ABSTRACT
http://dx.doi.org/10.1590/1678-775720130578
Effect of coffee and a cola- based soft drink on
t he color st abilit y of bleached bov ine incisor s
considering t he t im e elapsed aft er bleaching
Rodrigo PIROLO1, Rafael Francisco Lia MONDELLI2, Gisele Maria CORRER3, Carla Castiglia GONZAGA3, Adilson Yoshio FURUSE2
1- Private practice, Curitiba, PR, Brazil.
2- Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São, Paulo, Bauru, SP, Brazil. 3- Graduate Program in Dentistry, Positivo University, Curitiba, PR, Brazil.
Corresponding address: Adilson Yoshio Furuse - Departamento de Dentística, Endodontia e Materiais Odontológicos - Faculdade de Odontologia de Bauru, Universidade de São Paulo - Alameda Dr. Octávio Pinheiro Brisolla, 9-75 - Bauru - SP - Brazil - 17012-901 - Phone: +55 14 8323 - Fax: +55 14 3235-8523 - e-mail: furuse@usp.br
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here is no consensus about t he wait ing t im e necessary for t he pat ient t o st art consum ing bev erages cont aining colorant s again aft er bleaching. Obj ect iv e: To evaluat e t heLQÀXHQFHRIEHYHUDJHVZLWKFRORULQJDJHQWVRQEOHDFKHGERYLQHLQFLVRUVFRQVLGHULQJWKHWLPH
elapsed aft er bleaching. Mat erial and m et hods: Sixt y bovine incisors w ere bleached w it h
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The color was evaluat ed w it h a spect rophot om et er ( Spect ro Shade MI CRO) before and aft er bleaching, em ploying t he CI E- Lab syst em . Aft er bleaching, t he t eet h w ere exposed for 5 m in t o coffee or cola- based soft drink ( CBSD) at different periods aft er bleaching:
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from t he CI E- Lab coordinat es. Dat a w ere subj ect ed t o t w o- way ANOVA and Tukey HSD
WHVWVS5HVXOWV6LJQL¿FDQWGLIIHUHQFHVZHUHREVHUYHGEHWZHHQJURXSVIRUERWKWKH ¨/DQG¨(YDOXHVS$OOVSHFLPHQVSUHVHQWHGDGHFUHDVHLQEULJKWQHVVQHJDWLYH ¨/7KHKLJKHVW¨(YDOXHVZHUHREVHUYHGIRUWHHWKVWDLQHGZLWKD&%6'DWPLQDQGK DQGUHVSHFWLYHO\7HHWKSLJPHQWHGZLWKFRIIHHSUHVHQWHG¨(YDOXHVEHORZ
unit s for all evaluat ion t im es. Conclusion: The exposure t o coffee aft er bleaching causes less color changes t han t he exposure t o a CBSD regardless of t he t im e aft er bleaching.
Ke yw or ds: Toot h bleaching. Bleaching agent s. Color.
I N TROD UCTI ON
The search for opt im al aest het ics of t he sm ile is LQFUHDVLQJO\SUHVHQWLQGHQWDORI¿FHV7KLVLQFUHDVHG dem and for cosm et ic procedures m ay be slight ly LQÀXHQFHGE\WKHPHGLDVLQFHLWGHSLFWVWKHEHDXW\ of w h it e t eet h , alw ay s w it h per f ect sh ape an d alignm ent15. Am ong ot her cosm et ic t r eat m ent s,
t oot h w h it en in g is on e of t h e m ost r eq u est ed b ecau se i t i s a l o w - co st an d f ast p r o ced u r e. Moreover, t he various t echniques available are safe and w ell described in t he lit erat ure15,18. How ever,
t h er e ar e st ill u n cer t ain t ies r egar din g st ain in g aft er bleaching procedures2,3,13,17. This concern is
m ainly relat ed t o t he t im e t he pat ient should wait
unt il consum ing foods and beverages t hat cont ain st aining agent s.
