Abst ract
Submitted: December 30, 2016 0RGL¿FDWLRQ0DUFK Accepted: May 2, 2017
Com parat ive st udy bet w een laser
and convent ional t echniques for
class V cavit y pr eparat ion in gam m
a-ir radiat ed t eet h ( in vit r o st udy)
Ob j ect i v e: Th e p u r p ose of t h i s st u d y w as t o com p ar e l aser w i t h convent ional t echniques in class V cavit y pr eparat ion in gam m a- ir radiat ed t eet h. Met hods: For t y ext ract ed hum an t eet h w it h no car ious lesions w er e used for t his st udy and w er e divided int o t w o m ain gr oups: Gr oup I ( n= 20) was not subj ect ed t o gam m a radiat ion ( cont r ol) and Gr oup I I ( n= 20) was subj ect ed t o gam m a radiat ion of 60 Gray. St andar d class V pr eparat ion was per for m ed in buccal and lingual sides of each t oot h in bot h gr oups. Buccal sur faces w er e pr epar ed by t he Er,Cr : YSGG laser ( Wat er lase iPlus) 2780 nm , using t he gold handpiece w it h MZ10 Tip in non- cont act and t he “ H” m ode, follow ing param et er s of cavit y pr eparat ion – pow er 6 W, fr equency 50 Hz, 90% wat er and 70% air, t hen shift ing t o sur face t r eat m ent laser param et er s – pow er 4.5 W, fr equency 50 Hz, 80% wat er and 50% air. Lingual sur faces w er e pr epar ed by t he convent ional high- speed t ur bine using r ound diam ond bur. Teet h w er e t hen sect ioned m esio- dist ally, r esult ing in 80 specim ens: 40 of w hich w er e buccal laser- t r eat ed ( 20 cont r ol and 20 gam m a- ir radiat ed specim ens) and 40 w er e lingual convent ional high- speed bur specim ens ( 20 cont r ol and 20 gam m a- ir radiat ed specim ens) . Result s: Micr oleakage analysis revealed higher scores in bot h gam m a groups com pared wit h cont rol JURXSV &KLVTXDUH WHVW UHYHDOHG QR VLJQL¿FDQW GLIIHUHQFH EHWZHHQ ERWK FRQWUROJURXSVDQGJDPPDJURXSVS UHVSHFWLYHO\$VLJQL¿FDQW difference was revealed bet ween all 4 groups ( p= 0.00018) . Conclusion: Bot h laser and convent ional high- speed t ur bine bur show good bond st r engt h in cont r ol ( non- gam m a) gr oup, w hile m icr oleakage is evident in gam m a gr oup, indicat ing t hat gam m a radiat ion had a dram at ic negat ive effect on t he bond st r engt h in bot h laser and bur- t r eat ed t eet h.
Ke y w or ds: Laser. Gam m a ray. Amr H. M. RASMY1
Tarek A. HARHASH2
Rami M. S. GHALI3
Eman M. F. EL MAGHRABY1
Dalia H. EL ROUBY4
http://dx.doi.org/10.1590/1678-7757-2016-0663
1Egyptian Atomic Energy Authority, National Centre for Radiation Research and Technology (NCRRT),
Health Radiation Research Department, Cairo, Egypt.
2Cairo University, National Institution of Laser Enhanced Sciences, Medical Laser Applications
Department, Cairo, Egypt.
3$DFKHQ8QLYHUVLW\$DFKHQ'HQWDO/DVHU&HQWHU$DFKHQ*HUPDQ\$LQ6KDPV8QLYHUVLW\&DLUR
Egypt.
4Cairo University, Faculty of Oral & Dental Medicine, Oral Pathology Department, Cairo, Egypt.
I nt r oduct ion
Radiot herapy is a com m on t herapeut ic m odalit y for m alignancies of head and neck. I t is usually associat ed w it h som e possible com plicat ions such as radiat ion car ies, xer ost om ia, ost eonecr osis, loss of t ast e and t r ism us17.
Th e sy m p t o m s o f m i cr o l e a k a g e r a n g e f r o m post operat ive hypersensit ivit y or loss of t he rest orat ion due t o bond failur e t o dam age t o v it al dent in and pulp t issue, which in som e cases m ay be irreversible. Effect s of m icr oleak age include m ar ginal discolorat ion and secondar y car ies, w hich ar e due t o t he pr esence of bact er ia, t heir nut r ient s or hydr ogen ions, or iginat ing f r om p laq u e on t h e su r f ace an d leak in g in t o t h e in t er f acial sp ace. Bact er ial m ar g in al leak ag e h as been im plicat ed as an et iological fact or in r ecur r ent car ies and pulp ir r it at ion follow ing t he applicat ion of r est orat ions9.
