Electronic Microscopy Studies on the Adhesion of Total Etch Adhesive Systems in Glass-Ionomers and Compomers

Romanian Journal of Oral Rehabilitation Vol. 9, No. 3, July- Septembre 2017

ELECTRONIC MICROSCOPY STUDIES ON THE ADHESION OF TOTAL ETCH ADHESIVE SYSTEMS IN GLASS-IONOMERS AND COMPOMERS

Cristina-Angela Ghiorghe1, Gianina Iovan2*, Mihaela Sălceanu3*, Antonia Moldovan4, Cristina Iordache5 “Grigore T.Popa” University of Medicine and Pharmacy Iasi, Romania, Faculty of Dental Medicine

*Corresponding authors: Iovan Gianina e-mail: [email protected] Sălceanu Mihaela e-mail: [email protected]

ABSTRACT The aim of this study was to evaluate in vitro the adhesion and the type of bond failure when compomer or glass-ionomer cement was bonded with resin composite to total etches system. Scanning Electron Microscopy (SEM) was used for tested the compomer Dyract eXtra (D) and glass-ionomer cement Ketac Molar Easymix (KM) as basic restoration under two types of composite resins mycrohibride with total etch adhesive. A total number of 30 human molars were prepared with standardised cavities and were randomly divided in 3 groups. In the control group (F/Z), the cavities were filled only with composite resins (Filtek Z250-3M ESPE or Zmack Comp-Zermack). In group test 1 (G1 F-D/ G1 F-KM) the cavities were filled with Filtek Z250 in combination with Dyract, respectively Ketac Molar Easymix (as basic restoration). In group test 2 (G2 Z-D/G2 Z-KM) the cavities were filled with Zmack Comp in combination with Dyract, respectively Ketac Molar. The teeth were kept in distilled water at 37 ° C for 24 hours. The samples were longitudinally sectioned through the restoration and exposed to electron microscopy to see the adhesion of these materials to the dental tissues but also between them. The results indicated the bond strength of the composite resin to the conventional glassionomer cement was lower than that to the resin-modified glassionomer cement.

Key words: laminated technique, total etch adhesive, SEM microscopy, bond strength

INTRODUCTION characteristics of glass ionomers which may The use of laminate method is one of include adhesion to tooth structure and the recommended composite restorative cariostatic properties due to fluoride release. techniques used in dentistry, and it is [6] However, all compomer systems provide currently the subject of several studies. [1] dentin bonding agents similar to those used The technique benefits from the advantages with composites. Therefore Dyract was of GIC fluoride release in combination with combined with Dyract PSA and marketed aesthetic resin material to enhance clinical with Prime and Bond NT (Dentsply, serviceability. [2,3,4,5] Konstanz, Germany). However, compomers The concept of the lamination have a significantly lower fluoride release technique is to use two different restorative than glassionomer and because their materials to form one restoration. The mechanical properties and wear resistance are rationale behind the technique is to make the inferior to composite resins there is little most of the physical and aesthetic properties indication for their use. [6] of each material. These aesthetic restorative Considering the high standards of materials bond to tooth structure, and the GIC nowadays dentistry, dental material selection offers long term fluoride release that can be is the key process in the patient treatment recharged with a neutral topical fluoride plan. [7] application. [6] The lamination technique can be Dyract AP (DY) (Dentsply, Konstanz, applied for all deep and undermined cavities Germany) as a “compomer” combines the where composite resin is the primary choice. polymers of composite with the In particular cases where one or more

