|Year : 2015 | Volume
| Issue : 1 | Page : 43-47
Bonding of resin cements to zirconia
Priscila C Chagas, Luiz Gustavo C Bastos
Department of Dentistry, Escola Bahiana de Medicina E Saúde Pública, Salvador, Bahia, Brazil
|Date of Web Publication||2-Apr-2015|
Luiz Gustavo C Bastos
Rua Silveira Martins, 3386, Cabula. Cep: 41.150-100, Salvador, Bahia
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The mechanism of bonding between resin cements and zirconia is still not well defined in the literature. Due to zirconia composition, there is a greater difficulty on these cements in establishing a chemical interaction, conferring a clinical dilemma in modern dentistry. Chemical adhesion, established by resin cements, is the most responsible for the bonding to zirconia when compared to mechanical treatments; which makes necessary the selection of the type of cement. Perform a literature review concerning the adhesion of resin cements to zirconia, emphasizing its advantages, composition, properties, and surface treatments. Elements that help on the adhesion and micromechanics retaining systems are essential to confer a long lasting and resistant bonding. Resin cements chemically activated may be more indicated for zirconia cementation than duo cements. Yet, self-adhesive resin cements promotes adequate adhesive resistance to zirconia. Concerning surface mechanical treatments, the aluminum oxide blaster indicates great efficiency on ceramics decontamination. However, to guarantee a greater bonding resistance, some coatings may be used previously to silanization, like the application of silica.
Keywords: Resin cements, traction resistance, zirconia
|How to cite this article:|
Chagas PC, Bastos LC. Bonding of resin cements to zirconia. J Dent Implant 2015;5:43-7
| Introduction|| |
Due to many advantages of zirconia, such as better aesthetics, elimination of metallic brace, excellent biocompatibility, and good optical and mechanical properties, besides deflection resistance, this material became a frequent option to substitute metals on infrastructures making. 
Zirconia is composed basically by zirconium dioxide, free of silica inherent of conventional ceramics, which is responsible for surface roughness acquired during acid conditioning; contributing to improve the adhesion to cement agents. The absence of silica also makes it difficult silanization, due to the affinity to silane in establishing molecular bonding with silica. 
To empower the strength of bonding between zirconia and cement agents, it must be observed surface treatment (chemical or mechanical) and the properties inherent to cement.  A possibility of favoring this union is the use of blaster; which is a mechanical treatment with aluminum oxide or silica, which promotes surface roughness besides surface decontamination, facilitating the most intimate contact with the cement agent. 
In ceramic rehabilitations, free of metals, one of the most used cements is the resin cement and this type of cement acquired such an importance due to its high resistance, similar color to teeth, and mainly because of its insolubility in oral cavity and its ability of bonding to many substracts. 
Due to its composition, cohesive resistance, fluidity, and wetting capacity, resin cements have shown greater potentiality on bonding to zirconia than the others. Dual resin cements are containing "methacrylates of multifunctional acidity" contribute to a greater adhesion reacting to the ceramic surface. 
Therefore, the present study aims at performing a literature review about resin cements comprehending:
- Activation method (chemical, photoactivated, or dual)
- Adhesion mechanisms (total conditioning, self-conditioning, or self-adhesive)
- Surface treatments:
- Mechanical: Aluminum oxide blaster or silica
- Chemical: Silane or primer.
| Literature review|| |
Composition of resin cements
Resin cements are basically fluid composite resins with low viscosity. Its composition consists of a monomeric system Bisfenol-A glycidyl methacrylate (Bis-Gma) or Urethane dimethacrylate (UEDMA) added of particles of inorganic load (aluminum, lithium, and particles of glass, silica or colloidal silica) treated with a bonding agent, silane. It is also incorporated ceramic particles and colloidal silica, commonly used on microparticulate resins. It may also be constituted by a monomer of low viscosity triethylene glycol dimethacrylate (TEGDMA), ethyleneglycol dimethacrylate (EGDMA).  The amount of these polymers determines the fluidity of the material  and its polymerization may be performed by the chemical process, photoactivation or by these two combined together, being characterized as dual.  Its indications comprehend cementation of partial or total fixed prosthesis, bonding of orthodontic braces, and adhesive prosthesis. 
