The Effect of Delivery System and Light Activation on Tooth Whitening

RESEARCH ARTICLE

The Effect of Delivery System and Light Activation on ToothWhitening Eff|cacy and Hydrogen Peroxide Penetration

SOYOUNG PARK, BM, MM*, SO RAN KWON, DDS, MS, PhD, MS†, FANG QIAN, PhD‡, PHILIP W. WERTZ, PhD§

ABSTRACT

Purpose: To evaluate the whitening eff|cacy of a new two-layer technologyin-off|ce system compared to a conventional gel-type system and determine hydrogen peroxide penetration (HPP) into the pulp cavity. Materials and Methods: Extracted molars (n 5 60) were assigned to group NC: glycerol gel; group QPRO: 20% HP varnish (Zoom Quick Pro,Philips Oral Healthcare); group ZOOM_NL: 25% HPgel (Zoom ChairsideWhitening); and group ZOOM_WL: 25% HPgel (Zoom ChairsideWhitening) withlight-activation.HPP levels were estimated with

leucocrystal-violet and horseradish-peroxidase.Instrumental color measurements were performed at baseline (T0), 1-day post f|rst whitening (T1),1-day post second whitening (T2),1-day post third whitening (T3), and 1-month post whitening (T4).One-way analysis of variance followed by post hocTukey’s HSD test was performed to detect difference in DE*andHPpenetrationlevels(a 50.05). Results: DE*ofNCwaslowerthanothergroups,whereasDE* of ZOOM_WL was greater than the other three

groups, at T3 and T4.Mean HPP level obtained from ZOOM_WL (1.568 6 0.753 lg/mL) was signif|cantlygreater than those obtained fromthe other groups, whereas the mean HPP level observedin NC group (20.131 6 0.003 lg/m L) was signif|cantly lower than the other groups. Conclusions: Tooth whitening eff|cacy and HPP levels vary based on whitening systems used.

CLINICAL SIGNIFICANCE

The two-layer technology in-off|ce varnish system may be an alternative whitening option to reduce chair time in the off|ce. (JEsthet Restor Dent 00:00^00, 2016)

INTRODUCTION home whitening to a variety of over-the-counter products. Tooth whitening is a conservative and effective method to lighten discolored teeth and has become Among the different whitening modalities, an integral component of esthetic dentistry. The professionally administered in-office whitening has popularity is reflected by the wide scope of gained popularity due to the fact that it provides whitening options, ranging from professional in- instant whitening results and that there is no need to office procedures and custom fabricated tray-based wear a tray at home. The efficacy of a variety of

*Dentistry,University of Iowa College of Dentistry & Dental Clinics,Iowa City,Iowa,USA Associate Professor,Program Director,Student Research Program,Loma Linda University School of Dentistry Center for Dental Research,11175 Campus Street CSPA1010C Loma Linda,California,92350, USA `Associate Research Scientist/Adjunct Assistant Professor,Division of Biostatistics and Research Design and Department of Preventive and Community Dentistry,University of Iowa College of Dentistry & Dental Clinics, Iowa City,Iowa, USA ‰Professor,Oral Pathology,Radiology and Medicine, Dows Institute for Dental Research,University of Iowa College of Dentistry & Dental Clinics,Iowa City,Iowa, USA

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systems has been investigated, and many studies have MATERIALS AND METHODS shown that increasing the exposure time and frequency will improve efficacy in terms of tooth color Sample Selection and Preparation change.1–4 Active concentration of the whitening material is another important factor to consider. Sixty extracted human molars were collected prior to However, several studies have shown that the higher the study and stored in 0.1% Thymol at 48C. The the concentration the faster the whitening rate,5–7 University of Iowa Institutional Review Board approved other studies did not find significant differences the use of extracted human teeth with no identifiers in between various concentrations of carbamide this study (IRB ID# 201504753). Teeth were cleaned peroxide.8–10 Furthermore, activating light sources and observed for the absence of anomalies, caries, such as plasma arc lamps, laser systems with a variety existing restorations, and deep crack lines. The roots of wavelengths, and light emitting diodes (LED) have were marked 2 mm apical to the cementoenamel been used to enhance whitening efficacy. However, junction and trimmed off with a sectioning machine study results on the use of light activation in tooth (TechCut 4, Allied High Tech Products, Inc., whitening have been equivocal due to the variability of Compton, CA, USA). A cavity was prepared by study designs and the use of different whitening materials as well as different activating lights.11 enlarging the pulp chamber with pointed tapered diamond burs (NeoDiamond, Microcopy, Kennesaw, Whitening efficacy has also been related to the ability GA, USA) toward the lingual in order to maintain of hydrogen peroxide (HP) to diffuse into the tooth intact labial tooth structure of 2 mm thickness and structure.12 HP diffusion into the pulp cavity was encompass 50 mL of acetate buffer. A circular adhesive enhanced by higher HP concentrations,13 prolonged label 6 mm in diameter was adhered at the center of whitening time,14 heat,14 and large open dentinal the labial surface to establish a standardized color tubules of young teeth.15 LED light and laser activation reading and whitening area. The remaining tooth was demonstrated increased HP penetration levels into the painted with gray nail varnish (Sally Hansen, New pulp cavity,16 but HP levels seemed not to be York, NY, USA), and the adhesive label removed after correlated with whitening efficacy.12 drying, leaving a standardized window.

With the continuous introduction of new in-office whitening systems varying in delivery method and Whitening Protocol concentration, there is lack of information on the relative efficacy of these systems. Henceforth, the The specimens were randomly assigned into four purpose of this study was to evaluate the whitening groups as follows, group NC: glycerin gel (Sigma– efficacy of a new two-layer technology in-office system Aldrich, St. Louis, MO, USA) acting as the negative compared to a conventional gel-type system and control; group QPRO: 20% HP varnish (Zoom determine HP penetration into the pulp cavity. QuickPro, Philips Oral Healthcare); group ZOOM_NL: Additionally, degree of tooth color change was 25% HP gel (Zoom Chairside Whitening, Philips Oral correlated with HP penetration levels. The null Healthcare); without light activation and group hypotheses to be tested was that first, there would be ZOOM_WL: 25% HP gel (Zoom Chairside Whitening, no difference in tooth whitening efficacy in terms of Philips Oral Healthcare) with LED light activation tooth color change in DE*, DL*, and Db* among the (Zoom WhiteSpeed, Philips Oral Healthcare, three different systems tested. Second, there would be peak wavelength: 466 nm) set at high intensity no difference in HP penetration levels into the pulp (190 mw/cm2). The varnish was a one-time application cavity among the different groups. Third, there would for 30 minutes whereas the HP gel was removed and be no correlation between HP penetration levels and replenished with a new gel after 15 minutes as per degree of post whitening overall tooth color change. manufacturer recommendation. A jig was fabricated

2 Vol00No0000^002016 JournalofEstheticandRestorativeDentistry D O I 10.1111/jerd.12238 VC 2016 Wiley Periodicals, Inc. DELIVERY SYSTEM AND LIGHT ACTIVATION IN TOOTH WHITENING Park et al for each specimen by gently placing the lingual surface solution (1 mg/mL), and 1 mL of acetate buffer. The of each tooth into a polyvinyl siloxane impression ﬁnal color intensity was measured in an UV/Visible material (Aquasil Ultra Heavy, Dentsply Caulk, Spectrophotometer (Perkin Elmer, Model Lambda 20, Milford, DE, USA) at a 308 angle from the base. Teeth USA, Waltham, MA, USA) at a wavelength of 596 nm. were kept at room temperature (258C) in a closed A standard calibration curve with known amounts of humid chamber with 100% relative humidity (General HP was used to determine the amount in microgram Glassblowing Co. Lab Apparatus, Richmond, CA, equivalents in the samples. USA) throughout the 30-minute treatment procedure. All teeth were subjected to three whitening sessions with an interval of 3–5 days. Statistical Analysis

Descriptive statistics were conducted to profile all Color Measurements variables in the study. One-way analysis of variance (ANOVA), followed by the post hoc Tukey’s HSD Instrumental color measurements were performed with (honestly significant difference) test, was performed to a contact-type intraoral spectrophotometer (Vita detect both the difference in color parameter values as Easyshade Compact Advance, Vita Zahnfabrik, Bad well as the change in color parameters among the four S€ackingen, Germany) with a 5 mm diameter probe. groups at each post whitening time point. The change The Easyshade Compact was calibrated and placed in each color parameter is defined as the difference perpendicular and flush to the exposed tooth surface between baseline and each post whitening time point. according to manufacturer’s instruction. Color Moreover, one-way ANOVA with repeated measures, measurements were taken at baseline (T ), 1-day post 0 followed by the post hoc contrast test, was used to first whitening (T ), 1-day post second whitening (T ), 1 2 determine whether there was a significant difference in 1-day post third whitening (T ), and 1-month post 3 the color change in each color parameter within each whitening (T ). Measurements were performed under a 4 experimental group. color controlled lightening box (MM 4e GTI Mini Matcher, GTI Graphic Technology, Inc., Newburgh, One-way ANOVA, followed by the post hoc Tukey’s NY, USA) at CIE D , a color temperature of 6,500 K 65 HSD test, was performed to assess the difference in and light intensity of 1,200 lux. Color difference was the HPP levels among the four experimental groups. calculated as DE*ab from the Commission Additionally, Pearson correlation test was used to Internationale de l’Eclairage.17 It was calculated from evaluate the correlation between HPP level and color the following equation: change parameter DE* at 1-month post whitening. All tests utilized a significance level of 0.05. SAS for 2 2 2 1=2 DEab5 ½ðL22L1Þ 1 ða22a1Þ 1 ðb22b1Þ Windows (v9.4, SAS Institute Inc., Cary, NC, USA) was used for the data analysis.

Measurement of HP Penetration Levels RESULTS HP penetration (HPP) levels were measured after the ﬁrst 30-minute whitening treatment and estimated Analysis of Color Change Parameters according to the method of Mottola and colleagues.18 Acetate buffer (40 mL) retrieved from the pulp cavity Baseline color parameters showed that there was no was mixed with 1 mL of leucocrystal violet solution signiﬁcant effect of the type of experimental groups for (0.5 mg/mL), 0.5 mL of horseradish peroxidase L*, a*, and b*(p > 0.05 in all instances).

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Table 1 summarizes the comparison of color change dB dC dB aA parameters from baseline to each post whitening time E_T4 (0.69) (2.76) (SD) (2.82) (2.20) Mean 10.0 1. 3 8 11.74 15.15 D within each group and also comparison among the groups. Assessing the within group effects revealed dC dB dB that the negative control group NC showed no aA b_T4 9. 6 7 8.28 (1.02) (1.99) (SD) (3.06) (2.82) 13.6 6 0.11 D D D

Mean signiﬁcant difference in L*, b*, and E* at all D 2 2 2 treatment time points. Except for NC, there was a signiﬁcant difference in Db* and DE* and among the aA cB cB

aA,B four time points within QPRO, ZOOM_NL, and L_T4 0.40 (1.02) (3.12) (SD) (2.59) (2.37) Mean 5.87 5.35 D 4.45

2 ZOOM_WL with each with least to highest DE* values 0.05).Within each row under the >

p in 1-day post ﬁrst whitening, 1-day post second whitening, 1-day post third whitening, and 1-month cC cB cB aA E_T3 (0.68) (SD) (2.70) (2.06)

(2.54) post whitening, respectively. It is noteworthy to point 7.7 0 Mean 7. 2 3 1. 3 8 D 12.34 out that ZOOM_NL showed no signiﬁcant difference in DL* among the four different time points. When cC cB cB aA evaluating the difference among the groups at 1-day b_T3 (1.81) 5.85 6.57 (1.20) (2.31) (SD) 10.96 (2.36) Mean 0.35 D 2 2

2 post ﬁrst whitening, DE* of NC was lower than other 0.05).

> groups although no difference was found among p QPRO, ZOOM_NL, and ZOOM_WL. At 1-day post aA aB,C b,cC a,bB 0.41 L_T3

(2.51) second whitening, 1-day post third whitening, and (3.32) (SD) (0.67) (2.80) Mean D 2.41 3.36 4.90 2 1-month post whitening, DE* of NC was lower than other groups, whereas DE* of ZOOM_WL was greater aA bC bA,B bA,B than the other three groups. No difference was found E_T2 (1.82) (0.71) (2.01) (SD) (2.33) Mean 1.6 0 9. 5 6 D 6.17 6.63 between QPRO and ZOOM_NL. bB bC bB aA b_T2 4.67 4.39 (1.35) 8.25 (SD) (2.03) (2.24) (2.64) Analysis of HP Penetration Levels Mean 0.20 D 2 2 2

Descriptive statistics are presented in Table 2, and aA aB bB bB Figure 1 illustrates the HP penetration levels among L_T2 0.06 (3.13) (1.89) (1.58) (0.97) (SD) *) from baseline to each post whitening time point by group and within each group Mean 3.87 4.27 3.20 D 2 E the four experimental groups. D

*, and Results of the one-way ANOVA showed that there was aB aB aB aA b D E_T1 (1.81) (2.14) (SD) (0.86) (2.47) 4.51 Mean 1.4 6 4.4 0 3.77 a signiﬁcant effect of the type of whitening systems on D *, L

D the HP penetration levels (F(3,56) 5 33.15; p < 0.0001), indicating a signiﬁcant difference in mean HP aC aA,B aB,C aA penetration level among the four experimental groups. b_T1 3.16 (1.18) (1.57) (SD) 1.7 3 (2.06) (2.22) 0.85 Mean 0.29 D 2 2 2 The post hoc Tukey’s HSD test revealed that mean HP penetration level obtained from ZOOM_WL aB aB aB aA L_T1 (1.03) (3.24) (2.04) (2.27) (1.568 6 0.753 lg/mL) was signiﬁcantly greater than D Mean (SD) those obtained from the other three experimental

Comparison of color change ( groups, whereas the mean HP penetration level observed in NC (20.131 6 0.003 lg/mL) was signiﬁcantly lower than those observed in the other ZO OM _ NL 3.6 5 ZO OM _ WL 2 .21 ihnec ounudrec aibemaue,maswt h aeuprlte r o infcnl ifrn sn h othcue’ HSD the using test each under post each means measured, ( Within column the different with variable hocTukey’s same are upper letter not signif|cantly QPRO 1.95 same color means parameter, with the same lower are using letter the different not post signif|cantly hoc contrasttests ( Group 1-day post ﬁrst whitening 1-day post second whitening 1-day post third whitening 1-month post whitening NC 0.01

TABLE 1. three experimental groups. No signiﬁcant difference

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TABLE 2. Comparison of hydrogen peroxide penetration DISCUSSION levels (lg/mL) among the four groups Group N Mean Minimum Maximum Median The ADA Council on Scientific Affairs advised patients (SD) to consult with their dentist to determine the most NC 15 20.131 20.136 20.124 20.131 appropriate whitening treatment and emphasized that (0.003)A based on data accumulated over the last 20 years there QPRO 15 0.558 0.037 1.741 0.445 are no significant, long-term oral or systemic health (0.485)B risks associated with professional at-home tooth ZO OM _ NL 15 0.615 0.126 1.044 0.574 whitening materials containing 10% carbamide B (0.282) peroxide (3.5% HP).19 This may be the most important ZO OM _ WL 15 1.5 6 8 0.643 3.278 1.751 reason that clinicians use professional at-home tooth C (0.753) whitening as their first treatment option to treat Means withthe same letter are not signif|cantly different using the discolored teeth. Other benefits include relatively low post hocTukey’sHSD test (p > 0.05). cost for the whitening treatment, reduced chair-time, allocation of most of the task to the dental staff and was found between QPRO (0.558 6 0.485 lg/mL) and lower incidence and severity of tooth whitening ZOOM_NL (0.615 6 0.0.282 lg/mL). induced sensitivity when compared to in-office whitening using highly concentrated whitening material.20 However, it is vital to realize our patients’ Correlation of HP Penetration Levels and Overall Color needs and embrace alternatives to accommodate most Change at 1-Month Post Whitening everybody desiring whiter and brighter teeth. In-office whitening offers the benefit of faster whitening results No significant difference was found between HP that can motivate the patient to continue treatment. It penetration levels and DE* within NC, QPRO, is also highly appreciated by patients that cannot ZOOM_NL, and ZOOM_WL using the Pearson comply with wearing trays. However, the prolonged correlation test (p > 0.05 in all instances). However, chair time, advocated use of light activating units and there was a significant difference when combining all higher incidence of tooth sensitivity were significant groups together (p < 0.0001). Thus, the Pearson drawbacks that limited its use to patients that could correlation coefficient of 0.68 indicated a moderate afford the higher cost and would tolerate the tooth positive relationship between HP penetration levels and whitening induced sensitivity. overall color change Figure 2.

