122 > SummARy Background: Several tooth whiteners are available on the market, and the ideal choice should be determined by ef- ficacy and optimal clinical results. objectives: The purpose of this study was to compare the reported clinical success rates of different tooth whitening products. search strategy: The relevant literature (1998 - 2011) was studied, using as sources the databases: Google Scholar, Science Direct, Medline and Pubmed. selection criteria: The material was clearly identified, the manufacturers’ instructions were respected and the sample size stated. results and conclusions: This descriptive report on 49 papers focuses on the total colour change, measured with a calibrated shade guide and also numerically (colourime- ter, chromameter or spectrophotometer), the relapse of the colour change and tooth sensitivity. in general, the dentist- supervised at-home bleaching and the in-office treatment gave approximately the same initial percentage improvement of tooth whitening. However, the relapse after a four week or longer period was significantly higher for the in-office treat- ment. The treatment of choice should be a dentist super- vised at-home bleaching product which generally contains ~10% carbamide peroxide applied over about 14 days for about eight hours per night. Tooth sensitivity should not be a general problem although some subjects might choose to discontinue treatment as a result of sensitivity. bAckgRound Dentists in clinical practice are faced with a large number of tooth whiteners available and advertised on the market. Fur- thermore, they are bombarded with results based on labora- tory studies and to a lesser extent on clinical studies.1-4 How then does the dentist select a tooth whitener which will be effective and provide optimal clinical results? important also is the extent of colour relapse over time. Peroxide is the chemical most frequently used as a tooth whitening agent with two types being generally employed i.e. hydrogen peroxide (H2O2) or carbamide peroxide (CH6N2O3). Due to the instability of hydrogen peroxide it is mostly added to the whitener just before the application process, while carbamide peroxide is the more stable oxidising agent and can be included in the whitener itself. Thus, the hydrogen peroxide can be applied directly to the tooth surface as such or is produced from carbamide peroxide (CH6N2O3, or CH4N2O. H2O2) which dissociates into hydrogen peroxide (H2O2) and urea (N2H4CO) upon contact with water. 5,6 Urea further breaks down into ammonia and carbon dioxide. it has been reported7 that a 10% carbamide peroxide solu- tion can produce only about 3 – 3.35% hydrogen peroxide. Hydrogen peroxide is a very strong oxidising agent. When it decomposes it forms free radicals (O˙ and HO2˙) 5,6 which are responsible for the strong bleaching effect on organic and inorganic chemicals in and on enamel and dentine. However, more of the stronger per-hydroxyl (HO2˙) radical is formed in alkaline mediums with a resulting higher bleaching effect on teeth.6 To the public, the most important aspects of tooth whiteners are the effectiveness of the whitener, how long lasting is the effect, the cost of the treatment and the duration of the re- quired treatment. Therefore, if money is not an issue, the in- office treatment would basically be the treatment of choice, since the resultant whitening effect can be observed just after the chair session. Tooth-bleaching or tooth–whitening is mainly performed according to four different protocols: 1) dentist-supervised at-home bleaching, 2) in-office bleaching, 3) over-the- counter whitening products for self-application and 4) com- bination therapy (in-office followed by at-home treatment). in general, the most effective would be the first two, as the peroxide concentrations and application time of over- the-counter products are simply too low. in contrast, the saDJ april 2013, Vol 68 no 3 p122 - p129 ra Basson,1 sr Grobler,2 tJ vW Kotze,3 Y osman4 Guidelines for the selection of tooth whitening products amongst those available on the market MATERiAL REPORT ra Basson: 1. BA (Psy), BA (Hon), MA (Res