Its resin matrix may also be constituted by an adhesive monomer, which comprehends the 4-methacryloxyethyl trimellitic anhydride (4-META), o hydroxyethyl methacrylate or an organophosphate, which is usually phosphoric acid 10-methacriloiloxidecamethylene (MDP). The system composed with 4-META, is a liquid adhesive, which through the inclusion of polymers pearls, obtains the consistency of cements. Therefore, the is no need for applying other adhesive systems. 
Indication of resin cements
The success of adhesive prosthesis is directly related to chemical bonding or micromechanics established between the cement and the inner surface of the prosthesis. Resin cements have the great advantage of insolubility in the oral cavity  contributing to reduce marginal infiltration and to increase fracture resistance. 
Classification of resin cements
When used in restorations with ceramic infrastructures, such as zirconia, chemical activation method has to be selected because its opacity makes it difficult the adequate light transmission through this material, impeding the total activation of photosensitive agents, leading to a deficient polymerization.  An inadequate polymerization may cause various intercurrences such as availability to degradation, microfiltration, recurrence of cavities, postoperative sensitivity, reduction of abrasion resistance and of mechanical properties. 
However, due to the complexity that involves work timing and polymerization, chemically activated cements are being gradually substituted by duo cements, which guarantee the polymerization even on places where the access to halogen or light-emitting diode light is difficult. Besides having advantages such as a thin coat on cementation, good drainage and low viscosity, easy to manipulate, greater compressive and flexional resistance, lower chances of failures, and better clinical performance. 
Mechanisms of adhesion
Total conditioning cements
Consists on acid conditioning of surfaces and then the application of adhesive and cement. Promotes a greater bonding resistance, however, it requires a greater working time. It may be photoactivated or dual.  Exemples: Variolink II (Ivoclar-Vivadent, Schaan, Liechtenstein), RelyX ARC (3M ESPE, Seefeld, FB, Germany).
Consists on using a self-conditioning primer to conditioning surfaces and posterior application of the prepared cement. Its bonding strength is similar to the total conditioning cement.  Exemples: Multilink (Ivoclar-Vivadent, Schaan, Liechtenstein) and Panavia (Kuraray America, New York, NY, USA).
Usually, they have dual photopolymerization and do not need the use of acid conditioning and adhesives. Its bonding resistance varies according to commercial brands and are normally superior to total conditioning cements.  Exemples: SpeedCEM (Ivoclar-Vivadent, Schaan, Liechtenstein); RelyX U200 (3M ESPE, Seefeld, FB, Germany).
Due to the clinical success of zirconia infrastructures, there was a great evolution in developing resin cements even self-adhesives.  The reaction that occurs between self-adhesive cements and zirconia is the same that occurs on the dental surface, which implicates on higher values of bonding resistance when compared to the ones found on other cements. However, literature still needs more clarifications of how this bonding occurs. 
Surface treatments and bonding resistance
Surface treatments are a resource in an attempt to help the mechanism of adhesion and bonding between resin cements and zirconia, and there are 2 types: Mechanical treatment that provides a better adhesion between cement and prosthesis surface, and a blaster with aluminum oxide with different sizes of particles, which promotes micro-retentions that increases the contact area with the cement agente.  However, according to the type of particle, the intensity and the utilization time, the blaster may establish micro-fissures on zirconia surface, which reflects directly on material resistance, being impossible any repair by compensatory methods.  An alternative would be the use of smaller particles with lower air pressure, allowing decontamination and surface roughness needed. Particles of aluminum oxide covered by silica ("silica coating" technique) or pure silica,  are also used, but no significant difference was shown between them.  Silicatization consists in a method of silica deposition on prosthesis surfaces, which favors the interaction of these particles with silane, promoting a greater adhesion to resin cements. 
On the other hand, chemical treatment was elaborated aiming to improve the chemical bonding of resin cements to zirconia. The cement Metal/Zirconia Primer® , commercial brand Multilink® , has an exclusive primer to use on zirconia; such base is constituted by acid methacrylate. Another bonding agent is silane, recommended for ceramic cementation constituted by silica or surfaces previously treated by silica coating system.  However, zirconia does not have silica in its composition, which constitute vitreous phase, making difficult the bonding.  Silane promotes a better wetting, amplifying the contact surface between cement and zirconia, resulting in better adhesion, which is a property also inherent to adhesives. 