11 Romanian Journal of Oral Rehabilitation Vol. 9, No. 3, July- Septembre 2017 margins of restoration exist on the dentin, 1.5mm) were prepared on the buccal and oral lamination over a glassionomer cement is surfaces. The teeth were randomly divided in strongly recommended to enhance adhesion 3 groups. In the control group (F/Z), the to the dentin and limit microleakage. cavities were filled only with composite resins (Filtek Z250-3M ESPE or Zmack The aim of this study was to assess the Comp-Zermack). In group test 1 (G1 F-D/ G1 quality of adhesion between conventional F-KM) the cavities were filled with Filtek glassionomer cement or compomer and Z250 in combination with Dyract, composite resins in the laminated technique. respectively Ketac Molar Easymix (as basic restoration). In group test 2 (G2 Z-D/G2 Z- MATERIAL AND METHODS KM) the cavities were filled with Zmack 30 molars, extracted for orthodontic Comp in combination with Dyract, reasons, were cleaned and stored in distilled respectively Ketac Molar. water. Standardised cavities (3mm x 2mm x Table 1 The composition of the restorative materials used in study MATERIALS CATEGORY COMPOSITIONS MANUFACTURER Universal 3M ESPE Dental Bis-GMA, Bis-EMA, UDMA (0,01-3,5 μm Filtek Z 250 microhybrid Products, St. Paul, zirconium/silica filler) 60% by volume composite USA Bis-GMA, HEMA, dimethacrylates, ethanol, water, a novel photoinitiator system and a Adhesive 3M ESPE Dental Adper Single methacrylate functional copolymer of system Products, St. Paul, Bond 2 polyacrylic and polyitaconic acids (10 % by total etch USA weight of 5nm diameter spherical silica filler) Dymethacrylate resin (EBDADMA), Universal TEGDMA, photo initiators, stabilizer, fillers: Zmack Comp microhybrid barium-aluminium-borosilicate <1,5 μm; Zermack SpA, Italy composite highly dispersed silicon dioxide 0,04 μm; iron oxide pigments; titanium oxide (57% Carboxylic acid modified dimethacrylate; phosphoric acid modified acrylate resin; Zmack bond UDMA: methacrylate resin; TEGDMA: Adhesiv system total-etch methacrylate resin; HEMA; Zermack SpA, Italy total etch adhesive Camphorquinone: photoinitiator; Stabilizer: butylated benzenediol; Tertiary-butanol: solvent (< 25%) Liquid: Water, copolymer of acrylic acid- maleic acid; tartaric acid Ketac Molar Glass ionomer 3M ESPE, St.Paul, Powder: oxide glass ; copolymer of acrylic Easymix cement MN, USA acid-maleic acid; dichlorodimethylsilane reaction product with silica Ethoxylated Bisphenol-A dimethacrylate, urethane resin, triethylene glycol Dentsply De Trey Dyract eXtra Compomer dimethacrylate (TEGDMA), and Gmbh Germany trimethylolpropane trimethacrylate (TMPTMA); strontium fluorideglass 0.8 μm Di- and Trimethacrylate resins PENTA (dipentaerythritol penta acrylate monophosphate) Nanoﬁllers-Amorphous Prime&Bond Silicon Dioxide Photoinitiators Stabilizers Dentsply De Trey Adhesive NT Cetylamine hydroﬂuoride Acetone Gmbh Germany Caulk 34% Tooth Conditioner Gel: Phosphoric Acid Highly dispensed silicon dioxide Colorant Water

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The samples were longitudinally sectioned through the restoration and exposed to electron microscopy to see the adhesion of these materials to the dental tissues but also between them. For all the groups, the restorations were performed according to manufacturer‟s indications for each tested material. The light cured materials were polymerized using the lamp LEDidition - Ivoclaire Vivadent clinical, Austria. All Figure 2. Zmack Comp (group control Z) restorations were polished with polishing system Sof- Lex (3M ESPE). The teeth were The figure 3 present the restoration laminated kept in distilled water at 37°C for 24 hours. with Filtek Z 250 and Dyract eXtra. Appear a The samples were longitudinally sectioned mixed failure. through centre of restorations using a diamond disc. The sections were examined under microscope SEMQUANTA 200 3D (FEI, USA), in mode ESEM (Enviromental SEM). The SEM microscopy was evaluated the interfaces between the materials used for laminated technique. We observed some fractures which were called “adhesive failure” when the composite resin was removed from the glassionomer surfaces without residual debris, “cohesive failure” when fracture occurred inside the restoratives, Figure 3. Filtek Z250 –Dyract. (group and “mixed failure” when both occurred. test 1F-D)

RESULTS and DISCUSSIONS But in figures 4 we observed an adhesive In the figure 1 we observed that existed a failure between resine composite and glass good adhesion to enamel for resine composite ionomer cement. Filtek Z 250. We also observed an important adhesive layer (Adper Single Bond 2). In the figure 2 is the good adaption between resin composite Zmack Comp (with Zmack bond total-etch adhesive) and dental tissue.

