Bonding to caries-affected dentin

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1 Jpnese Dentl Science Review (2011) 47, vil bl e t cien cedir e ct.c om jou r nl h o mep ge: w ww.els evier.co m/lo c te/jd sr Review Article Bonding to cries-ffected dentin Mstoshi Nkjim *, Sitthikorn Kunwrote, Tweesk Prsnsuttiporn, Junji Tgmi Criology nd Opertive Dentistry, Deprtment of Restortive Sciences, Grdute School of Medicl nd Dentl Sciences, Tokyo Medicl nd Dentl University, Yushim, Bunkyo-ku, Tokyo , Jpn Received 10 December 2010; received in revised form 28 Februry 2011; ccepted 6 Mrch 2011 KEYWORDS Cries-ffected dentin; Dentin bonding; Bond strength; Adhesive interfce Summry Dentin dhesive systems hve drmticlly developed during the pst decdes. In prepred cvity for n dhesive composite restortion, lrge res of the cvity floor re composed of cries-ffected dentin fter removl of cries-infected dentin, not norml dentin. Cries-ffected dentin is different in morphologicl, chemicl nd physicl chrcteristics from norml dentin. Therefore, cries-ffected dentin hs still problems s bonding substrte compred with norml dentin. Tht is, cries-ffected dentin produces lower bond strength nd poor qulity of the hybrid lyer thn norml dentin. In ddition, when exposed the dhesive interfce of cries-ffected dentin in orl environment, the poor qulity of the hybrid lyer would compromise the longevity of the composite restortion due to hydrolysis of the resin nd collgen fibrils. The improvement of bonding potentil to cries-ffected dentin could led to reinforcement of tooth-composite restortion complex, protecting secondry cries nd tooth frcture. # 2011 Jpnese Assocition for Dentl Science. Published by Elsevier Ltd. All rights reserved. Contents Introduction Chrcteristics of cries-ffected dentin Minerl phse Orgnic phse Trnsprent lyer Wter content nd permebility Mechnicl properties Smer lyer Bonding to cries-ffected dentin Etch nd dhesive system Self-etch dhesive system * Corresponding uthor. Tel.: l; fx: E-mil ddress: nkjim.ope@tmd.c.jp (M. Nkjim) /$ see front mtter # 2011 Jpnese Assocition for Dentl Science. Published by Elsevier Ltd. All rights reserved. doi: /j.jdsr

2 Bonding to cries-ffected dentin 103 Bonding durbility to cries-ffected dentin Effect of cries removl methods on bonding to cries-ffected dentin Conclusion References Introduction Dentl cries is the most common pthologicl chnge of dentin. Fusym s reserch demonstrted tht crious dentin consists of two distinct lyers: n outer lyer of bcterilly infected dentin, nd n inner lyer of ffected dentin [1]. The outer lyer (cries-infected dentin) ws chrcterized s being highly deminerlized, physiologiclly unreminerzble nd showing irreversible dentured collgen fibrils with virtul disppernce of cross-linkges. The inner lyer (cries-ffected dentin) is uninfected, prtilly deminerlized nd physiologiclly reminerlizble, therefore should be preserved during clinicl tretment. Consequently, in cvity preprtion for n dhesive restortion fter removl of cries-infected dentin, lrge res of the cvity floor re composed of cries-ffected dentin. Therefore, in clinicl settings, bonding substrte is commonly criesffected dentin, not norml dentin. Mny studies on dentin bonding hve used norml dentin s bonding substrte, which hve contributed to the drmtic development of dentin dhesive systems during the pst decdes. On the other hnd, there is few study bout bonding to cries-ffected dentin, in which the bond strengths to cries-ffected dentin re lower thn those of norml dentin [2 13] (Tble 1). The inferior bonding efficcy of cries-ffected dentin would ffect the clinicl performnce of dhesive composite restortion. This rticle discusses bonding potentil to cries-ffected dentin nd lso reviews the chrcteristics of cries-ffected dentin. Chrcteristics of cries-ffected dentin Minerl phse The minerl phse of dentin is minly composed of crbonte-rich hydroxyptite. The dentinl cries process consists of dynmic, cyclicl episodes of deminerliztion nd reminerliztion. A Fourier-trnsform infrred imging (FTIR) study hs shown tht the minerl phse of criesffected dentin is less crystlline nd hs lower minerl content thn norml dentin [14]. Micro-Rmn spectroscopy investigtion hs suggested tht the reltive intensity of the minerl crbonte pek t 1070 cm 1 decresed drmticlly in cries-ffected dentin [15]. Electron probe micronlysis (EPMA) reveled tht cries-ffected dentin, s well s cries-infected dentin showed much lower mgnesium (Mg) content compred with intct dentin, lthough the densities of clcium (C) nd phosphorus (P) in criesffected dentin were reltively similr to intct dentin [8] (Fig. 1). The reduction in Mg content in dentin strts before the commencement of decrese in C nd P content in dentinl cries [16,17]. Chnges in Mg content could be the first sign of crious deminerliztion nd my indicte loss