Surfaces of Class V Carious Cavities Imitated by Direct Replicas Method with Composite Filling Materials SEM Study

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1 ORIGINAL PAPERS Dent. Med. Probl. 2007, 44, 2, ISSN X Copyright by Silesian Piasts University of Medicine in Wrocław and Polish Stomatological Association ROMAN PAWLICKI 1, ZOFIA KNYCHALSKA KARWAN 2, BARBARA NOWAK KWATER 3, TOMASZ NOWAK 4, KATARZYNA ZAGÓRSKA ŚWIEŻY 5 Surfaces of Class V Carious Cavities Imitated by Direct Replicas Method with Composite Filling Materials SEM Study Badanie SEM dna i morfologii ścian bocznych ubytków próchnicowych klasy V wypełnionych materiałem kompozytowym w metodzie bezpośredniej replikacji 1 The Department of Histology Jagiellonian University Medical College in Cracow, Poland 2 Prof. Jagiellonian University Medical College in Cracow, Poland 3 Practice of Preventive Dentistry and Endodontic of Institute of Stomatology Jagiellonian University Medical College in Cracow, Poland 4 PhD studies on Collegium Medicum of the Jagiellonian University Medical College in Cracow, Poland 5 Practice of scanning microscopy of Department of Laryngology Jagiellonian University Medical College in Cracow, Poland Abstract Background. Adhesion of materials which fill teeth s hard tissues cavities is the basic factor of its unharmed per sistence in the oral cavity, and depends on wide range of factors. Objectives. Estimation of the usage of the original direct replicas method to determine the stage of projection exactness of the carious cavity. Material and Methods. The study materials were fillings, which were acquired in vivo from class V carious cav ities. During in vitro tests in extracted teeth the fillings were placed according to appropriate procedures and than extricated from those teeth and its surfaces were morphologically analyzed. In above described tests the original direct replicas method was used and the rule of filling material s surface inviolability was maintained. After fol lowing, appropriate preparation and gold evaporation further SEM tests were performed. Results. On the replicated enamel s surface destroyed prisms cores were visible and persistence of inner parts and interprismatic spaces was higher. The surface of enamel s prisms was initially etched revealing the image of cross striations. On the replicated surface of dentine images of dental tubules various lengths were visible. Conclusions. The direct replicas method used in described studies revealed to be profitable for accurate replicas of fillings surfaces, independently of cavity s depth and size (Dent Med Probl 2007, 44, 2, ). Key words: adhesion, microscopy, teeth fillings. Streszczenie Wprowadzenie. Adhezja materiałów wypełniających ubytki substancji twardych zęba jest zasadniczym czynni kiem ich niezakłóconej obecności w jamie ustnej i zależy od wielu czynników. Cel pracy. Ocena zastosowania oryginalnej metody bezpośredniej replikacji do określenia dokładności odwzoro wania ubytku próchnicowego. Materiał i metody. Materiałem badawczym były wypełnienia, które pozyskiwano in vivo z ubytków próchnico wych klasy V. Podczas badań in vitro na usuniętych zębach wypełnienia były poddawane odpowiednim zabiegom, następnie usuwane z zębów, a ich powierzchnie były analizowane morfologicznie. Zastosowano oryginalną meto dę bezpośredniej replikacji z przyjęciem zasady nienaruszalności powierzchni materiału wypełniającego. Po prze prowadzeniu odpowiedniej preparacji oraz naparowaniu złotem wykonano badania w mikroskopie elektronowym.

