (0.0) E

10.8 (0.0) B

10.6 (0.0) C

50.0 (4.0) ab 47.1 (5.7) ab

42.5 (3.4) b

51.8 (3.5) a

47.8 (2.7) ab 50.8 (3.8) a

8.7 (0.0) E

8.0 (0.0) F

9.6 (0.0) B

9.1 (0.0) D

48.5 (3.6) ab 49.7 (5.0) a

41.5 (4.0) b

50.9 (2.2) a

47.7 (2.6) ab

10.2 (0.1) A

48.2 (1.5) a

51.2 (1.9) a 52.6 (2.0) a 10.6 (0.0) B

9.4 (0.0) C

VALO Conversion % at 10 minutes

51.4 (5.1) a

N = 5 specimens per group. Within a row, groups identified by similar letters are not significantly different (p > 0.05). Cells in grey indicate parameter not tested.

of the methacrylate groups (1,636/cm) to that of the aromatic C=C absorbance (1,608/cm) in the uncured and cured states.17 From these calculations, the proportion of available methacrylate C=C present at the bottom surface of the 2-mm thick increment prior to light-curing that had converted into C-C polymeric units was calculated. Five specimens were made for each LCU and each testing condition. Specimen fabrication within a given LCU was randomized among barrier types and specimen replications. Statistical treatment of data consisted of a one-way analysis of variance among radiant exposure and monomer conversion values within the various barrier treatments for a given light. Post-hoc, pair-wise means comparisons were performed using the Tukey test. All statistical testing was performed at a preset alpha of 0.05.

RESULTS Spectral irradiance profiles and relative spectral irradiance values through the barriers for the

C 2015 V © 2015Wiley WileyPeriodicals, Periodicals,Inc. Inc. DOI DOI10.1111 10.1111/jerd.12173 /jerd.12173

broad-banded light units (QTH and PAC) are displayed in Figure 1, left. The nonsymmetrical output profile of the QTH light is seen, with a peak value occurring at 470 nm, decreasing rapidly at wavelengths longer than this, and decreasing less rapidly at shorter wavelengths. Decrease in spectral irradiance of this light using each type barrier is displayed as an overlay graph. In this figure, moderate levels of light loss using all barriers are seen, with the Curelastic product demonstrating the lowest value. In the panel to the right, the percentage of irradiance through the barriers at each wavelength is displayed, relative to that when using no barrier (100%). These results confirm the trends seen with the spectral light loss profile on the right: most transmission is seen using one layer of food wrap barrier, slightly less transmission is seen using the dedicated barrier and three layers of food wrap, whereas the least transmission is found using Curelastic. However, it should be noted that there is no barrier showing a specific wavelength of absorption. All relative irradiance profiles seem to be fairly linear throughout the measured spectrum, indicating that no barrier was

Journal of of Esthetic andand Restorative Dentistry •• •28No •• 1•••–•• Journal Esthetic Restorative DentistryVol Vol  No 29^42 • 2015 2016

5 33

EFFECT OF CURING LIGHT BARRIERS BARRIERS AND AND LIGHT LIGHTTYPES TYPES Sword Swordetetalal

SPECTRAL IRRADIANCE

IRRADIANCE (mW/nm/cm2)

4.0

CURE SLEEVE

FOOD WRAP 3

CURELASTIC

DEDICATED

3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0

IRRADIANCE RELATIVE TO NO BARRIER

FOOD WRAP 1

PERCENT NO BARRIER IRRADIANCE

NONE

100 90 80 70 60 50 40 30 20 10 0

350

400

450

500

550

390 400 410 420 430 440 450 460 470 480 490 500 WAVELENGTH (nm)

WAVELENGTH (nm)

OPTILUX 501 (QTH light) SPECTRAL IRRADIANCE CURE SLEEVE

FOOD WRAP 1

FOOD WRAP 3

IRRADIANCE RELATIVE TO NO BARRIER 100

PERCENT NO BARRIER IRRADIANCE

IRRADIANCE (mW/nm/cm2)

25

NONE CURELASTIC

20

15

10

5

0

350

400

450

500

550

90 80 70 60 50 40 30 20 10 0

390 400 410 420 430 440 450 460 470 480 490 500 510

WAVELENGTH (nm)