of peritubulr dentin mtrix [18]. Moreover, lrger ptite crystls re present in reminerlized dentin fter crious deminerliztion, compred to the ptite crystls in intct dentin [17,19]. These indicte tht cries-ffected dentin cuses re-precipittion of CO 3 - nd Mg-poor ptite fter the dissolution of CO 3 - nd Mg-rich ptite [20,21]. Minerl crystls in cries-ffected dentin re scttered nd rndomly distributed, with lrger ptite crystllites nd wider intercrystlline spces compred with intct dentin [19]. Orgnic phse The dentin orgnic mtrix contins different extrcellulr proteins, such s type I collgen, proteoglycns, dentin phosphoproteins nd siloprotein. Chnges in dentin orgnic mtrix ssocited with cries hve been reported [15,22 24]. In the inner lyer (cries-ffected dentin), the generl pttern of mino cid composition shows no significnt differences from intct dentin [22]. In ddition, the reducible intermoleculr covlent cross-links of the collgen re prtly shifted to the precursor form, thus leding to decresed cross-links but this chnge is reversible [22], nd the 67- nm cross-bnds of the collgen fibrils remin [23]. These results support the ide tht cries-ffected dentin is reminerlizble. On the other hnd, the secondry structure of collgen is slightly ltered by the crious process [15], nd the distribution of ntigeniclly intct collgen fibrils nd proteoglycns is significntly lower in norml dentin [24]. Reductions in ntigenicity from the orgnic mtrix of sclerotic dentin under cries lesions rise concern bout the potentil of interfibirillr reminerliztion [24]. Trnsprent lyer Under cries process, continuous deposition of minerls occurs within the tubule lumen (Fig. 2). In fct, most of the dentinl tubules in cries-ffected dentin re occluded by minerl crystls [25]. The crystls in the tubule lumen render the refrctive index of the lumen similr to tht of the intertubulr dentin, mking the trnsprent lyer. In these minerl deposits, Mg ws identified lthough Mg ws brely present in intertubulr cries-ffected dentin [9]. Therefore, intrtubulr minerls consist of lrge rhombohedrl crystls of Mg-substituted b-tcp (whitlokite) [26], which is less soluble thn hydroxyptite. Wter content nd permebility As minerl is lost from the dentin mtrix during the crious process, its volume is replced by wter. The wter content of norml dentin is pproximtely 10%, wheres tht of cries-ffected dentin shows higher vlue, which vries from 14% to 53% [27]. On the other hnd, permebility of cries-ffected dentin decreses due to occlusion of the tubules. Tgmi et l. [28] found young crious molrs were

3 Tble 1 The review ppers concerning bout bond strength to cries-ffected dentin. Author Ref. Adhesive mteril Mnufcturer Bonding system Bonding procedure Test method Norml dentin Criesffected Nkjim et l. (1995) [2] All Bond 2 Bisco Etch nd (wet) 3-Step mtb(hourglss) p < Scotchbond Multi-Purpose 3 M Etch nd (dry) 3-Step NS Clerfil Liner Bond 2 Kurry Self-etch 2-Step p < Nkjjim et l. (1999) [3] Scotchbond Multi-Purpose 3 M Etch nd (wet) 3-Step mtb(hourglss) 42.4 NS 48.2 Nkjjim et l. (1999) [4] Clerfil Liner Bond 2 Kurry Self-etch 2-Step mtb(hourglss) 45.2 p < Clerfil Liner Bond 2V Kurry Self-etch 2-Step 57.4 p < ART Bond Coltene Self-etch 2-Step 24.9 NS 30.2 Yoshiym et l. (2000) [5] FluoroBond Shofu Self-etch 2-Step mtb(hourglss) 28.2 p < Single Bond 3 M ESPE Etch nd (wet) 2-Step 46.0 p < Single Bond Etch nd (dry) 2-Step 26.4 p < Yoshiym et l. (2002) [6] ABF (Clerfil Protect Bond) Kurry Self-etch 2-Step mtb(dumbbell) 44.9 p < Single Bond 3 M ESPE Etch nd 2-Step 50.9 p < Cebllos et l. (2003) [7] Prime nd bond NT Dentsply Etch nd 2-Step mtb(hourglss) 56.3 p < Scotchbond 1 3 M ESPE Etch nd 2-Step 43.9 NS 36.3 Clerfil SE Bond Kurry Self-etch 2-Step 35.5 p < Adper Prompt L Pop 3 M ESPE Self-etch 1-Step 18.2 NS 13.4 Doi et l. (2004) [8] Clerfil SE Bond Kurry Self-etch 2-Step mtb(hourglss) 41.2 p < Mc-Bond II Tokuym Self-etch 2-Step 35.0 p < Unifil Bond GC Self-etch 2-Step 27.2 p < Nkjim et l. (2005) [9]] Clerfil Protect Bond Kurry Self-etch 2-Step mtb(hourglss) 43.5 p < Sy et l. (2005) [10] Optibond Solo Plus Kerr Etch nd 2-Step mtb(hourglss) 38.7 p < Totl-etch (photo-cure) Optibond Solo Plus Self-etch 2-Step 44.2 p < Self-etch (photo-cure) Optibond Solo Plus Etch nd 2-Step 17.2 p < Totl-etch (dul-cure) Optibond Solo Plus Self-etch (dul-cure) Self-etch 2-Step 18.3 p < Pereir et l. (2006) [11] Single Bond 3 M ESPE Etch nd 2-Step mtb(hourglss) 43.3 NS 36.1 Adper Prompt L Pop 3 M ESPE Self-etch 1-Step 52.0 p < Wei et l. (2008) [12] Clerfil SE Bond Kurry Self-etch 2-Step msb p < Clerfil Tri-S Bond Kurry Self-etch 1-Step p < Single Bond 3 M ESPE Etch nd 2-Step p < Scholt nus et l. (2010) [13] Scotchbond 1XT 3 M ESPE Etch nd 2-Step mtb(br) 35 p < Clerfil Tri-S Bond Kurry Self-etch 1-Step 35 p < Clerfil SE Bond Kurry Self-etch 2-Step 33 NS M. Nkjim et l.

