|Year : 2018 | Volume
| Issue : 4 | Page : 369-372
|Comparison of bond strength of a composite resin with two different adhesive systems and a resin modified glass ionomer to calcium enriched mixture
Mehrshad Elmi1, Maryam Ehsani2, Behnaz Esmaeili2, Soraya Khafri3
1 Dental Student, Student Research Committee, Babol University of Medical Sciences, Babol, Iran
2 Dental Materials Research Center, Dental School, Babol University of Medical Sciences, Babol, Iran
3 Department of Social Medicine, School of Medicine, Babol University of Medical Sciences, Babol, Iran
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|Date of Submission||23-Mar-2018|
|Date of Decision||23-Apr-2018|
|Date of Acceptance||23-May-2018|
|Date of Web Publication||27-Jul-2018|
| Abstract|| |
Context: It is necessary to have a proper bond between pulp-capping agent and composite materials to maintain effective coronal seal.
Aims: This study aims to compare the shear bond strength of a composite resin with two different adhesive systems and a resin-modified glass ionomer (RMGI) to calcium-enriched mixture (CEM).
Methods: In this study, 30 acrylic blocks (with a central hole 4 mm diameter and 2 mm height) were prepared and filled with CEM. The blocks were divided into three groups: single bond2 (SB) with Filtek Z250, single bond universal (SBU) with Filtek Z250, and RMGI. The restorative materials were placed on the CEM, and shear bond strength was measured. Data were analyzed using one-way ANOVA and games Howell tests. P < 0.05 was considered statistically significant.
Result: Bond strength of both composite groups to CEM showed significantly higher values than RMGI-CEM group (both P < 0.001). The type of the adhesive system( total etch or universal) had no significant effect on the bond strength of composite to CEM (P > 0.05). All the failures in composite groups were as cohesive in CEM and in RMGI group was as adhesive.
Conclusions: Shear bond strength of composite resin to CEM cement was higher than RMGI irrespective of the type of the adhesive system. The universal bonding system is recommended for bonding of composite to CEM for ease of use.
Keywords: Calcium-enriched mixture; composite resins; glass ionomer; shear bond strength
|How to cite this article:|
Elmi M, Ehsani M, Esmaeili B, Khafri S. Comparison of bond strength of a composite resin with two different adhesive systems and a resin modified glass ionomer to calcium enriched mixture. J Conserv Dent 2018;21:369-72
|How to cite this URL:|
Elmi M, Ehsani M, Esmaeili B, Khafri S. Comparison of bond strength of a composite resin with two different adhesive systems and a resin modified glass ionomer to calcium enriched mixture. J Conserv Dent [serial online] 2018 [cited 2019 Jul 22];21:369-72. Available from: http://www.jcd.org.in/text.asp?2018/21/4/369/237728
| Introduction|| |
Vital pulp therapy is a conservative treatment to preserve the vitality and function of the pulp tissue in permanent teeth. For several years, mineral trioxide aggregate (MTA) has been used in many treatments such as furcation repair, internal root resorption, pulpotomy process, and direct/indirect pulp capping. In recent years, calcium-enriched mixture (CEM) was introduced to the market.,, CEM is a new endodontic material which powder is composed of calcium oxide, calcium sulfate, phosphate oxide and silicate as a main ingredient. CEM is an antimicrobial material which is able to make a good seal against leakage. It sets in a moisturized environment and leads to establish hydroxylapatite and hard tissue.
An exposed pulp can regenerate itself in a sterilized environment, but in the presence of bacteria, pulp inflammation and the subsequent necrosis would be inevitable. For this reason, it is important to have a proper bond between pulp-capping agent and restorative materials. Composites usually are the best candidate for restoration especially in the anterior teeth. Some studies showed that acid etching before composite filling and nature of solvent in the bonding system may have effect on the mechanical properties and bond strength of pulp capping agent to composite resin., On the other hand, the filling material over pulp-capping agents should have low-condensation forces such as composite resin or resin-modified glass ionomer (RMGI). The bonding of conventional glass ionomers to teeth is usually made through ionized structure whereas RMGI is bonded to tooth by ion exchanging and micromechanical interlocking.
Universal or multimode bonding is recently introduced as the latest generation of dentin bonding systems. The presence of acidic monomer in these materials allow for the self-etching properties. 10-methacryloyloxydecyl dihydrogen phosphate (MDP) is a phosphate monomer that causes adhesive to become acidic and lead to tooth demineralization and subsequently penetration of monomer. It also is able to have a chemical interchanging with mineral part of the tooth and long-lasting stabilized bonding.
