Tooth Bleaching by Different Concentrations of Carbamide ... · 1,000-grit silicon carbide paper in a lapping and polishing unit with water irrigation. It was then etched with 35%

V O L U M E 1 8 , N U M B E R 2 , 2 0 0 6 93

*Research fellow, Division of Restorative Dentistry, Department of Oral and Dental Science, University ofBristol Dental School, Bristol, England†Research technician, Division of Restorative Dentistry, Department of Oral and Dental Science, Universityof Bristol Dental School, Bristol, England‡Professor of restorative dentistry, Adult Dental Health Department, Dental School, Cardiff University,Heath Park, Cardiff, Wales§Reader in medical statistics, Department of Epidemiology, Statistics and Public Health, Cardiff University,Heath Park, Cardiff, Wales||Professor of periodontology, Division of Restorative Dentistry, Department of Oral and Dental Science,University of Bristol Dental School, Bristol, England

Tooth Bleaching by Different Concentrations of Carbamide Peroxide and Hydrogen PeroxideWhitening Strips: An In Vitro Study

MUNTHER SULIEMAN, BDS, LDS RCS (ENG), MSC, PHD*

EMMA MACDONALD, HND, BSC, MSC †

JEREMY S. REES, BDS, PHD, FDS RCS (EDIN)‡

ROBERT G. NEWCOMBE, PHD, CSTAT FFPH§

MARTIN ADDY, BDS, MSC, PHD, FDS RCS (ENG), FDS RCS (EDIN) | |

ABSTRACTObjective: To investigate the tooth whitening effects of various concentrations of carbamide per-oxide (CP) gels and 6% hydrogen peroxide (HP) whitening strips used on an intrinsic, in vitrostain model in a simulated home-applied bleaching protocol.

Method: Extracted third molars were sectioned and stained to Vita shade C4 using a standard-ized tea solution. Stained specimens were then bleached with 10, 15, 20, 22, and 30% CP gelsapplied in custom-made trays for 8-hour sessions for 14 days. A 6% HP whitening strip productwas also tested in a regimen of twice-daily 30-minute treatments for 14 days. Shades wereassessed at baseline and at 2, 5, 7, 10, and 14 days of treatment using a shade guide (SG) and ashade vision system (SVS), recorded as shade guide unit (SGU) changes from baseline, and CIEL*a*b* recordings using a chromometer.

Results: By day 14, all CP treatments resulted in at least 12 SGU improvements by SG and SVSmethods: the HP treatment mean was just less than 12 SGU. With the chromometer, the CPimprovements ranged from approximately 19 to 28 units and 16 units for the HP whiteningstrips. Observationally, by SG and SVS, CP treatments achieved the maximum improvement(12–13 SGU) at different time points: day 5 for 30% CP, day 10 for 22% CP, and day 14 for theother three treatments. SG and SVS data were virtually binary, switching from 0 to scores of 9 orabove as bleaching progressed. The differences between the six treatments in the mean day toachieve a positive SG or SVS score (9 or more units) approached significance. For each of the SG,SVS, and L*a*b* scores, the dose-response correlation with CP concentration was significant atone or more assessment times. SG and SVS showed extremely strong agreement in detectingchange and substantial agreement with L*a*b*.

Conclusion: This in vitro study supports the limited data available from the very few availablerandomized controlled clinical trials indicating that CP and HP home-use bleaching systems canachieve considerable tooth whitening outcomes, albeit at different rates, which appear to be con-centration dependent.

DOI 10.2310/6130.2006.00016

J O U R N A L O F E S T H E T I C A N D R E S T O R A T I V E D E N T I S T R Y94

T O O T H B L E A C H I N G B Y C A R B A M I D E P E R O X I D E A N D H Y D R O G E N P E R O X I D E W H I T E N I N G S T R I P S

Tooth whitening techniqueshave seen renewed interest

from the dental profession as aresult of the public’s desire forwhiter, brighter teeth. The tech-nique of bleaching or whiteningteeth was first described in 18771

but gained general acceptance bythe profession in 1989 with theintroduction of the so-called night-guard vital bleaching (NGVB) tech-nique, which involved theapplication of a 10% carbamideperoxide (CP)-based gel in a bleach-ing tray worn for up to 8 hours atnight.2 Since the introduction of theNGVB technique there have beenmany different modificationsinvolving the bleaching agents used,the type of tray provided, and thetreatment regimen employed.Bleaching agents have included dif-ferent concentrations of CP andhydrogen peroxide (HP) with dif-ferent flavors, thickeners such ascarbopol, and desensitizing agents,such as potassium nitrate. As thetechnique has developed, the traymaterial has tended to becomesofter and thinner and the traydesign has alternated between theuse of reservoirs and scalloping or astraight-cut tray without reservoirs.

