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An in Vitro Evaluation of Microtensile Bond Strengths of Two Adhesive Bonding Agents to Residual Dentine After Caries Removal Using Three Excavation Techniques 2010 Journal of Dentistry

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An in Vitro Evaluation of Microtensile Bond Strengths of Two Adhesive Bonding Agents to Residual Dentine After Caries Removal Using Three Excavation
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  An in vitro evaluation of microtensile bond strengths of twoadhesive bonding agents to residual dentine after cariesremoval using three excavation techniques  A. Banerjee* , S. Kellow, F. Mannocci, R.J. Cook, T.F. Watson King’s College London Dental Institute, KCL, United Kingdom 1. Introduction The increasing evidence and popularity of the  minimallyinvasive operativemanagementofcariousdentinehasbroughtinto question the apparent necessity for complete cariesremoval when restoring a cavitated lesion in a patient. 1,2 Thesuperficial necrotic zone of caries-infected dentine thatharbours the core bacterial biomass should be excavatedleaving only ‘‘residual’’ caries-affected dentine lining thecavitywithsoundenamelmarginsanddentineadjacenttothe  journal of dentistry 38 (2010) 480–489 a r t i c l e i n f o  Article history: Received 21 January 2010Received in revised form22 February 2010Accepted 2 March 2010 Keywords: DentineCariesExcavationMicrotensile bond strengthDentine bonding agentConfocal microscopyCompositeSiloraneCarisolv TM gelBiosolv a b s t r a c t Objectives:  To assess amounts of residual dentine retained after using three excavationtechniques; the microtensile bond strengths ( m TBS) to residual dentine, comparing etch-rinse vs. self-etching adhesives. Methods:  42 carious molars were subdivided ( N  = 21) dependent upon adhesive/compositesystem (Adper Scotchbond 1XT and Filtek Supreme vs. Filtek Silorane adhesive and com-posite). Dividing into three ( N  = 7), dependent upon caries excavation technique employed(hand vs.chemo-mechanical: Carisolv TM gel vs.experimental enzymatic gel (SFC-V)), cariesremovalwasassessedusingvisual/tactilecriteriaandinsituautofluorescence(AF)confocalfibre-optic micro-endoscopy (CFOME). Post-restoration/four-week hydrated storage, four0.9 mm 2 beams per tooth underwent  m TBS testing/microscopic analysis of fractured sur-faces. Three cavities from each excavation group were analysed using SEM. Results:  SEMrevealedsurfaceroughnesswithsmearlayeroccludingtubuleorificesinhand-excavated samples and a reduced, variable smear layer for both chemo-mechanical sys-tems. CFOME AF assessment indicated hand excavation left sound dentine, Carisolv TM leftaffecteddentineandSFC-Vslightlyunder-preparedclinically.Mean m TBSvaluesfrometch-rinse samples (27 MPa (SD 3.9), hand; 22 MPa (SD 5.1), Carisolv TM ; 26 MPa (SD 4.4), SFC-V)showed statistical differences between hand and Carisolv TM groups. Mean  m TBS data forself-etch samples (22 MPa(SD 3.3),hand; 27 MPa(SD6.1), Carisolv TM ;25 MPa(SD4.7), SFC-V)showed significant differences between hand and Carisolv TM , and hand vs. SFC-V. Failureloci distribution inetch-rinse samples was between dentine–adhesive, within adhesive andwithin composite whereas self-etch samples exhibited failure predominantly betweenadhesive and composite. Conclusions:  Data indicated that all null hypotheses were disproved. # 2010 Elsevier Ltd. All rights reserved.*  Corresponding author at : King’s College London Dental Institute, KCL, Floor 26, Tower Wing, Guy’s Dental Hospital, London Bridge,London. SE1 9RT. Tel.: +44 0207 188 1577 7486; fax: +44 0207 188 1577 7486.E-mail address: avijit.banerjee@kcl.ac.uk (A. Banerjee). available at www.sciencedirect.comjournal homepage: www.intl.elsevierhealth.com/journals/jden 0300-5712/$ – see front matter # 2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.jdent.2010.03.002  enamel–dentine junction (EDJ). 3,4 This will enable the bestperipheral seal to be achieved with the current adhesivedentine bonding systems, as long as sufficient moisturecontrol can be obtained.Identification of the histological transition zone betweeninfected and affected dentine is difficult to assess bothclinically and in the research laboratory. Change in colour isnot a good indicator as the gradual bacterial and histologicalchanges are not consistently colour-dependent. 5 Cariesdetector dyes based on propylene glycol were developed inorderto highlightalterationsindentinecollagenstructurebutpublications have shown that clinical and laboratory resultsproduced are open to considerable user-interpretation. 6–8 Therelative hardness/tactility of the dentine has clinical validity; 9 sound dentine is scratchy to a sharp dental explorer, infecteddentine has a soft, ‘‘mushy’’ consistency and affected dentinefallsin between, oftensimultaneouslyscratchyandtacky,butagain this method of identifying the transition zone is fraughtwith operator subjectivity. 