ABSTRACT
I n f lu en ce of pH, bleach in g agen t s, an d acid
et ching on surface w ear of bovine enam el
Ana Flávia SOARES1, Juliana Fraga Soares BOMBONATTI1 0DULQD 6WXGDUW $/(1&$51 (ODLQH &ULVWLQD &2162/0$*121+HLWRU0DUTXHV+21Ï5,22, Rafael Francisco Lia MONDELLI2
1- Universidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Dentística, Endodontia e Materiais Odontológicos, Bauru, SP, Brasil. 2- Universidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Odontopediatria, Ortodontia e Saúde Coletiva, Bauru, SP, Brasil.
&RUUHVSRQGLQJDGGUHVVRafael Francisco Lia Mondelli - Al. Dr. Octávio Pinheiro Brisolla, 9-75 - Bauru - SP - 17012-901 - C.P. 73 - Brazil - Phone: 55xx 14 3235-8265 - 55xx 14 98156-4686 - e-mail: [email protected]
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HYHORSPHQW RI QHZ PDWHULDOV IRU WRRWK EOHDFKLQJ MXVWL¿HV WKH QHHG IRU VWXGLHV WRevaluat e t he changes in t he enam el surface caused by different bleaching prot ocols. Obj ect ive: The aim of t his st udy was t o evaluat e t he bovine dent al enam el w ear in funct ion of different bleaching gel prot ocols, acid et ching and pH variat ion. Mat erial and Met hods: Sixt y fragm ent s of bovine t eet h w ere cut , obt aining a cont rol and t est areas. I n t he t est area, one half received et ching follow ed by a bleaching gel applicat ion, and t he ot her half, only t he bleaching gel. The fragm ent s w ere random ly divided int o six groups ( n= 10) ,HDFKRQHUHFHLYHGRQHEOHDFKLQJVHVVLRQZLWK¿YHK\GURJHQSHUR[LGHJHODSSOLFDWLRQVRI
m in, act ivat ed w it h hybrid light , diode laser/ blue LED ( HL) or diode laser/ violet LED ( VHL)
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( LPS35HL) ; 25% Lase Peroxide Sensy I I ( LPS25HL) ; 15% Lase Peroxide Lit e ( LPL15HL) ; and 10% hydrogen peroxide ( experim ent al) ( EXP10VHL) . pH values w ere det erm ined
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Tukey´ s t est s w ere applied (D= 0.05) . Result s: The pH show ed a slight decrease, except for Group LPL15HL. Group LPS25HL show ed t he highest degree of w ear, w it h and w it hout
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gels w ere able t o increase t he surface w ear values aft er sim ulat ed brushing. Acid et ching before bleaching increased surface w ear values in all groups.
Ke yw or ds: Toot h bleaching. Dent al acid et ching. Hydrogen- ion concent rat ion. Toot h wear.
I N TROD UCTI ON
Am ong t he t echniques t o reest ablish t he good aest het ics for discolor ed v it al t eet h, v it al t oot h bleaching is a m ore conservat ive and less invasive alt er nat ive t han dir ect and indir ect convent ional rest orat ion t echniques and has been w ell accept ed am ong pat ient s because t hey consider it a safe and effect ive t echnique22. The effect iveness of dent al EOHDFKLQJ LV LQÀXHQFHG E\ VHYHUDO IDFWRUV VXFK
as t he bleaching sy st em used, bleaching agent concent rat ion, applicat ion t im e and t he applicat ion of light1,16,26.
Lig h t sou r ces can b e u sed t o op t im ize t h e bleach in g pr ocedu r e in an at t em pt t o in cr ease t he rat es of peroxide dissociat ion and reduce t he
bleaching session2,7,16. Analyzing t he bovine enam el
w ear caused by different bleaching t echniques, t he
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enam el wear because sim ilar result s were obt ained wit h and wit hout light sources13,23. I n addit ion t o t he
above- m ent ioned fact ors, t he pH of t he bleaching agent s19 and acid et ching before t reat m ent6,12,16,25 DUH DOVR IDFWRUV WKDW FDQ GLUHFWO\ LQÀXHQFH WKH
w hit ening process. At t he present , m anufact urers have show n concern about t he acidit y of bleaching gels because a pH below t he crit ical point ( pH 5.5 t o 6.5)21 m ay result in t he dissolut ion of enam el,
m icrohardness alt erat ions14, increased sensit ivit y,
increased enam el w ear and surface roughness13,23.