Other treatment regimens devel-oped include day use of variousconcentrations of CP and HP forbetween 30 minutes and 4 to8 hours per day. Clinical studieshave shown that a 10% CP gel usedin a bleaching tray at night pro-duces predictable results,3–11 as do5 to 6% HP whitening strips.12 Alaboratory study found that a 16%CP solution bleached more quicklythan the same 5 or 10% solution.However, all concentrations pro-duced a bleaching effect if usedlong enough.13 Similarly, clinicalstudies have compared 10% CPwith 15% CP14 and 20% CP with7.5% HP.15 Both studies found nodifference in the eventual finalshade even though there were initialquicker results with the higher con-centration of CP. There have beenno reported controlled randomizedtrials or in vitro studies comparinga range of different concentrationsof CP that are available to the den-tal professional, namely, 10, 15, 20,22, and 30% solutions.

A recently developed in vitromethod that quantitatively assessesthe effects of tooth whitening prod-ucts16 was used to investigate the

effect of varying HP concentrations,from 5 to 35%, on the toothwhitening process.17 The relation-ship between the number of bleachapplications and the bleaching gelconcentration was exponentialrather than linear. The aim of thepresent study was to investigate thetooth whitening effects of a widerange of professionally availableconcentrations of CP gels (10, 15,20, 22, and 30%) and 6% HPwhitening strips used in simulatedhome-applied bleaching using thesame model in vitro.16

M A T E R I A L S A N D M E T H O D S

The in vitro model used in thisstudy involves the preparation ofinternally stained tooth specimensand three tooth shade assessmentmethods, as described previously.16

In brief, 15 third molar teeth under-went root removal and verticalbisection beginning at the occlusalfissure level. The exposed dentinsurface was polished using a1,000-grit silicon carbide paper in alapping and polishing unit withwater irrigation. It was then etchedwith 35% phosphoric acid toremove the smear layer and exposethe tubule network to promote

CLINICAL SIGNIFICANCEThere is a clear significant relationship for both concentration and duration of exposure for CPbleaching agents. The final shade change is independent of the concentration of bleaching agent,with time as the dominant variable. Higher concentrations of CP that have not been investigatedpreviously may be a treatment option for esthetic improvement of shade where time is at a pre-mium, but caution must be exercised in view of the possible increased incidence of sensitivity.

(J Esthet Restor Dent 18:93–101, 2006)

S U L I E M A N E T A L

V O L U M E 1 8 , N U M B E R 2 , 2 0 0 6 95

stain uptake into the tooth. Teethwere placed in a standard tea solu-tion for stain development for24 hours. The tea solution was pro-duced by boiling 2 g of tea (Marks& Spencer’s Extra Strong Tea,Marks & Spencer, London, UK) in100 mL of water for 5 minutes andfiltered through gauze to removethe tea from the infusion.

Three methods were used to assessstaining:

1. A standard Vita shade guide(SG) (Vita Zahnfabrik, BadSäckingen, Germany)

2. A commercially available clini-cal colorimeter with image-grabbing technology, ShadeVision System (SVS; X-rite,Grandville, MI, USA)

3. An electronic colorimeter (Chro-mometer, Minolta CR 221,Minolta UK, Milton Keynes, UK)

SG and SVS results were recordedas shade guide unit (SGU) values,whereas the chromometric methodyielded CIE L*a*b* values.18

Tooth specimens were prepared,and baseline shades were assessed.One investigator (M.S.) performedall the shade comparisons and wasblind to the allocation of speci-mens. Shade guide assessmentswere made with specimens lying ona black background under the samefluorescent lighting conditions. Ablack background was chosen fol-lowing initial work to determine

shade consistency using the SVS.16

The SVS was used to give a meanVita shade for each of the speci-mens. As with the SG, SVS record-ings were made with specimenslying on a black background. Thechromometer was applied to theouter surface of the enamel not at asingle site but across the wholewidth of the specimen and thereforewithout the use of a jig. The meanL*a*b* values for each specimenwere then calculated.