Besides many surface treatments that have been used, other mechanisms are being tested such as the use of cements constituted by MDP, organosilanes, and others. Among them, silicatization is still the most important because it provides a better durability besides a high adhesive resistance, even though this technique guarantees only 11% of silica deposition on the ceramic surface.  However, this durability has been commonly more conferred by cement than surface roughness, due to a greater chemical adhesion. 
The efficiency of the cleaning method on saliva's decontamination on zirconia adhesion was analyzed by Yang et al.,  in a study. They concluded that blaster with aluminum oxide was the most efficient method on removal of contaminant agents and saliva to provide an adequate ceramic surface and stability in a long lasting bonding.
Valandro et al., evaluated the effect of different surface treatments on resin bonding resistance with zirconia-alumina: Micro-traction test x shear. They concluded that there was not statistic difference between the 2 tests. Concerning surface treatments, the resistance showed results superior o silica and silene when compared to aluminum oxide and silane, no matter the type of test.
Piascik et al., analyzed zirconia surfaces modified by silanization. They concluded that surface treatment using chloride-silane increased bonding sites of zirconia surface, being able to improve resin adhesion to zirconia using traditional silanization.
In another study, Kitayama et al., analyzed the effect of an inner coating technique with micro-pearls of porcelain fused on bonding resistance of resin cements to zirconia. They concluded that the inner coating technique followed by silanization may successfully increase bonding resistance of resin cements to zirconia.
Aboushelib et al., analyzed bonding to zirconia using a new surface treatment selective infiltration etching (SIE): Coating with a glassy conditioning, basically composed of silica. They concluded that bonding resistance between zirconia and resin may be significantly improved using SIE technique.
Dias de Souza et al., analyzed the effect of metal primers on bonding resistance between zirconia and resin cements. They concluded that the use of primer increased significantly bonding resistance between zirconia and RU. The values of initial bonding resistance were greater for PA, as well as the reduction of this force after aging. Both cements obtained similar statistics after this phenomenon.
Attia et al., investigated the durability of bonding force between adhesive cementation and zirconia, after applying a new and universal primer. Then, they concluded that after 150 days of storing, the universal primer demonstrated a greater force of shear for SC-A than conventional silane, besides showing a long lasting resistant bonding, no matter the blaster and cleaning methods. The cleaning methods provided a small effect on cementation durability after 150 days of storing.
In a study, Aboushelib  assessed bonding resistance and its durability between zirconia and resin using a new conditioning technique and SIE. He concluded that micro-mechanical retention mechanisms and factors that promote adhesion are determinants to constitute a resistant and long lasting bonding when using zirconia-based materials.
| Discussion|| |
Due to its many advantages, resin cements determined its vast application in metal-free restorations.  Chemical adhesion, which is present on prosthesis interface allows better mechanics, greater durability on adhesive procedure, reduces imperfections on the inner part of the prosthesis, limiting the probability of failures.  However, it remains the difficulty in establishing the interaction between these cements and zirconia, due to its deficient vitreous phase (silica). 
To Ben-Amar et al., and Blatz et al., the system composed of 4-META, presents itself as a liquid adhesive, which through inclusion of polymers pearls, obtains the consistency of cements. Therefore, there is no need in applying other adhesive systems. As for Diaz-Arnold et al.,  resin matrix is constituted by Bis-Gma or UEDMA, and the particles of inorganic load may be aluminum, lithium, and silicone oxide; other components also may be incorporated, such as ceramic particles and low viscosity monomers, such as TEGDMA, EGDMA.
Biocompatibility occurs due to the capacity of cements in converting monomers into polymers. Any postoperatory sensitivity may be justified by its incorrect polymerization, due to zirconia opacity, which impedes the transmission of halogen light.  This way, chemically activated or dual cements are the most indicated for prosthesis' cementation. 
Concerning micro-infiltration, resin cements promote a significantly reduction, which contributes to rehabilitations longevity,  avoiding recurrent cavities, color alterations, sensitivity, resistance and mechanic properties endangerment. 