Figure 4. Filtek Z 250- Ketac Molar Easymix (group test 1 F-KM) There is a fracture in mass of composite

material (cohesive failure). Small voids Figure 1. Filtek Z 250 (group control F) appeared in the mass of the compomer. The

13 Romanian Journal of Oral Rehabilitation Vol. 9, No. 3, July- Septembre 2017 two materials show good adhesion between groups them. (Fig. 5) In the previous figure is the distribution of the failures on the study lots. It is found that the number of adhesive failures was higher in the groups G1 F-KM and G2 Z- KM, than groups G1 F-D and G2 Z-D. But the cohesive failures was higher to G1F-KM and mixed failures was important to Control F. The best results (without failures) were observed in the Z-D group.

Figure 5. Zmack Comp – Dyract (group DISCUSSIONS The literature data related to studies test 2 Z-D) In figure 6, the glass ionomer cement the microleakage of laminate technique that appears porous and presented cohesive failure glassionomer cement has a poor aesthetics, and adhesive failure. low mechanical strength and technique sensitivity to moisture contamination. [8]. In our study the numerous air inclusions were founded within glassionomer cement, which explains numerous failures reported on this material. Burrow et al. Believed that these air inclusions acted as stress points, thus giving rise to the increased likelihood of cohesive failure within this material. [9] Dyract eXtra, as a compomer material, is a polyacidmodified composite Figure 6. Zmack-KM. (group test 2 Z- resin containing either or both of the essential KM) components (basic glass and acidic polymer) SEM evaluation of the fractured of a GIC but at levels insufficient to promote surfaces indicated the presence of cracks in the acid base cure reaction in the absence of some interfaces between restorative laminated light. [10] After initial light-activated with Filtek Z250 and glass ionomer Ketack polymerization, the traditional glass-ionomer Molar Easymix (Fig. 3, 4). The adhesive reaction slowly emerges through the uptake failure which appears in Fig 4 is important of water, activation of carboxylic groups of and continues in the depth of the filling. the dimethacrylate monomer, and the establishment of an acid-base reaction. [11, 12] Dyract was combined with Dyract PSA (Primer Sealer Adhesive), a self-conditioning single step, as an acetone-based agent containing acidic monomers. It is marketed with Prime and Bond NT. [13] When they were introduced, acid etching was not required by manufacturers. It was subsequently demonstrated the use of an acid etch procedure significantly improved both the retention and marginal leakage of the compomers. [14] The mechanical properties of compomers are superior to that of glass ionomers. [15] Our results demonstrated that compomer was a better adhesion than glass Figure 7. The count of failures by study

14 Romanian Journal of Oral Rehabilitation Vol. 9, No. 3, July- Septembre 2017 ionomer cement, because it has a higher resin CONCLUSIONS content. [16] The SEM microscopy showed the best Different studies report that the adhesion to group Zmack Comp – Dyract chemical composition of adhesive systems eXtra. The results showed that glass ionomer determines clinical success. [17] Polyacrylic cement shows more failures than compomer. acid in Adper Single Bond 2 adhesive Marginal adaptation and laminate technique promotes chelation with calcium and the have demonstrated a significant performance formation of hydrogen bridges with dentin of compomers than conventional glass components; it may be the significant factor ionomer. resulting in higher shear bond strength values. Another component that may be responsible for the high bond strength values is the 5 nm silica nanofiller incorporated at 10% weight in Adper Single Bond 2 adhesive. These particles may have a role in the formation of a resin film that stabilizes the hybrid layer. [18] There are many factors such as wet ability, viscosity, and contact angle that influence bond strength values. It is also possible the bond strength could be influenced by the presence or absence of any chemical bonding mechanism that could occur between the two materials when a lamination technique is used.

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