2 162 R. PAWLICKI et al. Wyniki. Na replikowanych powierzchniach szkliwa były widoczne zniszczone części rdzenne pryzmatów, a trwa łość części koronnych i przestrzeni międzypryzmatycznych była większa. Została nadtrawiona powierzchnia pry zmatów szkliwnych w formie poprzecznego prążkowania. Na zreplikowanych powierzchniach zębiny były widoczne odwzorowania kanalików zębinowych o zróżnicowanej długości. Wnioski. Metoda bezpośredniej replikacji zastosowana w badaniach własnych okazała się korzystna do określe nia dokładności odwzorowania powierzchni wypełnień niezależnie od głębokości i wielkości ubytku (Dent. Med. Probl. 2007, 44, 2, ). Słowa kluczowe: adhezja, mikroskopia, wypełnienia zębów. Adhesion of materials which fill teeth s hard tissues cavities is the basic factor of its unharmed persistence in the oral cavity [1 3]. The condition of the optimal adhesion occurrence is strict sealing of the filling to the tooth s walls and cavity s bot tom. The adhesion is the main factor in a pulp s vitality protection, by reducing the micro leakage and its effects [4]. Durability and quality of adhesive materials is estimated variously. It lasts from 3 to 5 years, and only 50% of the adhesive materials have endured the period of 10 years in the environment of the oral cavity [5, 6]. Much longer durability, which is 6 20 years and more, apply to silver amalgam [7]. Tight adherence and fillings durability are connected with such factors as: the tooth s age, its hard tissues mineralization extent, proper activity of the dentine by bounding agents and environ mental conditions [8]. Furthermore hygiene of the oral cavity, caries frequency, proper cavity s con figuration, preparation of the filling material, fit step of each material s layer applied to the cavity are factors which play an important role. Addi tionally factors as: quality and physic chemical properties of those materials, duration of polymer ization process, polymerization shrinkage and thermal expansibility of filling materials may not be neglected [9, 10]. Studies of marginal fissure width, tightness and adherence of filling materials to teeth s tissues have been performed repeatedly [8, 11]. To esti mate results authors commonly use direct observa tions of the connection in SEM after the cut of the tooth (through tooth s tissues and filling through the whole adhesion border]. Authors commonly use reliefs made by indirect method by taking impressions with the usage of vinyl polysiloxane impression materials. Subsequently those impres sions are filled with liquid polymerizing resin mixture of Epon 812 [12 16]. The extent of marginal fissure usually is examined and measured after the usage of dye tests, such as: silver nitrate, 0.5% water solution of alkaline magenta, 2% or 5% water solution of methylene blue [7 25]. Tight fissure is ascertained when its width ranges up to 5 micrometers, aver age 5 15, and wide when the width is above 15 mi crometers [26]. Differences in adhesion of filling materials to tooth s hard tissues have indirect nature, and those are observed in relation to enam el and dentine. Adhesion to the enamel is provided by three dimensional prisms arrangement and their spatial orientation [27]. Enamel s etching increases the adhesion of composite resins in a mechanical and chemical way [2, 10, 28]. Exposure of enamel s internal surface leads to a chemical reaction with composite resin s components. Enamel s etching dilutes its non organic elements and produces attachments for the resin, which subsequently strongly connects in a mechanical way. The resin (composite s matrix) penetrates into etched enam el producing a villi zone. The penetration of etch ing factor is 10 micrometers deep, however it pen etrates into enamel s microcracks either [10]. Adhesion to the dentine is difficult; the state of intertubular dentine and dentinal tubules, as well as presence of smear layer, are of great importance [8, 29]. The preparation of the dentine with only laser and carisolv gel removes the smear layer and uncovers opened dentine canals [30]. Furthermore glass ionomer cements have lower adhesion com paring to new bonding systems. A creation of a hybrid layer is described [31]. Dentine s etching removes non organic components leading to the exposure of the net of collagenous fibers [32]. Reaction s products which are accumulated in dentinal tubules decrease theirs diameter [32]. Longer lasting dentine s etching may lead to lower adhesion, furthermore excessive dentine s drying is unfavorable either [32]. The adhesion to dentine is thought to be stronger than to enamel, however the marginal fissure much easier develops at the dentine connection [33, 34]. The estimation of tightness is predominatingly performed on class I cavities, less often class V cavities. In class V cavities enamel s etching performed at the margin of the cavity improves tightness and strength of the adhesion [9]. However complete marginal tightness of compos ite resins in cervical zone cavities still remains doubtful [35]. The aim of this study is to morphologically esti mate, in SEM, the bottom and side walls of class V carious cavities located in cervical zone, with the usage of the original direct replicas method.