WAVELENGTH (nm)

ARC II (PAC light) FIGURE 1. Effect of barrier presence on spectral irradiance from broad banded curing lights.

acting to selectively absorb light within a spectral range, relative to the other barriers tested. The mean values of emitted light radiant exposure through the barrier (or not), taking into account the product of irradiance and exposure duration, and the resulting monomer conversion at the bottom, 2-mm deep surface of composite for each type LCU 10

6 34

•• • No No1•• • ••–•• • 2015 Journal of Esthetic Restorative Dentistry Vol 28  29^42  2016 Journal of Esthetic and and Restorative Dentistry

minutes after exposure are shown in Table 3. Focusing attention on the broad-banded LCUs, for the QTH light, all barriers provided significantly lower radiant exposure values than when the tip was not covered. Significant differences in radiant exposure values existed among all barrier types, with the single layer of food wrap delivering the most, the dedicated barrier providing slightly lower, and the Cure Sleeve and three

C 2015 V DOI 10.1111/jerd.12173 Wiley Periodicals, Periodicals, Inc. DOI 10.1111/jerd.12173 © 2015 Wiley

EFFECT EFFECTOF OFCURING CURINGLIGHT LIGHTBARRIERS BARRIERSAND AND LIGHT LIGHT TYPES Sword Sword et et al

layers of food wrap yielding lower values, but not significantly different. Radiant exposure delivery through the Curelastic barrier was the lowest. Interestingly, when comparing the resulting monomer conversion values at the bottom surfaces of composite, either using no barrier or through all the different products, no significant differences were found. For the other broad-banded LCU (the PAC light), the spectral irradiance profile was somewhat similar to that of the QTH light, but the irradiance values were very much higher, and the peak emission was near 470 nm (Figure 1, bottom left). Differences in irradiance, when using the various barrier materials, were much more obvious with this light, than seen in the QTH. In addition, differences in relative spectral irradiance through the barriers (Figure 1, bottom right) were also much more widespread than in the QTH unit, but still demonstrated relatively straight lines, indicating that none of the barriers acted as a wavelength-specific filter. In Table 3, all radiant exposure values were significantly different, but as seen with the QTH source no significant differences were noted among composite conversion values at 2-mm depths, whether or not the tip was covered. The spectral irradiance profiles of the blue-only LED lights were quite similar, showing a symmetrical, narrow emission around a single peak output value: for the Elipar S10 at 450 nm, and for the FLASHlite Magna near 455 nm (Figure 2, left). When using the Elipar S10, the use of one or three layers of food wrap caused the least light loss, whereas lower values were observed using the Cure Sleeve. The lowest irradiance resulted with the use of the Curelastic barrier. As seen with the broad-banded lights, the relative spectral irradiance values through the barriers seems fairly linear, indicating that none of the barriers were affecting light throughout any frequency range measured (Figure 2, top right). For the FLASHlite Magna, the barriers tended to fall into two groups when observing spectral irradiance (Figure 2, bottom left). The use of one or three layers of food wrap resulted in similar spectral irradiance profiles and produced higher values than did the use of the Cure Sleeve or finger cot, which seemed to perform similarly and yielded lower irradi-

C 2015 V © 2015Wiley WileyPeriodicals, Periodicals,Inc. Inc. DOI DOI10.1111 10.1111/jerd.12173 /jerd.12173