In a previous study, the bond strength of the dental composite resin by applying two different types of total etch and a self-etch bonding system to MTA was the same as CEM. In a similar study by Oskoee et al. in 2014, no significant differences have been found between two types of bonding systems. There is little information on the adhesion of universal bonding systems to CEM cement. Therefore, the aim of the present study was the comparison of shear bond strength of a composite resin with the total etch and universal adhesive system and RMGI to CEM.
| Methods|| |
Composition of the materials used in this study is listed in [Table 1].
|Table 1: Chemical composition and application procedure of the materials|
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In this study, thirty acrylic blocks with dimension of 4 cm × 4 cm × 2 cm were prepared. CEM cement (Yektazist Dandan, Tehran, Iran) powder and liquid were mixed according to the manufacturer's instruction. Then, the blocks were filled with the prepared mixture. An appropriate condenser was used to condense the mixture. Then, CEM cement surface was flattened with a spatula and covered with a wet cotton pellet and a temporary filling material (cavit ESPE, Seefeld, Germany). The acrylic blocks were stored for 48 h at 37°C and 100% humidity.
After setting of CEM, the temporary filling material was removed, and the surfaces of the specimens were polished with 400-grit sandpaper. Then, the specimens were divided randomly into three equal groups (n = 10) Group one: composite resin Z250 (3M ESPE, St. Paul, MN, USA) with single bond 2 (SB) (3M, St. Paul, MN, USA), Group two: composite resin Z250 with SB universal (SBU) (3M, St. Paul, MN, USA), and Group three: RMGI (FUJI II LC, GC Corporation, Tokyo, Japan).
In group one, CEM cement surface was etched for 15 s with 35% phosphoric acid gel (Ultra Etch, Ultradent Products Inc, USA), rinsed for 10 s and dried with an air spray for 10 s. At the next step, two coats of SB 2 were applied and gently air-dried for 5 s and light-cured for 10 s at intensity of 1000 mW/cm 2 using VALO (Ultradent Products, South Jordan, UT, USA). After that, plastic cylinder molds with an internal diameter of 3 mm and a height of 2 mm placed on CEM and filled with composite resin. Composite was packed and light cured for 20 s.
In Group two, the surface of CEM was air dried and the SBU was applied onto the CEM for 20 s, gently air-dried, and cured for 10 s. Then, composite was placed into the plastic molds on prepared surface of CEM, packed, and light-cured for 20 s.
In RMGI group, the surface of CEM was dried. RMGI powder and liquid were mixed according to the manufacturer's instruction and then placed in the plastic molds and light cured for 20 s. After placement, the restorative materials on CEM, all of the samples were stored for 24 h in a temperature of 37°C and 100% humidity.
To evaluate the shear bond strength, samples were secured in the universal testing machine (Zwick/Roell 2020, Germany) and then sheared with a 0.5 mm knife-edge blade at 1 mm/min speed. The recorded force was divided by the adhesive surface area to calculate the bond strength. Failure modes were observed under a Stereomicroscope (Motic micro-optic, industrial group Co, LTD, Japan) at a magnification ×40 and classified as adhesive, cohesive or mixed. All data were analyzed by SPSS V.20 (IBM, Chicago, IL, USA). P< 0.05 demonstrated statistically significant.
| Results|| |
The highest bond strength value was recorded for Composite with SBU and the lowest bond strength was recorded for RMGI [Table 2].
|Table 2: Mean shear bond strength and standard deviation of the studied groups to calcium-enriched mixture cement|
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Analysis of data demonstrated statistically significant difference in the mean shear bond strength among the groups (P< 0.001). Shear bond strength between both composite groups and RMGI was statistically significant (Both P < 0.001); however, there was no significant difference between adhesive systems (P = 0.788). All the failures in composite groups were as cohesive in CEM and in RMGI group was as adhesive.
| Discussion|| |
According to less tooth discoloration of CEM compared to white MTA, CEM can be selective material for vital pulp therapy in the esthetic zone.
The results of the current study showed that the mean bond strength of composite to CEM was significantly higher than RMGI, and bonding system type had no effect on the bond strength of composite to the substrate (CEM). Failure mode in RMGI group was found as adhesive and in composite groups as cohesive in the CEM. These findings were in line with the results of Ajami and Jaberi-Ansari., They demonstrated that the different bonding systems (total-etch versus self-etch) did not have a significant effect on the bond strength of composite resin to pulp capping materials.