3 The SEM Study of Carious Cavities 163 Material and Methods The study material consisted of 5 dental fill ings, including 3 class V fillings acquired in vivo from incisors and 2 incisors, in which after theirs extraction because of periodonthological reasons class V cavities were prepared. Cavities 4 mm wide, 3 mm high and 2 mm deep were prepared with the usage of diamond burs. Prepared cavities were etched with 37% phosphoric acid (enamel for 30 seconds and dentine for 15 seconds) and the bonding agent was applied (Opti Bond Solo plus Kerr), than cavities were filled with two layered composite resin Herculite XRV Kerr. After 48 hours teeth were cut sagittaly, chemically impaired the material which was adhering to the teeth s hard tissues, and then it was pulled out. The original method of direct replication of studied space has been used, what ensured precise image of bottom and side walls of class V cavities. The described method preserved both conditions: technical dental preparation of cavity s bottom and side walls surface, as well as the integrity of filling material. The method was designed and tested by prof. Pawlicki. Fillings, which were used during tests, were rinsed with distilled water, dried on fil ter paper, dehydrated in rising concentrations of alcohol up to 100%, placed in vacuum chamber for 36 hours, evaporated with gold and theirs surfaces were analyzed in scanning electron microscope type Jeol JSM 35 CF. The observation was performed on the filling material s surface which contacted with enamel and dentine. Composite resin was used both as fill ing and replicating material. Fillings which sur faces remained untouched, both external surface as well as surfaces which were adjacent to cavi ty s bottom and side walls, ensured precise image of those places and were analyzed in SEM. Results On the replicated surface of treated, with the usage of burs, enamel the depressions, which are located circularly, parallel (Fig. 1) or linear (Fig. 2), may be seen. Furthermore the image is similar to formed honey comb (Fig. 2); interprismatic spaces were impaired by etching. Cores of prisms had higher durability which appears as honey comb shaped depressions on SEM images (Fig. 3). On the surface of replicated dentine prints of bur, formed as linear scratches and plug promi nences of composite resin which patterned dental tubules (Fig. 4) with projected internal structure of tubule s wall (Fig. 5), may be seen. Enamel s replica, after phosphoric acid treat Fig. 1. Prints of bur on the filling s surface formed as circular, parallel depressions (magnification 78) Ryc. 1. Replika rys na powierzchni wypełnienia w postaci kolistych równoległych zagłębień (powięk szenie 78 ) Fig. 2. Linearly oriented depressions, furthermore the image of replicated enamel similar to formed honey comb (magnification 2300) Ryc. 2. Linijne zagłębienia, ponadto obraz replikowa nego szkliwa podobny do plastra miodu (powiększenie 2300 ) ment, is observed. Prisms are oriented parallel, theirs surface is slightly affected; cross striations are clearly visible (Fig. 6). On replicated dentine s surface plug tubules images of various lengths are visible. It is com posite resin, which was placed into those tubules and polymerized (Fig. 7). Discussion The original method of direct replicas, which was used in presented study, enabled to obtain pre cise and objective images of carious cavity s bot tom and side walls. Materials which precisely replicated above mentioned surfaces were bond and composite resin, which are used to fill cavities as a standard. It enabled to project interfaces between enamel, dentine, bond, composite resin in

4 164 R. PAWLICKI et al. Fig. 3. On prepared surface of replicated enamel the image is similar to formed honey comb. Impaired core parts and interprismatic spaces. Cortical parts of enamel remained untouched (magnification 2600) Ryc. 3. Na opracowanej powierzchni replikowanego szkliwa obraz jest podobny do plastra miodu. Uszko dzone części jąder i przestrzeni międzypryzmatycz nych. Korowe części szkliwa pozostawały nienaruszo ne (powiększenie 2600 ) Fig. 5. Plug prominences located on the dentine s sur face; on some of them projected internal structure of dentine s tubules may be seen (magnification 1760) Ryc. 5. Wzniesienia na powierzchni zębiny; na nie których z nich można zobaczyć rzutującą się wewnę trzną strukturę kanalików zębinowych (powiększenie 1760 ) Fig. 4. Linear scratches of dentine and plug promi nences of composite resin which replicate dental tubules (magnification 1920) Ryc. 4. Linijne rysy zębiny oraz wzniesienia żywicy kompozytowej, co naśladuje kanaliki zębiny (powiększenie 1920 ) correctly formed filling placed in functional tooth, as well as in test fillings prepared in vitro. In similar investigations of SEM replicas made by indirect method various types of margin al adhesion were visible (smooth, with lack or excess of material) in various points of contact of the material with the teeth s hard tissues, so authors suggest analysis of the whole contour of the filling [14]. The enamel s image was very characteristic similar to formed honey comb and was obtained by other authors as well, who suggest irregular enamel dissolving by the etching agent [10, 36]. In other studies after the