Only specimens with shade C4 asassessed by the SG and SVS wereaccepted for the study. Thirty speci-mens were allocated randomly tosix treatment groups, each compris-ing five specimens. The shade tabswere arranged in a permutedsequence suggested by the manufac-turer, and each was assigned anumeric value ranging from 1 to 16(B1, A1, B2, D2, A2, C1, C2, D4,A3, D3, B3, A3.5, B4, C3, A4, C4).L*a*b* values for all specimenswere assessed using the chromome-ter. Five concentrations of commer-cially available CP home bleachingagents, 10%A, 15%A, 20%A,22%B, and 30%C, applied in cus-tom-made trays (10%A, 15%A,20%A Opalescence PF: UltradentProducts Inc., South Jordan, UT,USA; Polar 22%B: SDI, Bayswater,Victoria, Australia; 30%C Quickwhite: DMDS UK, Canterbury,UK), and one over-the-counterbrand of 6% HP (equivalent toapproximately 18% CP) polyethyl-ene whitening strip (Crest

Whitestrips, Procter & Gamble,Cincinnati, OH, USA) were used.

All exposed dentin surfaces weresealed using clear nail polish andthen fixed onto a microscope slideusing double-sided adhesive tape sothat only the enamel surface wasexposed for the application of thebleaching agents. The five speci-mens for each treatment groupwere adhered to the same micro-scope slide in line and separated byapproximately 5 mm. The CPbleaching agent was applied togroups 1 to 5 using custom-madebleaching trays. Thus, plasticimpression trays were cut and mod-ified with brown stick compound,and then an alginate impressionwas taken of the specimens on eachslide and a stone model was castwithin 30 minutes. Finally, awhitening tray was fabricated witha reservoir depth of 0.5 mm toallow the bleaching agent to beapplied to the enamel surface of thespecimens. Groups 1 to 5 weretreated with the appropriate con-centration of CP bleaching agentplaced in the trays for 8 hours.Group 6 specimens were treatedwith the HP whitening strips in amanner simulating the manufac-turer’s instructions for use. Thus,each strip was molded by hand toenvelop the five specimens on theslide and left in place for 30 min-utes. This procedure was performedtwice per day. The treatments werecarried out in an airtight containerwith a moist atmosphere created by



placing wet paper towels in thecontainer base, and all treatmentswere terminated after 14 days ofactive treatment. Following eachtreatment cycle, both the teeth andthe whitening tray were cleanedwith a toothbrush and rinsed withwater for 2 minutes. The teeth werethen placed in water for 16 hoursto allow them to rehydrate betweentreatments (Figure 1).

After rehydration following 2 daysof treatment, all samples wereassessed for shade using all threemethods. The bleachingtreatment/rehydration cycles werethen applied again, and the shadeassessments were repeated at 5, 7,10, and 14 days. The shade assess-ments were made in the order ofSG, SVS, and chromometer withgroups of specimens numericallycoded to achieve examiner blind-ness. The SVS and SG data wereexpressed as SGU change. Theequivalent chromometer data wereexpressed as overall color difference∆E* calculated using the followingexpression: ∆E* = √– [(∆L*)2 +(∆a*)2 + (∆b*)2].

The outcome measures for analysiswere SGU change as recorded bySG, SVS, and ∆E* change measuredby the chromometer.

