An Overview of Permanent Cements
What a general practitioner needs to know to select the appropriate dental cement.
In light of the new advances in dental materials technology, the decision-making in the selection of the suitable dental cement has become more difficult than ever before. The focus of this article is to provide the practitioner with a brief understanding of the properties and classifications of permanent cements.1 This will enhance the clinician’s overall ability to make the best selection of cement to enhance the success and longevity of an indirect restoration.
Dental Cements
Dental cements can be categorized by their main components into five main groups: zinc phosphate, zinc polycarboxylate, glass ionomer, resin-modified glass ionomers, and resin cements (Table).
Zinc Phosphate
Known as one of the very first permanent cements to emerge onto the dental market, zinc phosphate is the standard against which contemporary cements are assessed. The many uses of this cement include permanent cementation of crowns, orthodontic appliances, intraoral splints, inlays, post systems, and fixed partial dentures.2 Of the various manufacturers of zinc phosphate, the most commonly used brands include DeTrey Zinc Improved (DENTSPLY Caulk, www.caulk.com), Fleck’s Zinc (Mizzy, Pearson Lab, Pearson dental.com), Hy-Bond® (Shofu Dental Corporation, www.shofu.com), and Modern Tenacin (DENTSPLY Caulk).3 Zinc phosphate exhibits high compressive strength, moderate tensile strength, and clinically acceptable thin film thickness when applied properly according to the manufacturer’s instructions. The major disadvantages are its initial low pH, which has been reported to contribute to pulpal irritation, and its inability to bond chemically to tooth structure.4 Despite its disadvantages, this dental material has proven to have a significant amount of clinical success associated with its long-term use.1
Zinc Polycarboxylate
Invented in 1968, zinc polycarboxylate cement was the first cement to exhibit a chemical bond to tooth structure.1 Very little pulpal irritation is seen with its use due to the large size of the polyacrylic acid molecule.4 The many uses of this cement include permanent cementation of crowns, bridges, inlays, onlays, and orthodontic appliances.5 Polycarboxylate will bond to most alloys such as stainless steel, but not to gold.4 Of the various manufacturers of zinc polycarboxylate, some commonly used brands include Durelon™ (3M ESPE, www.3mespe.com), Shofu Polycarboxylate (Shofu), and Tylok® Plus/Poly-F-Plus (DENTSPLY Caulk).6 An encapsulated version of Durelon, Durelon™ Maxicap™ (3M ESPE), tackles the challenges of a short working time and an excessive film thickness displayed by this cement.6 Although zinc polycarboxylate has the advantage of producing a moderately high bond to enamel and dentin, its use has lessened over the years.4
Glass Ionomer
It was not until 1977 that glass-ionomer cements became available in the United States, after being introduced to the world in 1972 by Wilson and Kent.7 Its chemical make-up typically consists of a fluoroaluminosilicate glass powder and polyacrylic acid liquid. The many uses of this cement primarily include permanent cementation of crowns, bridges, inlays, onlays, posts, and orthodontic appliances. “Glass ionomer cements can chemically bond to stainless steel, base metals, and tin-plated noble metals, but not to pure noble metals or to glazed porcelain.”7 Of the various manufacturers of traditional glass-ionomer cements, some commonly used brands include non-encapsulated forms of Ketac™-Cem (3M ESPE), Glass Ionomer Type 1 (Shofu), the old and new versions of Fuji Ionomer Type 1 (GC America, www.gcamerica.com), the encapsulated products of Fuji I® (GC America), and Ketac™-Cem Aplicap™ (3M ESPE).7 In order to achieve clinical success with glass-ionomer cements, early protection from both moisture contamination and desiccation is necessary. The initial low pH that glass ionomers exhibit contributes to postoperative sensitivity. However, the advantages of chemically bonding to tooth structure, its bacteriostatic effect, fluoride release, and adequate compressive and tensile strength make this an acceptable cement.4 Glass-ionomer cements are still used today, but their use has seen a slight decline because they yield retention rates comparable to zinc phosphate.1
Resin-Modified Glass Ionomers