Psy). Oral and Dental Research institute, Faculty of Dentistry, University of the Western Cape, Private Bag X1, Tygerberg 7505, Cape Town, South Africa. sr Grobler: 2. BSc, BSc (Hon), MSc (Chem), PhD (Dent), DSc (Chem). Oral and Dental Research institute, Faculty of Dentistry, University of the Western Cape, Private Bag X1, Tygerberg 7505, Cape Town, South Africa. tJ vW Kotze: 3. BSc, MSc (Stats), DSc (Stats). Oral and Dental Research institute, Faculty of Dentistry, University of the Western Cape, Private Bag X1, Tygerberg 7505, Cape Town, South Africa. Y osman: 4. BChD, MChD, Hons BBA, MBA, PGDHM. Oral and Dental Research institute, Faculty of Dentistry, University of the Western Cape, Private Bag X1, Tygerberg 7505, Cape Town, South Africa. corresponding author sr Grobler: Tel: 021 937 3024; Fax: 021 937 3025. Email: srgrobler@uwc.ac.za < 123www.sada.co.za / SADJ Vol 68 No. 3 MATERiAL REPORT Table 1: Shade Guide Measurements 1 2 3 4 5 6 7 8 9 10 S tu dy # R ef er en ce P ro du ct % C P % H P C at eg or y A pp lic at io n To ot h S en si tiv ity % C ol ou r im pr ov em en t % C ol ou r r el ap se af te r 4 w ee ks + 1 Browning 20088 Opalescence PF (plus nitrate and fluoride) 10% - At-home 2 weeks / x6 hours per night 45% 88% 14% 2 Browning 20088 Opalescence formulation (F) 10% - At-home 2 weeks / x6 hours per night 62% 83% 0% 3 Matis, 19989 Opalescence Tooth Whitening Gel 10% - At-home 2 weeks/8 hrs per night mild 73% 41% 4 Matis, 200010 Opalescence F 15% - At-home 2 weeks/8 hrs per night - 69% 18% 5 Matis, 200711 Opalescence PF 15% - At-home 2 weeks/8 hrs per night mild 67% 24% 6 Mokhlis, 200012 Day White - 7.5 At-home 2 weeks/1hour twice a day mild 67% 13% 7 Mokhlis, 200012 Opalescence Tooth Whitening Gel PF 20% - At-home 2 weeks/ 1hour X2 daily - 67% 11% 8 Zekonis, 200313 Opalescence Tooth Whitening gel 10% - At-home 2 weeks/8 hrs per night mild 67% 46% 9 Matis, 200010 Opalescence Dental Whitening Agent 10% - At-home 2 weeks/8 hrs per night - 64% 15% 10 Matis, 200711 Nite White 16% - At-home 2 weeks/8 hrs per night mild 63% 55% 11 Deliperi, 200414 Opalescence Xtra Boost plus Opales- cence PF 10% 38% in-office & At-home 3 days (30 min in-office / 60 min at home none 56% - 12 Gurgan, 200915 Oplasecence Xtra Boost - 38% in-office X2 /15 min - 54% - 13 Matis200716 Brite Smile - 15% in-office 3 X 20 min - 54% 68% 14 Gurgan, 200915 Laser-White 1--La-ser Smile - 37% in-office X3 /8 min mild 54% - 15 Gurgan, 200915 By White-Biowhite - 38% in-office X2 / 20 min - 53% - 16 Deliperi, 200414 Opalescence Xtra plus Opalescence PF 10% 35% in-office & At-home 3 days (30 min in-office / 60 min at home none 53% - 17 Gurgan, 200915 Remewhite-Reme-cure - 35% in-office X3 / 20 min - 53% - 18 Giniger, 200517 ACP containing bleaching gel 16% - At-home 2 weeks / 3 hours per day mild 51% - 19 Browning, 200418 Experimental Product E 10% - At-home 2 weeks / 6 hours per night mild 50% 0% 20 Swift, 199919 Nupro Gold bleach-ing gel 10% - At-home 2 weeks / 8 hours per night - 50% 0% 21 Giniger, 200517 Nite White Excel 3 Regular 16% - At-home 2 weeks / 3 hours per day - 48% - 22 Kihn, 200020 Nupro Gold bleach-ing gel 10% - At-home 2 weeks / at least 4 hours per night - 48% - 23 Heymann, 199821 Colgate Platinum Professional Over- night Whitening System 10% - At-home 1 week / 8 hours per night mild 47% 24 Matis, 200716 PolaOffice - 35% in-office X3 / 12 min - 47% 69% 25 Matis, 200716 One-hour Smile - 35% in-office X3 /15 min - 44% 54% 26 Zekonis, 200313 StarBrite 35% - in-office X2 / 3x10min mild 44% 32% 27 Cibirka, 199922 Opalescence 10% - At-home 2 weeks / 8 hours per night - 44% - 28 Matis, 200716 Niveous - 25% in-office 3 X 15 min - 43% 72% 29 Matis, 200716 ArcBrite - 30% in-office 3 X 20 min - 41% 53% 124 > MATERiAL REPORT Table 1: Shade Guide Measurements (continued) 1 2 3 4 5 6 7 8 9 10 30 Matis, 200716 Zoom! - 25% in-office X3 / 20 min - 39% 50% 31 Matis, 200716 Accelerated - 40% and 30% in-office 5 X 3 Min - 39% 81% 32 Li, 200523 Opalescence Treswhite - 9% At-home 10 days / x1 hour daily mild 38% - 33 Auschill, 200524 Opalescence PF 10% - At-home 1 week / 8 hours per night - 38% - 34 Auschill, 