Summary statistics were calculatedfor the three outcomes by treatmentand duration of exposure. SG andSVS scores behaved in an essentiallybinary manner, starting at a shade

change of zero (baseline, C4) foreach specimen and switching to apositive shade change of 9 (C2) to13 (B2) SGUs from baseline atsome subsequent assessment. Thus,for each specimen, the day at whichit first reached a positive value ofnine SGU changes or greater wasdetermined. One-way analysis ofvariance was then used to assesswhether this differed between the

six treatments. To determinewhether there was a significantdose response for the CP treatments(ie, excluding the HP product), cor-relation coefficients at each mea-surement day (days 2, 5, 7, 10, and14) were calculated for L*a*b*,SG, and SVS. A cross-tabulationwas constructed to assess the simi-larity of SG and SVS, expressed asbinary variables. Finally, the degreeof agreement of binary SG and SVSwith L*a*b* was assessed using thestatistic U/mn, which is the Mann-Whitney U statistic divided by theproduct of the two sample sizes. Avalue of 1 (or 0) corresponds toperfect separation between L*a*b*values corresponding to positiveand negative SG or SVS and 0.5corresponds to no difference. Thisstatistic is equivalent to the areaunder the receiver operating curve.Finally, 95% confidence intervals(CIs) for U/mn were calculated. Allstatistical analysis was performedby the medical statistician author(R.G.N.).

R E S U L T S

Tables 1 and 2 show summary sta-tistics for the bleaching effect of thevarious gels measured using theSVS and SG expressed as SGUchange. The equivalent data, deter-mined using the chromometer, areshown in Table 3.

After 14 treatment days, all CPtreatments resulted in a mean of atleast 12 SGU improvements by SGand SVS methods: the HP treatment

Figure 1. Bleaching treatment cycle. CP= carbamide peroxide; HP = hydrogenperoxide.


V O L U M E 1 8 , N U M B E R 2 , 2 0 0 6 97

mean was just under 12 SGU.Assessed by the chromometer, theCP improvements in shade changeexpressed as ∆E* ranged from

approximately 19 to 28 (∆E*)units: the HP treatment achievedaround 16 (∆E*) units of improve-ment. As an observation both by

SG and SVS, CP treatments reachedthe final shade change (12–13 SGU)at day 5 for 30% CP, day 10 for22% CP, and day 14 for the other

TABLE 1. MEAN (SD) CHANGE IN SHADE VISION SYSTEM SCORES ON MEASUREMENT DAYS WITH CARBAMIDE PEROXIDE

AND HYDROGEN PEROXIDE TREATMENTS.

Bleaching Agent Day 2 Day 5 Day 7 Day 10 Day 14

10% CP 0.0 (0.0) 4.4 (6.07) 4.8 (6.57) 4.8 (6.57) 12.0 (0.0)

15% CP 4.8 (6.57) 7.2 (6.57) 7.2 (6.57) 9.6 (5.37) 12.0 (0.0)

20% CP 7.2 (6.57) 9.6 (5.37) 9.6 (5.37) 9.6 (5.37) 12.0 (0.0)

22% CP 4.8 (6.57) 9.6 (5.37) 9.6 (5.37) 12.0 (0.0) 12.0 (0.0)

30% CP 7.2 (6.57) 12.0 (0.0) 12.0 (0.0) 12.0 (0.0) 12.0 (0.0)

6% HP 0.0 (0.0) 4.8 (6.57) 4.8 (6.57) 7.2 (6.57) 11.4 (1.34)

CP = carbamide peroxide; HP = hydrogen peroxide.

TABLE 2. MEAN (SD) CHANGE IN SHADE GUIDE SCORES ON MEASUREMENT DAYS WITH CARBAMIDE PEROXIDE AND

HYDROGEN PEROXIDE TREATMENTS.


10% CP 0.0 (0.0) 4.0 (5.52) 4.4 (6.03) 4.8 (6.57) 12.0 (0.0)

15% CP 4.8 (6.61) 7.2 (6.57) 7.4 (6.77) 9.8 (5.50) 12.2 (0.45)

20% CP 7.0 (6.44) 9.8 (5.50) 9.8 (5.50) 9.8 (5.50) 12.2 (0.45)

22% CP 4.8 (6.57) 9.4 (5.27) 11.8 (0.44) 12.0 (0.0) 12.0 (0.0)

30% CP 7.2 (6.57) 12.0 (0.0) 12.0 (0.0) 12.0 (0.0) 12.0 (0.0)

6% HP 0.0 (0.0) 4.6 (6.31) 4.6 (6.31) 7.0 (6.40) 12.0 (0.0)


TABLE 3. MEAN (SD) CHANGE IN CHROMOMETER READINGS (∆E*) ON MEASUREMENT DAYS WITH CARBAMIDE PEROXIDE

AND HYDROGEN PEROXIDE TREATMENTS.