ance values than the other two barriers. The relative irradiance profiles, when using the FLASHlite Magna, are quite different from those previously seen (Figure 2, bottom right). The use of the finger cot yielded the lowest overall transmission value among wavelengths and was fairly linear in its profile. However, when either one or three layers of food wrap or the Cure Sleeve barrier was used, the linearity in irradiance values previously observed with the other lights was lost, and a decrease in light throughput between 420 and 470 nm was observed, with the greatest loss occurring when using the Cure Sleeve barrier. For the Elipar S10, all radiant exposure values through the barriers were significantly lower than the use of no barrier and were significantly different among barrier types (Table 3). The highest radiant exposure values were observed using one and three layers of food wrap, and the lowest value was seen using the Curelastic barrier. However, even with these observed differences in radiant exposure, there was no significant difference in composite conversion among barrier products for this light. All barriers resulted in significantly lower radiant exposure values using the FLASHlite Magna (Table 3). However, no significant difference was found between the use of either one or three layers of food wrap, the values of which were significantly greater than those when using the finger cot or the Cure Sleeve barriers, which themselves were not significantly different. Despite these differences, there were no significant differences in composite conversion 2 mm below the top, irradiated surface among all barrier treatments. The spectral profiles for the polywave lights both indicate the presence of individual emission peaks in the blue (460 nm) and violet (403 nm) ranges, but the VALO light demonstrated an additional blue output around 440 nm (Figure 3, bottom left). For the Bluephase 20i, little spectral loss was observed among the barrier types, with the exception of the Curelastic product, which yielded the lowest irradiance profile values. Interestingly, when comparing the relative

Journal of of Esthetic andand Restorative Dentistry •• •28No •• 1•••–•• Journal Esthetic Restorative DentistryVol Vol  No 29^42 • 2015 2016

7 35

EFFECT OF CURING LIGHT BARRIERS BARRIERS AND AND LIGHT LIGHTTYPES TYPES Sword Swordetetalal

SPECTRAL IRRADIANCE CURE SLEEVE

FOOD WRAP 3

CURELASTIC

IRRADIANCE RELATIVE TO NO BARRIER FOOD WRAP 1

100

PERCENT NO BARRIER IRRADIANCE

IRRADIANCE (mW/nm/cm2)

12

NONE

10 8 6 4 2 0

350

400

450

500

90 80 70 60 50 40 30 20 10 0

550

420

430

440

WAVELENGTH (nm)

450

460

470

480

490

WAVELENGTH (nm)

ELIPAR S10 SPECTRAL IRRADIANCE CURE SLEEVE

FOOD WRAP 3

FINGER COT

IRRADIANCE RELATIVE TO NO BARRIER FOOD WRAP 1

18 16 14 12 10 8 6 4 2 0

350

400

450

110

PERCENT NO BARRIER IRRADIANCE

IRRADIANCE (mW/nm/cm2)

20

NONE

500

550

100 90 80 70 60 50 40 30 20 10 0

420

430

440

WAVELENGTH (nm)

450

460

470

480

490

500

WAVELENGTH (nm)

FLASHlite MAGNA FIGURE 2. Effect of barrier presence on spectral irradiance from blue-only LED-based curing lights.

spectral irradiance profiles among barrier types within this LCU, the use of a single layer of food wrap, as well as the dedicated barrier sleeve, generated nonlinear profiles: slightly higher light transmission was seen from 390 to 410 nm, and between 430 and 460 nm, than the lower appearing dip in transmission centered at 430 nm (Figure 3, top right). The lowest irradiance value among the barriers appeared using the Curelastic material, with only 70% of light being transmitted, relative to use

8 36

•• • No No1•• • ••–•• • 2015 Journal of Esthetic Restorative Dentistry Vol 28  29^42  2016 Journal of Esthetic and and Restorative Dentistry

of no barrier. Table 3 indicates that the use of a barrier significantly decreased radiant exposure values, but there was very little difference among them, with the exception of the Curelastic film, which produced the lowest value. Unlike previous observations, significant differences in composite conversion were found among use of barrier products; when using this light with the different barrier films, use of the Curelastic product resulted in conversion values that were significantly

C 2015 V DOI 10.1111/jerd.12173 Wiley Periodicals, Periodicals, Inc. DOI 10.1111/jerd.12173 © 2015 Wiley

EFFECT EFFECTOF OFCURING CURINGLIGHT LIGHTBARRIERS BARRIERSAND AND LIGHT LIGHT TYPES Sword Sword et et al

SPECTRAL IRRADIANCE NONE

CURE SLEEVE

FOOD WRAP 1

FOOD WRAP 3

CURELASTIC

DEDICATED

100

PERCENT NO BARRIER IRRADIANCE

IRRADIANCE (mW/nm/cm2)