4 The autofluorescence (AF) of carious dentine has been proposed as a potential marker forthat carious dentine requiring excavation but srcinally, theconfocal microscopy equipment used to detect the AFsignature could only be useful in laboratory research experi-ments where extracted tooth sections could be prepared. 10–13 More recently, this technology has been developed into aconfocal fibre-optic micro-endoscope (CFOME) which canoperate in situ during active caries excavation in whole teeth,so providing immediate numerical, objective feedback of theAF quality of the residual carious dentine. 14 The selective removal of caries-infected dentine is noteasilyachievedwiththemostpopularcurrentoperativecariesexcavationtechniques–therotaryburandspoon-shapedhandexcavator. This is due to their relative tactile insensitivity andoperator variability in use leading to varying quantities of tissue removed. 13 Chemo-mechanical agents have beendeveloped to be used in conjunction with their own handinstrumentsandevidenceexiststoshowthattheircarefulusemay offer some element of selectivity between the infectedand affected dentine. One such gel system currently availablefor clinical use is based upon the controlledactivity of sodiumhypochlorite on dentine collagen, used with abrasive handinstruments (Carisolv TM gel–OraSolv AB, Gothenburg, Swe-den). 13,15 Another, based upon the enzymatic action of pepsinin an acidic environment (SFC-V, ‘‘Biosolv’’, 3MESPE AG,Seefeld, Germany) is at the clinical trial phase of itsdevelopment but shows promise. Another factor to considerin terms of restoring the resulting cavity with adhesivematerials, is the final dentine surface characteristics (surfaceroughness, presence of smear layer) which can affect the finalbond and seal achieved by adhesive systems. 16,17 In terms of factors affecting the long term success of adhesive restorations, the marginal integrity/potential formicroleakage at the tooth-restoration interface due to a poorseal, appear high on the list. 18,19 This in turn is closelyassociated with the quality of the bond achieved by moderndentine bonding systems. Current adhesives tend to fallbroadly into one of two groups—the etch-and-rinse systemswhich involve a separate etch phase with 37% orthopho-sphoric acid on both enamel and dentine for approximately20 s prior to placement of the primer and bond (adhesive), orthe self-etching systems which incorporate the acidic moi-eties within the primer phase of the bonding system, whichare incorporated into the final adhesive layer. There isevidence extolling the potential virtues of each system inthe strength of the bond achieved to varying dental sub-strates, 20–22 but less conclusive evidence when specificallyconsidering the bond to caries-affected dentine. 21,23–29 Therefore the null hypotheses to be investigated in thisstudy were:1. There are no differences in the amount and quality of carious dentine excavated by three different clinical handexcavation techniques (Carisolv TM gel, SFC-V and handexcavation).2. Using three different caries excavation techniques (Car-isolv TM gel, SFC-V and hand excavation) has no effect onadhesive bond strengths to the residual carious dentine,comparing total-etch and self-etching dentine bonding systems.3. Using three different caries excavation techniques (Car-isolv TM gel,SFC-Vandhandexcavation)hasnoeffectonthefailure mode and loci of failure when bonding to theresidual carious dentine, comparing total-etch and self-etching dentine bonding systems. 2. Materials and methods The materials used in this study are outlined in Table 1. WithGuy’s Hospital research ethics approval (04/Q0704/57), 51extracted,humancavitatedcariousmolars,storedinwaterfor Table 1 – Materials used in the study. Brand name Manufacturer Batch no. Type/constituents Adper Scotchbond 1XT 3MESPE AG, Germany 20050711 Total-etch dentine bonding agentFiltek Supreme 3MESPE AG, Germany 20030322 Hybrid resin compositeFiltek Silorane adhesive 3MESPE AG, Germany Experimental sample Self-etch dentine bonding agentFiltek Silorane 3MESPE AG, Germany 203905 Low-shrink siloxane–oxirane compositeCarisolv TM gel Orasolv AB, Sweden 06009 Chemo-mechanical caries removal gel(0.5%, w/v sodium hypochlorite; 0.1 Mglutamic acid/leucine/lysine, sodiumchloride, sodium hydroxide,carboxymethycelluloseSFC-V (‘‘Biosolv’’) 3MESPE AG, Germany 0540 Experimental chemo-mechanical cariesremoval gel (pepsin, phosphoric acid/sodiumbiphosphate buffer)  journal of dentistry 38 (2010) 480–489  481  no longerthan four weeks, wereselected and42 of these wererandomly divided into two experimental groups ( N  = 21),according to the type of adhesive restorative system used.Teeth in one group would be restored using an etch-and-rinsebonding agent plus a nano-hybrid resin composite (AdperScotchbond 1XT with Filtek Supreme resin composite(3MESPE, Seefeld, Germany)) whilst those in the other wouldbe restored with self-etching Filtek Silorane bond and low-shrink Filtek Silorane composite (see Table 1). Each of thesegroups was further subdivided into three subsets, dependentuponthecariesexcavationtechniqueemployed:conventionalhand excavation using a spoon-shaped hand excavator,Carisolv TM gel and SFC-V ‘‘Biosolv’’ ( N  = 7 in each). 