FIGURE 2. Correlation of hydrogen peroxide penetration FIGURE 1. Hydrogen peroxide penetration levels by groups. level to overall tooth color change.

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Manufacturers have put efforts in overcoming these controlled environment and a 50:50% acceptability drawbacks and realized that they could make a more threshold of DE* 5 2.7 was used to interpret tooth user-friendly system by changing their delivery method color change results.34,35 Notably, regardless of from the conventional gel type to a two-step varnish whitening system there was a significant increase system. Philips Zoom Quick Pro that was used in this with continuous whitening sessions. study is comprised of a first layer of 20% HP varnish followed by a second sealant layer that locks the HP The tooth is permeable and Bowles and Ugwuneri layer into place and prevents inadvertent exposure to were the first to spectrophotometrically detect the the surrounding tissue. The system was released in the amount of HP penetration into the pulp cavity.13 This USA in 2014.21 Upon application of the two layers, in vitro model proved useful for further studies which takes about 5 minutes in the office, the patient investigating various factors that might influence HPP can leave the office and peal off the adhesives at home into the pulp cavity and was also used for this study. after 30 minutes. This reduces the in-office chair time Our second null hypothesis was rejected, since there significantly and there is also no need for the use of was a significant difference in HPP levels among the light activation. However the efficacy and the four groups with the light activated group incidence of sensitivity associated with this two-layer (ZOOM_WL) demonstrating the highest HPP level technology have not been well documented. This and no difference between the varnish system (QPRO) study evaluated the efficacy of this new varnish and the nonlight activated (ZOOM_NL) group which system compared to a 25% HP gel used with and interestingly followed the same pattern as for overall without light activation. color change. The increase in HPP levels with light activation is very consistent with another study that Based on the results, our first null hypothesis was has shown increased levels with laser and LED lights.36 rejected. There was a significant difference in overall Increased concentration is also associated with higher color change based on the whitening system used. At penetration levels.13,37–39 Although there was a 1-month post whitening the light activated group difference in concentration between QPRO and (ZOOM_WL) demonstrated the highest overall color ZOOM_NL, the concentrations of HP found in the change supporting the efficacy of light activation buffer in the pulp cavities were not significantly used in conjunction with 25% HP. This is in different. The ability to penetrate into dental hard concordance with other studies that showed that tissue has also been related to the rheologic properties light activation enhances the degree of lightening and of the material.40 On the basis of viscosity difference, it reduction of chroma.22–28 The use of light activation would have been expected to observe more HPP with is still a topic of dispute and there are also in vitro the 25% HP gel compared to the 20% HP varnish. This and clinical trials indicating that light activation does suggests that other proprietary factors may have been not affect the change in color produced by exerting a modulating influence. This may have to be whitening.29–33 However, it important to point out investigated further to determine the effect of that the 20% HP varnish (QPRO) was as effective as formulation on HP penetration. the 25% HP gel without light activation (ZOOM_NL). To the best of our knowledge there are Our third hypothesis was rejected. Despite the fact no studies on the efficacy of this in-office varnish that within each group there was no correlation system compared to the gel system and although between overall color change and HPP levels, when there was a difference in formulation and combining all the groups together there was a modest concentration, it was as effective in terms of overall correlation (r 5 0.68) indicating that the higher the color change. Our study used the widely adopted HPP level the higher the overall color change. Studies color difference formula within dental research, that evaluated the correlation between HPP level to derived from the CIE-L*a*b* system. The 50:50% overall color change are scarce. One study compared perceptibility threshold of DE* 5 1 which is used in a 40% HP using a sealed technique without