200524 Opalescence Xtra Boost - 38% in-office 3 times / 15 min per time - 38% - 35 Auschill, 200524 Whitestrips - 5.3 At-home 2 weeks / 30 min twice daily - 38% - 36 Zantner, 200625 Odol-med3 gel - - at-home 2 weeks / X2 daily for 10 min none 33% 0% 37 de la Pena, 200626 Opalescence Ultradent 10% - At-home 4 weeks / 3 hours daily mild 31% - 38 de la Pena, 200626 FKD (Kin Lab) - 3.5 At-home 4 weeks / 3 hours daily mild 31% - 39 Calatayud, 200927 Vivastyle Paint on Plus - 6% At-home 10 days / X1 daily for 10 min - 30% - 40 Calatayud, 200927 Vivastyle Paint on Plus - 6% in-office 2 sessions 1 week apart/ 5 times 10 min - 29% - 41 Kugel, 200028 Crest Whitestrips - 5.3 At-home 2 weeks / X2 daily for 30 min - 28% - 42 Zantner, 200625 Colgate Simply White - 5.9 at-home 2 weeks / X2 daily for 15 min none 28% 3% 43 Abu Alenain, 200929 Opalescence Treswhite - 9% At-home 1 week / 60 min per day mild 28% - 44 Matis, 200716 illumine - 15% in-office X3 / 20 min - 25% 18% 45 Cibirka, 199922 Nite White Excel 10% - At-home 2 weeks / 8 hours per night - 25% - 46 Hannig, 200730 Whitestrips - 6% At-home 2 weeks / X2 daily for 30 min mild 24% - 47 Hannig, 200730 Vivadent Vivastyle 10% - At-home 2 weeks / x1 daily for 60 min mild 24% - 48 Abu Alenain, 200929 White-Smile 10% - At-home 1 week / 2 hours daily mild 21% - 49 Al Shethri, 200331 Star Brite - 35% in-office 2 treatments 1 week apart /X3 daily for 10 min mild 21% - 50 Bernardon, 201032 Whiteness HP maxx FGM - 35% in-office 2 sessions, 3 applications per session, 15 day interval - 21% - 51 Al Shethri, 200331 Opalescence Xtra Boost - 38% in-office 2 treatments 1 week apart / X3 daily for 10 min mild 20% - 52 Bernardon, 201032 Whiteness HP maxx FGM - 35% in-office 2 sessions / 3 applications of 15 min / 15 day interval - 19% - 53 Bernardon, 201032 Whiteness Perfect FGM 10% - At-home 2 weeks/8 hrs per night - 19% 0% 54 Leonard, 200133 Nightguard vital bleaching 10% - At-home 2 weeks / 8 hours per night mild 19% 0% 55 Meireless, 200834 Whiteness Perfect 10% - At-home 3 weeks / X2 hours daily - 14% 9% 56 Meireless, 200834 Whiteness Perfect 16% - At-home 3 weeks / x2 hrs daily - 13% 2% 57 dos Santos, 200835 Opalescence PF 10% - At-home 3 weeks / 8 hours per night 36% 13% - 58 Braun, 200636 Voco CP solution 0% (Con- trol) - At-home 1 week / 2 hours daily - 10% - 59 Abu, 200929 CleverWhite over-the-counter - 6% At-home 1 week / 30 min per day mild 8% - 60 Braun,200636 Voco CP solution 10% - At-home 1 week / 2 hours daily - 8% - 61 Braun, 200636 Voco CP solution 17% - At-home 1 week / 2 hours daily - 7% - Column 1: Study number Column 2: Author(s) Column 3: Product tested Column 4: % age carbamide peroxide Column 5: % age hydrogen peroxide Column 6: Category of bleaching (at home, in office, combination) Column 7: Schedule of bleaching process Column 8: Resultant tooth sensitivity Column 9: immediate tooth colour improvement Column 10: Relapse after four weeks or longer < 125www.sada.co.za / SADJ Vol 68 No. 3 peroxide concentrations (~35%) of the in-office bleaching whiteners are high (Table 1)8-36 and applied for short bursts of time (~30 minutes) which might be repeated in the same session (or occasionally over more sessions) to show the ef- fect before the patient goes home. Alternatively, the dentist- supervised at-home bleaching process normally makes use of lower peroxide concentrations (~10% carbamide perox- ide) and patient self-application at-home, mostly over-night and over several days, for a good result. objectIveS The objective of this study was firstly to evaluate and com- pare the clinical success rates of different commercially available tooth whitening products as reported in selected clinical trials in which the application was effected according to the instructions of the manufacturer. Secondly, to thereby enable clinicians to make an informed decision regarding the choice of the products which are most clinically effective. SeARch StRAtegy This was accomplished by means of a comprehensive study of the literature which had reported on relevant clinical tri- als between 1998 and 2011, using the databases: Google Scholar, Science