Resin cements features elevated flexural strength and traction resistance, fracture resistance, compression and union; elastic modulus, and hardness. ,
Due to its low solubility, erosions on the adhesive interface are hardly obtained, which promotes a limitation of marginal infiltration and eventual improvement on fracture resistance; are susceptible to water sorption, especially the ones based on UEDMA: The lower inorganic load, greater it will be the sorption, endangering mechanical properties. Although this phenomenon may compensate polymerization contraction. ,
According to Söderholm and Reetz  and Rosenstiel et al. concerning adhesiveness, resin cements have demonstrated a retention increase, due to the sticking in the preparation Its adhesion to porcelain has better results when using primers for metals or silane.
According to Braga et al., and Rosenstiel et al.,  polymerization contraction that occurs in resin cements may cause failures in the interface, lead to difficulty on material settlement bringing on sensitivity, micro-infiltration, and bacterial colonization. Chemically activated cements promote lower stress comparing to the ones photoactivated.
Aboushelib et al.,, concluded that, evaluating bonding resistance and its durability between zirconia and resin utilizing a new conditioning technique and SIE, retention micro-mechanical mechanisms and factors that promote adhesion favor a resistant and long lasting union.
To Valandro et al., resistance to traction showed superior results to silica and silane when compared to aluminum oxide and silane. However, the influence of saliva's contamination on zirconia adhesion analyzed by Yang et al.,  concluded that aluminum oxide blaster was more efficient on decontamination to promote an adequate surface to a long lasting union.
The effect of the use of metal primers increased union resistance between zirconia and resin cements, providing durability of bonding strength and demonstrating better performance than a conventional silane. ,
| Final considerations|| |
The mechanism of adhesion between resin cements and zirconia is still not well explained in the literature. However, it is known that the capacity of zirconia in constitute chemical interaction with cements is reduced. Resin cements with dual activation are the most indicated for zirconia cementation than the other cements that are chemically activated or photoactivated. As for self-adhesive cements, they promote adequate adhesive resistance to zirconia.
To promote a resistant and long lasting union between resin cements and zirconia, some aspects such as elements that promote adhesion and mechanisms of micro-mechanic retention are considered determinants. Among mechanical surface treatments, blaster with aluminum oxide indicates great efficiency on ceramic decontamination. However, to assure a greater union resistance, some coatings may be utilized previously to silanization. Better results are obtained when applied aizatio silica instead of aluminum oxide. The use of chloride-silane, INT coating technique, and SIE technique may also promote a superior adhesion.
| References|| |
Blatz MB. Cementation of zirconium-oxide ceramic restorations. Pract Proced Aesthet Dent 2004;16:14.
Amaral R, Ozcan M, Bottino MA, Valandro LF. Microtensile bond strength of a resin cement to glass infiltrated zirconia-reinforced ceramic: The effect of surface conditioning. Dent Mater 2006;22:283-90.
Ozcan M, Vallittu PK. Effect of surface conditioning methods on the bond strength of luting cement to ceramics. Dent Mater 2003;19:725-31.
Ozcan M, Cura C, Valandro LF. Early bond strength of two resin cements to Y-TZP ceramic using MPS or MPS/4-META silanes. Odontology 2011;99:62-7.
Valentino TA, Borges GA, Borges LH, Vishal J, Martins LR, Correr-Sobrinho L. Dual resin cement knoop hardness after different activation modes through dental ceramics. Braz Dent J 2010;21:104-10.
Passos SP, May LG, Barca DC, Ozcan M, Bottino MA, Valandro LF. Adhesive quality of self-adhesive and conventional adhesive resin cement to Y-TZP ceramic before and after aging conditions. Oper Dent 2010;35:689-96.
Diaz-Arnold AM, Vargas MA, Haselton DR. Current status of luting agents for fixed prosthodontics. J Prosthet Dent 1999;81:135-41.
Ben-Amar A, Liberman R, Apatowsky U, Pilo R. pH changes of glass-ionomer lining materials at various time intervals. J Oral Rehabil 1999;26:847-52.