Many different t echniques m ay be used t o evaluat e m icroleakage, including air pressure, bact erial st udies, r ad ioisot op e st u d ies, n eu t r on act iv at ion st u d ies, scanning elect r on m icr oscope, chem ical t racer s and dye penet rat ion st udies21,30,31.
$ VWXG\ SHUIRUPHG WR LQYHVWLJDWH WKH LQÀXHQFH
of t h er apeu t ic dose X- r ay s on t h e m icr oh ar dn ess and degr ee of conver sion of t w o differ ent aest het ic rest orat ive dent al m at erials found t hat t he t herapeut ic dose applied t o cur ed m at er ial can pr om ot e link ing an d b r eak in g of ch ain b on d s. Th u s, t h e au t h or s r ecom m ended t hat t he confect ion of a new dent al rest orat ion w it h a phot o- cured com posit e resin should be m ade aft er t he end of radiot herapy and nev er befor e, and old r est orat ions should be at t ended and r eplaced w hen necessar y7.
Bu lu cu , et al.5 ( 2 0 0 9 ) ev alu at ed t h e ef f ect of
radiot herapy on t he m icr oleak age of t hr ee adhesive
V\VWHPVDQGREVHUYHGQRVLJQL¿FDQWGLIIHUHQFHZKHQ
com p ar in g d if f er en t ad h esiv e sy st em s. How ev er,
VLJQL¿FDQWGLIIHUHQFHVZHUHREVHUYHGEHWZHHQHQDPHO
and dent in ( p< 0.01) , in w hich t he m icr oleak age at
t he dent in m ar gins was gr eat er t han at t he enam el
m ar gins.
Nav es, et al.1 6 ( 2 0 1 2 ) ev alu at ed t h e ef f ect of
gam m a radiat ion on t he m icr ot ensile bond st r engt h o f r esi n - b a sed co m p o si t e r est o r a t i o n t o h u m a n enam el and dent in per for m ed eit her befor e or aft er r adiot h er apy. Th e au t h or s con clu ded t h at gam m a
UDGLDWLRQKDGDVLJQL¿FDQWGHWULPHQWDOHIIHFWRQERQG
st r en g t h t o h u m an en am el an d d en t in w h en t h e adhesive r est orat ive pr ocedur e was car r ied out aft er radiot herapy.
Since pr ev ious st udies evaluat ed eit her t he effect of laser cav it y pr eparat ion or gam m a ir radiat ion on sur face r oughness and m icr oleak age, t he com bined effect of bot h var iables st ill needs t o be invest igat ed.
Ther efor e, t his st udy was car r ied out t o det ect t he sur face m or phology and pr esence of m icr oleak age in com posit e r esin r est orat ion follow ing et ched bur cav it y pr eparat ion an d laser cav it y pr eparat ion in ir radiat ed t eet h.
Mat er ial and m et hods
I n t his st udy, w e used 40 m olar t eet h w it h no car ious lesions, ex t ract ed fr om m ales of age 40- 50 year s fr om t he Sur ger y Depar t m ent of t he Facult y of Dent ist ry, Cairo Universit y, due t o periodont al diseases or in pr eparat ion t o r eceive a full dent ur e. Teet h w er e st or ed in a 0.1% t hy m ol solut ion unt il t he st udy was car r ied out26.
They w er e div ided int o t w o m ain gr oups:
Gr ou p I ( n = 2 0 ) w as n ot su bj ect ed t o gam m a radiat ion ( cont r ol) .
Group I I ( n= 20) was subj ect ed t o gam m a radiat ion of 60 Gray, w hich is t he t herapeut ic dose for head and neck lesions11.
Radiat ion exposur e
I r radiat ion of t eet h was per for m ed at t he Nat ional Ce n t r e f o r Ra d i a t i o n Re se a r ch a n d Te ch n o l o g y ( NCRRT) , in Cairo, Egypt , using t he 137- Cesium source Gam m acell® 40, at a dose rat e of 0.761 Gy / m in at t he
t im e of t he st udy.
Laser applicat ion
Cavit y pr eparat ion
A st andar d class V pr eparat ion was per for m ed on buccal and lingual sides of each t oot h in bot h gr oups w it h t h e f ollow in g d im en sion s: d iam et er 3 m m ; dept h 3 m m ; about 2 m m occlusally t o t he cem ent -enam el j unct ion25. Lingual sur faces w er e pr epar ed
by t he convent ional high- speed t ur bine using r ound num ber 3411 diam ond bur, while buccal surfaces were pr epar ed by t he Er,Cr : YSGG laser ( Wat er lase iplus) .
