Caklina i dentin po svojoj su kemijskoj građi dva različita supstrata pa ih je potrebno pažljivo i različito prirediti za postavljanje kompozitnoga materijala. Svrha rada bila je pokazati kako različit predtretman cakline i dentina (“total-etch” tehnika i samojetkajući adhezivi) utječe na kakvoću sveze s kompozitnim materijalom. Dobiveni su rezultati pokazali da je optimalno vrijeme jetkanja 37%- tnom ortofosfornom kiselinom 20 sekundi za caklinu i 10 sekundi za dentin.Enamel and dentin are, by their very chemical structure, two different substrates which necessitate different preparation before placing of composite resin. The aim of this study was to show how various enamel and dental pretreatment methods (“total etch” technique and self etching adhesives) affect the quality of bonding with composite resin. The results obtained showed optimal etching time, using 37% orthophospohoric acid, of 20 seconds for enamel and 10 seconds for dentin

Alena Knežević

Jozo Šutalo

Marija Ujević

Višnja Negovetić-Mandić

Vlatko Pandurić

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A S CActa Stomatol Croat, Vol. 38, br. 1, 2004. 53Influence of Prepared CavitySurface on Microleakage - PilotStudySummaryEnamel and dentin are, by their very chemical structure, two dif-ferent substrates which necessitate different preparation before plac-ing of  composite resin. The aim of this study was to show how variousenamel and dental pretreatment methods (“total etch” technique andself etching adhesives) affect the quality of bonding with composite resin.The results obtained showed optimal etching time, using 37%orthophospohoric acid, of 20 seconds for enamel and 10 seconds fordentin.Key words: etching, self etching adhesives, microleakage.Alena KneæeviÊ1Marija UjeviÊ2Goran ©alkoviÊ2Viπnja NegovetiÊ-MandiÊ1Vlatko PanduriÊ1Jozo ©utalo11Department of DentalPathology School of Dental MedicineUniversity of Zagreb2Fourth Year Students School of Dental MedicineUniversity of ZagrebActa Stomat Croat2004; 53-56PRELIMINARY REPORTReceived: October 15, 2003Address of correspondence:Alena KneæeviÊZavod za dentalnu patologijuStomatoloπki fakultetGunduliÊeva 5, 10000 ZagrebCroatiaIntroductionDurable and quality composite restoration notonly implies the right choice of composite materialand dental adhesives, but primarily adequate prepa-ration of the cavity for composite restoration. Sinceenamel and dentin have different chemical structuresthey require different preparation.Enamel surface preparation. Etching of enamelis a process that enables formation of a bond betweenenamel and restorative material. Margins of theenamel are etched with 37% orthophophosphoricacid which causes demineralization of hydroxylap-atite crystals and formation of microspaces. Thisprocedure causes removal of the old and chemical-ly saturated enamel surface, thus removing glyco-protein membrane and smear layer that forms as aresult of heat and plastic deformation of hard den-tal tissue while drilling. As a result, the reactive sur-face or enamel surface porosity increases, whichleads to significant increase in the area for penetra-tion and micromechanical wedging of low- viscos-ity composite resin (1, 2).Dental surface preparation. Because of differ-ences in the enamel and dentinal structure (enamelcontains 83-86% anorganic mattter, 2-5% organicand 12% water, while in dentin anorganic part equals65-70% weight, organic !8% and water 16%), denti-nal preparation will differ from enamel preparationfor composite resin filling application. Dental con-ditioning removes the smear layer and causes dem-ineralization of dentin to a certain depth. Dental con-ditioners affect smear layer differently. Kelation sys-tems like EDTA-e, polymaleic and polyacrylic acidA S C Acta Stomatol Croat, Vol. 38, br. 1, 2004.54Alena KneæeviÊ et al. Influence of Prepared Cavity Surface on Microleakageremove only the surface smear layer without simul-tanously opening dental tubules and demineralis-ing the dental surface (3-6).Treatment of the dental surface with phosphor-ic acid (10-37%) causes complete melting of thesmear layer as well as surface demineralization ofperi- and inter tubules dentine to the 10 µm and melt-ing of the inorganic component. Collapse of colla-gen fibers significantly decreases porosity of thedental surface as well as penetration of the adhesiveresin. Great differences in depth of resin infiltra-tion are found when etching with 10%, 35%, 65%phosphoric acid because it is a weak acid that doesnot completely