|Year : 2017 | Volume
| Issue : 4 | Page : 151-155
Comparison of marginal adaptation of a silorane-based composite versus two methacrylate-based composites in different depths of Class V restorations
Department of Operative Dentistry, Dental School, Rafsanjan University of Medical Science, Rafsanjan, Iran
|Date of Web Publication||21-Aug-2017|
Department of Operative Dentistry, Dental School, Rafsanjan University of Medical Science, Rafsanjan
Source of Support: None, Conflict of Interest: None
Aims: Determining the best restorative material to decrease microleakage in Class V restorations is of great importance in operative dentistry. This in vitro study compared the microleakage of a low-shrinkage silorane-based composite with two methacrylate-based composites in different depths of cavity in enamel and dentin. Materials and Methods: Class V cavities, with the length and width of 3 mm but two different depths of 1 and 1.5 mm, were prepared in the buccal surface of 72 extracted human premolars. Each group was randomly divided into three subgroups of 12 specimens. In Subgroup 1, enamel was etched with 37.5% phosphoric acid and cavities were restored with silorane-based resin composite (Filtek P90) with its dedicated adhesive system (P90 system adhesive). In Subgroups 2 and 3, the cavities were etched and restored with methacrylate-based resin composites (Point 4, with OptiBond Solo Plus adhesive and Filtek Z250 XT with Single Bond Universal adhesive). All the specimens were thermocycled and then immersed in 0.5% methylene blue for 24 h at 37°C, next were sectioned for taking digital photographs and were evaluated with Adobe Photoshop 8 software, with magnification of ×20. The results were subjected to Kruskal–Wallis and Mann–Whitney tests (P = 0.05). Results: All the three materials utilized in this study exhibited some degree of leakage. There were no significant differences between Filtek P90 and two methacrylate-based composite resins (P > 0.05). Furthermore, the results showed that there was no statistically significant relationship between preparations with different depths (P > 0.05); however, microleakage in enamel margins was significantly lower than dentin margins (P < 0.05). Conclusions: Silorane was not superior to the methacrylate-based composites in terms of microleakage. No significant relationship was found between the depth of cavities and the degree of microleakage, but microleakage was higher in dentinal margins.
Keywords: Dentin, depth, enamel, methacrylate-based composite, microleakage, silorane-based composite
|How to cite this article:|
Shakerian M. Comparison of marginal adaptation of a silorane-based composite versus two methacrylate-based composites in different depths of Class V restorations. J Int Oral Health 2017;9:151-5
|How to cite this URL:|
Shakerian M. Comparison of marginal adaptation of a silorane-based composite versus two methacrylate-based composites in different depths of Class V restorations. J Int Oral Health [serial online] 2017 [cited 2018 Jun 18];9:151-5. Available from: http://www.jioh.org/text.asp?2017/9/4/151/213490
| Introduction|| |
Today with the constant development of dental composite resins and their desirable esthetic properties, evaluation of the material properties serves as an important issue for their clinical application. Although composites are now the favorable materials for most restorations, their polymerization shrinkage remained a big challenge that causes marginal discrepancy., Manufactures and investigators try to improve composite materials such as matrix and filler ingredients, filler particles size, and adhesive systems to overcome this problem., When one of the cavity walls prepares in the dentin, the situation is more compromised. Placing an adaptable adhesive bonding layer under the composite resin, using an incremental placement technique, and composites with low-shrinkage properties are just some manipulations suggested to reduce shrinkage stresses. Siloranes are a totally different class of composite resins that their polymerization process occurs through a cationic ring-opening phenomena, which results in a lower polymerization contraction., The methacrylate-based resin composites polymerize through the radical addition of their carbon double bonds. The composite volume and cavity configuration (c-factor) are considered two important determinants of shrinkage stress in composite restorations., The higher the composite volume, the greater is the amount of monomers to convert and consequently the higher is the stress generated on the bonding interface. Composite contraction and as fallow polymerization stress can cause debonding and gap formation at the composite/tooth interface and contribute to cusp flexure, enamel cracks, discolorations of restoration margins, postoperative sensitivity, and recurrent caries, especially in Class V restorations when bonding interface is located below the cementoenamel junction (CEJ).,, Because of considerable microleakage in these cavities, this in vitro experimental study was conducted with the aim of comparing microleakage of two methacrylate-based composite materials with different bonding systems and a low-shrinkage silorane-based composite in different volume of cavities in Class V restorations.