Aft er war ds, t eet h w er e sect ioned m esio- dist ally, r esult ing in 80 specim ens, 40 of w hich w er e buccal laser- t r eat ed ( 20 cont r ol and 20 gam m a- ir radiat ed specim ens) and 40 w er e lingual convent ional high-speed bur specim ens ( 20 cont r ol and 20 gam m a-ir radiat ed specim ens) , r esult ing in t he four gr oups of t his st udy :
Cont r ol, laser- t r eat ed gr oup ( CL) ;
Con t r ol, con v en t ion al h ig h - sp eed b u r - t r eat ed gr oup ( CB) ;
Gam m a, laser- t r eat ed gr oup ( GL) ;
Gam m a, con v en t ion al h ig h - sp eed b u r - t r eat ed gr oup ( GB) .
Fr om each gr oup 10 specim ens w er e subj ect ed t o scanning elect r on m icr oscope ( SEM) t o st udy t heir sur face m or phology and 10 specim ens w er e used t o m easur e t he m icr oleak age, using st er eom icr oscope.
Scanning elect r on m icr oscope ( SEM)
To st u d y su r f ace m o r p h o l o g y u si n g scan n i n g elect r on m icr oscopy, specim ens w er e pr epar ed as follow s:
Each specim en was dehydrat ed in graded alcohol ( et hanol) ser ies ( 50, 70, 85, 90 and 100% ) for 10 m inut es at each concent rat ion, and t hen coat ed w it h
DWKLQ¿OPRIJROGE\VSXWWHULQJFRDWHU$QDO\VLVZDV
per for m ed using scanning elect r on m icr oscopy ( SEM, Philips XL30, % 600MD, Eindhoven, Net her lands) .
The m icr oleakage t est
Fo r m e a s u r i n g t h e m i c r o l e a k a g e u s i n g st er eom icr oscope ( SZ- DC Olym pus, Cam era Olym pus DC10, Japan) , specim ens ( bot h cont r ol and gam m a-ir radiat ed) w er e pr epar ed as follow s:
Each convent ional high- speed t urbine bur specim en was acid- et ched using phosphor ic acid 30% gel for 30 seconds and t hen wat er sprayed for anot her 30 seconds and dr ied w it h air for 20 seconds, w hile t he laser- t r eat ed specim en was used dir ect ly w it hout acid et ching. Bot h gr oups – laser t r eat ed and convent ional
high- speed t ur bine bur – w er e subj ect ed t o a bonding agent ( Adper Single Bond, 3M, ESPE, St . Paul, USA) and adhesiv e com posit e ( Filt ek Z 2 5 0 , 3 M, ESPE, St . Paul, USA, Shade A3) was light - act ivat ed using l i g h t - cu r i n g d ev i ce ( w i t h 8 0 0 m w / cm2 i n t en si t y,
Woodpecker, USA) for 20 seconds, accor ding t o t he m anufact urer ’s inst ruct ions. Rest orat ions were kept at
URRPWHPSHUDWXUHIRUKRXUVDQGZHUH¿QLVKHGDQG
polished using rubber cups. The m icroleakage t est was car r ied out w it h t he w hole t oot h sur face – except for
WKH¿OOHGFDYLWLHVDQGWKHUHJLRQDURXQGPPEH\RQG
t he m ar gins of t he cav it ies – was coat ed w it h a nail var nish; t hen, t he specim ens w er e im m er sed in a 2% m et hy lene blue solut ion under a t her m o- cycling bat h for 48 hour s, t hen washed. Specim ens w er e bisect ed at a bucco- lingual ( palat al) plane w it h a diam ond disc ( D&Z, Ger m any ) , and scor ed for any m icr oleak age using a st er eom icr oscope ( SZ- DC Oly m pus, Cam era Oly m pus DC10, Japan)2,25,29.
The degr ee of m icr oleak age was assessed using a 4- grade scale ( Figur e 1) and t he t echnician was not inform ed of t he nat ure and purpose of t he experim ent . Wh en bot h sides of t h e sam e specim en r ev ealed differ ent scor es, t he highest scor e was r ecor ded.
St at ist ical analy sis was t hen per for m ed using a com m er cially available soft war e pr ogram ( SPSS 19; SPSS, Chicago, I L, USA) t o com par e t he m icr oleakage scor es r ecor ded for differ ent gr oups using t he
Chi-VTXDUH WHVW 7KH OHYHO RI VLJQL¿FDQFH ZDV VHW DW
p< 0.05.