6 Vol00No0000^002016 JournalofEstheticandRestorativeDentistry D O I 10.1111/jerd.12238 VC 2016 Wiley Periodicals, Inc. DELIVERY SYSTEM AND LIGHT ACTIVATION IN TOOTH WHITENING Park et al replenishment of the whitening material versus the Research Grant, the University of Iowa College of conventional technique where the material is Dentistry. Whitening materials were kindly provided replenished every 20 minutes.12 However, another by Philips Oral Healthcare. study compared the use of 40% HP with and without light activation.23 Both studies found that there was no correlation between HPP levels and overall color REFERENCES change.12,23 This may seem contradictory to our results; however, it important to notice that even in 1. Kihn P, Barnes DM, Romberg E, et al. Clinical evaluation of our study we did not find any correlation within the a 15% in-office HP tooth-whitening touch-up agent. Comp Contin Educ Dent 2002;23:939–46. four groups. It was only when we combined all groups 2. Al SS, Matis BA, Cochran MA, et al. A clinical evaluation of together that we found a modest correlation. It is two in-office bleaching products. Oper Dent 2003;28:488–95. noteworthy to emphasize that penetration levels 3. de Silva GM, Brackett MG, Haywood VB. Number of in- cannot be measured clinically. It is also important to office light-activated bleaching treatments needed to point out that penetration studies are limited by the achieve patient satisfaction. Quint Int 2006;37:115–20. absence of the dynamics in the oral environment 4. Matis BA, Cochran MA, Franco M, et al. Eight in-office including the absence of positive pulpal pressure. tooth whitening systems evaluated in vivo: a pilot study. Oper Dent 2007;32:32227. Additionally, the pulp cavity has to be enlarged to 5. Sulieman M, Addy M, MacDonald E, Rees JS. The effect of enable quantification using acetate buffer, leucocrystal HP concentration on the outcome of tooth whitening: an in violet, and horseradish peroxidase that compromises vitro study. J Dent 2004;32:295–9. the resemblance to in vivo. Despite these limitations 6. Auschill TM, Hellwig E, Schmidale S, et al. Efficacy, side- higher HPP levels may be also associated with higher effects and patients’ acceptance of different bleaching incidence and severity of tooth whitening induced techniques (OTC, in-office, at-home). Oper Dent 2005;30: 156–63. sensitivity. As such, it would be beneficial to develop 7. da Costa JB, McPharlin R, Paravina RD, Ferracane JL. or aim for a whitening system with minimal HPP Comparison of at-home and in-office tooth whitening using without compromising tooth whitening efficacy. a novel shade guide. Oper Dent 2010;35:381–8. 8. Matis BA, Mousa HN, Cochran MA, Eckert GJ. Clinical Within the limitations of this study it can be evaluation of bleaching agents of different concentrations. concluded that the two-layer technology in-office Quint Int 2000;31:303–10. varnish system was as effective as the conventional gel- 9. Krause F, Jepsen S, Braun A. Subjective intensities of pain and contentment with treatment outcomes during tray type system without light activation and that light bleaching of vital teeth employing different carbamide activation enhanced the whitening efficacy. The peroxide concentrations. Quint Int 2008;39:203–9. hydrogen peroxide penetration levels were positively 10. Meireles SS, Heckmann SS, Leida FL, et al. Efficacy and correlated with overall tooth color change. Future safety of 10% and 16% carbamide peroxide tooth-whitening studies addressing the clinical efficacy, incidence and gels: a randomized clinical trial. Oper Dent 2008;33:606–12. severity of tooth sensitivity, patient satisfaction, and 11. Buchalla W, Attin T. External bleaching therapy with activation by heat, light or laser: a systematic review. Dent acceptance toward this new in-office varnish system Mater 2007;23:586–96. are needed to support the evidence behind this new 12. Kwon SR, Wertz PW, Dawson DV, et al. The relationship of technology. HP exposure protocol to bleaching efficacy. Oper Dent 2013;38:177–85. 13. Bowles WH, Ugwuneri Z. Pulp chamber penetration by HP DISCLOSURE AND ACKNOWLEDGEMENTS following vital bleaching procedures. J Endodont 1987;13: 75–7. 14. Rotstein I, Torek Y, Lewinstein I. Effect of bleaching time The authors do not have any financial interest in the and temperature on the radicular penetration of HP. companies whose materials are included in this article. Endodont Dent Traumatol 1991;7:196–8. This study was supported in part by funding from the 15. Camps J, de Franceschi H, Idir F, et al. Time-course Dows Student Research Fellowship and Iowa Dental diffusion of HP through human dentin: clinical significance

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