There are basically t w o m odalit ies of bleaching t r eat m en t s f or v it al t eet h : d en t ist - su p er v ised KRPHEOHDFKLQJDQGLQRI¿FHEOHDFKLQJ&XUUHQWO\ bleaching agent s can be present ed as hydrogen p er ox i d e ( H2O2) , an d car b am i d e1 0. Th e l at t er
undergoes chem ical decom posit ion releasing H2O2. Hydrogen peroxide act s prim arily by oxi- reduct ion, m aking long- chain chrom ophore m olecules sm aller and less color ful6. The differ ent t oot h w hit ening
t echniques have t he sam e goal and t heir result s have been proven9,16,18. How ever, cert ain variables
in f lu en cin g t h e f in al b leach in g ou t com e is t h e exposure t o st aining agent s present in foods and bev er ages1 1. Th e pr olon ged ex posu r e t o t h ese
agent s m ay cause sever e discolorat ion t o t eet h r e ce n t l y su b j e ct e d t o b l e a ch i n g p r o ce d u r e s. How ever, it is im por t ant t o not e t hat foods and beverages are not t he only possible st aining agent s. Tobacco and ot her dr ugs m ay also cause t oot h discolorat ion12,22.
Color in g agen t s ar e pr esen t in m ost f oods. Beverages such as cola- based soft drinks, black t ea, FRIIHHDQGUHGZLQHSURGXFHDJUHDWHULQÀXHQFHRQ t he st aining of t eet h28, and t he consum pt ion of such
beverages is highly popular w or ldw ide. Not ably, aft er t oot h w hit ening pr ocedur es, a per m anent t ot al ban of t hese liquids for aest het ic purposes is im pract ical for m ost people. Furt herm ore, it has been observed t hat suscept ibilit y t o st aining from dyes is higher aft er t oot h w hit ening procedures3.
How ever, t her e is a general lack of infor m at ion r egar ding t he est het ic dam age caused by dy es during or short ly aft er t he bleaching t reat m ent in relat ion t o t he visual percept ion of color change. The wait ing t im e necessary for t he pat ient t o ret urn t o consum ing beverages cont aining colorant s m ust also be assessed in order t o avoid an unaccept able color change caused by st aining agent s.
,QFRORULPHWULFVWXGLHVWKHFRORUYDULDWLRQƩ( obt ain ed f r om an aly sis em ploy in g t h e CI E- Lab ( Com m ission I n t er n at ion ale d e l' Eclair ag e L* , a* , b* ) color space has been com m only used t o specify possible clinical correlat ions in a way t hat DƩ(YDOXHVPDOOHUWKDQRQHXQLWLVQRWJHQHUDOO\
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bet ween 1 and 3.3 t he difference is perceivable, but generally considered accept able. This m eans t hat alt hough t here is a color variat ion, t he difference does not indicat e t he need of replacem ent of an est het ic rest orat ion nor t he need of repeat ing t he bleaching procedure. On t he ot her hand, w hen t he ¨(LVRYHUXQLWVLWLVFRQVLGHUHGXQDFFHSWDEOH due t o t he gr eat color differ ence pr esent23. The
DLPRIWKLVVWXG\ZDVWRLQYHVWLJDWHWKHLQÀXHQFH of bev erages w it h color ing agent s on bleached bovine incisors considering t he t im e elapsed aft er b leach in g . Th e h y p ot h esis ev alu at ed w as t h at bovine t eet h bleached wit h 35% hydrogen peroxide w ould pr esent an unaccept able color differ ence Ʃ(DERYHZKHQH[SRVHGWRFRORULQJDJHQWV regardless of t he wait ing t im e aft er bleaching.
M ATERI AL AN D M ETH OD S
Se le ct ion of t e e t h
Sixt y bovine incisors were select ed for t his st udy. They were pre- select ed according t o t heir condit ion DQGFRORU7HHWKZLWKVLJQL¿FDQWVSRWVDQGIUDFWXUHV were elim inat ed from t he set . From t he ext ract ion
in t he slaught erhouse unt il t he t est s, each t oot h was st ored in 0.5% chloram ine T and at no t im e suffered dehydrat ion. Each specim en was properly cleaned w it h Robson pr ophy lax is br ush, pum ice and wat er for 40 s across t he labial surface under m anual pressure on a low- speed cont ra angle. Aft er cleaning, t he t eet h w ere st ored in dist illed wat er at 37° C for no m ore t han 3 days before bleaching procedures.