Result s
Micr oleakage analysis
Result s of m icr oleak age analy sis r evealed higher scor es in bot h gam m a and cont r ol gr oups. The
Chi-VTXDUHWHVWUHYHDOHGQRVLJQL¿FDQWGLIIHUHQFHEHWZHHQ
bot h cont r ol gr oups, neit her bet w een bot h gam m a g r ou p s ( p = 1 , 0 . 8 1 9 , r esp ect iv ely ) . A sig n if ican t difference was revealed in all four groups ( p= 0.00018) ( Table 1, Figur es 2- 6) .
Scanning elect r on m icr oscope r evealed st r uct ural
changes of t he dent ine sur face m or phology subj ect ed t o l aser i n t h e co n t r o l g r o u p ( CL) . Th e t u b u l ar st r u ct u r e cou ld b e id en t if ied in som e sp ecim en s ( Figure 7) while in ot hers, t he dent ine surface revealed
FRQÀXHQFH RI WXEXODU DQG LQWHUWXEXODU VWUXFWXUHV LQ VRPH DUHDV ,UUHJXODU LQWHUODFLQJ FROODJHQ ¿EHUV
and par t ially oblit erat ed dent inal t ubules w er e also obser ved ( Figur es 8, 9) . I n t he gam m a laser ( GL) gr oup, t he int er- t ubular dent ine was ablat ed m or e t han t he per it ubular dent ine, giv ing t he appearance of ir r egular it y and pr ot r usion of t he dent inal t ubules ( Figur e 10) .
&RQÀXHQFHRIWXEXODUDQGLQWHUWXEXODUVWUXFWXUHV
was not ed in som e ar eas, w hile in ot her s t he t ubular st r u ct u r e w as m ain t ain ed an d r ev ealed v ar iat ion in t ubular diam et er w it h ir r egular dent ine sur face ( Figur es 11, 12) .
On t he ot her hand, in t he cav it y sur face pr epar ed w it h t he convent ional high- speed t ur bine bur in t he
FRQWURO &% JURXS GHQWLQDO WXEXOHV RUL¿FHV ZHUH
relat ively closed ( Figure 13) ; however, aft er t reat m ent w it h 3 7 % p h osp h or ic acid , t h e sm ear lay er w as r em oved and t he dent inal t ubules becam e obv ious.
Groups Score 0 Score 1 Score 2 Score 3 P1 value P2 value
Control groups Laser (N=10) 0 0 1ns
Bur (N=10) 0 0
Gamma groups Laser (N=10) 0 0.819ns
Bur (N=10) 0
QV QRQVLJQL¿FDQWVLJQL¿FDQWDWS
3VLJQL¿FDQFHRIGLIIHUHQFHEHWZHHQERWKFRQWURODQGJDPPDJURXSV 3VLJQL¿FDQFHRIGLIIHUHQFHEHWZHHQDOOJURXSV
Table 1-0LFUROHDNDJHVFRUHLQDOOJURXSVDQGVLJQL¿FDQFHRIWKHGLIIHUHQFH&KLVTXDUHWHVW
Figure 2- Photomicrograph of control group (laser) showing no micro leakage (score 0)
Figure 3- Photomicrograph of control group (bur) showing no micro leakage (score 0)
Figure 5- Photomicrograph of gamma group (bur) showing micro leakage (score 3)
Figure 6- Micro-leakage scores in all groups
Figure 7- Electron-micrograph in control (CL) group after cavity preparation with laser revealing a rough irregular surface. The smear layer was removed and the surface structure is maintained (x2,000)
Figure 9- Electron-micrograph in control (CL) group after cavity preparation with laser showing irregular dentinal tubules with partially obliterated lumen intermingled with areas where the WXEXODUVWUXFWXUHFDQ¶WEHLGHQWL¿HG[
Figure 8- Electron-micrograph in control group (CL) after cavity SUHSDUDWLRQZLWKODVHUVKRZLQJFRQÀXHQFHRIWXEXODUDQGLQWHU tubular structures in some areas. Irregular inter-lacing collagen ¿EHUV DQG SDUWLDOO\ REOLWHUDWHG GHQWLQDO WXEXOHV DUH DOVR QRWHG (x500)
The int er- t ubular dent ine was m or e ablat ed t han t he per it ubular one ( Figur e 14) .
Moreover, specim ens prepared wit h t he convent ional high- speed t ur bine bur in gam m a ( GB) gr oup ( befor e
DFLGHWFKLQJUHYHDOHGDÀDWVXUIDFHFRYHUHGZLWKD
sm ear layer, w it h m any crack s and debr is ( Figur e 15) . Sim ilar ly t o t he cont r ol gr oup, aft er t r eat m ent w it h 37% phosphor ic acid, t he sm ear layer was r em oved and t he dent inal t ubules becam e obv ious, w her e t he int er- t ubular dent ine appear ed m or e ablat ed t han t he per it ubular one ( Figur e 16) .
