Materials used to bond teeth or materials to teeth
Dental cements have a wide range of dental and orthodontic applications. Common uses include temporary restoration of teeth, cavity linings to provide pulpal protection, sedation or insulation and cementing fixed prosthodontic appliances.[1] Recent uses of dental cement also include two-photoncalcium imaging of neuronal activity in brains of animal models in basic experimental neuroscience.[2]
Traditionally cements have separate powder and liquid components which are manually mixed. Thus working time, amount and consistency can be individually adapted to the task at hand. Some cements, such as glass ionomer cement (GIC), can come in capsules and are mechanically mixed using rotating or oscillating mixing machines.[3] Resin cements are not cements in a narrow sense, but rather polymer based composite materials. ISO 4049: 2019[4] classifies these polymer-based luting materials according to curing mode as class 1 (self-cured), class 2 (light-cured), or class 3 (dual-cured). Most of the commercially available products are class 3 materials, combining chemical- and light-activation mechanisms.
Ideal cement properties
High biocompatibility – zinc phosphate cement is considered the most biocompatible material with a low allergy potential despite the occasional initial acid pain (as a consequence of inadequate powder/liquid ratio)
Non-irritant – polycarboxylate cement is considered the most sensitive type due to the properties of polyacrylic acid (PAA).
Antibacterial properties to prevent secondary caries
Provide a good marginal (bacteria-tight) seal to prevent marginal leakage
Resistant to dissolution in saliva, or other oral fluid – a primary cause of decementation is dissolution of the cement at the margins of a restoration
High strength in tension, shear and compression to resist stress at the restoration–tooth interface.
Low film thickness (maximum 25 microns acc. to ISO 9917-1).
Low allergy potential
Low shrinkage
Retention – if an adhesive bond occurs between the cement and the restorative material, retention is greatly enhanced. