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d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 165–169

avai lab le at www.sc iencedi rec t .com

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pectrophotometric and visual evaluation of vitalooth bleaching employing different carbamideeroxide concentrations

ndreas Braun ∗, Søren Jepsen, Felix Krauseepartment of Operative and Preventive Dentistry, University of Bonn, Welschnonnenstrasse 17, 53111 Bonn, Germany

r t i c l e i n f o

rticle history:

eceived 29 August 2005

ccepted 4 January 2006

eywords:

ital tooth bleaching

pectrophotometer

isual shade matching

arbamide peroxide

CH color space

ightness

hroma

a b s t r a c t

Objective. The aim of the present study was to assess the hypothesis that the efficiency of

vital tooth bleaching depends on the concentration of carbamide peroxide agents.

Methods. The front teeth of 30 subjects were bleached at home with 10%, 17% or 0% (con-

trol) carbamide peroxide for 1 week in a double-blind study design. Tooth shades were

determined in the LCH color space employing a visual shade matching system and a spec-

trophotometer. Differences in lightness (�l), chroma (�c) and hue (�h) were measured to

assess the treatment process. After 2 weeks of no treatment, tooth shades were evaluated

again to assess stability of the resultant shade.

Results. First-time changes of shade values could be observed after 3 days in the 17% group

and after 7 days in the 10% group. After 1 week, in both the 17% group (�l: 2.80, �c: −3.33,

�h: 0.60) and the 10% group (�l: 2.61, �c: −2.54, �h: 0.09), values for lightness and chroma

were significantly different from the control (�l: 0.13, �c: 0.14, �h: 0.21, p < 0.05) with no

difference between the test groups (p > 0.05). Two weeks after treatment, a rebound of shade

ue values could be observed in the test groups (p < 0.05).

Significance. The study indicates that higher concentration bleaching agents might whiten

teeth faster with major changes in lightness and chroma. However, by bleaching daily for 1

week, similar effects can be achieved with both a high and a low concentration agent. After

treatment, a regression of the resultant shade has to be expected.

© 2006 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

. Introduction

ital tooth bleaching is an increasingly requested dental treat-ent. Especially by whitening their front teeth, patients want

o improve their esthetic appearance. In contrast to moreggressive methods like crowns or resin-bonded veneers, vitalooth bleaching is considered a more conservative approach to

act chemically with organic pigment molecules contained indental hard tissues, reducing them to smaller, less pigmentedmolecules [3]. In the past, a 10% concentration of carbamideperoxide was considered as the standard [4,5]. In an attempt toincrease the efficiency of the bleaching agents, higher concen-trations were also used [6,7]. However, most studies on toothwhitening relied solely on a subjective color matching tech-

ightening teeth. Carbamide peroxide is a well-accepted agentor at-home bleaching supervised by a dentist [1,2]. Usually ael, it is applied to the external surfaces of teeth with a cus-omized tray. Bleaching occurs as unstable free radicals inter-

∗ Corresponding author. Tel.: +49 228 287 2428; fax: +49 228 287 2444.E-mail address: andreas.braun@uni-bonn.de (A. Braun).

109-5641/$ – see front matter © 2006 Academy of Dental Materials. Puoi:10.1016/j.dental.2006.01.017

nique to evaluate the outcome of bleaching procedures [8–11]and only a few controlled clinical trials reported the effectsof higher concentration agents. Therefore, the aim of thepresent study was to evaluate the efficiency of two different

blished by Elsevier Ltd. All rights reserved.

l s 2 3 ( 2 0 0 7 ) 165–169

Fig. 1 – Assessment of color changes employing thespectrophotometer software: photos were superimposeddigitally (a), changes in the LCH color space were calculated

166 d e n t a l m a t e r i a

concentrations of carbamide peroxide using both a subjectiveshade matching system and a spectrophotometric analysis ina double-blind study design. Also, any possible rebound effectafter discontinuation of treatment should be assessed, regard-ing changes in lightness, chroma and hue in the LCH colorspace.

2. Materials and methods

Thirty patients, each of whom had no teeth discolored forextrinsic or intrinsic reasons, were treated in a double-blindstudy design. The local Ethics Committee had been notifiedand patients had given their informed consent to their par-ticipation in the study. Calculus and stain were removed withan ultrasonic instrument (Siroson S, Siemens, Bensheim, Ger-many), a rubber cup and a polishing paste (Proxyt, Vivadent,Ellwangen, Germany) at least 2 weeks before the bleachingtreatment phase of the study was initiated. During the samevisit, alginate impressions were taken of the maxillary andmandibular arch of each patient. The facial surfaces of thefront teeth were blocked out on the study cast from a dis-tance of approximately 0.5 mm coronally to the gingival mar-gin to the incisal edge. Customized trays were fabricated by avacuum-formed process according to the manufacturer’s rec-ommendations. The oral and facial surfaces of the trays weretrimmed just short of the gingival margins.

Tooth shades of the upper and lower front teeth weredetermined in the LCH color space by an operator experi-enced in color evaluation employing a visual shade matchingsystem with all shades systematically placed at exactly �E(Vitapan 3D, Vita Zahnfabrik, Bad Saeckingen, Germany). First,lightness of the teeth was assessed by selecting the closestmatch from one of five value groups. Second, chroma wasassessed within that group from three choices. Third, huewas selected by determining if the tooth was more reddish ormore yellowish than the shade sample selected. All subjectiveshade assessments were made under constant light condi-tions. Additionally, tooth shades of the upper and lower frontteeth were determined in the LCH color space using a spec-trophotometer (SpectroShadeTM, MHT, Niederhasli, Switzer-land), which allowed images to be taken that were uninflu-enced by variables that could affect a visual determination,such as visual perception, office lighting or time of day. Valuesfor lightness, chroma and hue were displayed by the personalcomputer of the spectrophotometer system. Tooth dehydra-tion during the shade evaluation procedures was avoided byallowing the patients to close their mouth frequently through-out the shade matching process.

The bleaching agents used in the study were fabricatedand analyzed by the manufacturer (Voco, Cuxhaven, Germany)to determine the exact percentage of carbamide peroxide.Unmarked syringes containing either a 0% (control), 10% or17% concentrated gel were packed in equal treatment kitsnumbered consecutively, so that neither the operator nor thepatient was aware of the concentration. After stratification of

the patients by gender, age and baseline shade, these kits wereassigned to the patients by a different operator who was awareof the peroxide concentrations but did not participate in thestudy otherwise. Subjects were instructed to wear the bleach-

and given numerically (b) and graphically (c).

ing trays from 7 p.m. to 9 p.m. every day for 1 week starting onMonday. Tooth shades were assessed daily from Tuesday toFriday and on Monday of the next week, employing the visualshade matching system. At the end of the treatment phase onMonday an additional spectrophotometric shade analysis wasperformed (Fig. 1). During the following 2 weeks patients didnot perform any bleaching procedure. Tooth shades were eval-uated again with the visual shade matching system after 1 andafter 2 weeks to assess any possible rebound effect followingdiscontinuation of treatment. To avoid bias, all results werenoted on separate forms by a second operator. Additionally, atthe end of the second week another spectrophotometric anal-ysis was performed.

For statistical analysis, normal distribution of the valueswas evaluated with the Shapiro–Wilk test. As both the valuesof the visual shade matching system and the spectrophotome-ter were normally distributed, analysis of variance (ANOVA)with subsequent comparison of mean values (Scheffe) wasused to compare lightness, chroma and hue for the differ-ent carbamide peroxide concentrations over time. Changesin lightness, chroma and hue directly after bleaching and 2weeks after treatment were analyzed using the Wilcoxon two-sample paired signed rank test. Differences were consideredas statistically significant at p < 0.05.

3. Results

3.1. Visual shade matching system

First-time application of the bleaching gels did not result inany increase of lightness in either the control or the exper-imental groups (p > 0.05, Table 1). Hereupon, in the 17% per-

d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 165–169 167

Table 1 – Visually assessed tooth lightness during the 1 week of bleaching and weekly after treatment depending on theconcentrations of the bleaching agents

Lightness [U]

0% 10% 17%

Mean S.D. p (0%–10%) Mean S.D. p (10%–17%) Mean S. D. p (0%–17%)

Baseline 2.8 0.4 >0.05 2.9 0.3 >0.05 3.0 0.5 >0.05Day 1 2.6 0.3 >0.05 2.5 0.3 >0.05 2.6 0.4 >0.05Day 2 2.7 0.3 >0.05 2.5 0.3 >0.05 2.3 0.4 >0.05Day 3 2.5 0.3 >0.05 2.3 0.2 >0.05 2.0 0.5 0.017Day 4 2.6 0.4 >0.05 2.2 0.2 >0.05 1.9 0.6 0.005Day 7 2.5 0.3 0.002 2.0 0.3 >0.05 1.8 0.3 <0.001Day 14 2.5 0.3 0.013 2.1 0.3 >0.05 1.9 0.4 0.001Day 21 2.7 0.4 <0.001 2.0 0.3 >0.05 1.9 0.3 <0.001

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Differences between the groups were evaluated using ANOVA with suFrom the seventh day values in the 10% peroxide group and from the(p < 0.05).

xide group a faster increase in lightness could be observedhan in the 10% group; from the seventh day, values in the0% peroxide group and from the third day, values in the 17%

eroxide group differed from the control group (p < 0.05). Afterdays of treatment, whitening of the teeth in the 17% perox-

de group (lightness: 1.8 ± 0.3 U) was no more efficient thann the 10% group (lightness: 2.0 ± 0.3 U) (p > 0.05). Both val-

ig. 2 – Spectrophotometrically evaluated tooth colors. Afterleaching for 1 week in both test groups, a significantncrease in lightness, decrease of chroma and slightncrease in hue could be observed as compared to theontrol. There was no difference between the values in theest groups (p > 0.05). After 2 weeks, a statisticallyignificant decrease in values for lightness and chromaith no difference between the test groups could be

bserved.

ent Scheffe test and considered as statistically significant at p < 0.05.day values in the 17% peroxide group differed from the control group

ues were statistically different from lightness in the controlgroup (2.5 ± 0.3 U). Two weeks after bleaching, lightness in bothtest groups decreased, but was still higher than in the controlgroup (p < 0.05). Values for chroma tended to decrease in thetest groups with no statistical difference to the control group(p > 0.05), and values for hue did not change (p > 0.05).

3.2. Spectrophotometric analysis

Overall, directly after bleaching for 1 week, in both test groupswith either 17% (�l: 2.80, �c: −3.33, �h: 0.60) or 10% peroxide(�l: 2.61, �c: −2.54, �h: 0.09) a significant increase of light-ness, decrease of chroma and slight increase in hue could beobserved, as compared to the control group (�l: 0.13, �c: 0.14,�h: 0.21, p < 0.05, Fig. 2). There was no statistical differencebetween the values in the 17% and the 10% groups (p > 0.05).After 2 weeks, a statistically significant decrease in the valuesfor lightness and chroma could be observed in the test groups(p < 0.05) with no change of hue (p > 0.05). Since there was asimilar decrease in the 17% group (�l: 2.07, �c: −2.35, �h: 0.07)and in the 10% group (�l: 1.98, �c: −2.31, �h: 0.47), final valuesdid not differ (p > 0.05). Regarding the different types of teethincluded in the study, major changes of shade values couldbe found for canines (Fig. 3). Changes of lightness, chromaand hue were statistically different from those observed forincisors (p < 0.05).

4. Discussion

Using the same parameters as of the spectrophotometer todescribe the tooth shade in the LCH color space, the visualshade matching system employed in the present study and thespectrophotometer complemented one another. The visualmatching system allowed the daily effects of the whiteningprocedures to be noticed, and the spectrophotometer valuesverified these effects at intervals of 1 and 2 weeks. Employ-

ing this study design, the major hypothesis that the efficiencyof vital tooth bleaching does depend on the concentrationof carbamide peroxide agents could only be verified to someextent. Even though whitening of the teeth in the 17% per-

168 d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 165–169

Fig. 3 – Spectrophotometrically assessed lightness, chroma and hue after bleaching in the 10%, 17% and control groups fordifferent jaw and tooth types directly after bleaching for 1 week and after an additional 2 weeks without performing any

antly

bleaching procedure. Values for the canines differed signific

oxide group could be observed earlier than in the 10% group,after 1 week, shade values assessed both with visual shadematching and the spectrophotometer did not differ among thegroups. This result raises the question as to whether highlyconcentrated agents are necessary for vital tooth bleaching. Itis widely accepted that tooth sensitivity is a common sideef-fect of external tooth bleaching [12]. This sensitivity normallypersists for up to 4 days after cessation of the treatment [13].However, a longer duration of sensitivity of up to 39 days hasalso been reported [14,15]. The mechanisms that cause dis-comfort have not yet been fully established, but they might beassociated with peroxide penetration of enamel and dentin[16], reaching even the pulp chamber [17]. The amount of per-oxide in the pulp chamber is related to the concentration ofthe bleaching agent [18]. As the present study could demon-strate that the whitening effect of either a 10% or a 17% agentis not different after 1 week, a low concentrated bleachinggel seems to be more advisable to prevent tooth sensitivity.Reviewing biological aspects, the recommendation is to avoid

the use of concentrations higher than 10% carbamide perox-ide for external vital bleaching [19]. Furthermore, evaluatingthe efficiency of a tooth whitening gel containing 25% car-bamide peroxide and a gel containing 8.7% hydrogen peroxide,

from values measured for the incisors (p < 0.05).

no statistical difference in tooth whitening could be observed[20]. Another study compared a tooth whitener containing 5%and one containing 10% carbamide peroxide. Assessing theefficiency of bleaching over a period of 1 week the authorssuggested that the whitening gels were clinically equivalent[21]. Using a value-oriented shade guide, there was no sta-tistical difference between the outcome of a 10% and a 15%carbamide peroxide containing gel after 1 week’s application[6].

In the present study, bleaching trays were constructed withfacial reservoirs for the whitening agent. One could argue thatthe thickness of these reservoirs might have influenced theeffectiveness of the bleaching gels. Assessing the impact ofreservoirs on tooth whitening, it could be demonstrated by acolorimeter that teeth treated with trays without reservoirswere significantly darker than teeth lightened with reservoirs[22]. However, the difference was below the threshold of visualdifferentiation. The reservoirs of bleaching trays in the presentstudy did not differ to a great extent. Thus, the size of the facial

reservoirs might have had only a minor impact on the presentresults.

Assessment of tooth color can be affected by the surround-ing light [23]. In the present study, it was not important to

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udge the color shade which matches the tooth in daylight buto assess color changes caused by the bleaching procedure.or this reason, visual shade matching took place under con-tant light conditions in a room only illuminated by artificialight. Spectrophotometric shade analysis was not affected byhe surrounding light, as it was possible to isolate a tooth withhe optical mouthpiece of the optic handpiece. Likewise, thepectrophotometric evaluation was not performed to assesshe exact tooth color in daylight but focused on assessing colorhanges over time.

Employing subjective and objective methods for assessingooth color variations, the present study indicates that both

10% or a 17% concentrated bleaching gel might result inimilar tooth whitening after 1 week. The higher concentra-ion bleaching agent is capable of whitening teeth faster with

ajor changes in lightness and chroma. However, taking intoccount the biological aspects, it is advisable to use the lowoncentration agent to avoid side effects such as tooth sensi-ivity.

e f e r e n c e s

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[2] Attin T, Hannig C, Wiegand A, Attin R. Effect of bleaching onrestorative materials and restorations: a systematic review.Dent Mater 2004;20:852–61.

[3] Feinman RA, Goldstein RE, Garber DA. Bleaching teeth.Chicago: Quintessence Publ. Co.; 1987.

[4] Haywood VB. Nightguard vital bleaching: current conceptsand research. J Am Dent Assoc 1997;128(Suppl.):19–25.

[5] Haywood VB, Robinson FG. Vital tooth bleaching withnightguard vital bleaching. Curr Opin Cosmet Dent1997;4:45–52.

[6] Kihn PW, Barnes DM, Romberg E, Peterson K. A clinicalevaluation of 10 percent vs. 15 percent carbamide peroxidetooth-whitening agents. J Am Dent Assoc 2000;131:1478–84.

[7] Matis BA, Mousa HN, Cochran MA, Eckert GJ. Clinical

evaluation of bleaching agents of different concentrations.Quintessence Int 2000;31:303–10.

[8] Brunton PA, Ellwood R, Davies R. A six-month study of twoself-applied tooth whitening products containing carbamideperoxide. Oper Dent 2004;29:623–6.

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[9] Heymann HO, Swift Jr EJ, Bayne SC, May Jr KN, Wilder Jr AD,Mann GB, et al. Clinical evaluation of two carbamideperoxide tooth-whitening agents. Compend Contin EducDent 1998;19:359–62.

[10] Sielski C, Conforti N, Stewart B, Chaknis P, Petrone ME,DeVizio W, et al. A clinical investigation of the efficacy of atooth-whitening gel. Compend Contin Educ Dent2003;24:612–8.

[11] Swift Jr EJ, May Jr KN, Wilder Jr AD, Heymann HO, Bayne SC.Two-year clinical evaluation of tooth whitening using anat-home bleaching system. J Esthet Dent 1999;11:36–42.

[12] Tam L. The safety of home bleaching systems. J Can DentAssoc 1999;65:453–5.

[13] Schulte JR, Morrissette DB, Gasior EJ, Czajewski MV. Theeffects of bleaching application time on the dental pulp. JAm Dent Assoc 1994;125:1330–5.

[14] Leonard RH, Haywood VB, Phillips C. Risk factors fordeveloping tooth sensitivity and gingival irritationassociated with nightguard vital bleaching. Quintessence Int1997;28:527–34.

[15] Tam L. Clinical trial of three 10% carbamide peroxidebleaching products. J Can Dent Assoc 1999;65:201–5.

[16] Sulieman M, Addy M, Macdonald E, Rees JS. The bleachingdepth of a 35% hydrogen peroxide based in-office product: astudy in vitro. J Dent 2005;33:33–40.

[17] Thitinanthapan W, Satamanont P, Vongsavan N. In vitropenetration of the pulp chamber by three brands ofcarbamide peroxide. J Esthet Dent 1999;11:259–64.

[18] Goekay O, Yilmaz F, Akin S, Tuncbılek M, Ertan R. Penetrationof the pulp chamber by bleaching agents in teeth restoredwith various restorative materials. J Endod 2000;26:92–4.

[19] Dahl JE, Pallesen U. Tooth bleaching: a critical review of thebiological aspects. Crit Rev Oral Biol Med 2003;14:292–304.

[20] Nathoo S, Stewart B, Petrone ME, Chaknis P, Zhang YP,DeVizio W, et al. Comparative clinical investigation of thetooth whitening efficacy of two tooth whitening gels. J ClinDent 2003;14:64–9.

[21] Nathoo S, Santana 3rd E, Zhang YP, Lin N, Collins M, KlimpelK, et al. Comparative seven-day clinical evaluation of twotooth whitening products. Compend Contin Educ Dent2001;22:599–604.

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