Direct, Medline and Pubmed respectively, with any combination of the keywords: tooth whitening, tooth bleaching, clinical studies, at-home, and in-office. The search was performed only on published, peer-reviewed articles. cRIteRIA FoR SeLectIon oF StudIeS The papers included were clinical studies in which: the whiteners had been applied according to the manu-• facturers’ instructions. (The performance of the product could then be fairly evaluated in the circumstances un- der which it was expected to be applied in practice); the brand name of the tooth whitener was clearly specified; • the sample size had been recorded. • Reporting the degree of relapse was not a criterion for inclu- sion, nor was assessment of tooth sensitivity, although, in the small number of cases where it was measured, the latter data were recorded on a word ordinal scale and in some cases as a percentage. ASSeSSIng coLouR chAngeS Basically, there are two different ways to measure the effect of tooth whiteners, namely, by means of matching with a calibrat- ed shade guide or numerically (colourimeter, chromameter or spectrophotometer). Some papers provided the shade guide assessments and some, numerical values, while a few pro- vided both. These varied methods of reporting complicated the summary of the research results. Evaluations using a shade guide are subjective, while the numerical measurements are objective, providing more reliable and accurate results.1,2 Most important are the improved accuracy and the quantification of colours by measurement in a three dimensional colour space, of which the L*a*b* (also known as the CiELAB3) is presently the most popular for the measurement of tooth colour (Figure 1). in this space L* indicates lightness/darkness (white/black), a* var- ies from green (negative side) to red (positive side), while the b* value varies from blue (negative side) to yellow (positive side).4 (The asterisk is used to differentiate the CiELAB system from previous colour space descriptions.) As with the shade guide, colour change measurements with the spectrophotometer can be given in one value, namely the ∆E*ab (Minolta), where ∆E*ab = [(∆L*)2 + (∆a*)2 + (∆b*)2]1/2 and ∆L*, ∆a* and ∆b* provide the changes which occurred in these components. mAteRIALS And methodS Based on the above selection criteria a total of ~49 full-length published articles were included. Most of these articles report- ed on two or more studies on different products and some 45 products had been tested. All data were recorded in Excel® tables. The variables for which data were sought are as follows: Product name; percentage carbamide peroxiCP) and hydro- gen peroxide (HP); Category (in-office or at-home bleaching); Application method; Tooth Sensitivity; percentage colour im- provement; total colour change obtained immediately after the treatment process; percentage colour relapse after 4 weeks; and ∆E*ab after treatment. Where the percentage colour im- provement or relapse was not given, it was calculated from the results. These results were summarised in two tables (1 and 2). Table 1 reflects data according to shade guide measurements and Table 2 those according to numerical values (spectropho- tometer, chromameter and colourimeter). Each study included a number of trials from which the spe- cific authors had calculated an average for their sample for colour changes. To gain an impression of the average ef- ficacy in tooth whitening achieved by the products under test, the reported averages were added and an average of the averages derived. These data were used to compare the general efficacy of in-office and at home treatments. ReSuLtS Table 1 provides a summary of the results reported (or cal- culated) in the selected clinical studies assessing the effica- cy of tooth bleaching through shade guide assessments.8-36 The data were sorted from the highest to lowest percentage perceived colour improvement just after bleaching accord- ing to column 9 and the studies were numbered (column 1). The percentage colour relapse after a four week or longer period had been assessed and was recorded in column 10. in a few studies where