10% CP 9.85 (4.46) 13.25 (6.14) 16.25 (6.94) 17.63 (7.95) 19.42 (8.67)

15% CP 8.71 (4.36) 13.75 (5.47) 14.75 (4.73) 16.15 (5.83) 18.55 (5.80)

20% CP 10.17 (2.01) 14.24 (2.29) 15.71 (2.61) 16.39 (2.89) 20.02 (3.16)

22% CP 15.56 (3.21) 19.04 (5.13) 23.01 (5.94) 24.54 (6.31) 28.63 (7.11)

30% CP 13.26 (3.15) 17.68 (7.10) 20.32 (10.32) 22.02 (10.06) 25.27 (11.33)

6% HP 9.64 (5.03) 13.21 (3.76) 12.23 (4.98) 14.37 (4.98) 16.49 (4.46)




three treatments. For the HP treat-ment, not all specimens reached the12 to 13 units of improvement byday 14. Chromometer values gener-ally showed steadily increasing val-ues with increasing duration ofexposure to bleaching agents.

Table 4 shows summary statisticsfor the day on which specimens ineach treatment group reached apositive score (9 SGU or higher).For CP treatments the shortest timewas for 30% CP, after which timeincreased successively as the CPconcentration decreased; HP and10% CP were essentially similar.Analysis of variance over the sixtreatments approached significance(SG, p = .064; SVS, p = .091).

Table 5 shows dose-response corre-lation coefficients for CP treatmentoutcome at each measurement dayfor SG, SVS, and L*a*b*. All corre-lations were positive, and eachmeasurement system gave a signifi-cant correlation on at least oneoccasion. For both SG and SVSscores, the time to switch to positiv-ity was, correspondingly, signifi-cantly inversely correlated with CPconcentration. The order of sensi-tivity to detect a significant positivedose-response relationship appearsto be SG > SVS > L*a*b*. Cross-tabulation of SG by SVS as binaryvariables shows that their patternsof switching from negative to posi-tive are very similar, with only onedisagreement for the 150 assess-ments. The degree of agreement of

SG and SVS with L*a*b* usingU/mn was 0.764 (95% CI0.671–0.835) for SG and 0.760(95% CI 0.667–0.831) for SVS,indicating substantial but not per-fect separation.

D I S C U S S I O N

The aim of this study was to assessthe effect of various concentrations

of commercially available home-applied bleaching agents on theresponse of internally stained teethto bleaching. In common with pre-vious studies in vitro,16,17 it seemsthat teeth bleach to an approximateend point (Vita shade D2 in thisstudy).16,17 The present in vitrostudy showed that the HP gel andeach concentration of CP could

TABLE 4. MEAN DAY TO ACHIEVE A POSITIVE SHADE CHANGE SCORE (9 UNITS

OR GREATER) BY SHADE GUIDE AND SHADE VISION SYSTEM WITH CARBAMIDE

PEROXIDE AND HYDROGEN PEROXIDE TREATMENTS.

Treatment Measurement Mean SD

10% CP SG or SVS 10.4 4.9

15% CP SG or SVS 6.6 5.3

20% CP SG or SVS 5.0 5.2

22% CP SVS 4.8 3.3

22% CP SG 4.2 2.2

30% CP SG or SVS 3.2 1.6

6% HP SG or SVS 9.6 4.5

CP = carbamide peroxide; HP = hydrogen peroxide; SG = shade guide; SVS = shade vision system.Based on five specimens per group.

TABLE 5. PEARSON CORRELATION COEFFICIENTS (WITH P VALUES) BETWEEN

CARBAMIDE PEROXIDE CONCENTRATION AND SHADE CHANGE ON EACH

MEASUREMENT DAY RECORDED BY L*A*B*, SHADE GUIDE, AND SHADE VISION

SYSTEM METHODS.