M a in t e n a n ce of t e m pe r a t u r e a n d h u m idit y I n or d er t o m ain t ain t h e t em p er at u r e an d h u m i d i t y o f t h e t e e t h d u r i n g t h e b l e a ch i n g pr ocedu r es, a special dev ice con sist in g of t w o plast ic t rays of different sizes, a pum p, a t herm ost at and a heat er, was assem bled ( Figure 1) . The largest t ray ( 54 cm x 38 cm x 8 cm ) was used as t he m ain wat er reservoir. I nside t his t ray, a sm aller one ( 40 cm x 27 cm x 4.5 cm ) was insert ed wit h it s opening f acin g t h e b ot t om of t h e lar g er t r ay. Th e t w o diagonal corners of t he sm aller t ray w ere rem oved t o allow free circulat ion of wat er.
Ten one- cent im et er- diam et er perforat ions w ere m ade at t he cent er of t he base of t he sm allest t ray w it h t w o cent im et er s of dist ance bet w een perforat ions. The perforat ions w ere capped w it h a rubber dam ( Madeit ex, São José dos Cam pos, SP, Brazil) . Pen m arkings w ere m ade on t he dam in t he cent er of each m arking for perforat ion and t he m arkings w ere punched w it h an Ainsw ort h rubber dam punch ( SS Whit e, Rio de Janeiro, RJ, Brazil) . Aft erwards, t he dam was at t ached t o t he perforat ed t ray w it h adhesive t ape.
For t he cir culat ion and heat ing, t w o heat er s and a pum p w er e subm er ged in t he wat er. The pum p was inst alled in a corner of t he larger t ray. Th e r eser v oir h ad a t h er m ost at t o con t r ol t h e t em perat ure and an auxiliary heat er t o m aint ain t he FLUFXODWLQJZDWHUWHPSHUDWXUHFRQVWDQWDW§& A digit al t herm om et er was also insert ed int o t his syst em for t he visual m onit oring of t he t em perat ure. During t he bleaching procedures, each t oot h was insert ed int o a perforat ion, w it h only t he root in con t act w it h t h e cir cu lat in g w at er. Th e cr ow n s w ere m aint ained above t he rubber dam separat ion t o replicat e a clinical condit ion. Figure 1 show s a schem at ic represent at ion of t he device assem bled t o m aint ain t he t eet h t em perat ure.
S p e c t r o p h o t o m e t e r m e a s u r e m e n t , ble a ch in g a n d dyin g
Figure 1- Device assembled to maintain temperature and humidity of teeth during bleaching procedures. The arrows
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m ar k ings t o ensur e t hat t he spect r ophot om et er was aligned t o t he long axis and am elo- cem ent al j unct ion of t he t oot h. Only t he cent er port ion of t he t oot h was used for t he collect ion of dat a according t o t h e CI E- La b ( Co m m i ssi o n I n t e r n a t i o n a l e d e l’Eclair ag e L* , a* , b * ) color sp ace b y t h e Spect ro ShadeTM MI CRO ( MHT Opt ic Research AG,
Milan, I t aly) spect r ophot om et er. The device was calibrat ed beforehand, using t he w hit e and green st andards cont ained in it s rechargeable base. The coordinat e syst em t ranslat es t he CI E lum inosit y ( L* ) num erically, and t he m at ch in red ( + a* ) or green ( - a* ) and yellow ( + b* ) or blue ( - b* ) . To obt ain t he dat a, t he sequence follow ed t hese st eps: sam ple visualizat ion, im age capt ure for spect rophot om et ry, det erm inat ion of t he area t o be analyzed, select ion of t he m iddle t hird, and acquisit ion of t he values of L* , a* and b* .