14

IRRADIANCE RELATIVE TO NO BARRIER

12 10 8 6 4 2 0

350

400

450

500

90 80 70 60 50 40 30 20 10 0

550

390

400

410

420

WAVELENGTH (nm)

430

440

450

460

470

480

490

480

490

WAVELENGTH (nm)

BLUEPHASE 20i SPECTRAL IRRADIANCE CURE SLEEVE

FOOD WRAP 1

FOOD WRAP 3

CURE LASTIC

DEDICATED

IRRADIANCE (mW/nm/cm2)

9 8 7 6 5 4 3 2 1 0

100

PERCENT NO BARRIER IRRADIANCE

10

IRRADIANCE RELATIVE TO NO BARRIER

NONE

350

400

450

500

550

90 80 70 60 50 40 30 20 10 0

390

WAVELENGTH (nm)

400

410

420

430

440

450

460

470

WAVELENGTH (nm)

VALO FIGURE 3. Effect of barrier presence on spectral irradiance from polywave-based curing lights.

lower than those when using only one food wrap layer or when using the dedicated barrier sleeve. Spectral analysis for the VALO light indicates the greatest irradiance loss occurs when using the Curelastic product, with values from the other barriers spread in between (Figure 3, bottom left). In general, the spectral transmission values for each barrier product seem to be fairly linearly related to the output

C 2015 V © 2015Wiley WileyPeriodicals, Periodicals,Inc. Inc. DOI DOI10.1111 10.1111/jerd.12173 /jerd.12173

spectrum (Figure 3, bottom right). The use of each barrier resulted in significantly lower radiant exposure levels compared with using no barrier. Among barrier products, radiant exposure was also significantly different, with the lowest value occurring in the Curelastic product (Table 3). Among all the barriers used, the Curelastic product resulted in significantly lower composite conversion values than the use of all other barrier materials.

Journal of of Esthetic andand Restorative Dentistry •• •28No •• 1•••–•• Journal Esthetic Restorative DentistryVol Vol  No 29^42 • 2015 2016

9 37

EFFECT OF CURING LIGHT BARRIERS BARRIERS AND AND LIGHT LIGHTTYPES TYPES Sword Swordetetalal

DISCUSSION The first research hypothesis stated that, regardless of curing light type, there will be no significant difference in radiant exposure within a given curing light among the different barriers, when compared with the nonbarrier covered tip. The experimental findings indicated that the use of any type barrier resulted in significantly lower radiant exposure delivery, when compared with the noncovered control (Table 3). These findings are similar to others who measured the differences in irradiance values among three different barrier materials, but only for a QTH light.8 In that study, radiant exposure values were not determined or compared. In addition, the use of a plastic wrap was found to not significantly reduce irradiance levels, when compared with the noncovered, control tip,8 but it did in certain curing lights in the present study. This result could have arisen from different commercial products that are used to represent a clear, thin, flexible barrier material between the two studies, as well as from different methods of measurement. The second research hypothesis proposed that, within a given LCU, there would be a significant difference in emitted radiant exposure levels among the use of various barrier materials. This hypothesis was upheld by examining the findings presented in Table 3. In general, there was a trend in radiant exposure noted. Among all light units, the use of only a single layer of food wrap consistently provided the highest radiant exposure levels. In one case, radiant exposure measured through the dedicated barrier cover was not significantly different than when using a single layer of food wrap material (Table 3, Bluephase 20i). Lights having other dedicated barrier covers (QTH and VALO) provided significantly less radiant exposure than did the use of only a single layer of food wrap, but significantly more than three layers of the same food wrap material. For the remainder of comparisons, the order of radiant exposure was three layers of food wrap providing significantly greater values than use of Cure Sleeve, and delivery through the Curelastic product the least. Substituting a finger cot for Curelastic when using the Magna light, radiant exposure was not significantly