| Materials and Methods|| |
Seventy-two sound human premolars extracted for the orthodontic reasons were collected for use in this study. The teeth were cleaned and carefully rinsed with water to remove the residual debris and then were examined with light from a light-curing unit for the presence of cracks. Only intact teeth free of defects were included. The teeth were stored in a disinfectant solution for 24 h.
In all of the examined teeth, standardized Class V cavities were prepared at the buccal surface, with the gingival margin 1 mm below the CEJ. Two groups of cavities were prepared with straight diamond fissure bur No. 835 (D+Z, DIAMANT GmbH, Germany) in a high-speed handpiece (W and H, Austria). In one group, the outline of the cavities had 3 mm width, 3 mm height, and 1 mm depth. In another group, the outline had 3 mm width, 3 mm height, and 1.5 mm depth. It was made sure that no cavity preparation caused to pulpal exposure. The dimensions of cavities were calibrated using a periodontal probe. After each five cavity preparation, a new bur was replaced. The margins were prepared with nonbeveled butt joint cavosurface line angles. Each cavity group (composed of 36 teeth) was randomly divided into three subgroups:
- Subgroup 1 – restored with the low-shrinkage silorane-based composite Filtek P90 (3M. ESPE, USA). The composite system was used according to the manufacturer's instruction with its corresponding adhesive system (P90 system adhesive, 3M, ESPE, USA), which is a two-component, two-step, sixth-generation adhesive system consisting of a self-etch primer and a bond. The enamel was etched with 37.5% phosphoric acid gel (3M, ESPE, USA) for 15 s and then rinsed thoroughly with water spray and gently air-dried (selective enamel etching). The primer was applied to the entire surface of the cavity with a disposable brush, then air-dried gently and light cured 10 s with a LED light-curing unit (Demetron, Kerr, USA) with the intensity of 1000 mW/cm 2. Then, the bonding was applied to the entire surface of the cavity and light cured for 10 s. The Filtek P90 composite resin was applied to the cavity preparations in one increment and light cured for 40 s.
- Subgroup 2 – In this group, point 4 resin composite (Kerr, Italia. S.r.l) with OptiBond Solo Plus adhesive (Kerr, Italia, S.r.l) was used. After acid etching with 37.5% phosphoric acid gel for 15 s, the cavity was rinsed with water and gently air-dried without dehydration of the dentin and then the bonding system was applied and light cured for 20 s. The composite point 4 was applied bulky in the cavities and cured for 40 s.
- Subgroup 3 – Filtek Z250 XT composite resin (3M, ESPE, USA) and Single Bond Universal (3M, ESPE, USA) were used. The cavity was etched with phosphoric acid for 15 s, then rinsed and gently air-dried. The Single Bond Universal adhesive was applied to the entire of cavity surface and light cured for 10 s. The composite resin was bulk filled in the cavity and light cured for 40 s.
The materials and their chemical compositions are shown in [Table 1]. For all composites, A2 shade was chosen and the light intensity was constantly monitored by its integrated radiometer.
A microfine diamond bur No. 863 (D+Z, DIAMANT GmbH, Germany) was used for gross reduction of composite excesses and aluminum oxide abrasive disks (kerrHawe SA, Switzerland) were used in sequence to finish and polish the restorations surface. All the specimens were stored in distilled water for 1 week at room temperature and then subjected to the thermocycling (TC) test for 500 cycles (the ISO TR 11450 standard, 1994) at 5°C and 55°C with a dwelling time of 30 s and transfer time of 5 s. Then, the root apex of each tooth was sealed with sticky wax and the root and crown surfaces of each tooth were coated with two layers of nail varnish except for 1 mm around the restoration margins. For insurance that the second layer of varnish was properly applied on the first layer, two different colors of nail varnishes were used.