Aft er t he init ial color analysis, dist illed wat er w a s a d d e d t o t h e t e m p e r a t u r e m a i n t e n a n ce syst em and t he t em perat ure was raised t o 37° C. Each int act t oot h was insert ed int o a perforat ion, w i t h o n l y t h e r o o t b ei n g i n co n t act w i t h t h e cir cu lat in g w at er. Th e cr ow n s w er e m ain t ain ed a b o v e t h e r u b b er d a m sep a r a t i o n . Th e 3 5 % hy dr ogen per ox ide gel was m ixed follow ing t he m anufact ur er ’s r ecom m endat ions ( Whit eness HP Max, FGM, Joinville, SC, Brazil) , and t he bleaching gel was applied t o t he buccal surface and left for 45 m in t o prom ot e t he act ion of t he bleaching agent . The t eet h w er e r insed in t ap w at er and st or ed in dist illed w at er. The bleaching pr ocedur e w as repeat ed for t hree consecut ive days. At t he end of t he t hird day, a color m easurem ent was recorded wit h t he spect rophot om et er. This m easurem ent was considered t he baseline color analysis.
The gr oups ( n= 6) w er e div ided accor ding t o
t he t im e before being exposed t o t he drinks. Aft er bleaching, t he t eet h w ere exposed t o eit her cola-based soft drink ( CBSD) ( Coca Cola, Curit iba, PR, Brazil) or inst ant coffee ( Nescafé, Nest lé, São Paulo, SP, Brazil) for 5 m in. The coffee w as pr epar ed according t o t he m anufact urer› s inst ruct ions – 100 m l of wat er for 2 level t easpoons. The coffee was allow ed t o cool t o a m ean t em perat ure of 50° C before conduct ing t he experim ent . The t em perat ure of t h e sof t d r in k u sed w as 1 0 ° C. Th e st u d ied t im es w ere 10 m in, 1 h, 24 h, 48 h and 72 h aft er bleaching.
Th e d i f f er en ces ( f i n a l v a l u e m i n u s i n i t i a l ) EHWZHHQ WKH &,(/DE FRRUGLQDWHV Ʃ/ ƩD DQG ƩE ZHUH FDOFXODWHG IRU HDFK H[SHULPHQWDO t im e. Wit h t his inform at ion, t he value of t he color YDULDWLRQƩ(UHVXOWZDVGHWHUPLQHGDFFRUGLQJWR t he form ula:
Ʃ( >Ʃ/2ƩD2ƩE2]1/ 2
ZKHUH Ʃ/ ƩD DQG ƩE DUH WKH GLIIHUHQFHV in t he respect ive values before and aft er st aining.
,QWKHSUHVHQWVWXG\Ʃ(YDOXHZDVFRQVLGHUHG clin ically u n d et ect ab le if sm aller t h an 1 u n it , clin ically accept able if bet w een 1 an d 3 . 3 an d unaccept able if great er t han 3.323,25.
St a t ist ica l a n a lysis
Dyes Time ¨/ ¨(
CBSD 10 min -1.78 (0.58)abc 4.11 (0.64)b
1 h -2.47 (0.98)a 4.16 (0.95)b
24 h -2.07 (0.27)abc 3.15 (0.59)b
48 h -2.28 (0.52)ab 3.38 (0.26)b
72 h -1.05 (0.58)bcd 1.93 (0.78)a
Coffee 10 min -0.77 (1.12)cd 1.49 (0.51)a
1 h -0.73 (0.33)cd 1.49 (0.52)a
24 h -0.13 (1.14)abc 1.69 (0.47)a
48 h -1.50 (0.46)abc 1.80 (0.45)a
72 h -1.77 (0.19)abc 2.06 (0.14)a
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RESULTS
The effect iveness of t he bleaching procedures ZDV FRQ¿UPHG E\ WKH PHDQ RYHUDOO Ʃ( YDOXH IRU all bleached t eet h ( 4.2± 1.3) . Aft er bleaching, t he pigm ent at ion of t he t eet h had decreased, i.e., a* decreased ( less yellow color) , show ing a negat ive ƩD YDOXH E GHFUHDVHG OHVV UHG FRORU VKRZLQJ D QHJDWLYH ƩE YDOXH DQG/EULJKWQHVVLQFUHDVHGZLWKDSRVLWLYHƩ/ value, w it h a m ean of 3.2± 1.2.