10 38

•• • No No1•• • ••–•• • 2015 Journal of Esthetic Restorative Dentistry Vol 28  29^42  2016 Journal of Esthetic and and Restorative Dentistry

different from when using the Cure Sleeve. No similar studies could be found in the literature that determined the effect of accumulation of irradiance levels over the duration of an LCU exposure: radiant exposure. Although small differences in irradiance through barriers might be found, it is the accumulated impact of these differences over time on the total number of photons delivered that results in polymerization providing adequately cured restorative materials. It is this aspect that will affect the ability of a composite to polymerize, especially when light of very low value is present at the bottom of a typical 2-mm thick composite increment.7 Other studies have examined light transmission through barriers as well. Irradiance measurements through barrier materials similar to those used in the present study (Cure Sleeve, Curelastic, and a “cling wrap” food barrier) were tested.8–10 The results of those findings were similar to those of the present study, but multiple layers of food wrap were not tested, and only irradiance values were presented: not radiometric energy levels. One study recommended that physical property testing need not be performed to test the effect of barriers, because although significant differences in irradiance levels were found among barriers the absolute differences found were very small.8 However, the current work utilized radiant exposure levels calculated for recommended exposure times, which have the capability to alter the accumulated total amount of energy delivered to a composite. The radiant exposure is derived not only from irradiance values but is also calculated from the product of irradiance multiplied by the recommended exposure duration. Because composite materials require different radiant exposure levels, it is important to take into account the effect of the recommended exposure times on the end result of composite cure. In addition, most of the previous testing only evaluated a QTH light,5,6,8,9 whereas the present work evaluated a representative curing light within each classification of available models. One of the authors recommended that physical property testing of specimens exposed using the different barrier material need not be performed because of the slight attenuation values found when using the barrier materials.8

C 2015 V DOI 10.1111/jerd.12173 Wiley Periodicals, Periodicals, Inc. DOI 10.1111/jerd.12173 © 2015 Wiley

EFFECT EFFECTOF OFCURING CURINGLIGHT LIGHTBARRIERS BARRIERSAND AND LIGHT LIGHT TYPES Sword Sword et et al

The third research hypothesis assumed that the attenuation of spectral irradiance through each barrier would be linear across the emitted spectrum, indicating that the barrier material itself was not acting as a wavelength-dependent light filter. For the most part, this hypothesis was upheld, as seen in the findings presented in Figures 1–3. When using either of the broad-banded output lights (Figure 1), spectral light loss through the different barriers is seen as a straight line. However, when looking at the blue-only LEDs, light attenuation using the Elipar S10 unit provided linear loss over the output spectral range, whereas the use of the FLASHlite Magna indicated a decrease in transmission levels for the Cure Sleeve, food wrap oneand food wrap three-layer barriers (Figure 2). This nonlinear pattern is seen again with one of the polywave lights (the Bluephase 20i,) when using one layer of food wrap as well as the dedicated barrier, in which a slight decrease in transmission is seen around 430 nm (Figure 3). Profiles using the VALO light indicate slight spectral nonlinearity when using food wrap in one or three layers and when using the Curelastic barrier. This aberration indicates a slightly lower transmission at shorter wavelengths (less than 420 nm). The reasons for this anomalous behavior are not clear, but may be the result of interaction of the tip end optics and composition of the barrier material, including the possibility of trapping air between the two. All of the films attributing to this data appeared visibly clear to the eye, indicating no preference of wavelength-dependent absorption. A spectral shift of light output caused by the barrier film could also result in profiles similar to those observed. No other studies have been performed that directly assess the trend in spectral attenuation of light through curing barrier materials. One study did look at shifts in peak emission values from a QTH unit and did not find any significant influence.8 That study only subtly addressed general spectral profile differences, and did not measure transmission throughout the entire emission range, and in addition only tested one type of LCU. The fourth research hypothesis stated that within a given barrier material, the type of curing light will have