both the shade guide and ∆E*ab val- ues were given in a study, the average percentage improve- ment of the two was calculated and noted (Table 1). Table 22,4,9-13,15,16,25,31,32,34,37-45 includes the same columns as for Table 1, except Column 9 now shows the ∆E*ab values MATERiAL REPORT Figure 1: Representation of colour solid for L*a*b* colour space from Minolta.3 126 > MATERiAL REPORT Table 2: Numerical measurements 1 2 3 4 5 6 7 8 9 10 S tu dy # R ef er en ce P ro du ct % C P % H P C at eg or y A pp lic at io n To ot h S en si tiv ity ∆ E* ab a fte r tre at m en t % C ol ou r r el ap se af te r 4 w ee ks + 1 Zekonis, 200313 Opalescence Tooth Whitening gel 10% - At-home 2 weeks / 8 hrs per night mild 12.32 46 2 Matis , 200010 Opalescence F 15% - At-home 2 weeks / 8 hrs per night - 11.03 - 3 Matis, 200711 Opalescence PF 15% - At-home 2 weeks / 8 hrs per night mild 9.57 57 4 Tsuburu, 200537 Polanight 10% - At-home 2 weeks / 8 hrs per night mild 9.23 - 5 Mokhlis, 200012 Day White - 7.50% At-home 2 weeks / 1hour twice a day mild 9.2 - 6 Matis, 200010 Opalescence Dental Whitening Agent 10% - At-home 2 weeks / 8 hrs per night - 8.79 - 7 Matis, 19989 Opalescence Whitening Gel 10% - At-home 2 weeks / 8 hrs per night mild 8.6 41 8 Bernardon, 201032 Whiteness Perfect FGM 10% - At-home 2 weeks / 8 hrs per night - 8.4 0 9 Zantner, 200625 Colgate Simply White - 5.90% At-home 2 weeks / X2 daily for 15 min none 8.38 3 10 Zantner, 200625 Odol-med3 gel chlorite chlorite At-home 2 weeks / X2 daily for 10 min none 8.22 0 11 Matis, 200716 Niveous - 25% in-office 3 X 15 min - 8.1 72 12 Matis, 200716 Nite White 16% - At-home 2 weeks / 8 hrs per night mild 8.04 55 13 Matis, 200716 Brite Smile - 15% in-office 3 X 20 min - 7.9 68 14 Tsuburu, 200537 Opalescence 10% - At-home 2 weeks / 8 hrs per night mild 7.78 - 15 Mokhlis, 200012 Opalescence Tooth Whitening Gel PF 20% - At-home 2 weeks / 1hour X2 daily - 7.6 - 16 Matis, 200716 ArcBrite - 30% in-office 3 X 20 min - 6.8 53 17 Bernardon, 201032 Whiteness HP maxx FGM - 35% in-office 2 sessions / 3 applications of 15 min / 15 day interval - 6.64 - 18 Matis, 200716 Accelerated - 40% and 30% in-office 5 X 3 Min - 6.6 82 19 Bizhang, 20094 illumine Home 10% - At-home 2 weeks / 8 hrs per night - 6.57 24 20 Matis, 200716 Zoom! - 25% in-office X3 / 20 min - 6.4 50 21 Bernardon, 201032 Whiteness HP maxx FGM - 35% in-office 2 sessions, 3 applications per session, 15 day interval - 6.17 - 22 Matis, 200716 PolaOffice - 35% in-office X3 / 12 min - 5.9 69 23 ishikawa-Nagal, 20042 Opalescence PF 10% - At-home 2 weeks / 4 hours daily mild 5.84 - 24 Bizhang, 20094 illumine Office 15% - in-office 45 min / X3 over 3 weeks - 5.77 20 25 Gurgan, 200915 Laser-White 1--Laser Smile - 37% in-office X3 / 8 min mild 5.69 - 26 Gurgan, 200915 Oplasecence Xtra Boost - 38% in-office X2 /15 min - 5.54 - 27 Matis, 200716 illumine - 15% in-office X3 / 20 min - 5.5 36 28 Gurgan, 200915 By White-Biowhite - 38% in-office X2 / 20 min - 5.43 - 29 Matis, 200716 One-hour Smile - 35% in-office X3 /15 min - 5.4 54 30 Zekonis, 200313 StarBrite 35% - in-office X2 / 3x 10min mild 5.32 32 31 Grobler, 201038 Nite White ACP 10% - At-home 2 weeks / 8 hrs per night low 5.29 27 32 Grobler, 201139 Nite White ACP 10% - At-home 2 weeks / 8 hrs per night low 5.29 31 33 Gurgan, 200915 Remewhite-Remecure - 35% in-office X3 / 20 min - 5.28 - 34 Benbachir, 200840 Vivastyle Paint On Plus - 6% in-office 3 days over 2 weeks / 10min X5 times per session - 5.25 - 35 Grobler, 201139 Opalescence PF 10% - At-home 2 weeks / 8 hrs per night low 5.2 18 36 ishikawa-Nagal, 20042 Nite White Excel 10% - At-home 2 weeks / 4 hours daily mild 5.03 - 37 Luo, 200741 Crest White Strips - 6% At-home 2 weeks / 30 min X2 daily - 4.95 -- 38 Meireless, 200834 Whiteness Perfect 16% - At-home 3 weeks / x2 hrs daily - 4.6 2 39 Gerlach, 200242 Crest Professional Whitestrips - 6.50% At-home 2 weeks / 30 min X2 daily - 4.55 - 40 Meireless, 200834 Whiteness Perfect 10% - At-home 3 weeks / X2 hours daily - 4.3 9 41 Bizhang, 20094 Whitestrips - 6% At-home 2 weeks / 30 min X2 daily - 3.58 16 42 Salem, 201043 Yotuel Special - 35% in-office 20 min X3 (1 session) mild 3.56 53 43 Grobler, 201044 Opalescence PF 10% - At-home 2 weeks / 8 hrs per night low 3.25 8 44 Karpinia, 200245 Professional crest Whitestrips - 6.50% At-home 3 weeks / 30 min X2 daily mild 3.15 - 45 Gerlach, 200242 Nite White Excel 2-tray system 10% - At-home 2 weeks / X2 hour daily - 2.55 - 46 Al Shethri, 200331 Opalescence Xtra Boost - 38% in-office 2 treatments 1 week apart / X3 daily for 10 min mild 2.45 - 47 Al Shethri, 200331 Star Brite - 35% in-office 2 treatments 1 week apart /X3 daily for 10 min mild 2.31 - 48 Karpinia, 200245 Nite White Excel2 10% - At-home 2 weeks / 2 hours daily mild 1.94 - 49 Luo, 200741 Colgate Great regular Flavour - 0% (control) At-home 2 weeks / x1 min x2 daily - 1.27 - Column 1: Study number Column 2: Author(s) Column 3: Product tested Column 4: % age carbamide peroxide Column 5: % age hydrogen peroxide Column 6: Category of bleaching (at home, in office, combination) Column 7: Schedule of bleaching process Column 8: Resultant tooth sensitivity Column 9: immediate tooth colour improvement Column 10: Relapse after four weeks or longer < 127www.sada.co.za / SADJ Vol 68 No. 3 MATERiAL REPORT (total colour change) which indicate the colour improvement as measured numerically and column 10 the percentage re- lapse as calculated from the ∆E*ab values. This table was also sorted according to highest to lowest ∆E*ab values (column 9) immediately after treatment. dIScuSSIon The values of shade guides cannot be directly compared with those numerically measured. A shade guide provides only a combination value for the three colour components (e.g. L*, a* and b*). The linear rankings of a tooth shade guide are not the same as those obtained from sequential delta E* (∆E*). The shades represented on a shade guide are not equi-distant when measured by the scientific and objective distances delta E* which relies on the three colour compo- nents (ie. L*, a* & b*). The distances between before and af- ter colour measurements on each treated tooth differ when estimated with shade guides or taken numerically and these values could not be directly compared. Hence these data are assembled separately in two tables (Table 1 and Table 2). As ∆E* is a difference between two values the percentage change could only be determined in the relapse phase when there are indeed two such ∆E*values. in relapse calculations where both methods had been used to determine the chang- es (a few cases only), the percentage relapses determined by shade guide and by numerical methods were first separately calculated and the average of the two then noted. The percentage improvement (Table 2) could not be cal- culated for studies where only ∆E*ab values were given as ∆E*ab gives the difference between the tooth colour at base-line and that after treatment. For the shade guide values, (Table 1), the top ten achievers were at-home products and likewise according to ∆E*ab (Table 2) the top ten achievers were also at-home products. The high- est values reported (Tables 1 and 2) were with a 10% or 15% carbamide peroxide treatment over a relatively long treatment period (two weeks 6/8 hours per night). in general, the treatment periods for top achievers (Table 1 and 2) were all scheduled over relatively long time-periods which, as seen in Table 1, varied from two hours/day for two weeks, to six hours/night for two weeks and to eight hours/night for two weeks. For Table 2 the first eight study achievers were for eight hours/night for two weeks (with the exception of study # 5 which was for one hour twice daily for two weeks. The shortest treatment period (Table 1) within the ten top achievers (study # 6 and 7) was one hour/twice-a-day for 14 days but this was a trial using 7.5% HP (~25% CP) and 20% CP in comparison with the more general treatment which uses 10% carbamide peroxide. in Table 2 the shortest treatment period within the top ten at-home achievers was twice a day for 15 min (study # 9) but as for Table 1, this study relied on a high peroxide concentration (5.9% HP). The other treatment with a short ap- plication time was with chlorite (study # 10). Therefore, it can be