0HDQVDQGVWDQGDUGGHYLDWLRQVRIWKHƩ/DQG Ʃ(YDOXHVDIWHUSLJPHQWDWLRQDUHVKRZQLQ7DEOH All t eet h showed a decrease in lum inosit y ( negat ive YDOXHRIƩ/DIWHUEHLQJH[SRVHGWRWKHHYDOXDWHG G\HV7KHUHZHUHVLJQL¿FDQWGLIIHUHQFHVEHWZHHQ t h e t y pes of dy es ( p< 0 . 0 0 0 1 ) . Th e t im e af t er EOHDFKLQJKDGQRHIIHFWRQWKHGHFUHDVHRIWKH¨/
YDOXH S $ VLJQL¿FDQW LQWHUDFWLRQ HIIHFW bet w een t he t ype of dye and t im e aft er bleaching was also observed ( p= 0.0002) . Sm aller decreases in L* values occurred when t he t eet h were exposed t o coffee for 10 m in, 1 h or 24 h. When considering WKH ¨( YDOXHV WKHUH ZHUH VLJQL¿FDQW GLIIHUHQFHV bet w een t he t ypes of dyes ( p< 0.0001) and t im e aft er bleaching ( p= 0.008) . An int eract ion effect was also observed ( p< 0.0001) . The highest values of Ʃ(ZHUHREVHUYHGLQWKHVSHFLPHQVSLJPHQWHGZLWK t he CBSD. Teet h pigm ent ed w it h coffee present ed D Ʃ( YDOXH EHORZ IRU DOO WLPHV HYDOXDWHG $V REVHUYHGLQ)LJXUHWKHYDOXHVRI¨(WHQGHGWR decrease over t im e for t he CBSD, while it t ended t o be const ant for coffee. Teet h pigm ent ed w it h CBSD VKRZHG¨(YDOXHVVLPLODUWRWHHWKSLJPHQWHGZLWK FRIIHHKDIWHUEOHDFKLQJ$OOƩ(YDOXHVREWDLQHG were higher t han one unit and, for t his reason, were
not considered clinically undet ect able.
D I SCUSSI ON
The hypot hesis evaluat ed was rej ect ed, since t he WHHWKH[SRVHGWRFRIIHHVKRZHGƩ(YDOXHVVPDOOHU t han 3.3 unit s for all t im es post - bleaching. There ZDVDVLJQL¿FDQWGLIIHUHQFHEHWZHHQWHHWKH[SRVHG t o coffee and a CBSD for all t im es evaluat ed, except for t eet h pigm ent ed wit h a CBSD for 72 h. Alt hough coffee show ed sm aller pigm ent at ion pot ent ial, it was st ill capable of causing clinically det ect able FRORU FKDQJHV UHSUHVHQWHG E\ ¨( YDOXHV KLJKHU t han one unit . A differ ent r esult w as obser v ed when bleached bovine t eet h were exposed t o coffee by Lipor oni, et al.14 ( 2010) , w hich obser ved no
VLJQL¿FDQWGLIIHUHQFHVEHWZHHQWKHZDLWLQJWLPHVRI 30 and 150 m in post - bleaching w hen bovine t eet h were whit ened and t hen pigm ent ed for 10 m in wit h coffee and red w ine13. According t o t hese aut hors,
cof f ee d oes n ot seem t o cau se st ain in g af t er bleaching, while red wine was able t o st ain bleached enam el at 30 and 150 m in aft er bleaching13.
I n t he pr esent st udy t w o differ ent solut ions frequent ly consum ed in daily life w ere select ed as FRORULQJDJHQWV7KH&%6'KDVDORZS+S+§ and higher erosive pot ent ial, which creat es rougher enam el surfaces. Rougher surfaces associat ed wit h t he pigm ent s could be relat ed t o t he CBSD’s higher pigm ent at ion pot ent ial. The inst ant coffee, on t he RWKHU KDQG KDV D KLJKHU S+ S+ § $QRWKHU difference bet w een t he t w o solut ions m ay relat ed t o t he size of st aining part icles since inst ant coffee t end t o hav e lar ger par t icles, w hich could also explain it s decreased pigm ent at ion pot ent ial.