C 2015 V © 2015Wiley WileyPeriodicals, Periodicals,Inc. Inc. DOI DOI10.1111 10.1111/jerd.12173 /jerd.12173

no significant influence on monomer conversion at 2-mm composite depth, when conversion values are compared using the barrier with those without the same barrier present. It should be noted that, in the current study, the LCU tip was held at 2-mm distance from the composite surface, which is a much more clinically relevant method than actually contacting the tip to the uncured material, which is commonly performed.18 Despite significant differences in radiant exposure among the barriers, there were only two circumstances where the monomer conversion of composite at 2-mm depth was significantly lower than the nonbarrier-covered, control value, with the Curelastic barrier using either types of polywave LED light: the Bluephase 20i and the VALO. It should be noted that the composite tested utilized only camphorquinone as photoinitiator, and thus requires photons between 420 and 490 nm (preferably between 450 and 480 nm) for optimal performance. Table 4 provides an indication of the radiant exposure levels of the different lights delivered through the various barriers, but with values partitioned between the shorter wavelength range (350–420 nm), violet range, where photons are used to activate the alternative photoinitiators (such as Lucerin TPO), and those in the longer wavelength range (420–520 nm), blue light, necessary for activation of camphorquinone. The spectral output of both the polywave and broad-banded lights has components within each of the wavelength ranges of interest. However, for the composite tested, it is light emission in the blue spectral range that is effective toward activation of camphorquinone, and thus has the potential to polymerize the composite. When examining only the blue radiant exposure portion of Table 4, it can be seen that the lowest values are seen for the two polywave lights: 6.4 J/cm2 for the Bluephase 20i and 6.7 J/cm2 for the VALO, both values obtained through the Curelastic barrier material. Recall that these two specific curing conditions were the only ones that resulted in significantly lower conversion values at the bottom surface of composite among all tested combinations. However, the blue-only Elipar S10 delivered 7.8 J/cm2 to the composite, and resulted in a conversion value through the Curelastic barrier that was not significantly

Journal of of Esthetic andand Restorative Dentistry •• •28No •• 1•••–•• Journal Esthetic Restorative DentistryVol Vol  No 29^42 • 2015 2016

11 39

EFFECT OF CURING LIGHT BARRIERS BARRIERS AND AND LIGHT LIGHTTYPES TYPES Sword Swordetetalal

TABLE 4. Radiant exposure (J/cm2) values for curing lights and various barrier covers when considering spectral range of light emission Violet light (350–420 nm) Light unit classification

Broadbanded

Blue-only LED

Polywave LED

Lightcuring unit

Blue light (420–520 nm)

Barrier type

Barrier type

None

Dedicated

Food 1

Food 3

Cure Sleeve

Finger cot

Curelastic

None

Dedicated

Food 1

Food 3

Cure Sleeve

Finger cot

Curelastic

Optilux 501 (QTH)

4.5

3.9

4.2

3.9

3.8



2.8

12.9

11.6

12.2

11.3

11.3



8.6

ARC II M (PAC)

10.2



9.8

9.2

3.5



7.1

36.9



35.6

33.5

26.3



12.6

Magna

0.2



0.2

0.2

0.2

0.1



14.0



13.0

12.7

10.6

10.2



Elipar S10

0.3



0.3

0.3

0.3



0.2

10.4



9.7

9.7

9.0



7.8

BP 20i

2.1

2.0

2.1

1.9

1.9



1.4

9.2

8.6

8.8

8.6

8.1



6.4

VALO

1.7

1.5

1.6

1.5

1.4



1.3

8.5

7.8

8.0

7.6

7.3



6.7

different from that of the uncovered tip for that light (Table 3, 48.2%). In addition, the use of the Cure Sleeve and the VALO light produced 7.3 J/cm2, and resulted in a bottom composite conversion value that was not significantly different from that when no barrier was used for that light. Thus, it seems that this specific composite requires a minimum radiant exposure of approximately 7.3 J/cm2 of blue light to adequately photo-polymerize a 2-mm thick increment. In addition, these results emphasize the fact that polywave lights generally tend to provide less irradiance in the blue spectral region compared with the blue-only units (Table 4). The literature has reported a wide range of energy values necessary to adequately cure a range of composites. These values can be as small as 5.86 J/cm2,19 and as large as 10 J/cm2,20 depending upon the method of analysis and test conditions used. The critical energy level to optimally polymerize this composite determined in the present study of (7.3 J/cm2) is actually confirmed using the composite manufacturer directions for use. For this composite (Premise), the manufacturer recommends 10 seconds of exposure using a LEDemetron I light (blue only) to adequately cure a 2.5-mm thick increment. Our database of 30 LEDemetron LCUs indicates an average value of approximately 900 mW/cm2. A 10-second exposure from this light would thus supply 9 J/cm2. However, adjusting for the more shallow depth of 2 mm indicates that 7.2 J/cm2 should be delivered at that depth.15 Therefore, using manufacturers’ stated