Around the early 1990s, advancements with glass-ionomer cements involved supplementing part of the polyacrylic acid in traditional glass-ionomer cements with hydrophilic methacrylate monomers, resulting in resin-modified glass-ionomer cements.1 The many uses of this cement primarily include permanent cementation of crowns, bridges, inlays, onlays, posts, and orthodontic appliances. Resin-modified glass-ionomer cements typically are indicated for use with the following dental materials: metallic and PFM restorations, zirconia and alumina-based ceramics, and lithium-disillicate pressed and milled (CAD/CAM) inlays and onlays.8 All-ceramic crowns such as IPS Empress® (Ivoclar Vivadent, www.ivoclarvivadent.com) or VITA In-Ceram® (Vident™, https://vident.com) should not be cemented with these cements because of potential clinical fractures.3 Of the various manufacturers of resin-modified glass-ionomer cements, some commonly used brands include FujiCEM™ and Fuji PLUS (GC America), RelyX™ Plus Luting Cement (3M ESPE), and Riva Luting Plus (SDI Limited, www.sdi.com). In addition to the chief advantages seen with traditional glass ionomers, resin-modified glass-ionomer cements have shown improvements in postoperative thermal sensitivity and are insoluble in the oral cavity.8 Yet, adequate retention is not exhibited on preparations with poor retention and resistance from using resin-modified glass-ionomer cements.1
Resin Cements
Resin cement contains dimethacrylates, such as bisphenol A-glycidyl methacrylate (Bis GMA), urethane dimethacrylate (UDMA), and tetraethyleneglycol dimethacrylate (TEGDMA), or, which can polymerize in variable ratios to achieve the desired viscosity. The dimethacrylate allows polymerization of the resin cement into a dense cross-linked polymer, which is similar in consistency to flowable composite.9
As a result of the polymerization process, resin cements are highly resistant to moisture and, therefore, become highly durable cements.11 The many advantages of resin cements are shade selection, translucency, greater retention by the bonding process, low film thickness, and adhesion that occurs between the tooth preparation and the ceramic in direct restorations.4 The adhesion process is facilitated by resin cement and can be polymerized by light, chemicals, or a dual process.10 According to the clinical circumstances, a clinician has a choice of using three different resin cements, which include: light-cured, dual-cured, and self-cured.11
Light-Cured Resin Cements—Light-cured cements are indicated when the ceramic restoration has a thin thickness, and is positioned in an easily accessible part of the mouth, allowing moisture control. These cements are well suited for bonding ceramic inlays and onlays and veneers. Examples of these cements include: Variolink® Veneer (Ivoclar Vivadent), RelyX™ Veneer Cement (3M ESPE), Calibra® (DENTSPLY Caulk) and CHOICE™ 2 Veneer Cement (BISCO Dental Products, www.bisco.com)15 Most of these manufacturers provide numerous shade selections for these cements, which makes them ideal for esthetic restorations.13
Dual-Cured Resin Cements—Dual-cured cements are most suitable for when the ceramic restoration is too thick or too opaque for light penetration, or the restoration is not easily accessible to light. Examples include NX3 Nexus® Third Generation (Kerr Dental Corporation, www.kerrdental.com), RelyX™ ARC Adhesive Resin Cement (3M ESPE), Multilink® Automix (Ivoclar Vivadent), DUO-LINK™ (BISCO), RelyX™ Unicem Self-Adhesive Universal Cement (3M ESPE), SpeedCEM® (Ivoclar Vivadent), and Maxcem Elite™ (Kerr).9 The dual-cured cements are extremely technique-sensitive and benefit from using the light polymerization.
Auto-Cured Resin Cements—Self-cured or auto-cured cements do not require the light for polymerization; they are cured by a chemical reaction. They are best suited for cementing metal or opaque ceramics like NobleProcera™ Alumina (Noble Biocare, www.noblebiocare.com), and VITA In-Ceram® Alumina (Vident). The advantages of these cements are ease of use and simplification, saving valuable chairtime for the practitioner. Unfortunately, clinical results and in vitro studies have shown these cements to have lower bond strength than light-cured or dual-cured cements.12,13 Examples of these cements include Panavia™ F2.0 (Kuraray Dental, www.kuraraydental.com) and C&B Metabond® (Parkell, Inc., www.parkell.com).9 The manufacturers of these cements only offer a few varieties of shade selection and translucency.