Blatz MB, Sadan A, Kern M. Resin-ceramic bonding: A review of the literature. J Prosthet Dent 2003;89:268-74.
Scherrer SS, de Rijk WG, Belser UC, Meyer JM. Effect of cement film thickness on the fracture resistance of a machinable glass-ceramic. Dent Mater 1994;10:172-7.
Söderholm KJ, Reetz EA. Factors affecting reliability of a resin-based cement joint. Gen Dent 1996;44:296-8, 300, 302.
Sadan A, Blatz MB, Lang B. Clinical considerations for densely sintered alumina and zirconia restorations: Part 1. Int J Periodontics Restorative Dent 2005;25:213-9.
Braga RR, Cesar PF, Gonzaga CC. Mechanical properties of resin cements with different activation modes. J Oral Rehabil 2002;29:257-62.
Rosenstiel SF, Land MF, Crispin BJ. Dental luting agents: A review of the current literature. J Prosthet Dent 1998;80:280-301.
Pavan S, dos Santos PH, Berger S, Bedran-Russo AK. The effect of dentin pretreatment on the microtensile bond strength of self-adhesive resin cements. J Prosthet Dent 2010;104:258-64.
Guarda GB, Gonçalves LS, Correr AB, Moraes RR, Sinhoreti MA, Correr-Sobrinho L. Luting glass ceramic restorations using a self-adhesive resin cement under different dentin conditions. J Appl Oral Sci 2010;18:244-8.
Radovic I, Monticelli F, Goracci C, Vulicevic ZR, Ferrari M. Self-adhesive resin cements: A literature review. J Adhes Dent 2008;10:251-8.
de Oyagüe RC, Monticelli F, Toledano M, Osorio E, Ferrari M, Osorio R. Influence of surface treatments and resin cement selection on bonding to densely-sintered zirconium-oxide ceramic. Dent Mater 2009;25:172-9.
Zhang Y, Lawn BR, Malament KA, Van Thompson P, Rekow ED. Damage accumulation and fatigue life of particle-abraded ceramics. Int J Prosthodont 2006;19:442-8.
Fischer J, Grohmann P, Stawarczyk B. Effect of zirconia surface treatments on the shear strength of zirconia/veneering ceramic composites. Dent Mater J 2008;27:448-54.
Piascik JR, Swift EJ, Thompson JY, Grego S, Stoner BR. Surface modification for enhanced silanation of zirconia ceramics. Dent Mater 2009;25:1116-21.
Oliveira AS, Ramalho ES, Ogliari FA, Moraes RR. Bonding self-adhesive resin cements to glass fibre posts: To silanate or not silanate? Int Endod J 2011;44:759-63.
Matinlinna JP, Heikkinen T, Ozcan M, Lassila LV, Vallittu PK. Evaluation of resin adhesion to zirconia ceramic using some organosilanes. Dent Mater 2006;22:824-31.
Yang B, Lange-Jansen HC, Scharnberg M, Wolfart S, Ludwig K, Adelung R, et al.
Influence of saliva contamination on zirconia ceramic bonding. Dent Mater 2008;24:508-13.
Valandro LF, Ozcan M, Amaral R, Vanderlei A, Bottino MA. Effect of testing methods on the bond strength of resin to zirconia-alumina ceramic: Microtensile versus shear test. Dent Mater J 2008;27:849-55.
Kitayama S, Nikaido T, Maruoka R, Zhu L, Ikeda M, Watanabe A, et al.
Effect of an internal coating technique on tensile bond strengths of resin cements to zirconia ceramics. Dent Mater J 2009;28:446-53.
Aboushelib MN, Feilzer AJ, Kleverlaan CJ. Bonding to zirconia using a new surface treatment. J Prosthodont 2010;19:340-6.
Dias de Souza GM, Thompson VP, Braga RR. Effect of metal primers on microtensile bond strength between zirconia and resin cements. J Prosthet Dent 2011;105:296-303.
Attia A, Kern M. Long-term resin bonding to zirconia ceramic with a new universal primer. J Prosthet Dent 2011;106:
Aboushelib MN. Evaluation of zirconia/resin bond strength and interface quality using a new technique. J Adhes Dent 2011;13:255-60.