disassociate at any concentration. Itis proven that 65% phosphoric acid etches shallow-er at any time frame than 10% acid. Phosphoric acidcontains a large concentration of dehydrogen sulfatewhich by chemical reactions forms relatively meltableproducts that still might have a passing influence onmonomer and resin infiltration by precipitating asCa salts (7,8). The amount of adhesive on the sur-face and subsurface layer are substantially differ-ent which results in the breakage of bonds and lowquality of filling and as a consequence marginalleakage (9)After etching and rinsing of acid, primers areused, integral parts of adhesive systems of 3rd, 4th,5th and 6th generation. Applied to the wet dentinesurface they penetrate through the demineralizedareas where they give support to the collapsed col-lagen fibers, lift them up, widen intercollagen spacesand allow for better adhesive penetration and for-mation of strong interface between the dentinal tis-sue and monomer at the molecular level. Newlyformed compound is called hybrid layer. In thebroader sense, the hybrid layer represents resin infil-trated dentin. It forms by micromechanical nettingof demineralized collagen net with low-viscosityresin. For formation of the hybrid layer two factorsare necessary to enable penetration and diffusionbetween collagen fibers i.e. appropriately preparedsubstrate achieved by removing the smear layer anddemineralization of dentin as well as an appropri-ate resin monomer. The hybrid layer can act as an“elastic repellent” because it absorbs polymeriza-tion stress which prevents formation of a marginalgap (10-12).Purpose of the studyIn order to show whether there is correlationbetween the length of enamel and dentin etchingtime and marginal leakage in cavities containingcomposite filling, a pilot study was carried out, inwhich microleakage of composite fillings placed onvariously treated enamel or dentin surfaces wasmicroscopically examined.Materials and methodsOn 15 extracted teeth, 7 molars and 8 premolars,two cavities were prepared, one on the oral and theother on the vestibular side. Cavities were preparedusing diamond fissure burr 2mm deep and 4 mmwide with beveling of enamel margins. The teethwere separated into five groups and each demand-ed different pretreatment of enamel and dentinbefore application of adhesive and composite resin.For groups I, II and III total-etch technique wasused in such a way that;Group I. - etching time was 15 sec for enamel and5 sec for dentinGroup II. - etching time was 20 sec for enamel and10 sec for dentinGroup III.- ething time was 30 sec for enamel and15 sec for dentin.37% orthophosphoric acid (Vivadent, Schaan,Liechtenstein) was used for etching. After rinsingof acid and drying of cavity, Te-Econom (Vivadent,Schaan, Liechtenstein) dental adhesive was placedon enamel and dentin in one layer, gently air-blownand polymerized for 20 seconds by Elipar Trilight(ESPE, Seefeld, Germany) halogen lamp. Cavitywas filled with Tetric Ceram (Vivadent, Schaan,Liechtenstein) composite material (color A3).For group IV and group V self-etch techniquewas used:Group IV. - enamel was etched for 15 seconds, afterrinsing and drying self-etching adhe-sive Prompt-L-Pop (ESPE, Seefeld,Germany) was placed.Group V. - on non-etched enamel and dentin self-etching adhesive Prompt-L-Pop wasplaced.A S CActa Stomatol Croat, Vol. 38, br. 1, 2004. 55Alena KneæeviÊ et al. Influence of Prepared Cavity Surface on MicroleakageSelf-etching adhesive was polymerized for 20seconds and the cavity filled with composite mate-rial Tetric ceram (color A3).After the placement of composite filling, thetooth crown was cut from the root and the coronarysection coated with protective enamel. Preparedsamples were immersed for 48 hours in black ink.After passing of the stated time, the samples weredried and  each cavity was cut down the middle inthe vestibulo-oral direction in order to form twoequal halves. Samples obtained in this way wereexamined using an Olympus Stereomicroscope(Olympus Optical Co. Europa, GMBH, Hamburg,Germany). The research system applied in this investigationwas composed of five basic parts:1. Research stereomicroscope Olympus SZX-12with cold light source2. Olympus DP-12 digital camera3. PC Pentium IV4. Olympus DP-Soft 3.2 programme for digitalimage analysis.Each sample was photographed and the photo-graph examined for the depth of ink penetration indegrees:Degree 0 - no leakageDegree 1 - leakage up to 1/3 enamel depthDegree 2 - leakage up to 2/3 enamel