Figure 11- Electron-micrograph in gamma and laser (GL) group showing irregular dentine surface after cavity preparation. The tubular structure is maintained in most areas and reveals variation in tubular diameter (x2,000)
Figure 12- Electron-micrograph in gamma (GL) group subjected to laser showing dentine surface after cavity preparation. &RQÀXHQFHRIWXEXODUDQGLQWHUWXEXODUVWUXFWXUHVLVQRWHGLQVRPH areas, while in other areas, the tubular structure is maintained and reveals variation in tubular diameter (blue arrow), (x500)
Figure 13- Electron-micrograph in control (CB) group subjected to conventional high speed turbine bur before acid etching showing
WKHGHQWLQDOWXEXOHVRUL¿FHVZHUHUHODWLYHO\FORVHG[ Figure 14- Electron-micrograph in control (CB) group subjected
to conventional high speed turbine bur after acid etching where the smear layer was removed and the dentinal tubules were obvious. The intertubular dentine appears more ablated than the peritubular one (x2,000)
Discussion
Cav it y pr eparat ion per for m ed by t he Er,Cr : YSSG laser of wavelengt h 2780 nm show ed t he possibilit y t o perform cavit ies wit hin a few m inut es. However, t he required t im e for use of t he laser was m uch longer t han t he use of t he convent ional high- speed bur because
WKHUHPRYDORIHQDPHOWLVVXHVZDVPRUHGLI¿FXOWZLWK
t he use of laser. Hence, cut t ing t hr ough t he enam el
E\ODVHUKDGDORZHUHI¿FLHQF\WKDQFXWWLQJWKURXJK
t he dent ine because of t he less quant it y of wat er and or ganic cont ent s of enam el st r uct ur es if com par ed w it h dent ine st r uct ur es1.
Laser param et er s used in t his st udy r evealed t hat t he surface m ean t em perat ure did not exceed 4º C t hat is believed t o be safe for pulp v it alit y13.
Af t er per f or m in g t h e m icr oleak age t est , som e dye m ay have penet rat ed int o t he r esin in a m uch-diffused way such t hat scor e 0 m eans low- level dye penet rat ion.
Pr ev ious m or phological st udies of enam el sur face show ed pr ot r uding pr ism sheat hs w it hout er osion, w hile t he dent ine sur face show ed ex posed dent inal t u b u l e s o r i f i ce s. Th i s i s b e l i e v e d t o b e d u e t o m icr oex plosion ef f ect s cau sed by t h e h ar d t issu e ablat ion wit h t he Er,Cr: YSSG laser of wavelengt h 2780
QP0RUHRYHUVXUIDFHVVKRZVFDO\RUÀDN\LUUHJXODU
appearance1. How ever, in case of acid et ching dur ing
norm al rest orat ive procedures, chem ical changes m ay lead t o incr easing dent ine per m eabilit y and w et ness
DQG LQFUHDVLQJ LQ SXOS LUULWDWLRQ ZLWK PRGL¿FDWLRQ RIWKHRUJDQLFFRPSRQHQWDQGGHFDOFL¿FDWLRQRIWKH
inor ganic par t of t he har d t oot h st r uct ur es4,19.
Acco r d i n g t o a st u d y co n d u ct ed b y Yam ad a, et al.2 8 ( 2 0 0 0 ) , w h o u sed dif f er en t dy e t y pe an d
concent rat ion but t he sam e soaking t im e for m easuring
WKH PLFUROHDNDJH WHVW VXUIDFH URXJKQHVV LQÀXHQFH
t h e m icr oleak ag e t est or b on d st r en g t h b ecau se a r ougher sur face for a given cr oss sect ional ar ea w ou ld h av e a gr eat er su r f ace ar ea, decr easesin g m icroleakage and increasing bond st rengt h. Therefore, t he highly ir r egular sur faces or r oughness w it hout a sm ear layer in laser cav it ies could pr ov ide a suit able sur face for good adhesion or st r ong bonding w it h r est orat ive m at er ials in com par ison w it h acid- et ched sur faces – t hus, it is possible t o avoid acid et ching12,27.
+RZHYHURXU¿QGLQJVDUHLQDJUHHPHQWZLWKWKDWRI
Subram aniam and Pandey2 6 ( 2 0 1 6 ) , w ho used t he
sam e dye t ype and concent rat ion but different soaking
WLPH IRU PHDVXULQJ WKH PLFUROHDNDJH WHVW ¿QGLQJ QR VLJQL¿FDQW GLIIHUHQFH LQ PLFUROHDNDJH EHWZHHQ
com posit e r esin bonded t o lased enam el and dent ine and t eet h pr epar ed w it h convent ional m et hod. The aut hor s also not ed t hat t he m icr oleak age obser ved in bot h gr oups was due t o t he pr esence of gaps at t he resin- t oot h int erface and t hat t his, in t urn, m ay be due t o poor adapt at ion or less penet rat ion of resin m at erial int o dent inal t ubules, ent rapped air and inadequat e
FXULQJ RI WKH PDWHULDO 7KXV UHVLQV ZLWK JRRG ÀRZ
charact erist ics and surface t reat m ent of laser- prepared cav it ies have been suggest ed for bet t er w et t ing and penet rat ion29.