4 Bonding to cries-ffected dentin 105 Figure 1 Light microscopic photogrphs nd EPMA mpping imges of crious tooth [9]. (A) Cross-sectioned specimen of crious tooth; (B) specimen A stined by cries detector solution; (C) mpping imges of elementl distribution (C, P, Mg) nd bcksctter electronic imge of specimen A observed by EPMA. Mg-depleted re corresponds well to the morphologicl chnges seen in light microscope imges (A nd B). only 14% s permeble s young norml dentin nd suggested tht the trnsprent lyer would be effective in decresing permebility. Mechnicl properties Cries-ffected dentin is softer thn norml dentin, with bout hlf the hrdness, even though minerl depositions occlude dentinl tubules [2,7,11,25,29 31]. In ddition, ultimte tensile strength (UTS) of cries-ffected dentin is lso lower thn tht of norml dentin, nd there is positive correltion in cries-ffected dentin between the UTS nd the Knoop hrdness number [6]. On the other hnd, Nishitni et l. [32] reported tht the mtrix of deminerlized criesffected dentin ws s strong s tht of norml deminerlized dentin. These results would indicte tht lower UTS nd hrdness of cries-ffected dentin re due to loss of minerl in intertubulr dentin. Mrshll et l. [29] reported tht the men elstic modulus (18.2 GP) nd nnohrdness (0.8 GP) of intertubulr dentin on the trnsprent lyer were slightly, but significntly lower thn those of the unffected intertubulr dentin (20.6 nd 1.0 GP, respectively). On the other hnd, for rrested cries, the elstic modulus of the trnsprent lyer of cries-ffected dentin is not significntly different from the underlying norml dentin lthough its hrdness is lower thn norml dentin [30,31]. Smer lyer Figure 2 Scnning electron microgrph (SEM) of the trnsprent lyer of cries-ffected dentin [28]. Mny minerl csts occludes dentinl tubules. Cvity preprtion with rotry instruments or others results in the formtion of smer lyer on the dentin surfce, in which the cutting method ffects smer lyer chrcteristics (i.e. thickness, density). The smer lyer fills the orifices of dentinl tubules, to form smer plugs, leding to reduction in dentin permebility. However, sub-micron porosities in the smer lyer still llow for the diffusion of dentinl fluid. The dentin smer lyer with smer plugs is composed mostly of submicron prticles of minerlized collgen debris [33,34], which differs little in composition from the underlying dentin [33 35]. Therefore, the smer lyer formed on criesffected dentin would be different in morphologicl nd chemicl structures from tht of norml dentin, becuse cries-ffected dentin is prtilly deminerlized, leding to different minerl/orgnic contents compred to norml dentin. Indeed, the smer lyer of cries-ffected dentin is

5 106 M. Nkjim et l. Figure 3 Schemtic illustrtion of smer lyers of norml nd cries-ffected dentin. Cries-ffected dentin smer lyer is thick with enriched orgnic components compred with norml dentin smer lyer. thicker nd ppers to be enriched with orgnic components compred with tht of norml dentin (Fig. 3) [36,37]. Bonding to cries-ffected dentin Cries-ffected dentin produces lower bond strengths thn norml dentin, regrdless of the type of dhesive system (etch nd system or self-etch system; one-, two- or three-step of bonding procedure) [2 13,36 39], in which cohesive filure of specimens in dentin increses in resinbonded cries-ffected dentin [6,7,10]. A reduction in the cohesive strength of cries-ffected dentin would be one of the resons for lower bond strength vlues to cries-ffected dentin compred with norml dentin [6]. On the other hnd, Wei et l. [12] demonstrted tht when nlyzing the effect of dentin type (norml nd cries-ffected dentin) on bond strength fter removing the vrince for which hrdness ccounted s covrite, it ws found tht the condition of dentin hd significnt effect on bond strength: even if norml nd cries-ffected dentin hd similr intertubulr hrdness, bond strength to cries-ffected dentin would still be significntly lower thn to norml dentin. The chnge in chemicl nd morphologicl chrcteristics of criesffected dentin would be lso resons for the lower bond strength. The hybrid lyers creted to cries-ffected dentin re thicker thn those of norml dentin, becuse criesffected dentin is more susceptible to the cid etching due to prtilly deminerliztion, resulting in the formtion of deeper deminerlized zone [2 6,8 10,15,38,40]. Etch nd dhesive system When phosphoric cid etchnts re pplied to norml nd cries-ffected dentin surfce, the smer lyer is completely removed, nd both dentinl sub-surfces re deminerlized nd the collgen fibrils re exposed. In order to produce superior resin dentin interfce, resin monomers must penetrte into these deminerlized dentinl sub-surfces. However, even though for norml dentin, it hs been demonstrted tht there re discrepncies between the depths of deminerliztion nd resin monomer penetrtion. The wet bonding technique is effective for infiltrtion of resin monomers into deeper cid-etched deminerlized lyers in cries-ffected dentin compred with the dry bonding technique, leding to higher bond strength [4,5]. Nevertheless, deeper deminerlized zone is more difficult for resin monomer to penetrte to the bottom of the exposed collgen mtrix. In ddition, lrger quntity of wter in the deeper deminerlized zone would compete with penetrtion of the dhesive resin monomers. Besides the residul wter, criesffected dentin my contin substnces tht interfere with free rdicl genertion or propgtion, leding to poor polymeriztion of dhesive monomers. It is reported tht the degree of conversion of dhesive gent tht penetrted the etched dentin in the cries-ffected dentin specimen ws lower thn in the norml dentin specimens [14]. The minerl deposits in dentinl tubules in the trnsprent lyer re highly cid resistnce. Etching with phosphoric cid cnnot completely dissolve the deposits tht exist in dentinl tubules without dissolution. The presence of minerl deposits inside dentinl tubules would interfere with resin monomer infiltrtion peripherl to the dentinl tubules s well s resin tg formtion, leding to lower bond strength [2,5]. The hybrid lyer of etch nd system in criesffected dentin ws thicker but susceptible to the cid nd bse tretment in scnning electron microscopy (SEM) observtion of resin/cries-ffected dentin interfce [2] (Fig. 4). Trnsmission electron microscopy (TEM) observtion demonstrted more porous zone long the bse of the hybrid lyer in cries-ffected dentin creted [6]. Micro- Rmn spectroscopy investigtion suggested tht the cries-ffected dentin interfce ws more complicted, whereby the wider deminerlized mtrix