bleaching gel and, consequent ly, t oot h bleaching16,
t he acid et ching t echnique can be used befor e t he bleaching pr ocedur e6. This t echnique w or k s
by pr oducing changes in t he enam el sur face in t w o dist in ct w ay s. Fir st , t h e acid r em ov es t h e surface layer and, consequent ly, t he plaque and a cq u i r ed f i l m a r e r em ov ed a n d , seco n d , t h e rem aining enam el wit h a m ore porous surface layer is also r em oved20.A gr eat er abilit y for per ox ide
penet rat ion was obt ained w hen t he previous acid et ching was per for m ed w it h a light sour ce6. An
increasing num ber of t oot h- bleaching product s are com m ercially available w it h different com posit ions and concent rat ions11, and now aday s, t her e is a
t rend t owards decreasing t he gels’ concent rat ion values and diver sify ing t heir for m ulat ions1,3,23,24. 7KHGHYHORSPHQWRIWKHVHQHZPDWHULDOVMXVWL¿HV
t he need for st udies t o evaluat e t he changes in t he enam el surface caused by different bleaching prot ocols.
Th u s, t h e aim of t h is in v it r o st u dy w as t o evaluat e t he bovine dent al enam el wear in funct ion of different bleaching gel prot ocols, t he acid et ching and pH variat ion.
M ATERI AL AN D M ETH OD S
This is an in v it r o st udy, and t he experim ent al design for pH analisys was divided int o t w o st udy
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agent s based on hydrogen peroxide ( H2O2) , t w o at 35% , one at 25% , one at 15% , and one at 10% ] and t im e periods ( at t w o levels: before and aft er bleaching) . Wear analysis consist ed of one st udy
fact or: t reat m ent [ in 11 levels: Cont rol ( did not receive t he acid et ching and bleaching gel) , and t w o at H2O2 35% , one at 25% , one at 15% , and one at 10% , wit h or wit hout acid et ching] . Different
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f act or s becau se dif f er en t bleach in g t r eat m en t s use different light sources follow ing t he prot ocol indicat ed by t he m anufact urer. The cont rol group
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Figure 1.
M a t e r ia l
The m at er ials and equipm ent s used for t his st udy are out lined in Figure 1.
M e t h ods
Spe cim e n pr e pa r a t ion
A t ot al of 60 bovine m andibular cent ral incisors w er e chosen for t he st udy. They w er e cut int o rect angular shapes and em bedded in slow- set t ing
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surface was produced by w et polishing w it h 320, 400, 600 and 1200- gr it silicon car bide abrasive papers. To cont rol t he individual variat ion in t he enam el surface charact erist ics am ong t he t est ed t eet h, each specim en was divided int o t w o halves, pr ov idin g a con t r ol ar ea an d a t est ar ea1 3 , 1 8 , 2 3.
The t est area was furt her divided, w it h one- half receiving 37% phosphoric acid ( Alpha Et ch; Nova DFL I ndúst r ia e Com ér cio S. A., Rio de Janeir o, Brazil) for 30 seconds follow ed by t he bleaching gel prot ocols, and t he ot her half receiving only t he bleaching gel prot ocols ( Figure 3) .
Material/Manufacturer Description
(Nova DFL Indústria e Comércio S.A., Rio de Janeiro, Brazil)
35% Hydrogen Peroxide gel
Lase Peroxide Sensy
(DMC Equipamentos Ltda., São Carlos, SP, Brazil)
35% Hydrogen Peroxide gel
Lase Peroxide Sensy II
(DMC Equipamentos Ltda., São Carlos, SP, Brazil)
25% Hydrogen Peroxide gel
Lase Peroxide Lite
(DMC Equipamentos Ltda., São Carlos, SP, Brazil)
15% Hydrogen Peroxide gel with nitrogen-doped titanium oxide nanoparticles
Experimental
(DMC Equipamentos Ltda., São Carlos, SP, Brazil) (Anvisa 25351.706466/2008-29)
10% Hydrogen Peroxide gel with nitrogen-doped titanium oxide nanoparticles
Alpha Etch
(Nova DFL Industry and Trade S.A., Rio de Janeiro, Brazil)
37% Phosphoric Acid
Whitening Lase II (Hybrid Light) (DMC Equipamentos Ltda., São Carlos, SP, Brazil)
6 Blue LEDs: 460 to 480 nm; 350 mW/cm2 each
Experimental Hybrid Light
(DMC Equipamentos Ltda., São Carlos, SP, Brazil)
6 Violet LEDs: 415 nm; 350mW/cm2 each
Ble a ch in g pr oce du r e
The specim ens w ere random ly divided int o six groups ( n= 10) described in Figure 2.