The teeth then were immersed in 2% methylene blue dye (pH = 7) for 24 h, washed, and dried. Teeth were embedded in blocks of auto-polymerizing acrylic resin (Acropars, Marlic, Tehran, Iran) and then were sectioned longitudinally/buccolingually using a slow-speed diamond disk mounted in a sectioning machine (CNC, Nemo, Mashhad, Iran) with water coolant.
Dye penetration in occlusal and gingival margins of restorations was measured with digital photographs (Nikon D3200, Bangkok, Thailand) and Photoshop software 8 at ×20 magnification and a 10th mm accuracy. Dye penetration was scored as described in [Table 2].
The results were analyzed statistically using SPSS software version 21 (SPSS Inc, Chicago, IL, USA). The scores were subjected to statistical analysis using the nonparametric Kruskal–Wallis analysis of variance test and the Mann–Whitney test at 95% significance level.
| Results|| |
Descriptive statistics of mean and standard deviations scores for dye penetration test are listed in [Table 3]. Kruskal–Wallis test showed no significant differences between groups.
In comparison of different three composites in [Table 4], the test indicated no significant differences (P = 0.115). In comparison of cavity volume (depth), there were no significant differences in microleakage (P = 0.075), but cavities with 1.5 mm depth showed more microleakage. In comparison of microleakage between enamel and dentin, Friedman test showed that the results were statistically significant (P < 0.000) and cavity margins established in enamel showed less microleakage [Table 5].
|Table 4: Comparison of microleakage between three groups of composites in Kruskal-Wallis test|
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|Table 5: Comparison of microleakage between enamel and dentin in Friedman test|
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As shown in Graph 1, the most microleakage was in Point 4 composite resin in preparations with 1.5 mm depth and margins in dentin and the least microleakage was seen in P90 and Z250 XT composite resins in preparations with 1 mm depth and margins in enamel.
| Discussion|| |
An important issue in promoting the composite resin success is the marginal and internal adaptation of the restoration. Many factors encounter in gap formation such as polymerization contraction of composite resin, temperature variations, and composite volume. Composite consists of fillers embedded in a chemically reactive organic resin matrix. Polymerization shrinkage is an intrinsic property of the resin matrix. Upon curing, the single-resin molecules move toward each other and are linked by chemical bonds to form a polymer network. This reaction leads to molecular densification due to the shortening of intermolecular separations and causes a significant volume contraction. Polymerization shrinkage and the resulting stresses lead to microleakage which is among the major factors for composite material failures.,
Microleakage evaluation is the most common method of assessing the sealing efficacy of the restoration's margins. The most widely accepted method of assessing the margin quality is the dye penetration test. Dye penetration may provide an easy and fast preclinical screening method to compare marginal gaps. In the present study, all the specimens exposed to aging treatment to subject the restoration to thermal expansion and contraction challenges to simulate the oral conditions. Weakening of adhesive resin due to thermo-mechanical loads can accelerate destruction of bond between the tooth structure and restoration margins.,
All the three materials utilized in this study exhibited some degree of leakage. The low-shrinkage composite Filtek P90 showed no statistically significant difference with Filtek Z250 XT (nanohybrid) and Point 4 (microhybrid) composite resins. The polymerization process of Filtek P90 restorative occurs through a cationic ring-opening reaction which results in a lower polymerization contraction, in comparison with the methacrylate-based resins which polymerize through a radical addition of their double bonds. The ring-opening step significantly reduces the amount of polymerization shrinkage which occurs in the curing process. Manhal in an evaluation of a silorane-based and methacrylate-based packable and nanofilled posterior composite concluded that Filtek P90 showed significantly less microleakage when the tooth restoration interface was located in enamel. Krifka et al., in a study with the goal of comparison of the marginal integrity of Class V silorane and methacrylate composite restorations, concluded that initially and after TC, the silorane system showed statistically better marginal integrity on both enamel and dentin than the methacrylate system. Attia et al. in a study evaluated 1-year clinical follow-up of a silorane-based composite (Filtek P90) versus a methacrylate-based composite in Class I cavities. They concluded that Filtek P90 composite resin had no obvious