2XU ¿QGLQJV DUH LQ FRQWUDVW ZLWK WKDW RI VWXGLHV
of Palm a- Dibb, et al.18 ( 2002) , Cor ona, et al.6 ( 2003)
and Roebuck , et al.23 ( 2000) , w ho used differ ent dye
t y pe, concent rat ion and soak ing t im e for m easur ing t he m icr oleak age t est , r epor t ing a higher degr ee of m icr oleak age ar ound com posit e r est orat ions w hen cav it y p r ep ar at ion w as p er f or m ed b y t h e Er : YAG l aser. Pal m a- D i b b , et al .1 8 ( 2 0 0 2 ) d em o n st r at ed
t hat , by scanning elect r on m icr oscope ( SEM) , t he m or phology of lased sur faces r ev eals an ir r egular ab lat ion p at t er n an d n on - su f f icien t et ch in g w it h presence of uncondit ioned dent al surface areas, which
PD\EHGXHWRGLI¿FXOW\LQREWDLQLQJDXQLIRUPSXOVH
adm inist rat ion.
Co n s e q u e n t l y , l a s e r c r e a t e s n o n - u n i f o r m m i c r o p o r o s i t i e s a n d p r o m o t e s a d i s o r g a n i z e d dest r uct ion of enam el pr ism s. These ir r egular m icr o-ret ent ions vary from t he acid et ching pat t ern result ing in poor adhesion w it h adver se effect on effect iveness
of cav it y m ar gin sealing19. Mor eover, Cor ona, et al.6
( 2003) dem onst rat ed t he sam e r esult s, but at t r ibut ed t h e m t o t h e ca v o su r f a ce m a r g i n s p r o d u ce d b y Er : YAG laser ir radiat ion, w hich pr ov ide a quit e r ough appearance com par ed t o m ar gins pr oduced by high-speed cut t ing, t hus m ar ginal cont our ing could r esult in incr eased m icr o- spacing and gr eat er leak age.
Roeb u ck , et al.2 3 ( 2 0 0 0 ) also st at ed t h at t h e
m or phological changes on t oot h st r uct ur e caused by laser irradiat ion m ight affect t he degree of perform ance of rest orat ive m at erials, especially adhesives syst em s. Addit ionally, incr easing t he pulse ener gy m ight r esult in deeper crat er pat t er n in t oot h sur face, w hich m ay
LQÀXHQFH WKH DGDSWDWLRQ RI UHVWRUDWLYH PDWHULDO WR
cav it y walls; t her efor e, differ ent pulse ener gies ar e r equir ed for opt im um cav it y sealing at enam el and dent ine m ar gins and for differ ent m at er ials.
The bonding pr ocess could be im pair ed due t o t he pr esence of fr ee radicals w it hin t he st r uct ur e of dent al t issu es pr ev iou sly ex posed t o ion izin g r adiat ion1 5.
These fr ee radicals act in a sim ilar way t o hydr ogen per ox ide ( O- highly r eact iv e radicals int er fer e w it h
polym er izat ion)3,20, sodium hypochlor it e ( fr ee radicals
act on collagen denat urat ion)8, or blood cont am inat ion
( hem oglobin ir on- dependent radicals)22.
Mor eover, t he hydr ox y lapat it e cr y st als of dent al har d t issues cont ain som e sodium , m agnesium and car bonat e by ent rapm ent dur ing t heir for m at ion16, in
w hich sodium and m agnesium m ay subst it ut e calcium and car bonat e can subst it ut e phosphat e and hydr ox y l gr oup; t hose subst it ut ions dist or t t he dent al st r uct ur e and m ake it m or e soluble24. Aft er ir radiat ion, t hese
defect s could be m obilized fr om t he sur face lay er of cr y st als, r em ov ing ent rapped ions and m odify ing t h e den t al cr y st al st r u ct u r e, t h u s in t er f er in g w it h adhesion t o r est orat ion. This occur s m or e in enam el, w h ich con t ain s h igh er in or gan ic m at t er com par ed w it h dent ine14,16,24,25. The m or phologic, m et abolic and
com posit ional alt erat ion in int ra- and int er- t ubular collagen m ight have an effect on bond st r engt h t o dent in10,16.