ws not protected by the criticl Bis-GMA [15]. Light microscopy evlution with Msson s trichrome stin indicted wider regions of nonencpsulted collgen in the cries-ffected dentin interfce [40]. These would be due to reduced penetrtion of the resin monomers into the etched cries-ffected dentin becuse of the deeper deminerlized zone nd the presence of the minerl deposits inside the dentinl tubules (Fig. 5). Etching with phosphoric cid might be too ggressive for prtilly deminerlized intertubulr cries-ffected dentin. However, stronger cids nd n extended etching time re suggested for solubilizing cid resistnt minerl deposits within the cries-ffected tubule lumens, leding to more lterl penetrtion of the dhesive monomer from the tubule lumens. When One-Step (Bisco) with 10% phosphoric cid etchnt ws pplied to cries-ffected dentin, it resulted in lower bond strength thn norml dentin, however this significnt difference disppered following the ppliction of 32% phosphoric cid [38]. Arris et l. [39] reported tht extending the etching time for 35% phosphoric cid from 15 s to 45 s durtion improved the bond strength of Single Bond (3M ESPE) to cries-ffected dentin. However, its bond

6 Bonding to cries-ffected dentin 107 Figure 4 Scnning electron microgrphs (SEM) of dentin specimens bonded with ll bond 2 fter cid nd bse chllenge [2]. (A) Norml dentin: the hybrid lyer is bout 3 4 mm thick nd ws resistnt to cid/bse chllenge; (B) cries-ffected dentin: the hybrid lyer is 5 7 mm thick The middle of the hybrid lyer ws prtilly removed by cid/bse chllenge. Tube-like structures of the resin tgs would indicte presence of residul minerl csts before cid/bse chllenge. R = resin; H = hybrid lyer; D = dentin. Figure 5 Schemtic illustrtion of interfce of norml nd cries-ffected dentin using etch nd dhesive. The minerl deposits in dentinl tubules interfere with resin monomer infiltrtion peripherl to the dentinl tubules s well s resin tg formtion. Criesffected dentin produces thicker hybrid lyer, in which there re poorer infiltrtions of resin monomers into etched dentin becuse of the deeper deminerlized zone nd the presence of the minerl deposits inside the dentinl tubules. strength ws still lower thn tht of norml dentin. Since longer etching time would deepen the zone of deminerlized intertubulr dentin, the discrepncy between the deminerlized lyer nd resin monomer penetrtion could not be eliminted. Recently, the ppliction of chemicl cross-linker in the bonding procedures hs been introduced, which my potentilly increse dentin collgen stbility due to higher number of collgen cross-linkges [41]. When etch nd systems (One-step Plus, Bisco; Single Bond Plus, 3M ESPE) were used, ppliction with the chemicl cross-linking gents (glutrldehyde nd grpe seed extrct) for 1 h fter cid etching significntly improved bond strength to criesffected nd sound dentin, in which the cross-linked dentin mtrix might mechniclly strengthen incomplete resininfiltrted deminerlized zone t the bottom of the hybrid lyer [41]. Self-etch dhesive system Self-etch systems hve lso exhibited lower bond strengths to cries-ffected dentin thn norml dentin, nd their hybrid lyers in cries-ffected dentin re lso thicker thn those of norml dentin but bsolutely thinner thn those of etch nd systems [2,6,10,40]. Using self-etch dhesives, it hs been generlly ccepted tht there re fewer discrepncies between depths of deminerlized zone nd resin monomer penetrtion, becuse deminerliztion nd resin monomer penetrtion occur simultneously. However, TEM observtion reveled porous zone beneth the hybrid lyer of self-etch system in cries-ffected dentin [6]. Nkjim et l. [9] reported tht there ws thicker nitrogen-rich lyer t the cries-ffected dentin interfce of 2-step self-etch system using EPMA nlysis, which is indictive of collgenrich phse (Fig. 6). Light microscopy evlution with Msson s trichrome stin indicted wider regions of non-encpsulted collgen in the cries-ffected dentin interfce of 1-step nd 2-step self-etch systems [40]. These results indicte tht self-etch dhesives could not fully infiltrte dhesive monomers into the deminerlized zone in cries-ffected dentin. Self-etch system cnnot dissolve nd remove cid-resistnt minerl deposits in dentinl tubules of cries-ffected dentin becuse of their higher ph. Therefore, n etch nd dhesive system using 30 35% phosphoric cid with stronger cidity might hve the upper hnd compred with self-etch systems, lthough phosphoric cid etching could not completely dissolve the minerl deposits in dentinl tubules in cries-ffected dentin. However, using the sme bonding gent of Optibond Solo Plus (Kerr), totl-etch technique with phosphoric cid did not hve ny beneficil effect on cries-ffected dentin compred with the self-etch technique [10]. Even though for norml dentin, the mild cidity of self-etch systems is not sufficiently effective in the dissolution of smer plugs, therefore smer plugs re retined in the dentinl tubules s prt of the hybridized complex with less resin tg formtion. In this sitution,

7 108 M. Nkjim et l. Figure 6 EPMA line nlysis of C, P, Mg, nd N t the dhesive interfce of Clerfil Protect Bond [9]. () Norml dentin; (b) cries-ffected dentin. N peks were observed in the deminerlized zones in both interfces. An increse in N content occurred from the interfce, peked then decresed to level similr to tht of the underlying dentin. Deminerlized zones in norml dentin nd cries-ffected dentin were 3.5 nd 7 mm thick, respectively. D = dentin; A = dhesive resin; T = dentinl tubule. The line nlysis ws performed in two white line. lterl penetrtion of the dhesive monomers from the dentinl tubules could not contribute to hybrid lyer formtion of self-etch dhesives. Therefore, for self-etch systems, the presence of minerl deposits in dentinl tubules would not be n importnt reson why cries-ffected dentin cuses less penetrtion of dhesive monomers, leding to lower bond strength thn norml dentin, but deeper minerlized zone would be the min reson. On the other hnd, in the cse of self-etch systems, the dentin smer lyer would ffect penetrtion of the dhesive monomers into the underlying dentin. Severl studies using norml dentin hve demonstrted tht dentin smer lyer chrcteristics hve been reported to compromise the bonding efficcy of self-etch systems. The smer lyer on dentin is composed of disorgnized collgen debris binding submicron minerl prticles [33,34]. The smer lyer of cries-ffected dentin is thick nd irregulr, nd ppers to be enriched with orgnic components compred with tht of norml dentin [36,37]. The disorgnized collgen nd/or the minerl trpped