Assessment Time Chromometer SG Score SVS Score

Day 2 0.411 (.042) 0.365 (.073) 0.363 (.074)

Day 5 0.331 (.106) 0.491 (.013) 0.471 (.018)

Day 7 0.297 (.150) 0.520 (.008) 0.447 (.025)

Day 10 0.293 (.155) 0.465 (.019) 0.475 (.016)

Day 14 0.337 (.099) 0.124 (.554) —

Time to reach positive — –0.521 (.008) –0.504 (.010)value (9 or higher)

SG = shade guide; SVS = shade vision system.N = 25 throughout.


V O L U M E 1 8 , N U M B E R 2 , 2 0 0 6 99

improve the shade of internallystained extracted teeth by 12 SGUin 14 days of use. Using the day toreach a positive change (9 SGU orgreater units), the mean SG andSVS scores showed a clear pattern,with 22% and 30% CP achievingthese effects earlier than other con-centrations. The results obtainedwere in agreement with those ofprevious researchers who compareddifferent concentrations of CP.13

The magnitude of the shade changein the present study was larger thanthe previous study in which theteeth used were less heavily stained:the acceptance criterion for theLeonard and colleagues study beingshade A3,13 which is much lowerthan shade C4 used in the presentstudy. Leonard and colleaguesfound the average shade change tobe 4.9 and 6 for incisors andcanines, respectively.13 Similarly, thehigher concentration of 16% CPproduced faster shade changes than5 and 10% CP, but, by the end oftreatment, all teeth reached approx-imately the same end point whiten-ing for all concentrations.

The present study employed theoriginal intrinsic stain modeldevised to study bleaching invitro.16 The same model was usedto investigate the effect of differentconcentrations of HP on the out-come of tooth whitening.16 In bothstudies the total magnitude ofbleaching was similar to thatachieved in the present study.16,17

There was also a clear, significant

dose-response relationship for theduration of exposure in the HPconcentration study,17 as alsoshown here for CP. For all measure-ment methods the correlation coef-ficients were significant on at leastone recording day, with the greatestsensitivity shown with SG and theleast with the chromometer. Never-theless, the agreement betweendichotomized SG and SVS wasextremely high, with substantialagreement between these systemsand L*a*b*. The magnitude ofshade changes in the present studywas broadly similar to, albeit largerthan, that of previous clinical stud-ies.19–21 Heymann and colleaguesreported a mean change of 7 unitson the Vita shade guide afterbleaching with a 10% CP gel over7 days,20 whereas Gerlach andZhou reported a mean change of5.5 units using a whitening strip(6% HP); a quarter of their samplehad a shade change in excess of8 units.19 In the present study, themean change in color (∆E*) bychromometer was used, which ismainly dependent on the change inlightness/darkness (∆L*). Observa-tionally, changes in a* and b* wereas expected, representing a reduc-tion in redness and yellowness, aneffect reported by others.16,17,19,22

The chromometer was applied tothe outer surface of the enamel notat a single site but across the wholewidth of the specimen and thereforewithout the use of a jig. The shadeof each specimen was recorded

from three separate locations takenacross the full width of the speci-men, working from right to left: theinstrument automatically takingthree readings from each site andproviding the average on the print-out. Although a jig is used to ensurerepeat chromometer measurementfrom the same point on a toothclinically, the nature of the speci-mens and their setup on the slidesin this study meant that the use of ajig would not be possible. Hence,readings across the whole width ofthe specimen from right to left pro-vided a mean change in shadeacross the specimen.

The results of the present study, incommon with previous uses of thismodel in vitro, must be interpretedwith caution. With in vivo condi-tions in vital teeth, there is a contin-uous outward movement of fluidthrough dentinal tubules andporous enamel, which would tendto impede the penetration of anapplied bleaching agent. The use ofextracted teeth devoid of dentinalfluid probably allowed the bleach-ing agent to permeate the toothmore quickly than would occur invivo. Indeed, it would be of interestto determine in vivo whether nonvi-tal teeth bleach more easily thanvital teeth. In spite of this reserva-tion, the results of the present studysuggest that the final color changeis independent of the concentrationof bleaching agent used and thattime is the dominant variable. Prac-titioners, however, may wish to use



a higher concentration of bleachingagent to achieve a quicker result forthose patients for whom time is at apremium. This approach may run agreater risk of side effects, such astooth sensitivity.