enamel s etching a destructive processes of this tissue were visible Fig. 6. Enamel with visible marks of chemical interac tion. Parallel oriented replicas of enamel s prisms. Slight damage of the surface, caused by etching, visible as cross striations (magnification 2600) Ryc. 6. Szkliwo z widocznymi oznakami interakcji chemicznej. Równolegle ułożone odwzorowania pry zmatów szkliwnych. Nieznaczne uszkodzenie po wierzchni wywołane przez wytrawianie widoczne jako poprzeczne prążkowanie (powiększenie 2600 ) [8]. In SEM images between amalgam and enam el fissures, which were filled with corrosion prod ucts, as well as destruction of prisms structure were visible [7]. In our studies inner parts of enamel prisms were etched, while cortical parts remained untouched. They make, in parallel formed prisms placed in enamel s bundles, varied surface to the depression system, which strongly fixes placed composite resin. Cross striations, which were observed in prisms, are usually the effect of daily growth which takes place during developmental period. In such cases it may be the

5 The SEM Study of Carious Cavities 165 Fig. 7. On dentine s surface plug tubules images of various lengths are visible. It is composite resin, which was placed into those tubules and polymerized (magnification 8800) Ryc. 7. Na powierzchni zębiny są widoczne kanaliki o różnej długości. Tutaj znajduje się także żywica kompozytowa, która została nałożona do tych kanali ków i spolimeryzowana (powiększenie 8800 ) proof of various enamel s prisms resistance to the influence of etching factor, which were used dur ing cavity s preparation. On the surface of prisms striations additional, smaller depressions are visi ble, which circularly border the prism. It produces additional sculpture of the prisms surface. Those additional depressions make the opportunity to achieve strong connection between enamel, con sidered entirely, and the filling material. In our studies, in all dentine s images on its surface very significant plug elements of equal diameter, which correspond with dentine tubules, may be seen. It is the result of composite resin s penetration into dentine tubules and its polymeralyzation. The material which fills dentine tubules of soft or even liquid consistency adapts to tubule s form and its internal sculpture. The poly merization of the material has the influence on strong fixation of the material and its connection with dentine in a mechanical way. Furthermore in observations of silicon cements and amalgams leaks, demineralization processes, obliteration of canals structure with modifications in peri and inter tubular dentine were found [36, 37]. Previous studies, which were performed with the usage of different techniques, have not repro duced in such detailed way the direct morphologi cal image of cavity s surface and etching results, which do not stay neutral to tooth s hard tissues, as the replicas method used in those studies. Furthermore they were focused mainly of margin al fissure, its image and size [8, 11, 18]. Received SEM images of the morphology of carious cavi ty s bottom and side walls evidence that cavi ty s treatment procedures, performed before the application of the filling material, were optimal for precise, strong and tight filling achievement, which prevents microleakage and successive pulp s complications. The authors conclude that original method of direct replication of studied space ensured precise image of bottom and side walls of carious cavities. It shows the method of cavity s preparation, as well as the results of tooth s hard tissues etching. Furthermore it describes objectively the adhesion of the filling to teeth s hard tissues. References [1] DUBIELECKA KITTEL M.: Mechanizmy adhezji pośredniej i adhezji bezpośredniej. Dentico 2005, 1, [2] LIMANOWSKA H.: Adhezja tkanek zębów i materiałów dentystycznych oraz warunki jej uzyskania. Pozn. Stomat. 1991, [3] SULIBORSKI G.: Zjawisko adhezji. Magazyn Stomat. 1998, 8, 2, [4] TORRES G. et al.: Effects of dentin collagen removal on microleakage of bonded restorations. J. Adhes. Dent. 2004, 6, [5] DOWNER M. et al.: How long do routine dental restorations last? A systemic review. Brit. Dent. J. 1999, 187, [6] SKOMRO P. et al.: Porównanie trwałości wypełnień ubytków klasy I i II z materiałów złożonych i z amalgamatu srebra. Czas. Stomat. 1997, [7] PAWLICKI R. et al.: Obserwacje w SEM tkanek twardych zębów przylegających do wypełnień amalgamatowych założonych do ubytków przed 20 laty. Twój Mag. Med. 2002, 2, [8] STOPA J., MATTHEWS BRZOZOWSKAT.: Ocena ultrastrukturalna połączenia wypełnień z różnych materiałów kom pozycyjnych z tkankami zęba. Czas. Stomat. 1995, 48I, [9] SOKOŁOWSKI J., PACYK A.: Rola adhezji w połączeniu materiałów kompozytowych ze szkliwem zębów. Dentico 2005, 1, [10] SULIBORSKI S., SOKOŁOWSKI J.:Adhezja materiałów kompozycyjnych do szkliwa. Magazyn Stomat. 1998, 4, [11] BACHANEK T., NIEWCZAS A.: Problem szczelności brzeżnej wypełnień kompozytowych. Forum Stomat. 2005, 2, [12] CHADWICK R. et al.: A novel approach to evaluating the reproducibility of a replication technique for the manu facture of electroconductive replicas for use in quantitative clinical dental wear studies. J. Oral Rehab. 2004, 31,

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