within the geltinized collgen cnnot be esily removed even when etched with phosphoric cid [43]. The disorgnized collgen nd the geltinous lyer within the smer lyer my hinder resin monomer infiltrtion nd prevent perfect sel t the resin dentin interfce [34,43]. Therefore, the cries-ffected dentin smer lyer enriched with orgnic components would contribute to the inferior dhesion of self-etch dhesives to cries-ffected dentin (Fig. 7). Sodium hypochlorite solution (NOCl) cn effectively dissolve orgnic substrtes from biologicl mterils. Tniguchi et l. [36] demonstrted tht NOCl tretment of smer lyercovered cries-ffected dentin eroded nd thinned the smer lyer due to dissolution of superficil orgnic components of smer lyer (Fig. 8). Furthermore, they reported tht pretretment with 6% NOCl for 15 s could significntly improve the bond strengths of 1-step nd 2-step self-etch system to cries-ffected dentin, while NOCl-30 s pretretment did not ffect them [36]. On the other hnd, for norml dentin, NOCl- 15 s pretretment did not lter the bond strengths, but NOCl- 30 s pretretment reduced them [36]. It hs been speculted tht pplying NOCl for 30 s or longer results in rective residul free-rdicls being present on the NOCl-treted dentin tht hve been produced by the oxidizing effect of NOCl nd these compete with the propgtion of vinyl freerdicls generted during light ctivtion, resulting in premture chin termintion nd incomplete polymeriztion [44]. Applying reducing gent (Accel; p-toluenesulfinic cid sodium slt: Sun Medicl) is effective in recovering the negtive effect of NOCl-oxidized dentin for 30 s on polymeriztion, leding to incresed bond strengths to norml nd criesffected dentin [36]. Kunwrote et l. [37] reported the ppliction of mild cidic HOCl solution (Comfosy: Hccpper Advntec) s pretretment gent insted of NOCl solution. Mild cidic HOCl solution is n ntiseptic nd n irrignt, which hs outstnding properties becuse not only does it exhibit biocomptibility nd low cytotoxicity but lso hs immedite nd highly effective ntimicrobil nd deproteinizing properties. The 5 s pretretment with 50 ppm Comfosy significntly improved the bond strengths of 2-step self-etch system to cries-ffected dentin, but the 5 s pretretment with 6% NOCl did not ffect them [37]. Pretretment with mild cidic HOCl solution could be ble to improve the qulity of the hybrid lyer of cries-ffected dentin creted by self-etching dhesives due to removl of disorgnized/geltinized collgen Figure 7 Schemtic illustrtion of interfce of norml nd cries-ffected dentin using self-etch dhesive. The geltinized collgen in smer lyer is not completely removed, forming hybridized smer lyer. The thick geltinous lyer of cries-ffected dentin smer lyer would hinder resin monomer infiltrtion into underlying deminerlized zone, resulting in poorer qulity of the hybrid lyer.

8 Bonding to cries-ffected dentin 109 Figure 8 Scnning electron microgrphs (SEM) of the #600 SiC-pper ground norml (A) nd cries-ffected dentin (B) surfces [36]. () No tretment; (b) treted with 6% NOCl for 15 s; (c) treted with 6% NOCl for 30 s. For norml dentin, smer lyer ws smooth nd compct. There were no significnt ltertions in surfce morphologicl form. For cries-ffected dentin, dentin surfce ws covered with thick nd irregulr smer lyer with sludge-like formtion in which fibril-like structures were seen. After tretment with NOCl, the smer lyer ws eroded nd thinned in which fibril-like structures were not seen. nd enhncement of resin monomer penetrtion (Figs. 9 nd 10), leding to more stble bonding to cries-ffected dentin in long term (Tble 2). Bonding durbility to cries-ffected dentin Adhesive restortions re exposed to severe environment in the orl cvity. Occlusl stress, therml stress nd chemicl ttck by cid nd enzymes ffect the dhesive interfce, compromising the integrity of dhesive restortion. A known degrdtion fctor of resin dentin bond is exposure to wter. The exposed, ltered collgen fibrils t the resin dentin interfce would be susceptible to further collgen disorgniztion or denturtion in the direct wter exposure, leding to degrdtion of the bonded interfce. Durbility studies on bonding to cries-ffected dentin re still limited [40,45 47] (Tble 3). Erhrdt et l. [40] reported tht criesffected dentin reduced the bond strengths regrdless of the dhesive systems fter direct exposure of the interfce to wter for 6 months. They indicted tht the bonded interfces of cries-ffected dentin re more prone to hydrolytic degrdtion thn those of norml dentin. Recently, Pshley et l. [48], demonstrted tht host-derived mtrix metlloproteinses (MMPs) enzymes in the dentin mtrix promote the degrdtion of exposed, unprotected collgen within incompletely resin-infiltrted cid-etched dentin. The use of MMP inhibitor such s chlorhexidine, fter cid etching, could prevent nd minimize the degrdtion of exposed collgen within incompletely resin-infiltrted hybrid lyers, contributing to the long-term stbility of the hybrid lyer nd bond strength. Komori et l. [45] reported tht chlorhexidine tretment for 60 s fter cid etching significntly lowered loss of bond strengths of etch nd systems to norml

9 Tble 2 The review pper concerning bout improvement effect on bonding to cries-ffected dentin. Author Ref. Adhesive mteril Nkjim et l. (2000) Arrris et l. (2004) Erhrdt et l. (2008) Tniguchi et l. (2009) Mcedo et l. (2009) Mnufcturer Bonding system [38] One-step Bisco Etch nd Single Bond 3 M ESPE Etch nd [39] Clerfil SE Bond Bonding procedure Test method Norml dentin Criesffected 32% H 3 PO 4 Bond mtb(hourglss) 49.7 NS % H 3 PO 4 Bond 47.7 p < % H 3 PO 4 Bond 49.5 p < % H 3 PO 4 Bond 51.7 p < Kurry Self-etch Self-etching primer Bond mtb(hourglss) p < Single Bond 3 M ESPE Etch nd [42] Scotchbond 1 3 M ESPE Etch nd H 3 PO 4 etching + Bond p < self-etching primer H 3 PO 4 Bond p < Extending H 3 PO 4 etching for 45 s Bond p < H 3 PO 4 Bond mtb(hourglss) 31.9 p < EDTA Bond 28.1 NS 24.9 H 3 PO 4 + chlorhexidine Bond 27.3 NS 23.8 [36] Clerfil Protect Bond Kurry Self-etch Self-etching primer Bond mtb(hourglss) 40.9 p < NOCl (15 s) Self-etching primer Bond 42.0 NS 41.6 NOCl (30 s) Self-etching primer Bond 34.3 NS 33.3 NOCl (30 s) + ccel Self-etching primer Bond 37.5 NS 39.9 Bond Force Tokuym Self-etch Bond 44.0 p < NOCl (15 s) Bond 43.7 NS 40.6 NOCl (30 s) Bond 30.4 NS 31.4 NOCl (30 s) + ccel Bond 36.8 NS 35.6 [41] Single Bond Plus One-Step Plus 3 M ESPE Etch nd Bisco Etch nd H 3 PO 4 Bond mtb(bem) p < H 3 PO 4 + glutrldehyde Bond p < H 3 PO 4 + grpe seed extrct Bond p < H 3 PO 4 Bond p < H 3 PO 4 + glutrldehyde Bond p < M. Nkjim et l.