The bonding mechanism of composite to CEM is probably micromechanical and the result of penetration of the adhesive system into the rough surface of CEM. Kayahan used scanning electron microscope to examine the effect of phosphoric acid on MTA, and after the etching, as a result of removing matrix around the crystals; he observed a honeycomb shape which is desirable for resin bonding (7). Oskoee et al. also reported the selective loss of matrix in the periphery of crystal structures in etched CEM specimens. It seems that the phosphoric acid removes the smear layer and increases micromechanical interlocking by creating porosity on the surface of CEM.
Contrary to the results of this study, previous researches on the bond strength of composite resin to MTA with the use of etch-and-rinse bonding systems have shown higher bond strengths compared to self-etch bonding systems., This result may be related to the effect of the primer solvent which is important for the ultimate strength of the adhesives. The higher vapor pressure of acetone (in Prime and Bond NT) rather than water or ethanol (in AdheSe, Xeno III, Adper Prompt L-Pop) helps the monomer diffusion and higher bond strengths. On the other hand, the combination of acidic hydrophilic and hydrophobic monomers into a self-etch bonding may compromise the polymerization process of the adhesive, and consequently bond strength of the composite to CEM; but in our study, bond strength of SBU was higher than SB, although the difference was not statistically significant. It is possible the silane in the composition of SBU chemically bind to silica compounds in CEM. Besides, MDP as phosphate monomer both gently conditions CEM surface and create micromechanical retention or chemically bonds with the calcium ions present at CEM.
Failure mode in all of composite specimens was cohesive. This can be attributed to the sensitivity of CEM and other calcium silicate cements to acidic environment.
Wang et al. assumed that acidic environment can be detrimental to the hardness of tricalcium silicate cements. The stronger acid creates a more destructive surface than the weaker acid.,
The results of our study demonstrated that the lowest bond strength was in RMGI group and failure mode was as adhesive, which represents less bond strength between CEM and RMGI in compare with higher cohesive strength of CEM. This outcome was in consistent with the results of the study by Cantekin and Avci., CEM is composed of different calcium compounds such as calcium oxide, calcium carbonate, calcium phosphate, calcium silicate, and synthetic calcium aluminates. Bonding between RMGI and CEM must be mostly chemical (which is made by bonding to calcium compounds in CEM); with also a small amount of micromechanical bonding.
Adhesive failure probably is due to the inability of the adaptation to the substrate so that no interaction would be possible at the molecular level. In addition, contamination of the substrate surface and trapped air in the interface can prevent an acceptable contact. High-viscosity materials are prone to air retention because of their stiffness, thus they bridge the pores and cracks in the substrate surface instead of flowing into them.
Considering the fact that failure mode in all of the composite samples was cohesive in the CEM, it can be concluded that the bond strength of composite and CEM is higher than cohesive strength of CEM. Therefore, in fact, the recorded bond strength shows cohesive strength of CEM instead of actual bond strength of composite-CEM. It has been reported that when cohesive failure occurs within any of the materials rather than between the two materials, the bond will be acceptable. Kayahan reported phosphoric acid degrades the cement surface and reduces the cohesive strength of MTA. It is possible both of bonding systems, acid etching in SB or phosphate monomer in SBU, are destructive for CEM surface and they reduce cohesive strength of CEM. Time interval between placement of CEM and the final restoration is important. Vanderweele expressed as the time between material placement and final restoration increased, cohesive failure is reduced and the failure mode is more likely to be adhesive. Adl et al. reported the setting of CEM was not complete after 3 days. It can be justified that the strength of the material bulk increases over the time. For this reason, cohesive strength of CEM in different articles was not the same.
Based on the results of the present research, because of higher bond strength of composite to CEM, the use of composites on the CEM is preferred to RMGI. In addition, due to noneffectiveness of bonding system types in bond strength of composite to the CEM, the universal bonding system is recommended for bonding of composite to CEM for its simple usage.
Since in several papers, the values of cohesive strength of CEM have been reported variously, further investigations in the cohesive strength of CEM and effective factors on it are suggested.
| Conclusions|| |
Within the limitation of in vitro study, the bond strength of composite resin with single bond 2 and single bond universal to CEM was higher than that of RMGI to CEM. Therefore, to achieve a proper bond, use of composite resin on the CEM is suggested. Also the type of the adhesive system had no effect on the bond strength between composite and CEM.
Financial support and sponsorship
This study was financially supported by Babol University of medical sciences.
Conflicts of interest
There are no conflicts of interest.
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Dr. Behnaz Esmaeili
Dental Materials Research Center, Dental School, Babol University of medical sciences, Babol
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2]
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