12 40

•• • No No1•• • ••–•• • 2015 Journal of Esthetic Restorative Dentistry Vol 28  29^42  2016 Journal of Esthetic and and Restorative Dentistry

requirements as well as measured light output, the current test results correspond well with manufacturers’ stated instructions. The clinical implications of these findings are significant. In general, the use of barrier films does significantly reduce the amount of energy delivered during an exposure; most of the time, the reduction in radiant energy is not sufficient to result in compromise of the cure of an appropriate thickness of composite increment. However, there are conditions where this trend might not be applied. These data show that a clinician needs to consider the amount of radiant exposure according to the spectral range of the photoinitiator known to be present within the specific product being used. In addition, composite materials are known to have minimum radiant energy requirements for optimal polymerizing.7 Physical property testing of the specimens was not performed, but it may be inferred that composites with higher levels of conversion would demonstrate superior performance.13,14 The selection of a custom barrier (if available) or one-size-fits-all light types (Cure Sleeve and Curelastic) are possibilities and are relatively inexpensive. However, perhaps the most effective and least expensive barrier is the use of a single film of food barrier wrap. In addition, this film could easily be extended to cover the body portion of the curing light, protecting buttons and

C 2015 V DOI 10.1111/jerd.12173 Wiley Periodicals, Periodicals, Inc. DOI 10.1111/jerd.12173 © 2015 Wiley

EFFECT EFFECTOF OFCURING CURINGLIGHT LIGHTBARRIERS BARRIERSAND AND LIGHT LIGHT TYPES Sword Sword et et al

convoluted curing light surfaces from contamination. However, the operator needs to ensure that, if the curing unit relies on air-cooling during operation, the intake or output ports for air flow are not restricted, or thermal damage to the light may result. The limitations of the current study include the fact that only one commercial brand of composite was evaluated, as well as testing a product containing only one type of photoinitiator—camphorquinone—needing only blue light. Future work should focus on the effects of composite shades as well as commercial composites containing multiple photoinitiators, requiring the simultaneous application of both blue and violet light to obtain optimal polymerization, and thus maximum physical properties. In addition, the permeability of commercial barrier materials to oral bacteria and viruses needs to be investigated.

CONCLUSIONS Based on the limitations imposed in the current study, the following conclusions may be drawn:

Mr. Don Mettenburg is thanked for his assistance in infrared spectral measurements.

REFERENCES 1.

2.

3.

4.

5.

6. 7.

There is a significant difference in radiant energy transmission among the different barriers when compared with the nonbarrier-covered tip end. Within a given LCU, there is a significant difference in emitted energy levels among the barrier materials. The attenuation of spectral irradiance through each barrier is generally linear across the emitted spectrum, indicating that the barrier material itself is not acting as a wavelength-dependent light filter. For most all cases, within a barrier material, the type of curing light has no significant influence on monomer conversion at 2-mm composite depth, when conversion values are compared using the barrier with those without the same barrier present. However, the combination of a polywave LED light and a latex-based barrier film might significantly decrease composite conversion.

8.

DISCLOSURE AND ACKNOWLEDGEMENTS

14.

The authors do not have any financial interest in the companies whose materials are included in this article.

15.

C 2015 V © 2015Wiley WileyPeriodicals, Periodicals,Inc. Inc. DOI DOI10.1111 10.1111/jerd.12173 /jerd.12173

9.

10.

11.

12.

13.