10 Bonding to cries-ffected dentin 111 Bond p < H 3 PO 4 + grpe seed extrct [37] Clerfil SE Bond Kurry Self-etch Self-etching primer Bond mtb(hourglss) p < NOCl (5 s) Self-etching primer Bond p < HOCl 50 ppm (5 s) Self-etching primer Bond NS HOCl 100 ppm (5 s) Self-etching primer Bond p < Figure 9 Trnsmission electron microgrph (TEM) of the dhesive interfce of Clerfil SE Bond in cries-ffected dentin. The interfce exhibited irregulr with thicker nd more porous hybrid lyer, in which hybridized smer lyer ws seen with the fuzzy crpet ppernce long the top of the hybrid lyer. Kunwrote et l. (2011) Figure 10 Trnsmission electron microgrph (TEM) of the dhesive interfce of Clerfil SE Bond in cries-ffected dentin pretreted with 50 ppm HOCl solution for 5 s. The hybrid lyer ws thinner nd uniform without hybridized smer lyer.

11 Tble 3 The review ppers concerning bout bonding durbility to cries-ffected dentin. Author Ref. Adhesive mteril Nkjim et l. (2006) Omr et l. (2007) Erhrdt et l. (2007) Komori et l. (2009) Mnufcturer Bonding system Bonding procedure Test method [47] mtb (hourglss) Clerfil SE Bond Degrdtion stress Storge with hydrosttic pulpl pressure Norml dentin Cries-ffected dentin 24 h 1 month 24 h 1 month Kurry Self-etch 2-Step 47.3 p < NS 28.3 [46] mtb(stick) Thermocycling Before After Before After Scotchbond MP 3 M Etch nd 3-Step p < NS Clerfil SE Bond Kurry Self-etch 2-Step NS NS Xeno IV Dentsply/ Culk Self-etch 1-Step NS NS 14.8 [40] mtb (hourglss) Storge in wter 24 h 6 months 24 h 6 months Scotchbond 1 3 M Etch nd 2-Step 42.6 NS p < Clerfil Protect Kurry Self-etch 2-Step 39.2 NS p < Bond AdheSE Ivoclr Vivdent Self-etch 2-Step 28.2 NS p < [45] mtb(bem) Storge in rtificil sliv Scotchbond MP 3 M ESPE Etch nd 3-Step Scotchbond MP with 2%CHX Single Bond 2 3 M ESPE Etch nd 2-Step Single Bond 2 with 2%CHX 24 h 6 months 24 h 6 months NS p < 0.05 p < 0.05 p < 0.05 NS NS p < 0.05 NS 112 M. Nkjim et l.

12 Bonding to cries-ffected dentin 113 dentin fter 6-month storge in rtificil sliv, but it did not lter the bond strength of cries-ffected dentin. Thermocycling showed no significnt effects on the bond strength of 3-step etch nd system to cries-ffected dentin, lthough there were significnt reductions in bond strength to sound dentin. Moreover, for 1-step nd 2-step self-etch dhesives, no significnt effect on bond strength ws detected when bonded to sound nd cries-ffected dentin [46]. Fluid penetrtion into the resin dentin interfce occurs vi dentinl tubules under constnt hydrosttic pulpl pressure, s well s vi the dentin mrgin. Therefore, the presence of minerl deposits in dentinl tubules my lter the bonding durbility between norml nd cries-ffected dentin. Nkjim et l. [47] reported tht constnt hydrosttic pulpl pressure during 1-month storge significntly decresed the bond strength of 2-step self-etch system to norml dentin, but did not ffect the bond strength to criesffected dentin. The lower dentin permebility of criesffected dentin my therefore reduce wter penetrtion into the interfce, leding to long-term stbility of the interfce when there is no direct exposure to wter in presence of the surrounding bonded enmel. Tubulr occlusion my prevent wter entrpment, being mnifesttions of evportive nd convective wter flux from dentin, t the resin dentin interfce [49]. Current one-step self-etch dhesives show higher hydrophilicity, nd ttrct wter from the hydrted dentin substrte during ppliction on the dhesive surfce nd bsorb wter even fter polymeriztion. Ultrstructurlly, wter entrpment in the 1-step self-etch dhesive lyer is observed in the bonded norml dentin specimen s wterfilled chnnels (i.e. wter-tree, wter-droplet), however wter-treeing nd wter-droplet formtion cn be eliminted in the bonded cries-ffected dentin specimen [49]. In the bsent of wter fluxes from cries-ffected dentin, one-step self-etch dhesives might initilly estblish better sel long the interfce. However, the bsorbed wter in the dhesive lyer would cuse hydrolytic degrdtion of resinous mterils over time, compromising the integrity of the resin dentin interfce. Effect of cries removl methods on bonding to cries-ffected dentin Some reserchers hve evluted the effect of cries removl method on bonding to cries-ffected dentin [50,51]. Using etch nd system of Single Bond (3M), cries removl methods (steel bur in slow-speed hndpiece, ir brsion with luminum oxide prticle, prtilly dimond-coted oscillting tip with irscler, hnd excvtor with Crisolv) did not ffect the bond strength to cries-ffected dentin [50]. This result is in greement with nother study using etch nd system of OptiBond Solo Plus Totl-Etch (Kerr), in which there were no significnt differences in bond strength to criesffected dentin between excvtion by steel round bur in slow-speed hndpiece, Er:YAG lser nd 600-grit SiC pper [51]. On the other hnd, in this study, the 2-step self-etching system of Clerfil Protect Bond (Kurry Medicl) exhibited lower bond strength to cries-ffected dentin excvted by steel round bur thn Er:YAG lser nd 600-grit SiC pper. These results indicte tht dhesion to cries ffected dentin might be influenced by the cries-removl method in conjunction with the dhesive system used. Conclusion Cries-ffected dentin is very different in morphologicl, chemicl nd physicl chrcteristics from norml dentin. Cliniclly, resin composite is bonded into prepred cvity fter removl of cries-infected dentin, in which the cvity floor commonly consists of cries-ffected dentin with lower bonding efficcy. The intrinsic wekness of cries-ffected dentin my not be clinicl problem, if there is surrounding norml dentin nd/or enmel tht cn provide high bond strength to the dhesives [6]. However, given tht dhesion to the cvity floor is strongly influenced by the contrction stress of the resin composite, low bonding efficcy to criesffected dentin would cuse further deteriortion of the dhesive interfce t the cvity floor in the restored cvity. In ddition, when exposed the dhesive interfce of criesffected dentin in orl environment, the poor qulity of the hybrid lyer of cries-ffected dentin would compromise the longevity of the composite restortion due to hydrolysis of the resin nd collgen fibrils. The specific composition in dhesives my ffect bonding to cries-ffected dentin. However, improvement effect of composition in dhesives on bonding to cries-ffected dentin is uncler. One study [3] compred the bond strengths of Scotchbond Multi-Purpose (3M) with nd without polylkenoic cid copolymer in the primer. It ws reported tht the polylkenoic cid in the primer contributed to high bond strength to cries-ffected dentin [3]. The improvement of bonding potentil to cries-ffected dentin should be considered in new development strtegies of dhesive mterils nd crious tretment, which could led to reinforcement of tooth-composite restortion complex, protecting secondry cries nd tooth frcture. References [1] Fusym T. Two lyers of crious dentine: dignosis nd tretment. Oper Dent 1979;4: [2] Nkjim M, Sno H, Burrow MF, Tgmi J, Yoshiym M, Ebisu S, Ciucchi B, Russel CM, Pshley DH. Tensile bond strength nd SEM evlution of cries-ffected dentin using dentin dhesives. J Dent Res 1995;74: [3] Nkjim M, Sno H, Zheng L, Tgmi J, Pshley DH. Effect of moist vs dry bonding to norml vs. cries-ffected dentin using scotchbond multi-purpose plus. J Dent Res 1999;78: [4] Nkjim M, Ogt M, Okud M, Tgmi J, Sno H, Pshley DH. Bonding to cries-ffected dentin using self-etching primers. Am J Dent 1999;12: [5] Yoshiym M, Urym A, Kimochi T, Mtsuo T, Pshley DH. Comprison of conventionl vs self-etching dhesive bonds to cries-ffected dentin. Oper Dent 2000;25: [6] Yoshiym M, Ty FR, Doi J, Nishitni Y, Ymd T, Itou K, Crvlho RM, Nkjim M, Pshley DH. Bonding of self-etch nd totl-etch dhesives to crious dentin. J Dent Res 2002;81: [7] Cebllos L, Cmejo DG, Fuentes MV, Osorio R, Toledno M, Crvlho RM, Pshley DH. Microtensile bond strength of totletch nd self-etching dhesives to cries-ffected dentine. J Dent 2003;31: [8] Doi J, Itot T, Torii Y, Nkbo S, Yoshiym M. Micro-tensile bond strength of self-etching primer dhesive systems to humn coronl crious dentin. J Orl Rehbil 2004;31:

13 114 M. Nkjim et l. [9] Nkjim M, Kitsko Y, Okud M, Foxton RM, Tgmi J. Elementl distributions nd microtensile bond strength of dhesive interfce to norml nd cries-ffected dentin. J Biomed Mter Res B Appl Biomter 2005;72B: [10] Sy EC, Nkjim M, Penwongse P, Soymn M, Ozer F, Tgmi J. Bonding to sound vs cries-ffected dentin using photo- nd dul-cure dhesives. Oper Dent 2005;30:90 8. [11] Pereir PNR, Numes MF, Miguez PA, Swift Jr EJ. Bond strength of 1-step self-etching system to cries-ffected nd norml dentin. Oper Dent 2006;31: [12] Wei S, Sdr A, Shimd Y, Tgmi J. Effect of cries-ffected dentin hrdness on the sher bond strength of current dhesives. J Adhes Dent 2008;10: [13] Scholtnus H, Purwnt K, Dogn N, Kleverln CJ, Feilzer AJ. Microtensile bond strength of three simplified dhesive systems to cries-ffected dentin. J Adhes Dent 2010;12: [14] Spencer P, Wng Y, Ktz JL, Misr A. Physicochemicl interctions t the dentin/dhesive interfce using FTIR chemicl imging. J Biomed Opt 2005;10(3): [15] Wng Y, Spencer P, Wlker MP. Chemicl profile of dhesive/ cries-ffected dentin interfces using Rmn microspectroscopy. J Biomed Mter Res A 2007;81(2): [16] Sug S, Soejim H, Tnk Y. Electron probe X-ry tissues. J Dent Res 1967;46: [17] Tkum S, Ogiwr H, Suzuki H. Electron probe nd electron microscope studies of crious dentinl lesions with reminerlized surfce lyer. Cries Res 1975;9: [18] Tjäderhne L, Hietl E-L, Lrms M. Minerl element nlysis of crious nd sound rt dentin by electron probe micronlyzer combined with bck-scttered electron imge. J Dent Res 1995;74: [19] Dculsi G, Kerebel B, Le Cbellec M-T, Kerebel L-M. Qulittive nd quntittive dt on rrested cries in