deduced that to obtain the same success rate as with 10% car- bamide peroxide it seems that a shorter treatment period might be indicated but using a higher peroxide concentration. in general, it can be seen that in-office treatments (even with high peroxide concentrations) were far less successful (Table 1 and 2) than at-home treatments with ~10% carbamide peroxide. On the ranking list, in-office applications came in well below the highest achievers at study # 11 (Table 1) and study # 11 (Table 2). Why then is the high peroxide concen- tration treatment unexpectedly found to be less successful? The reason may be found in the length of the application pe- riod. in-office applications (Table 1, studies # 11-17; Table 2, study 11 and others) were performed over a short period in comparison with the dentist supervised at-home treatment procedures. The in-office treatment periods were normally short bursts, for example three x 15minutes/session, three x 20 minutes/session, etc. (Table 1 and 2). However, there were a few examples (Table 1, # 40, 49-52) where the in-office ses- sions were repeated over days but only two of these studies (Table 1, #11, 16) were further extended to an at-home treat- Table 3: Descriptive statistics of colour improvement (shade guide assessment) immediately after treatment for ‘At-home’ and ‘in- office’ treatment. Category Values At-home In-office Number of studies 40 19 Number of studies indicating % colour improvement 19 9 Average of average of % colour improvements 39.3% 38.8% Std Dev of % colour improvement 22.4% 12.7% Min % colour improvement 6.9% 19.1% Max % colour improvement 88.1% 54.4% Table 4: Descriptive statistics of colour relapse (shade guide as- sessment) after four weeks for ‘At-home’ and ‘in-office’ treatment. Category Values At-home In-office Number of studies 40 19 Number of studies indicating % colour relapse after 4 weeks 19 9 Average of average % colour relapses after 4 weeks 13.1% 55.2% Std Dev of % colour relapse after 4 weeks 17.0% 20.2% Min % colour relapse after 4 weeks 0.0% 18.0% Max % colour relapse after 4 weeks 55.0% 81.0% Table 5: Descriptive statistics of colour improvement (∆E*ab -scale) immediately after treatment for ‘At-home’ and ‘in-office’ treatment. Category Values At-home In-office Number of studies 29 20 Number of studies indicating colour im- provement 13 11 Average of average ∆E*ab after treatments 6 .36 5.60 Std Dev of ∆E*ab after treatment 2.80 1.48 Min ∆E*ab after treatment 1.27 2.31 Max ∆E*ab after treatment 12.32 8.1 Table 6: Descriptive statistics of colour relapse (∆E*ab - scale) after 4 weeks for ‘At-home’ and ‘in-office’ treatment. Category Values At-home In-office Number of studies 29 20 Number of studies indicating % colour relapse 13 11 Average of average of % colour relapses 26.02% 53.60% Std Dev of % colour relapses 18.98% 18.65% Min % colour relapse 2.17% 20.45% Max % colour relapse 57.37% 81.82% 128 > ment. However, to allow subjects to personally handle such a high peroxide concentration is very risky and should not be recommended. There are probably two main reasons for the short applica- tion period of in-office treatments: the first reason is financial, in that the longer the in-chair session the more expensive the treatment becomes, the second is that high peroxide application has a possible hazardous effect (related to the oxidising strength) on the soft tissue of the oral cavity. From Table 3 (shade guide) it can be deduced that over- all both at-home (39.3%) and in-office (38.8%) treatments showed more or less the same initial colour improvement. However, a major difference could be seen in the relapse after a four week or longer period (at-home 13.1%; in-office 55.2% :Table 4). From the ∆E*ab (Table 5) numerical values, the initial colour improvements for in-office and at-home were also about the same (5.60 against 6.36). When the relapse was calculated from ∆E*ab values (Table 6), in-office treatment gave a value of 53.6%, similar to that found with the shade guide assessments (55.2%) (Ta- ble 4). However, the at-home relapse was 26.02% (Table 6) which is about double that when calculated