M e a sur e m e nt of pH le ve ls of ble a ching ge ls
To analyze t he pH levels of t he bleaching gels, a port able pHm et er wit h a digit al display ( Model 1001 Sent ron, Sent ron, WA, USA) was used. This device has an elect rode of sm all dim ensions, com pat ible w it h t he size of t he specim en. I t could m ake a readout w it h an accuracy of 0.01 in a few seconds and w it h m inim al wast e of bleaching gel. Before beginning each gr oup of r eadout s, t he pHm et er was calibrat ed w it h double st andar d subst ances
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t he bleaching gels w ere obt ained from t he average
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was t aken 30 seconds aft er t he cont act bet w een t he bleaching gel and t he bov ine enam el, and, t he second readout , 30 seconds aft er t he end of t he t im e used, w it h act ivat ion w it h a hybrid light source23.
Br u sh in g a br a sion
All t est ar eas, of t h e 6 0 st u died specim en s
( d i v i d ed i n t o si x g r o u p s) , w er e su b j ect ed t o sim u lat ed t oot h b r u sh in g . Th e t oot h - b r u sh in g m ach in e r em ain ed in a con t r olled t em per at u r e o f 3 7 ± 2 ° C w i t h so f t n y l o n b r i st l e s ( Co l g a t e Classic CLEAN, Colgat e Palm olive I ndust rial Lt da., Osasco, SP, Brazil) , applying a load of 300 gram s on t he sam ples. Slur r y was pr epar ed by m ixing 2: 1 of deionized wat er and Colgat e MFP ( Colgat e Palm olive, Osasco, SP, Brazil) dent ifrice by w eight im m ediat ely before t est ing. One hundred t housand brushing st rokes were perform ed for each specim en and t he br ist les w er e changed at t he half- cycle point . Aft er t est ing, t he specim ens w er e r insed under running wat er and cleaned in a sonic device ( Crist ófoli Biosafet y Equipm ent Lt da., Londrina, PR, Brazil) in deionized wat er for 10 m inut es, and t hen st ored in fresh deionized wat er ( 37± 2° C)13,15,18,23.
W e a r de t e r m in a t ion
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m e t e r ( H o m m e l w e r k e Gm b H r e f. # 2 4 0 8 5 1 , Schwenningen, Germ any) connect ed t o a PC w it h
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of t he surfaces t est ed. For each segm ent of t he specim en, six m easurem ent s w ere carried out at
Description Enamel Pretreatment Bleaching Protocol
Control (C)
---35% Lase Peroxide Sensy (LPS35HL)
25% Lase Peroxide Sensy II (LPS25HL)
15% Lase Peroxide Lite (LPL15HL)
---37% phosphoric acid for 30 seconds
---37% phosphoric acid for 30 seconds
---37% phosphoric acid for 30 seconds
---37% phosphoric acid for 30 seconds
applications:
One minute after the gel application, three consecutive minutes of diode laser/blue LED hybrid light activation were performed followed by a one minute interval and another three minutes of hybrid light activation.
Total of 40 min gel application
(Total of 30 min of light activation)
10% H2O2 (experimental) (EXP10VHL)
---37% phosphoric acid for 30 seconds applications:
One minute after the gel application, three consecutive minutes of diode laser/violet LED hybrid light activation were performed followed by a one minute interval and another three minutes of hybrid light activation.
Total of 40 min gel application
(Total of 30 min of light activation)
random , t hree readout s w ere perform ed on each por t ion ( w it h or w it h ou t acid et ch in g) an d t h e m ean w ear value was calculat ed ( Figure 3) . These
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su r f a ce ( p r o t ect ed a r ea ) o n o n e si d e t o t h e opposit e one, crossing t he surface exposed t o t he experim ent al procedures. Thus, t he w ear readout
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t he dist ance in m icr om et er s bet w een t he graph m idline, corresponding t o t he specim en plane line ( int act area) and t he deepest valley corresponding t o t he ground area8,13,18,23.
St a t ist ica l a n a lysis
For correlat ion analyses bet w een pH and w ear,
t h e Pear son cor r elat ion t est w as u sed. For pH an aly sis, t w o- w ay r ep eat ed m easu r es ANOVA follow ed by t he Tukey` s t est w ere used. For w ear, one- way ANOVA follow ed by t he Tukey’s t est w ere
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adopt ed.
