|Year : 2013 | Volume
| Issue : 6 | Page : 499-502
|The effect of various primers on shear bond strength of zirconia ceramic and resin composite
Sasiwimol Sanohkan1, Boonlert Kukiattrakoon2, Narongrit Larpboonphol3, Taewalit Sae-Yib3, Thibet Jampa3, Satawat Manoppan3
1 Department of Prosthetic Dentistry; Maxillofacial Prosthodontics Rehabilitation Research Unit, Faculty of Dentistry, Prince of Songkla University, Hat Yai, Songkhla, Thailand
2 Department of Conservative Dentistry, Dental Materials Research Unit; Maxillofacial Prosthodontics Rehabilitation Research Unit, Faculty of Dentistry, Prince of Songkla University, Hat Yai, Songkhla, Thailand
3 Department of Prosthetic Dentistry, Faculty of Dentistry, Prince of Songkla University, Hat Yai, Songkhla, Thailand
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|Date of Submission||05-Jun-2013|
|Date of Decision||18-Aug-2013|
|Date of Acceptance||29-Aug-2013|
|Date of Web Publication||2-Nov-2013|
| Abstract|| |
Aims: To determine the in vitro shear bond strengths (SBS) of zirconia ceramic to resin composite after various primer treatments.
Materials and Methods: Forty zirconia ceramic (Zeno, Wieland Dental) specimens (10 mm in diameter and 2 mm thick) were prepared, sandblasted with 50 μm alumina, and divided into four groups (n = 10). Three experimental groups were surface treated with three primers; CP (RelyX Ceramic Primer, 3M ESPE), AP (Alloy Primer, Kuraray Medical), and MP (Monobond Plus, Ivoclar Vivadent AG). One group was not treated and served as the control. All specimens were bonded to a resin composite (Filtek Supreme XT, 3M ESPE) cylinder with an adhesive system (Adper Scotchbond Multi-Purpose Plus Adhesive, 3M ESPE) and then stored in 100% humidity at 37°C for 24 h before SBS testing in a universal testing machine. Mean SBS (MPa) were analyzed with one-way analysis of variance (ANOVA) and the Tukey's Honestly Significant Difference (HSD) test (α = 0.05).
Results: Group AP yielded the highest mean and standard deviation (SD) value of SBS (16.8 ± 2.5 MPa) and Group C presented the lowest mean and SD value (15.4 ± 1.6 MPa). The SBS did not differ significantly among the groups (P = 0.079).
Conclusions: Within the limitations of this study, the SBS values between zirconia ceramic to resin composite using various primers and untreated surface were not significantly different.
Keywords: Primer; resin composite; shear bond strength; zirconia ceramic
|How to cite this article:|
Sanohkan S, Kukiattrakoon B, Larpboonphol N, Sae-Yib T, Jampa T, Manoppan S. The effect of various primers on shear bond strength of zirconia ceramic and resin composite. J Conserv Dent 2013;16:499-502
|How to cite this URL:|
Sanohkan S, Kukiattrakoon B, Larpboonphol N, Sae-Yib T, Jampa T, Manoppan S. The effect of various primers on shear bond strength of zirconia ceramic and resin composite. J Conserv Dent [serial online] 2013 [cited 2020 Jan 25];16:499-502. Available from: http://www.jcd.org.in/text.asp?2013/16/6/499/120948
| Introduction|| |
Zirconia ceramic, a structured oxide ceramic, has been widely used for construction of fixed dental prostheses such as veneers, crowns, and fixed partial dentures. This is due to its superior properties compared to other types of restorative materials. Its light absorption and scattering are more similar to natural teeth than resin composite. , Its mechanical properties are comparable to stainless steel as its bending strength is 900-1,200 MPa and its compressive strength can range to 2,000 MPa.  Therefore, zirconia ceramic can be utilized in cases of long span fixed partial dentures on both anterior and posterior teeth. , It also has a high corrosion resistance  and chemical stability, as well as biological compatibility to oral tissue. ,
However, as zirconia ceramic has high corrosion resistance and surface stability, this makes it difficult to achieve a good bonding. Al-Amleh et al.,  reported a 54% incidence of veneering ceramic fracture on a zirconia substructure, especially in posterior teeth. There are several reasons which can explain this failure including mismatch of the coefficient of thermal expansion between the veneering ceramic and the zirconia substructure, porosity of the zirconia surface, improper support of the zirconia substructure, and residual stress from cooling.
After a veneering ceramic fracture, restoration replacement may be required, which results in issues related to clinical and laboratory time, as well as additional cost.  Consequently, patients may prefer to have fractured ceramics repaired. The principles of repairing zirconia restorations are similar to repairing fractured ceramics of metal-ceramic restorations. This restoration can be accomplished in two ways. The first way is to repair directly in the mouth using a resin composite. The second approach is to repair indirectly through overcasting, inlays, or onlay restorations. Between these two repairing techniques, repairing the fractured ceramic with resin composite is the most commonly used method for this task. It is inexpensive and easy to manipulate.  The properties of currently available resin composite materials have also been and are being continuously improved for this task.