US Department of Health and Human Services. MMWR Guidelines for Infection Control in Dental Health-Care Settings—2003. 2003, 52, 66. Caughman GB, Caughman WF, Napier N, Schuster GS. Disinfection of visible-light-curing devices. Oper Dent 1989;14:2–7. Rueggeberg FA, Caughman WF, Comer RW. The effect of autoclaving on energy transmission through light-curing tips. J Am Dent Assoc 1996;127:1183–7. Nelson SK, Caughman WF, Rueggeberg FA, Lockwood PE. Effect of glutaraldehyde cold sterilants on light transmission of curing tips. Quintessence Int 1997;28:725–30. Chong SL, Lam YK, Lee FK, et al. Effect of various infection-control methods for light-cure units on the cure of composite resins. Oper Dent 1998;23:150–4. Warren DP, Rice HC, Powers JM. Intensity of curing lights affected by barriers. J Dent Hyg 2000;74:20–3. Erickson RL, Barkmeier WW, Halvorson RH. Curing characteristics of a composite—part 1: cure depth relationship to conversion, hardness and radiant exposure. Dent Mater 2014;30:e125–33. Scott BA, Felix CA, Price RB. Effect of disposable infection control barriers on light output from dental curing lights. J Can Dent Assoc 2004;70:105–10. Hodson NA, Dunne SM, Pankhurst CL. The effect of infection-control barriers on the light intensity of light-cure units and depth of cure of composite. Prim Dent Care 2005;12:61–7. Pollington S, Kahakachchi N, van Noort R. The influence of plastic light cure sheaths on the hardness of resin composite. Oper Dent 2009;34:741–5. Bagis YH, Rueggeberg FA. Mass loss in urethane/TEGDMA- and Bis-GMA/TEGDMA-based resin composites during post-cure heating. Dent Mater 1997;13:377–80. Davidson CL, Duysters PP, De Lange C, Bausch JR. Structural changes in composite surface material after dry polishing. J Oral Rehabil 1981;8:431–9. Ferracane JL, Mitchem JC, Condon JR, Todd R. Wear and marginal breakdown of composites with various degrees of cure. J Dent Res 1997;76:1508–16. Ferracane JL, Berge HX. Fracture toughness of experimental dental composites aged in ethanol. J Dent Res 1995;74:1418–23. Premise Technical Info, Instructions for Use. 2014. Available at: http://www.kerrdental.com/kerrdental

Journal of of Esthetic andand Restorative Dentistry •• •28No •• 1•••–•• Journal Esthetic Restorative DentistryVol Vol  No 29^42 • 2015 2016

13 41

EFFECT OF CURING LIGHT BARRIERS BARRIERS AND AND LIGHT LIGHTTYPES TYPES Sword Swordetetalal

16.

17.

18.

19.

14 42

-composites-premise-techinfo-2 (accessed December 2, 2014). Rueggeberg FA, Daronch M, Browning WD, De Goes MF. In vivo temperature measurement: tooth preparation and restoration with preheated resin composite. J Esthet Restor Dent 2010;22:314–22. Rueggeberg FA, Hashinger DT, Fairhurst CW. Calibration of FTIR conversion analysis of contemporary dental resin composites. Dent Mater 1990;6:241–9. Price RB, Derand T, Sedarous M, et al. Effect of distance on the power density from two light guides. J Esthet Dent 2000;12:320–7. Nomoto R, Asada M, McCabe JF, Hirano S. Light exposure required for optimum conversion of

•• • No No1•• • ••–•• • 2015 Journal of Esthetic Restorative Dentistry Vol 28  29^42  2016 Journal of Esthetic and and Restorative Dentistry

light activated resin systems. Dent Mater 2006;22:1135–42. 20. Price RB, Felix CM, Whalen JM. Factors affecting the energy delivered to simulated class I and class v preparations. J Can Dent Assoc 2010;76:a94.

Reprint requests: Rhoda Joyner Sword, DMD, College of Dental Medicine, Georgia Regents University, Room GC 4330, 1120 15th Street, Augusta, GA 30912, USA; Tel.: 706-721-2881; Fax: 706-721-8349; email: [email protected] Presented at the 41st Annual Meeting of the AADR, Tampa, FL, March 23, 2012.

C 2015 V DOI 10.1111/jerd.12173 Wiley Periodicals, Periodicals, Inc. DOI 10.1111/jerd.12173 © 2015 Wiley

Effect of Curing Light Barriers and Light Types on Radiant Exposure and Composite Conversion.

Previous research investigated the effects of curing tip barriers on light output and composite properties, but no study has measured the effect of a ...
824KB Sizes 0 Downloads 12 Views