In conclusion, this in vitro studysupports the limited data from thefew available randomized con-trolled clinical trials involving dif-ferent concentrations indicatingthat CP and HP home-use bleach-ing systems can achieve consider-able tooth whitening outcomes,albeit at different rates, whichappear to be concentration depen-dent. In addition, the study showedthat even using the higher concen-tration of 30% CP gave the sameend shade result as the lowest con-centration of 10% CP, but thewhitening result was achieved muchmore quickly.

D I S C L O S U R E

The authors do not have any finan-cial interest in the companies whosematerials are discussed in this article.

R E F E R E N C E S

1. Greenwall L. Bleaching techniques inrestorative dentistry. London: MartinDunitz; 2001.

2. Haywood VB. History, safety, and effec-tiveness of current bleaching techniquesand applications of the nightguard vitalbleaching technique. Quintessence Int

1992;23:471–8.

3. Haywood VB, Heymann HO. Nightguardvital bleaching. Quintessence Int1989;20:173–6.

4. Howard J. Patient-applied tooth whiten-ers. J Am Dent Assoc 1992;132:57–60.

5. Kowitz GM, Nathoo SA, Rustogi KN, etal. Clinical comparison of Colgate Plat-inum Tooth Whitening system and Rem-brandt Gel Plus. Comp Contin Educ Dent1994;17:S46–51.

6. Matis BA Cochran MA, Eckert G, Carlson TJ. The efficacy and safety of a10% carbamide peroxide bleaching gel.Quintessence Int 1998;29:555–63.

7. Reinhardt JW, Eivins SC, Swift EJ. Clini-cal study of nightguard vital bleaching.Quintessence Int 1993;24:379–84.

8. Russell CM, Dickinson GL, Johnson MH.Dentist-supervised home bleaching with ten per cent carbamide peroxide gel: a six-month study. J Esthet Dent 1996,8:177–82.

9. McCaslin AJ, Haywood VB, Potter BJ, et al. Assessing dentin colour changes fromnight guard vital bleaching. J Am DentAssoc 1999;130:1485–90.

10. Heymann HO, Swift EJ, Bayne SC, et al.Clinical evaluation of two carbamide per-oxide tooth whitening agents. CompendContin Educ Dent 1998;19:359–62.

11. Papathanasiou A, Bardwell DS, Kugel G.A clinical study evaluating a new chairsideand take-home whitening system. Com-pend Contin Educ Dent 2001;22:289–94.

12. Gerlach RW, Zhou X. Vital bleachingwith whitening strips: summary of clinicalresearch on effectiveness and tolerability. J Contemp Dent Pract 2001;2:1–15.

13. Leonard RH, Sharma A, Haywood VB.Use of different concentrations of car-bamide peroxide for bleaching teeth: anin-vitro study. Quintessence Int 1998;29:503–7.

14. Matis BA, Mousa HN, Cochran MA, Eckert GJ. Clinical evaluation of bleachingagents of different concentrations. Quin-tessence Int 2000;31:303–10.

15. Mokhlis GR, Matis BA, Cochran MA,Eckert GJ. A clinical evaluation of car-bamide peroxide and hydrogen peroxidewhitening agents during daytime use. J Am Dent Assoc 2000;131:1269–77.

16. Sulieman M, Addy M, Rees JS. Develop-ment and evaluation of a method in vitroto study the effectiveness of tooth bleach-ing. J Dent 2003;31:415–22.

17. Sulieman M, Addy M, MacDonald E, Rees JS. The effect of hydrogen peroxideconcentration on the outcome of toothwhitening: an in vitro study. J Dent2004;32:295–9.

18. Commission Internationale de l’Eclairage.The L*a*b* system. Wien, Austria: Com-mission Internationale de l’Eclairage;1976.

19. Gerlach RW, Zhou X. Vital bleachingwith whitening strips: summary of clinicalresearch on effectiveness and tolerability. J Contemp Dent Pract 2001;2:1–15.

20. Heymann HO, Swift EJ, Bayne SC, et al.Clinical evaluation of two carbamide peroxide tooth whitening agents. CompContin Educ Dent 1998;19:359–62.