Bonding resin composite to ceramic surfaces requires ceramic surface treatments. Etching with hydrofluoric acid in combination with silane, a well-accepted pretreatment for preparing ceramic surfaces for resin composite bonding, are often not successful in anchoring the zirconia surface,  due to high corrosion resistance and surface stability. One of the zirconia ceramic surface treatments for enhanced bonding (intraoral use) is coating with a primer. A primer is easy to apply and cost-effective, and does not require the use of a proprietary tool. ,
Various primers have been introduced to enhance the bonding strength of zirconia ceramic. Numerous studies support the use of a 10-methacryloxydecyl dihydrogen phosphate (MDP)-containing primer on the zirconia surface. The results have shown that phosphate monomers are assuring chemical agents for improving zirconia bonding. ,,, The plausible mechanism is the ability of phosphate monomers to form chemical bonds with the zirconia surface and have polymerizable resin terminal end groups (e.g., methacrylate), which enable cohesive bonding to appropriate resin cements. , In addition to a MDP-containing primer for zirconia bonding, a silane primer or silane plus phosphoric acid methacrylate and a sulfide methacrylate component have also been proposed to expand their use to zirconia surfaces.  Therefore, the objective of the present study was to evaluate the effect of various primers on the shear bond strength of zirconia ceramic and resin composite.
| Materials and Methods|| |
Forty zirconia ceramic specimens, 10 mm in diameter and 2 mm thick, were prepared from a presintered zirconia ceramic block (Zeno, Wieland Dental, Germany). The block was cut into pieces by a cutting machine (ISOMET 4000, Buehler, USA). Then the specimens were heated at 1,450°C for 12 h. After the specimen had cooled to room temperature (23°C), the specimens were mechanically polished (Phoenix 4000, Buehler, USA) under running water using 600- and 1200-grit silicon carbide paper (3M ESPE, USA).
Each specimen was embedded in a clear acrylic resin cylinder, 3 cm in diameter and 3 cm in height (Takilon, Rodent srl, Italy). Subsequently, all specimens were sandblasted with 50 μm alumina with a 25 mm distance between the specimen and the abrasion tip for 15 s.  Finally, the specimens were ultrasonically cleaned (PC3, L&R Mfg Co, USA) in distilled water for 10 min.
The specimens were then divided into four groups of 10: Group C was the control group (no primer treatment), Group CP was coated with a RelyX Ceramic Primer (3M ESPE), Group AP was painted with an Alloy Primer (Kuraray Medical Inc., Japan), and Group MP was covered with Monobond Plus (Ivoclar Vivadent AG, Liechtenstein).
Prior to bonding with resin composite, the zirconia ceramic specimens were treated with primers (according to the above defined three groups) for 1 min with a clean brush; two layers were applied and then air-dried. A bonding agent (Adper Scotchbond Multi-Purpose Plus Adhesive, 3M ESPE) was applied and light-polymerized with visible light (600 mW/cm 2 at a wavelength of 400-500 nm; Optilux 501, Kerr GmbH, Germany) for 20 s.
A thin plastic tube (AP Extrusion, USA) with 3 mm inner diameter and 2 mm thickness was positioned at the center of each porcelain specimen, and the tube was held in place with plastic pliers fixed onto a metal lab stand. Resin composite (Filtek Supreme XT, 3M ESPE) was filled into the tube and light-polymerized for 40 s, and again for 40 s after the plastic tube had been cut with a blade and removed. Subsequently, all ceramic specimens were stored in 100% humidity at 37°C for 24 h before testing.
The shear bond strength of zirconia ceramic specimens to resin composite was tested by using a single-bladed Instron Machine (model 5583, Instron Corp., USA) at a crosshead speed of 0.2 mm/min. The load at failure was recorded and converted to shear bond strength expressed in Mega Pascals (MPa) as shown in the following formula:
Shear bond strength = F/πr², where F is a load force at fracture in Newtons, and r is the radius of the resin composite cylinder in meters. The surfaces of the specimens were subsequently examined under a stereoscope (model SMZ 1500m, Nikon Instech, Kanagawa, Japan) at Χ40 magnification in order to determine the mode of failure. , Mode of failure was recorded by one observer as either adhesive (between zirconia ceramic or resin composite and the bonding agent), cohesive (in the ceramic, resin composite or bonding agent) or a combination of adhesive and cohesive fractures.