advantage compared to methacrylate-based composite. The low shrinkage associated with Filtek P90 may not be a determinant factor for its high clinical performance. Our results showed that the Filtek P90 composite resin had microleakage score similar to Z250 XT with Single Bond Universal adhesive, especially in cavities with 1 mm depth and restoration margins in enamel. Although, overall, the Z250 XT composite resin was better than silorane-based Filtek P90 after TC, the difference was not significant. Also, Filtek P90 has low-shrinkage properties due to innate ring opening polymerization reaction of the silorane monomers, but we can conclude that methacrylate-based composite resins better withstand TC fatigue at the tooth-restoration interface. It can be attributed to the properties of the silorane system adhesive and the Single Bond Universal. The recent innovation in adhesive technology involves the introduction of one-step self-etch adhesives, known as all-in-one adhesives, in which the conditioner, primer, and bonding resin are combined to facilitate application. All-in-one adhesives are the most user-friendly adhesive systems currently available. The most recently introduced adhesive systems, multimode adhesives, that can be applied in both etch and rinse and self-etch modes, enable the operator to decide for a specific adhesive protocol and would be very desirable. The chemical formulation of these adhesive systems, in specific the functional monomers, certainly plays an important role for the adhesive long-term bonding performance. Chemical bonding in Single Bond Universal between 10-MDP and enamel/dentin may play an important role in providing a stable and durable interface. The chemical bonding provided by the 10-MDP molecule in the primer was combined with the excellent mechanical properties and high conversion rate of its filled hydrophobic resin., Because silorane primer contains the etching monomers and is cured prior to the application of silorane bonding component, it should be considered and compared with one-step systems. Ernst et al. proved that the microleakage of teeth restored with silorane adhesive was greater than others restored with methacrylate composites with the self-etch adhesives, Clearfil SE bond and S 3 bond. Santini and Miletic showed that thickness of the hybrid layer of the silorane adhesive system observed by micro-Raman spectroscopy was significantly thicker than one-step self-etch adhesives but was thinner than etch and rinse adhesives. Micro-Raman spectroscopy gives precise indication of dentin demineralization and monomer infiltration and highlights the intermediate zone of approximately 1 mm between silorane primer and bond.
The cavity configuration was considered one of the main determinants of shrinkage stresses in composite restoratives. The volume of composite is also strongly related to shrinkage stress and microleakage of restoration. The higher the composite volume, the greater is the amount of monomer to convert and the higher is the stress generated on the bonded interface. The result of our study about depth of composite restoration on microleakage showed no statistically significant differences between preparations with 1 and 1.5 mm depth, but the cavities with 1.5 mm depth showed more microleakage (mean rank of 78.23 vs. 66.77). Braga et al. compared composite Class V restorations in depth of 1 and 2 mm and concluded that shrinkage stress and microleakage were higher in restorations with larger diameter and depths. They concluded that it seems microleakage be related to a restoration's volume but not to its c-factor.
In the present study, microleakage in enamel in all tested composite resins was significantly lesser than dentin that was in agreement with Kermanshah et al. and Krifka et al., who concluded that dye penetration at enamel margins was significantly lower than dye penetration at dentin margins. There are structural and substructural differences in enamel and dentin. Enamel has more inorganic substrate (90% by volume) that requires the application of hydrophobic materials, but dentin is naturally a complex and wet substrate with more inorganic materials and water, as the result is wet and bonding to dentin is more compromised.,,
| Conclusions|| |
Within the limitation of this in vitro study, it can be concluded that microleakage could not be prevented entirely. All three composite resins with different adhesives showed similar microleakage values between the occlusal and gingival sites, and silorane-based composite resin was not superior to the methacrylate-based composites. No significant relationship was found between the depth of cavities and the degree of microleakage, but microleakage in dentin was significantly higher than in enamel margins.
The author gratefully acknowledges professor Mostafa Sadeghi from Rafsanjan University of Medical Science for his valuable guidance.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]