RESULTS
Th er e w as n o cor r elat ion b et w een p H an d w ear. When analyzing t he pH values ( Table 1) , a
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Peroxide Lit e act ivat ed w it h hybrid light group. The low est values w er e found in t he 35% hydr ogen
Groups Time of measurement Mean ± Standard Deviation*
TBO35HL Initial
Final
6.42±0.27A
6.01±0.11B
LPS35HL Initial
Final
7.08±0.25C
6.11±0.11B
LPS25HL Initial
Final
7.12±0.05C
6.42±0.08A
LPL15HL Initial
Final
7.59±0.08D
7.47±0.07D
EXP10VHL Initial
Final
9.23±0.05E
8.99±0.07F
Tukey´s method
Table
peroxide Groups act ivat ed w it h hybrid light at t he end of t he bleaching agent applicat ion. The group t hat show ed m ore alkaline was t he experim ent al 10% hydrogen peroxide Group wit h nit rogen- doped t it anium oxide nanopart icles, act ivat ed w it h violet hybrid light , w hich had a low er concent rat ion of
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m easurem ent s.
The one- w ay ANOVA t est for evaluat ing t he su r f a ce w e a r sh o w e d st a t i st i ca l l y si g n i f i ca n t differences bet w een t he t est ed groups ( p< 0.05) . Next , t he Tukey’s t est was applied for t he values obt ained ( Table 2) . All groups, except t he 35% Tot al
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i n cr e a se w h e n a ci d e t ch i n g w a s p r e v i o u sl y perform ed. The low est w ear value was found in cont rol group ( Group C) , w hich did not undergo t he acid et ching and dent al bleaching, and t he 25% Lase Peroxide Sensy I I Group ( LPS25HL) w it h prior acid et ching show ed t he highest w ear value. The Group LPS25HL w it hout acid et ching show ed sim ilar result s ( p< 0.05) t o t he ot her groups w here t he et ching was done ( Figure 4) .
D I SCUSSI ON
Most st udies on dent al bleaching invest igat es t he m orphological changes in t he enam el10,13,14,23 and
t he pulp dam age5,17 caused by different t echniques,
how ever, t he changes caused by differences of t he bleaching gels’ pH is st ill cont r over sial23. I n t his
st udy w hen observing t he result s obt ained by pH analysis of bleaching agent s, one could conclude t hat t here was a t rend t owards a decrease in t he
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per iods, except for t he 15% Lase Per ox ide Lit e Group act ivat ed w it h hybrid light [diode laser/ blue
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differences ( Table 1) . Anot her im port ant fact t hat has already been described in t he lit erat ure23,27 and
corroborat es w it h t his st udy, is t hat t he higher t he concent rat ion of hydrogen peroxide, t he m ore acidic is t he pH in t he bleaching gels.
I n t h is st u d y, t h e EXP1 0 VHL ex p er im en t al gr ou p ( gel w it h n it r ogen - doped t it an iu m ox ide nanopar t icles) act ivat ed w it h hybr id light [ diode laser/ violet LED ( VHL) ( experim ent al) ] , present ed t he highest pH values in com parison t o t he ot her gr oups evaluat ed. The HL and VHL hy br id light so u r ce s e m p l o y e d t o a ct i v a t e t h e b l e a ch i n g gels pr esen t ed a m in im u m in cr ease ( less t h an 2 ° C) in p u lp ch am b er t em p er at u r e1, assu r in g
Figure 4- Graphic of mean (μm) and standard deviation of wear of the groups (C - without etching and without bleaching - and other groups with only bleaching or acid etching prior to bleaching)
Groups Mean ± Standard
Deviation*
C (no bleaching) 4.86±1.28A
TBO35HLB 10.47±1.58BD
TBO35HLA 12.49±1.60CDE
LPS35HLB 9.97±1.42BD
LPS35HLA 14.21±0.83C
LPS25HLB 13.85±1.71C
LPS25HLA 23.67±3.93F
LPL15HLB 9.80±1.52B
LPL15HLA 13.51±1.38CE
EXP10VHLB 11.13 ±0.82BDE
EXP10VHLA 14.70±0.40C
difference between lines, at the level of 5% calculated by the Tukey´s method
effect ive dent al bleaching w it h low pulp risk6. The
values obt ained for t he pH of hydrogen peroxide, regardless of t he group st udied, rem ained above t he level considered crit ical for enam el dissolut ion ( pH 5.5 t o 6.5)21. How ever, it was not ed t hat as t he
concent rat ion of t he gel dim inished, it s pH increased ( Table 1) . Therefore, t he pH of t hese bleaching gels is unlikely t o cause severe m orphological changes on t he surface of t he enam el.
Aci d co n d i t i o n i n g p r i o r t o b l e a ch i n g i s a procedure st ill used in dent al pract ice, how ever,
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DUHVWLOOQRWFODUL¿HG$UHFHQWVWXG\6 show ed t hat
t here is no difference in t he color analysis w hen acid con dit ion in g is pr ev iou sly don e, added t o t his, t his st udy show ed an increased w ear due t o t he acid condit ioning w hen t he sam e bleaching gel concent rat ion was analyzed. Only t he Group TBO35HL show ed no increased w ear in t he area w it h acid et ching, in com par ison w it h t he ar ea t hat received only t he bleaching gel ( Table 2) . I n t he com parison bet w een groups, Group LPS25HL show ed t he highest w ear for t he area w it h acid et ching ( Table 2) .