depthDegree 3 - leakage up to enamel-dentin junctionDegree 4 - leakage in dentine.For each sample three images were made: one ofthe entire cavity (magnification 32X), one of themesial section (magnification 40X) and one of thedistal section (magnification 40X).ResultsAnalysis of the images gained showed that ifmarginal leakage existed, it encompassed mostlypart of the enamel in the beveled area of enamel mar-gins (Figure 1).Greatest leakage was observed in the sampleswhere self-etching dental adhesive Prompt-L-Popwas used (groups IV and V) (Figure 2, 3), and in thesamples where enamel was etched for 15 secondsand dentin for 5 seconds (Figure 4).In Group II, where enamel was etched for 20, anddentin for 10 seconds, and in Group III (Figure 5),where enamel was etched for 30 and dentin for 15seconds, no microleakage was observed.Figure 6 presents a graphical illustration ofmicroleakage based on sample groups and degree ofleakage.DiscussionAdhesion of composite material to enamel anddentin is reached differently because of differencesin composition and chemical structure of these twotissues. Enamel is built rather homogeneously, fromhydroxylapatite crystals, with a small amount oforganic matter and water, while dentin structure isvery heterogeneous, consisting of more organic mat-ter and water. These differences demand longer etch-ing of enamel than dentin (13).Ernst et al. investigated microleakage on 160extracted teeth, divided into 8 groups in which theyused various combinations of dental adhesives andcomposite materials to produce fillings. After prepa-ration, teeth were immersed in methylene blue for10 seconds. Depth of penetration was measured ona stereomicroscope. Deepest average marginal pen-etration of methylene blue  as well as the largestnumber of color penetrated marginal parts of the fill-ing were found precisely in the group where self-etching addhesive Prompt-L-Pop was used (14, 15).Despite usage of different means for markingmikroleakage and shorter color exposure time, thedescribed study is in accordance with our own find-ings, because greatest mikroleakage was observedin those samples where identical self-etching adhe-sive was used as well as in the group where enam-el was etched for 15 and dentin for 5 seconds.Nakabayashi et al. also investigated microleak-age of composite fillings. They immersed samplesof prepared teeth in silver nitrate for 24 hours andfound existence of mikroleakage by light micro-scope. Observing the same samples on an electronmicroscope they found silver in the hybrid layer inthe absence of microgap between the composite fill-A S C Acta Stomatol Croat, Vol. 38, br. 1, 2004.56Alena KneæeviÊ et al. Influence of Prepared Cavity Surface on Microleakageing and hybrid layer. They named this processnanoleakage in order to distinquish it from microleak-age. (16).Furthermore, the age of the tooth, compositeapplication technique, source of polymerization lightand polymerization shrinkage as a negative conse-quence of polymerization all have an influence onthe final results. It can be concluded that optimaletching time for enamel is 20 seconds and for dentin10 seconds, while it is recommended that the enam-el of permanent young teeth as well as scleroticdentin should be etched for 30 seconds and dentinfor 15 seconds which is in accordance with the cur-rent research of some authors (16, 17).Every marginal leakage that leads to diffusion oforal fluid, bacteria and their products into the dentinarea can lead to pulp damage and secondary caries.Numerous research has showed that marginal rela-tionship between cavity surface and filling materi-al is not fixed, inert and impermeable margin, butrather consists of microgaps in which intensive trans-fer of ions and molecules occurs (10).ConslusionAnalysis of images obtained determined the exis-tence of marginal leakage mostly in the area ofenamel margins in the samples where enamel wasetched for 15 and dentin for 5 seconds as well as inthe samples where self-etching adhesive was used,while in the samples where enamel was etched for20 or 30 seconds and dentin 10 or 15 seconds nomicroleakage was observed.On the basis of the results obtained it can be con-cluded that etching time influences the quality of thebond between composite material and hard dentaltissue and further deduced optimal etching time forenamel to be 20 seconds and for dentin 10 seconds.

Influence of Prepared Cavity Surface on Microleakage - Pilot Study

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