Colorim et ry is t he qualit at ive and quant it at ive m easur em ent of color. Com m on color st andar ds a r e : CMYK, RGB, HSL a n d CI E- La b . Fo r t h e evaluat ion of t he color in t eet h and ot her m at erials, var ious m et hods can be em ployed, such as t he u se o f sp ect r o p h o t o m et er s, co l o r i m et er s an d com put erized im age analysis2. I n t he present st udy,
t he spect rophot om et er was used, providing great er accu r acy f or t h e m easu r em en t s. Accor d in g t o Gehrke, et al.8 ( 2009) , t he spect rophot om et er used
in t heir w ork show ed 82% accuracy bet w een t w o consecut ive m easurem ent s of t he sam e specim en, w hile t he colorim et er account ed for only 70% . The device used in t he present st udy em ploys a digit al cam era connect ed t o a LED spect r ophot om et er t hat analyzes t he t oot h surface. This aspect m ay be an advant age considering t he irregular buccal sur faces of bov ine incisor s. Mor eover, accor ding t o t he m anufact urer, environm ent al aspect s t hat PD\DIIHFWWKHYLVXDOSHUFHSWLRQGRQRWLQÀXHQFH t he result s obt ained. The spect rophot om et er shows t he color reading on various param et ers including t he CI E- Lab color space2,13,17. This color space is
current ly t he m ost em ployed in dent al research. The advant age of using t he CI E- Lab color space is relat ed t o t he calculat ion of t he color variat ion Ʃ(IURPWKHYDULDWLRQRIWKHFRRUGLQDWHV/D DQGE$VSUHYLRXVO\VWDWHGIURPWKHƩ(YDOXHRQH can m ake a com parison w it h a clinically observable color change21,23,25.
A co n cer n r el at ed t o t h e m et h o d w as t h e st andardizat ion of all procedures. For t his purpose, special care was t aken at all t im es, from t he select ion of t eet h and t he t em perat ure m aint enance during bleaching t o color readings. The choice of t he m iddle t hird of t eet h crow ns as t he area for t he evaluat ion of color was det erm ined by som e possible variables t hat could alt er t he result s. The elim inat ion of t he t ranslucent area, t he w orn incisal and policrom at ic crow n in t heir ent iret y was suggest ed t o prevent int erference in t he color analysis. Ot her st udies also use only t he m iddle t hird of crow ns t o evaluat e t he color change in bleached t eet h17.
The pr esent st udy descr ibed a sim ple dev ice designed t o m aint ain t he t em perat ure and hum idit y during t he bleaching procedure. This approach was chosen t o replicat e t he clinical condit ion, and due t o t he fact t hat t he great difference bet w een t he RI¿FHURRP§&DQGRUDOFDYLW\WHPSHUDWXUH WRRWKFDQFHUWDLQO\LQÀXHQFHWKHUHDFWLRQUDWHRI t he bleaching m at erial. This sam e concern occurs w hen evaluat ing ot her clinical- relat ed procedures such as adhesion t o dent in and enam el. Moreover, WKHGHVFULEHGGHYLFHFRXOGEHHDVLO\PRGL¿HGWR¿[ sam ples for t he evaluat ion cem ent at ion of post s on endodont ically t reat ed root canals. I n such cases, a PRGL¿FDWLRQLQWKHGHYLFHWRVLPXODWHWKHLQWUDSXOSDO pressure would be int erest ing. I n t he present st udy WKHUHVHUYRLUZDV¿OOHGZLWKGLVWLOOHGZDWHULQVWHDG RIVDOLQHVROXWLRQRUDUWL¿FLDOVDOLYDWRVWDQGDUGL]H t he wat er int ake by t eet h during t he experim ent s.
Bov ine t eet h w er e used in t his st udy due t o sev eral fact or s. The absence of car ious lesions and good general condit ion should be considered for conduct ing such an experim ent . The ease of obt aining bovine incisors was also decisive in t he choice because hum an incisors wit h sim ilar anat om y ZRXOG EH KDUG WR ¿QG LQ VXI¿FLHQW QXPEHUV $V w ell, bovine t eet h have sim ilar physical chem ist ry t o hum an t eet h24 and supposedly provide sim ilar
r esult s w hen w hit ening pr ocedur es and st aining are evaluat ed2. Addit ionally, bovine t eet h are oft en
used in ot her st udies, such as w hen evaluat ing t he adhesion of r esin- based m at er ials t o dent al st ruct ures5,7 and t he w ear and roughness19. I t is
im port ant t o not e t hat by em ploying bovine t eet h inst ead of hum an t eet h, possible physical, chem ical and m orphological differences should be considered relevant w hen int erpret ing t he result s29. Anot her
w hich could increase t he st aining capabilit y, when com pared t o hum an incisors.