Data were statistically analyzed using Statistical Package for Statistical Science (SPSS) 15.0. A one-way analysis of variance (ANOVA) was used to find differences between groups. Tukey's Honestly Significant Difference (HSD) Test was used for post hoc comparisons (α = 0.05).
| Results|| |
Results of the one-way ANOVA as well as the results of multiple comparisons using Tukey's HSD tests revealed that the shear bond strength did not differ significantly among groups (P = 0.079). The mean values of the shear bond strength of the ceramic to resin composite at fracture are presented in [Table 1]. Group AP yielded the highest mean and standard deviation (SD) value of shear bond strength (16.8 ± 2.5 MPa), whereas Group C presented the lowest mean and SD (15.4 ± 1.6 MPa).
|Table 1: Mean shear bond strength (MPa) and standard deviation (SD) of zirconia ceramic to resin composite|
Click here to view
The mode of failure for all specimens, evaluated under a stereoscope, was found to be adhesive failure at the zirconia ceramic and bonding agent interface.
| Discussion|| |
Sandblasting the ceramic surface before applying a primer is an appropriate bonding preparation method for oxide ceramic and precious alloys. , This produced an activated microroughened zirconia surface, increased the bonding area, and modified the surface energy and wettability; hence improving the formation of resin-ceramic bond strength. ,,,
Three primers used in this study were selected according to the different type of functional monomers. RelyX Ceramic Primer has a silane functional monomer, whereas an Alloy Primer is composed of 6-(4-Vinylbenzyl-N-propyl) amino-1, 3, 5-triazine 2,4-dithione (VBATDT) and MDP. In addition, the Monobond Plus primer which is claimed to be a universal primer for all dental alloys and dental ceramics, has three components: An alcohol solution of silane methacrylate, phosphoric acid methacrylate, and sulfide methacrylate. The adhesion mechanisms of Alloy Primer and Monobond Plus are described below. For Alloy Primer, which is recommended for noble alloys surface treatment, sulfur atoms of VBATDT (a thione-thiol tautomer) bonds chemically to the noble metal atoms, while the double bonds on the other end of the molecule copolymerize with the resin monomers. The presence of MDP helps the reaction between VBATDT and noble metals, resulting in increased bond strength.  The results in this study presented the highest shear bond strength in Group AP, which might indicate that Alloy Primer can be repaired on zirconia surface treatments. For Monobond Plus, methacrylate monomers with a functional phosphoric acid group are used to establish a bond to zirconia (a formed methacrylate zirconium oxide compound) which has high affinity to phosphoric acid; a typical trait of zirconia ceramic. While for the RelyX Ceramic Primer, the role of silane in adhesion is that it increases the bond strength by performing two functions. , Firstly, silane provides a chemical link between dental ceramic and resin composite as already described above. Secondly, the organic portion of the silane molecule increases the wettability of the ceramic surface and thus, enhances the flow of the resin cement into the complicated archetype of the microundercuts of the ceramic surface, resulting in a more intimate micromechanical bond. This also effectively reduces the size and numbers of the surface flaws, and thus strengthens the ceramic. However, previous studies ,, showed that these roles are not amenable to adhesion in zirconia ceramic due to its inert properties. Even though these primers have mechanisms to bond to zirconia, results from this present study did not present that.
Therefore, as the results in the present study revealed no significant difference in bond strength values, these might imply that the role of primers used have no effect on shear bond strength. In the control group (Group C, no primer treatment), it was observed that the shear bond strength values received might from the sandblasted surfaces, to some degree.
Even though there was no significant difference in bond strength values, the highest shear bond strength was found in Group AP, which had VBTDT and MDP functional monomers. In agreement with recent studies, this study showed that phosphate monomers are chemical agents that provide a good bond strength to zirconia. ,,,
The failure modes of the experimental groups were investigated by a stereoscope. The results showed no damage to the ceramic surfaces in any group. It has been reported that if the bond strength between the ceramic and the adhesive resin is greater than 13 MPa, the ceramic will fracture.  In this study, all groups obtained values greater than 13 MPa, which resulted in adhesive failures. Ceramic fractures were not observed. This observation is important because if refracture occurred after repairing, it might not cause redamage to the ceramic surfaces, which would affect the esthetics and strength of the restoration.
In regard to clinical recommendation for repairing fractured zirconia ceramic restoration, data from the present study advocates treating the ceramic with sandblasting using 50 μm alumina and applying either type of primer with adhesive resin. Even though there was no significant difference in bond strength values, bond strength in primer groups were greater than the untreated group, which may be clinically helpful. All types of primers used should be clinically acceptable.
In the present study, a higher shear bond strength between the zirconia ceramic and the resin composite was found in all groups. However, there are several limitations to this in vitro study. The oral cavity presents a different testing environment. For example, the presence of water, temperature change, and pH level in the oral cavity may considerably affect bond strengths of ceramics to resin composite. In addition, the present study evaluated only one type of resin composite and adhesive bonding (Filtek Supreme XT with Scotchbond Multi-Purpose Plus Adhesive), and only three primers were used. Therefore, further studies are required to elaborate upon the others.
| Conclusion|| |
Within the limitations of this study, the shear bond strength values between zirconia ceramic and resin composite using various primers were not significantly different. The mode of failure for all specimens was found to be adhesive failure at the ceramic and bonding agent interface.
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Department of Conservative Dentistry, Dental Materials, and Maxillofacial Prosthodontics Rehabilitation Research Unit, Faculty of Dentistry, Prince of Songkla University, Hat Yai, Songkhla
Source of Support: Faculty of Dentistry Research Fund, Prince
of Songkla University, Conflict of Interest: None
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