Finally, t he high degr ee of m icr oleak age in gam m a gr oup denot es t hat gam m a radiat ion had a dram at ic negat ive effect on bond st rengt h in bot h laser and bur-t r eabur-t ed bur-t eebur-t h. This m ighbur-t be abur-t bur-t r ibubur-t ed bur-t o albur-t erabur-t ion in t he cryst alline st ruct ure and t he chem ical com posit ion of bot h enam el and dent ine sur face.
Conclusion
Bot h laser and convent ional high- speed t urbine bur m ay have good bond st rengt h in cont rol ( non- gam m a) gr oup. How ever, bot h gr oups show ed a high degr ee of m icr oleak age in t he gam m a gr oup, suggest ing t hat gam m a radiat ion had a dram at ic negat ive effect on bond st r engt h in bot h laser and bur- t r eat ed t eet h.
Refer ences
1- Aok i A, I shik awa I , Yam ada T, Ot suk i M, Wat anabe H, Tagam i J,
et al. Com par ison bet w een Er : YAG laser and convent ional t echnique
for r oot car ies t r eat m ent in v it r o. J Dent Res. 1998; 77( 6) : 1404- 14.
2- Bahr ololoam i Z, Heydar i E. Assessm ent of t oot h pr eparat ion v ia
Er : YAG Laser and bur on m icr oleak age of dent ine adhesives. J Dent
( Tehran) . 2014; 11( 2) : 172- 8.
%DUERVD&06DVDNL57)ORULR)0%DVWLQJ57,QÀXHQFHRIWLPHRQ
bond st rengt h aft er bleaching wit h 35% hydrogen peroxide. J Cont em p
Dent Pract . 2008; 9( 2) : 81- 8.
4- Ber t olot t i Rl. Condit ioning of t he dent ine subst rat e. Oper Dent .
1992; 5: 131- 6.
5 - Bu l u cu B, Av sa r A, D e m i r y ü r e k EO, Ye si l y u r t C. Ef f e ct o f
radiot herapy on t he m icr oleak age of adhesive sy st em s. J Adhes Dent .
2009; 11( 4) : 305- 9.
6- Cor ona SA, Bor sat oo MC, Pecora JD, De Sa Rocha RA, Ram os
TS, Palm a- Dibb RG. Assessin g m icr oleak age of dif f er en t class V
r est orat ions aft er Er : YAG Laser and bur pr eparat ion. J Oral Rehab.
2003; 30: 1008- 14.
7 - Cr u z AD, Sin h or et i MA, Am br osan o GM, Rast elli AN, Bagn at o
VS, Boscolo FN. Effect of t herapeut ic dose X- ray s on m echanical
an d ch em ical pr oper t ies of est h et ic den t al m at er ials, Mat er Res.
2008; 11( 3) : 313- 8.
(UGHPLU $ $UL + *QJQHú + %HOOL 6 (IIHFW RI PHGLFDWLRQV
for r oot canal t r eat m ent on bonding t o r oot canal dent in. J Endod.
2004; 30( 2) : 113- 6.
9- González- Cabezas C, Li Y, Gr egor y RL, St ookey GK. Dist r ibut ion of
cariogenic bact eria in carious lesions around t oot h- colored rest orat ion.
Am J Dent . 2002; 15( 4) : 248- 51.
10- Gr öt z KA, Duschner H, Kut zner J, Thelen M, Wagner W. New
ev idence for t he et iology of so- called radiat ion car ies. Pr oof for dir ect
radiogenic dam age of t he enam el- dent in j unct ion. St rahlent her Onkol.
1997; 173( 12) : 668- 76.
11- I onescu C, Per ieanu MV, Craciun LS. Nanom echanical pr oper t ies
of dent al sur faces st udy as an ir radiat ed t r eat m ent sim ulat ion. Rom
Rep Phy s. 2016; 68( 2) : 693- 701.
12- Keller U, Hibst R. Effect s of Er : YAG Laser on enam el bonding of
com posit e m at er ials. Pr oc SPI E. 1993; 1880: 127- 33.
13- Khan MF, Yonaga K, Kim ura Y, Funat o A, Mat sum ot o K. St udy of
m icr oleak age at Class I cav it ies pr epar ed by Er : YAG Laser using t hr ee
t y pes of r est orat ive m at er ials. J Clin Laser Med Sur g. 1998; 16: 305- 8.
14- Kielbassa AM, Wr bas KT, Schult e- Mönt ing J, Hellw ig E. Cor r elat ion
of t ransversal m icro radiography and m icro hardness on in sit u- induced
de- m ineralizat ion in irradiat ed and non irradiat ed hum an dent al enam el.