dentin. Cries Res 1979;13: [20] LeGeros RZ, Tung MS. Chemicl stbility of crbonte- nd fluoride-contining ptites. Cries Res 1983;17: [21] LeGeros RZ, Ske T, Butist C, Retino M, LeGeros JP. Mgnesium nd crbonte in enmel nd synthetic ptites. Adv Dent Res 1996;10: [22] Kuboki Y, Ohgushi K, Fusym T. Collgen biochemistry of the two lyers of crious dentin. J Dent Res 1977;56(10): [23] Ohgushi K, Fusym T. Electron microscope structure of the two lyers of crious dentin. J Dent Res 1977;54: [24] Supp P, Ruggeri Jr A, Ty FR, Prti C, BisottoM, Flconi M, Pshley DH, Breschi L. Reduced ntigenicity of type I collgen nd proteoglycns in sclerotic dentin. J Dent Res 2006;85: [25] Ogw K, Ymshit Y, Ichijo T, Fusym T. The ultrstructure nd hrdness of the trnsprent lyer of humn crious dentin. J Dent Res 1983;62:7 10. [26] Dculsi G, Legeros RZ, Jen A, Kerebel B. Possible physico-chemicl processes in humn dentin cries. J Dent Res 1987;66: [27] Ito S, Sito T, Ty FR, Crvlho RM, Yoshiym M, Pshley DH. Wter content nd pprent stiffness of non-cries versus cries-ffected humn dentin. J Biomed Mter Res Prt B Appl Biomter 2005;72B: [28] Tgmi J, Hosod H, Burrow MF, Nkjim M. Effect of ging nd cries on dentin permebility. Proc Finn Dent Soc 1992;88(Suppl. 1): [29] Mrshll GW, Hbelitz S, Gllgher R, Blooch M, Blooch G, Mrshll SJ. Nnomechnicl properties of hydrted crious humn dentin. J Dent Res 2001;80: [30] Zheng L, Hilton JF, Hbelitz S, Mrshll SJ, Mrshll GW. Dentin cries ctivity sttus relted to hrdness elsticity. Eur J Orl Sci 2003;111: [31] Zheng L, Nkjim M, Higshi T, Foxton RM, Tgmi J. Hrdness nd Young s modulus of trnsprent dentin ssocited with ging nd crious disese. Dent Mter J 2005;24: [32] Nishitni Y, Yoshiym M, Ty FR, Wdgonkr B, Wller J, Agee K, Pshley DH. Tensile strength of minerlized/deminerlized humn norml nd crious dentin. J Dent Res 2005;84: [33] Pshley DH, Ciucchi B, Sno H, Horner JA. Permebility of dentin dhesive gents. Quintessence Int 1993;24: [34] Spencer P, Wng Y, Wlker MP, Swfford JR. Moleculr structure of cid-etched dentin smer lyers in situ study. J Dent Res 2001;80: [35] Ruse ND, Smith DC. Adhesion to bovine dentin surfce chrcteriztion. J Dent Res 1991;70: [36] Tniguchi G, Nkjim M, Hosk K, Iwmoto N, Iked M, Foxton RM, Tgmi J. Improving the effect of NOCl pretretment on bonding to cries-ffected dentin using self-etch dhesives. J Dent 2009;37(10): [37] Kunwrote S, Nkjim M, Foxton RM, Tgmi J. Pretretment effect of mild cidic HOCl solution on dhesive to cries-ffected dentin using self-etch dhesive. Eur J Orl Sci 2011;119(1): [38] Nkjim M, Sno H, Urbe I, Tgmi J, Pshley DH. Bond strengths of single-bottle dentin dhesives to cries-ffected dentin. Oper Dent 2000;25:2 10. [39] Arris CAG, Ginnini M, Nkjim M, Tgmi J. Effect of dditionl nd extended cid etching on bonding to cries-ffected dentin. Eur J Orl Sci 2004;112: [40] Erhrdt MCG, Toledno M, Osorio R, Piment LA. Histomorphologic chrcteriztion nd bond strength evlution of criesffected dentin/resin interfces: effect of long-term wter exposure. Dent Mter 2008;24: [41] Mcedo GV, Ymuchi M, Bedrn-Russo AK. Effect of chemicl cross-linkers on cries-ffected dentin bonding. J Dent Res 2009;88: [42] Erhrdt MCG, Osorio R, Toledno M. Dentin tretment with MMPs inhibitors does not lter bond strengths to cries-ffected dentin. J Dent 2008;36: [43] Wng Y, Spencer P. Anlysis of cid-treted dentin smer debris nd smer lyers using confocl Rmn microspectroscopy. J Biomed Mter Res 2002;60: [44] Li SC, Mrk YF, Cheung GS, Osorio R, Toledno M, Crvlho RM, Ty FR, Pshley DH. Reversl of compromised bonding to oxidized etched dentin. J Dent Res 2001;80: [45] Komori PCP, Pshley DH, Tjäderhne L, Breschi L, Mzzoni A, de Goes MF, Wng L, Crrilho MR. Effect of 2% chlorhexidine digluconte on the bond strength to norml versus criesffected dentin. Oper Dent 2009;34: [46] Omr H, El-Bdrwy E, El-Mowfy O, Att O, Sleem B. Microtensile bond strength of resin composite bonded to criesffected dentin with three dhesives. Oper Dent 2007;32: [47] Nkjim M, Hosk K, Ymuti M, Foxton RM, Tgmi J. Bonding durbility of self-etching primer system to norml nd cries-ffected dentin under hydrosttic pulpl pressure in vitro. Am J Dent 2006;19: [48] Pshley DH, Ty FR, Yiu C, Hshimoto M, Breschi L, Crvlho RM, Ito S. Collgen degrdtion by host-derived enzymes during ging. J Dent Res 2004;83: [49] Ty FR, Pshley DH, Hirishi N, Imzto S, Rueggeberg FA, Slz U, Zimmermnn J, King NM. Tubulr occlusion prevents wtertreeing nd through-nd through fluid movement in singlebottle, one-step self-etch dhesive model. J Dent Res 2005;84: [50] Cehreli Z, Yzici AR, Akc T, Ozgunlty G. A morphologicl nd micro-tensile bond strength evlution of single-bottle dhesive to cries-ffected humn dentine fter four different cires removl technique. J Dent 2003;31: [51] Sttbnsuk V, Burrow MF, Shimd Y, Tgmi J. Resin dhesion to cries-ffected dentine fter different removl methods. Aust Dent J 2006;51:162 9.