Adhesive Systems
Clinicians are also faced with decision-making regarding the adhesive system, which allows the cement to adhere to the tooth structure. The two main categories of resin cement’s mechanism of adhesion are as follows: total-etch bonding agent and self-etching bonding system.10
Total-Etch Bonding Agent
The total-etch bonding system involves using phosphoric acid on enamel and applying hydrofluoric acid (silane) treatment to the inside surface of the ceramic veneer or onlay before the restoration is bonded. This technique allows maximum adhesion to enamel; however, it may cause postoperative sensitivity. It is best suited for veneers and translucent inlays and onlays, allowing the operator to modify and enhance the shade.12,13
Self-Etching Bonding System
Most clinicians prefer this system for its simplified technique, which combines the etch and adhesive steps, followed by the application of cement.14 Postoperative sensitivity seems to be significantly reduced by sealing the dentinal canals and providing bond to dentin and enamel.13
Bond strength may be lower and adhesion to enamel may be the drawbacks of the self-etching bonding system.15 Tooth-colored inlays and onlays, and moderate-strength all-ceramic crowns are the most appropriate restorations for the self-etch bonding system.12
Conclusion
The prevalence and demand of all ceramic restorations has increased in the past decade to meet the esthetic demands of patients. As a result, resin cements have become more prevalent in cementation of tooth-colored restorations. Given that a universal cement is not yet available, it is the responsibility of the clinician to assess the tooth preparation and the characteristics of the indirect restoration in order to make the best selection of cement.
References
1. Burgess J, Ghuman T. A Practical Guide To The Use Of Luting Cements-A Peer Reviewed Publication. Available at: https://www.ineedce.com/courses/1526/PDF/APracticalGuide.pdf. Accessed August 6, 2012.
2. Fundamentals of Dental Materials. Characteristics of Zinc Phosphate Cement. Available at:www.free-ed.net/sweethaven/medtech/dental/dentmat/lessonMain.asp?iNum=fra0111".free-ed.net/sweethaven/medtech/dental/dentmat/lessonMain.asp?iNum=fra0111. Accessed August 6, 2012.
3. Dental Luting Cements. Available at: https://airforcemedicine.afms.mil/idc/groups/public/documents/afms/ctb_108338.pdf. Accessed August 6, 2012.
4. Shillingburg H. Cements. In: Fundamentals of Fixed Prosthodontics. 3rd ed. Carol Stream, IL: Quintessence Publishing Co; 1997:400-405.
5. Poly-F-Plus. 5. Available at: .dentsply.co.uk/Products/Restorative/Cements/PolyF-Plus.aspx. Accessed August 6, 2012.
6. Cements. Available at: https://airforcemedicine.afms.mil/idc/groups/public/documents/afms/ctb_109843.pdf. August 6, 2012.
7. Glass Ionomer Cements. Available at: https://airforcemedicine.afms.mil/idc/groups/public/documents/afms/ctb_108335.pdf. Accessed August 6, 2012.
8. Dental Cements: An Overview. Available at: www.dentistrytoday.com/dental-materials/6151-dental-cements-an-overview. Accessed August 6, 2012.
9. Simon JF, de Rijk WG. Dental cements. Inside Dentistry. 2006;2(2):42-47.
10. Vargas MA, Bergeron C, Diaz-Arnold A. Cementing all-ceramic restorations: Recommendations for success. J Am Dent Assoc. 2011;142(Suppl 2):20S-24S.
11. O’Brien JO. Dental Materials and their Selection. 3rd ed. Chicago: Quintessence Pub. Co; 2002.
12. Polack M. Contemporary dental cements: An inside look at a vital dental material. Dental Products. June 28, 2011.
13. Christensen GJ. Should resin cement be used for every cementation? J Am Dent Assoc. 2007;138(6):817-819.
14. ADA Professional Product Review. Dual Cure Resin-based Cements: Expert Panel Discussion. Vol. 1: Issue 2 Fall 2006 (Online). Available at: ww.ada.org/goto/pprw. Accessed August 17, 2012.
15. Radovic I, Monticelli F, Goracci C, et al. Self-adhesive resin cements: a literature review. J Adhes Dent. 2008;10(4):251-258.
About the Authors
Mojdeh Dehghan, DDS
Assistant Professor
University of Tennessee College of Dentistry
Memphis, Tennessee
Ashanti D. Braxton, DDS
Assistant Professor
University of Tennessee College of Dentistry
Memphis, Tennessee
James F. Simon, DDS, MEd
Professor and Director of Esthetic Dentistry
University of Tennessee College of Dentistry
Memphis, Tennessee