Ar ch Oral Biol. 1999; 44( 3) : 243- 51.
1 5 - Magh r aby AM. I on izin g r adiat ion in du ced r adicals. I n : Nen oi
M. Cu r r en t t opics in ion izin g r adiat ion r esear ch : cr u cial r oles in
developm ent of m oder n sciences and t echnologies. Rij ek a: I nTech;
16- Naves LZ, Novais VR, Arm st rong SR, Correr- Sobrinho L, Soares CJ.
Effect of gam m a radiat ion on bonding t o hum an enam el and dent in.
Suppor t Car e Cancer. 2012; 20( 11) : 2873- 8.
17- Ném et h Z, Som ogy i A, Tak ácsi- Nagy Z, Barabás J, Ném et h G,
Szabó G. Possibilit ies of pr event ing ost eoradionecr osis dur ing com plex
t herapy of t um ors of t he oral cavit y. Pat hol Oncol Res. 2000; 6( 1) : 53- 8.
18- Palm a- Dibb RG, Cor ona SA, Bor sat t o MC, Fer r eira KC, Ram os
RP, Pecora JD. Assessing m icr o leak age on class V com posit e r esin
r est orat ions aft er Er : YAG Laser pr eparat ion var y ing t he adhesiv e
sy st em s. J Clin Laser Med Sur g. 2002; 20( 3) : 129- 133.
19- Pashley DH. The effect s of acid et ching on t he pulpodent in com plex.
Oper Dent . 1992; 17( 6) : 229- 42.
20- Pat usco VC, Mont enegr o G, Lenza MA, Alves de Car valho A. Bond
st r engt h of m et allic bracket s aft er dent al bleaching. Angle Or t hod.
2009; 79( 1) : 122- 6.
21- Pradelle- Plasse N, Wenger F, Picar d B, Colon P. Evaluat ion of
m icr oleak age of com posit e r esin r est orat ions by an elect r ochem ical
t echnique: t he im pedance m et hodology. Dent Mat er. 2004; 20( 5) :
425-34.
22- Raffaini MS, Gom es- Silva JM, Torres- Mant ovani CP, Palm a- Dibb RG,
Bor sat t o MC. Effect of blood cont am inat ion on t he shear st r engt h at
resin/ dent in int erface in prim ary t eet h. Am J Dent . 2008; 21( 3) : 159- 62.
2 3 - Roeb u ck EM, Sau n d er s WP, Wh it t er s CJ. I n f lu en ce of t h r ee
Erbium : YAG Lasers energies on t he m icroleakage of class V resin- based
com posit e r est orat ions. Am J Dent . 2000; 13( 5) : 280- 4.
24- Sakaguchi RL, Powers JM, eds. Craig’s rest orat ive dent al m at erials.
13. ed. Saint Louis: Mosby ; 2011.
25- Soares CJ, Cast ro CG, Neiva NA, Soares PV, Sant os- Filho PC, Naves
LZ, et al. Effect of gam m a ir radiat ion on ult im at e t ensile st r engt h of
enam el and dent in. J Dent Res. 2010; 89( 2) : 159- 64.
26- Subram aniam P, Pandey A. Assessm ent of m icr oleak age of a
com posit e r esin r est orat ion in pr im ar y t eet h follow ing class I I I cav it y
pr eparat ion using Er,Cr : YSSG laser : an in vit r o st udy. J Laser s Med
Sci. 2016; 7( 3) : 172- 6.
27- Visur i SR, Gilber t JL,Wr ight DD, Wigdor HA, Walsh JT Jr. Shear
st rengt h of com posit e bonded t o Er: YAG laser- prepared dent ine. J Dent
Res. 1996; 75( 1) : 599- 605.
28- Yam ada Y, Hossain M, Kawanak a T, Kinoshit a J, Mat sum ot o K.
Rem oval effect s of t he Nd: YAG laser and Car isolv on car ious dent in. J
Clin Laser Med Sur g. 2000; 18( 5) : 241- 5.
29- Yam ada Y, Hossain M, Nak am ura Y, Murak am i Y, Mat sum ot o K.
Micr oleak age of com posit e r esin r est or at ion in cav it ies pr epar ed
by Er : YAG laser ir radiat ion in pr im ar y t eet h. Eur J Paediat r Dent .
2002; 3( 1) : 39- 45.
30- Yav uz I ,At ak ul F. Evaluat ion of m icr oleak ing in differ ent in vit r o
rest orat ions of cow perm anent t eet h. Balkan J St om at ol. 2001; 5: 42- 5.
31- Yav uz I , Aydin AH. New m et hod for m easur em ent of sur face ar eas
of m icr oleak age at t he pr im ar y t eet h by bim olecule charact er ist ics