Com paring t he cont rol group, w hich underw ent brushing cycles only, w it h t he ot her groups, it was
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less w ear ( Table 2) t han t he experim ent al groups in t h e ar ea t r eat ed w it h bot h t h e acid et ch in g and bleaching gel and t he area t reat ed only w it h bleaching gel. Cert ainly, t hese differences in w ear are due t o t he changes caused by t he bleaching ag en t s on t h e d en t al en am el, r esu lt s alr ead y found in t he lit erat ure, in w hich t oot h- bleaching t ech n iqu es led t o in cr eased su r f ace r ou gh n ess and w ear if subj ect ed t o sim ulat ed t oot h brushing, w hen com pared w it h t he cont rol group t hat was only brushed13,16,23.
Not e t hat in t his st udy t he dent al bleaching m ay have left t he surface of t he bovine enam el m ore suscept ible t o wear caused by t he 100,000 sim ulat ed brushing cycles, w hich is in agreem ent w it h t he
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m ak es t he enam el sur face m or e suscept ible t o a b r a si o n a n d m o r p h o l o g i ca l ch a n g es1 , 9 , 1 3 , 2 3 , 2 8.
The adopt ed sim ulat ed t oot h br ushing ( 100,000 sim ulat ed brushing cycles) caused w ear bet w een
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because ot her fact ors cont ribut e t o t he loss of t his st ruct ure. These cycles are equivalent , on average, t o t w o years of brushing in v iv o4,15, a period t hat
was adopt ed for being considered as a safe int erval bet w een bleaching sessions.
The analysis of t his research’s result s, associat ed
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evaluat ion t hat , in general, t he 25% Lase Peroxide Sensy I I Gr oup act ivat ed w it h hy br id light ( HL) ( diode laser/ blue LED) present ed t he highest w ear
values, causing gr eat er aggr ession t o t he t oot h st ruct ure. The acid et ching was m ore severe in all
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Group. Alt hough a direct correlat ion was not found w it h t he result s of w ear, it was observed t hat t he low er t he bleaching gel concent rat ion, t he m ore alkaline it t ended t o be.
Acid et ching prior t o bleaching can be indicat ed
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obt aining sat isfact or y r esult s aft er at t em pt s by con v en t ion al w h it en in g t ech n iq u es, esp ecially in pat ient s w it h a high degr ee of pigm ent at ion, seek ing a gr eat er penet rat ion of t he gel t o t he e n a m e l . Ho w e v e r, f e w st u d i e s e v a l u a t e t h i s procedure and it s consequences, t hus j ust ifying t he obj ect ive of t his st udy, w hich, despit e being an in v it r o st udy, seeks t o answ er quest ions t hat m ay
assist in t he clinical pract ice of t he procedure. The result s of t his st udy show t hat et ching w it h 37% phosphoric acid can lead t o increased enam el wear, and should not be used as a rout ine procedure, only w hen necessary in an at t em pt t o avoid m ore invasive procedures such as cavit y preparat ion and product ion of indirect rest orat ions.
How ever, furt her st udies relat ed t o t he effect s of acid et ching, pH, and different concent rat ions
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ext rapolat e t he result s t o t he clinical cont ext .
CON CLUSI ON S
Wit hin t he lim it at ions of t his in v it r o st udy, t he following conclusions can be draw n:
There was a t rend t owards a decrease in t he init ial pH at t he end, except in t he Lase Peroxide Lit e 15% Group. There was no direct correlat ion bet w een t he values of pH and surface w ear.
Differ ent bleaching gels ar e able t o incr ease t he surface w ear values aft er sim ulat ed brushing, m ainly in t he Lase Peroxide Sensy 25% Group.
Acid et ch in g befor e bleach in g in cr eased t h e surface w ear values in all groups.
ACKN OW LED GEM EN TS
Th e au t h or s t h an k t h e Nat ion al Cou n cil f or
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7) .
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![Table 2- Means ( μ m) and standard deviation of wear of the groups studied, comparing the two treatments [bleaching (B) and acid etching + bleaching (A)] and the control group](https://thumb-eu.123doks.com/thumbv2/123dok_br/14984219.511497/5.892.88.794.839.1119/standard-deviation-studied-comparing-treatments-bleaching-etching-bleaching.webp)