2.1. Caries excavation Under 3   magnification dental loupes, a tungsten carbidefissure bur in an air-turbine handpiece (No. 57, Smartbur,Bridgewater Corners, USA) was used to remove any overlying,undermined enamel, so exposing the full extent of occlusalcariousdentineincluding aperipheryofsounddentine.Seventeeth from each of the two main groups underwent clinicalcariesexcavationusingaspoon-shapedhandexcavator,using operator-dependent tactility to determine the endpoint of caries excavation (see Fig. 1). A separate seven teeth in eachgroupunderwentcariesexcavationusingCarisolv TM gelaspermanufacturer’s instruction, using an abrasive metal mace-tipinstrument provided. The pre-mixed gel was introduced intothe cavity for 40 s prior to agitating the mixture against thedentine using the mace-tip instrument. Once the gel hadbecome cloudy with a ‘‘muddy’’ consistency, it was rinsedaway and a second fresh mix of gel was applied and furtheragitated.Excavationwasdeemedcompletewhenthegelfailedto become cloudy and the cavity was checked with a dentalprobe for hardness. The remaining seven teeth in each groupunderwent chemo-mechanical caries removal using SFC-Vsolution, with the same mace-tip instrument. The SFC-V wasintroducedintothecavityandwasimmediatelyagitatedusing the mace-tip hand instrument and washed away with furthersubsequent applications until the gel did not remove anyfurther dentine and did not become turbid (see Fig. 2). 2.2. Scanning electron microscopy (SEM) The remaining nine teeth with cavitated occlusal caries weresubdivided into three groups ( N  = 3) according to the cariesexcavation technique employed (see above). After excavation,rinsing and drying the final cavities, addition-cured light bodysilicone impressions were taken (President, Coltene AG,Switzerland) and from these, epoxy resin replicas created,gold sputter-coated and imaged using SEM (Hitachi S520-Hitachi Scientific Instruments, Wokingham, Berks., UK),12 kV). 2.3. CFOME AF measurements The confocal laser imaging system (Cellvizio 1 Mauna KeaTechnologies, Paris, France) was configured with a 600 m mdiameter plane-ended mini-o 1 surface contact optical fibrebundle objective probe (0–15 m m focal plane depth,  < 5 m m Fig. 1 – Caries excavation using a spoon-shaped hand excavator. (a) Original cavitated mandibular molar, (b) carious dentinewith peripheral sound dentine exposed after enamel removal, (c) infected dentine excavated with hand instrument, and (d)completed caries excavation with ‘‘scratchy’’ sound dentine remaining.  journal of dentistry 38 (2010) 480–489 482  lateral resolution, approximately 15 m m axial resolution andno distal optical element). After enamel preparation, the pre-excavation autofluorescence of the carious dentine in allsamples was recorded using 488 nm laser illumination. AFwavelengths, detected via the same coherent fibre elements,were delineated from reflected illumination wavelengthsusing  > 505 nm long-pass filtration. At the full imaging framerate of 12 fps, the individual non-contiguous fibre spot imageswere recorded in real-time and reconstructed as micro-endoscopic real-time fluorescence maps with ten separatereadingsmappedacrosstheocclusalextentofeachlesion.Foreach field of view (600 m m), the supplied software calculatedthe mean numerical fluorescence intensity (arbitrary units).Astherewasnocontrastinafullywhite(i.e.saturated)image,and no data in a fully black field (sound dentine), thenumerical measure of greyscale represented the degree of AF saturation of the image. The confocal fibre was peroxide-bleached(standardisedmanufacturerprotocol)betweeneveryreading to eliminate fluorescent debris transfer betweenmeasurement sites and between readings from a site. Asubsequentreadingwasonlytakenwhennofluorescencewasrecorded from the probe tip in air, representing a zero-calibration. Readings taken from the exposed sound dentineactedasinternalsamplecontrols.Apilotstudyconfirmedthatcontact imaging AF measurements from both sound andcarious dentine samples showed no discernable AF datavariationwithdarknesstobrightdaylightambientconditions.Ten post-excavation CFOME readings were finally mappedfrom the remaining dentine cavity surface following theprotocol outlined above. Fig. 2 – Caries removal using chemo-mechanical Carisolv  TM gel. (a) The srcinal occlusally cavitated carious lesion in amandibular molar. (b) The full extent of the carious dentine and sound margin exposed after enamel removal. (c) Clear gelapplied and left for 40 s before (d) agitation against the dentine using a mace-tip abrasive hand instrument. (e) Turbidity of the gel prior to rinsing and (f) the final excavation when no further caries is dissolved by the gel, leaving affected dentine.  journal of dentistry 38 (2010) 480–489  483
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