21. Papathanasiou A, Bardwell DS, Kugel G.A clinical study evaluating a new chairside and take-home whitening system.Comp Contin Educ Dent 2001;22:2.

22. Rosensteil SF, Gegauff AG, Johnston WM.Randomised clinical trial of the efficacyand safety of a home bleaching procedure.Quintessence Int 1996;27:413–24.

Reprint requests: M Sulieman, BDS, LDSRCS (ENG), MSc, Department of Oral andDental Science, University of Bristol DentalSchool, Lower Maudlin Street, Bristol BS12LY, UK; e-mail: [email protected]©2006 Blackwell Publishing, Inc.


V O L U M E 1 8 , N U M B E R 2 , 2 0 0 6 101

*Private practice, Pediatric Dentistry, Doylestown, PA; Adjunct professor, Pediatric Dentistry, University of Texas Health Science Center atSan Antonio (Dental School), San Antonio, TX

COMMENTARY

TOOTH BLEACHING BY DIFFERENT CONCENTRATIONS OF CARBAMIDE PEROXIDE

AND HYDROGEN PEROXIDE WHITENING STRIPS: AN IN VITRO STUDY

Theodore P. Croll, DDS*

Experienced dental clinicians who appreciate dental research and its importance to the progression of clinical science intheir practices learn to be wary of in vitro studies. All too often, such studies, regardless of how carefully conceived orrendered, do not take into account that laboratory simulations of intraoral experiences can have limited relevance toactual clinical care. The attraction of the Sulieman and colleagues study is that the investigators understand the prob-lems of in vitro versus in vivo experimentation and designed and executed this work with the goal of gathering resultsmeaningful to clinical dentists.

Levitt and Dubner, in their current bestseller Freakonomics: A Rogue Economist Explores the Hidden Side of Every-

thing, discuss the problems of blindly accepting conventional wisdom and how logical assumptions can be completelydistorted when one takes only a superficial view.1 How surprised the reader is to learn that some bouts in the honorablesport of sumo may be predetermined and that some teachers may be cheating for their students, so that they may appearto be better teachers and receive certain benefits from that deception! By our nature, we apply logic to how we perceiveall things around us and assume that things should be a certain way. Dental experiments and new clinical treatmentideas usually begin with someone’s assumption, and dental science advances as evidence mounts proving or disprovingthe initial thought.

It is logical for a dentist who applies (or prescribes application of) tooth bleaching solutions to patients’ teeth thathigher concentrations of those solutions would work more efficiently. It is also logical to assume that various concen-trations of tooth bleaching solutions would give similar tooth whitening results if the lower concentration fluids wereused for longer times. This study proves those assumptions using three different tooth shade measuring systems andcarefully quantifies the shade measurements.

The authors are prudent and generous to the reader by urging caution in interpreting their results. They cite the phe-nomenon of dentinal fluid dynamics, which could influence internal bleach penetration and saturation. Extracted teethwould not be subject to that variable. Their chief finding, “that the final color change is independent of the concentra-tion of bleaching agent used and that time is the dominant variable,” is a valuable piece of information for the clinicaldentist. Based on this in vitro work, it is now logical for dentists using 10% CP over a longer time period to feel confi-dent that their patients are achieving results similar to those using much higher concentrations. Likewise, dentists usinghigher concentrations of solution whose patients are complaining of tooth sensitivity may be able to offer identicalbleaching results to their patients, with less chance of tooth sensitivity, simply by offering a lower concentration of solution with the recommendation of a longer treatment course.

The value of this work is its practicality and immediate usefulness to dental clinicians. In addition, just as it is elucidat-ing to learn that one’s assumption is incorrect, it is refreshing and encouraging to have one’s correct assumption scien-tifically confirmed.

REFERENCE

1. Levitt, SD, Dubner, SJ. Freakonomics: a rogue economist explores the hidden side of everything. New York: Wm Morrow; 2005.

Documents

Tooth Bleaching by Different Concentrations of Carbamide ... · 1,000-grit silicon carbide paper in a lapping and polishing unit with water irrigation. It was then etched with 35%