Th e r ou g h n ess of t h e en am el is in cr eased w it h w h it en in g4 , 2 7, w h ich cou ld also con t r ibu t e
t o st aining aft er bleaching. Dahl and Pallensen6
( 2 0 0 3 ) su g g est ed t h at t h is in cr eased su r f ace roughness caused by t oot h whit ening creat es m ore su scep t ib ilit y t o ex t r in sic p ig m en t s. Mor eov er, int rinsic pigm ent at ion is also boost ed by t he act ion of hydrogen peroxide3. I t was observed t hat t he
predisposit ion t o st aining t ends t o be higher w hen t he t oot h is exposed t o 35% hydrogen peroxide26.
According t o t he result s of t his st udy, CBSD st ained m or e t han coffee. I t is possible t o suggest t hat t his product , w hich has a low pH level, could st ain m ore due t o t he increase of porosit y of t he surface pr ov ided by a pot ent ial dem ineralizat ion of t he t oot h surface. Not ably, along w it h t he change in roughness, bleaching t reat m ent s have also been associat ed w it h decreased enam el hardness, but t his change in hardness t ends t o reverse over t im e1.
Therefore, it can be hypot hesized t hat prolonged exposure t o a CBSD aft er dent al w hit ening could furt her increase enam el roughness and decrease hardness. I n a sim ilar way, it has been observed t h a t t o o t h b r u sh i n g i m m e d i a t e l y a f t e r d e n t a l bleaching m ay increase enam el roughness19 and
t hat post poning oral hygiene for one or t w o hours aft er bleaching is adv ised20. I t should be not ed
WKDWLIVDPSOHVZHUHVWRUHGLQDUWL¿FLDOVDOLYDDIWHU bleaching, t heir abilit y of being st ained could be reduced due t o t he pot ent ial rem ineralizing effect t his solut ion.
Th er e w er e sig n if ican t d if f er en ces b et w een WKH WLPHV HYDOXDWHG DQG QRQH RI WKH Ʃ( YDOXHV obt ained was sm aller t han one unit . These dat a should be int erpret ed as a warning against absolut e rest rict ions on subst ances cont aining t he st udied d y es. Th e d at a su g g est t h at ev en 7 2 h af t er bleaching, t her e is st ill r isk of pigm ent at ion of t eet h subm it t ed t o dent al bleaching. Moreover, t he pigm ent at ion pot ent ial seem s t o be dependent on t he coloring agent , m ore t han on t he t im e elapsed DIWHUEOHDFKLQJ7KLVLGHDLVFRQ¿UPHGLQWKHSUHVHQW VWXG\ E\ WKH VWDWLVWLFDOO\ VLJQL¿FDQW LQWHUDFWLRQ HIIHFWVREVHUYHGIRUERWKWKH¨/DQG¨(YDOXHV2Q t he ot her hand, it would be int erest ing in t he fut ure t o evaluat e t he post - bleaching wait ing t im es using longer and short er t im es of exposure t o t he dyes.
CON CLUSI ON S
Considering t he lim it at ions of t his in v it r o st udy,
t he dat a obt ained suggest t hat :
7KH Ʃ( YDOXH ZDV GHSHQGHQW RQ WKH FRORULQJ agent wit h higher values being observed in t he t eet h pigm ent ed w it h a cola- based soft drink.
7HHWKSLJPHQWHGZLWKFRIIHHSUHVHQWHGƩ(YDOXHV
below 3.3 for all t im es in t he evaluat ion, but none RIWKHƩ(YDOXHVREWDLQHGZDVFRQVLGHUHGFOLQLFDOO\ undet ect able.
ACKN OW LED GM EN TS
The authors thank Mr. Fabio Grachiki for preparing t he schem at ic drawing of t he heat ing device used t o m aint ain t he t eet h t em perat ure and hum idit y, and Mr. Bruno Skronski Ton for his t echnical assist ance during t he experim ent . The aut hors are also in debt of Laborat ório de Prót ese Odont ológica Calgaro for providing t he spect rophot om et er em ployed in t he present st udy.
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