from shade guide measurements (13.1%) (Table 4). Other findings reported on the combination of dentally su- pervised at-home treatments: Leonard et al.33 revealed that the whitening effected by 10% carbamide peroxide (Nite White Classic; eight to ten hours per day for 14 days) re- ported five tabs lighter teeth, an effect which lasted over a 3.8 year period. in two different articles 46,47 reporting on 10% carbamide peroxide which was applied for two hours per day for three weeks, no relapse was reported after one year. No comparable results were reported for any in-office treatment. Only two studies reported results for a combi- nation of in-office and at-home treatments (Studies # 11 and 16). Study 11 showed a colour improvement of 56% (Table 1) and study 16 also showed a high colour improve- ment of 53%. These results may indicate that a combination of the in-office and at-home treatments could produce the most positive results. Unfortunately no assessment on any colour relapse was reported in these two studies. The most commonly tested product was Opalescence PF, a material evaluated in 11 studies. The average of the average colour improvements as reflected on the shade guide scale, was 54% compared with 36% for all the other products. With regard to numerical measurements, the five studies using that method of assessment recorded 6.9 (∆E*) for the average of the average colour improve- ments for Opalescence PF and an average of 5.95 (∆E*) for all the other products. These values can be considered high spectrophotometer readings, possibly highlighting the accuracy of the technology in comparison with shade guide measurements. The mean relapse measured numerically after four weeks was 27.8% for Opalescence (n=3) which is considerably lower than the mean of 40.2% recorded for all the other products (n=21). Not all studies recorded relapse values (Opalescence 3 of 5; other products: 21 of 44) and these findings should therefore be regarded only as an indication of relapse potentials. The next question which may be posed is which of the in- office or dentist supervised at-home treatments would give the lowest tooth sensitivity scores? Not all studies reported on this, but the data recorded in Tables 1 and 2 reveals no significant differences in tooth sensitivities between the routines, and overall these effects were low - with an excep- tion of the two top achievers in bleaching (Table 1), where a higher sensitivity was in fact noted (62% and 45%). However, it should also be observed that in some instances during treatments, the sensitivity might be so high that the individ- ual prefers to terminate the application. Some of the manu- facturers (studies # 1 and 4) added chemicals (potassium nitrate and fluoride) to their bleaching products in an attempt to counteract sensitivity. However, the clinical data (Table 1) indicates uncertainty on the possible positive effects of those materials, or on amorphous calcium phosphate and no general conclusion could be reached.11,16,17,38,48,49 Further- more, from the published results (Tables 1 and 2), it can also be concluded that in general, where tooth sensitivity was noted during the whitening process, it disappeared sponta- neously after the treatment period. concLuSIon This analysis of the data shows that the dentist-supervised- at-home-bleaching and the in-office treatment gave nearly the same initial tooth whitening improvement. However, the relapse after a four week or longer period was found to be much higher for the in-office treatment at a relapse of ~55% on average, while the at-home treatment showed a much low- er relapse over the same period of about 13% to 26%. Overall, it can be concluded that the treatment of choice should be a dentist supervised at-home bleaching process using a prod- uct which in general contains about 10% carbamide peroxide applied over ~14 days and for ~8 hours per night on average. Tooth sensitivity should not be seen as a consistent problem although some subjects might choose to discontinue treat- ment as a result of experiencing the problem. 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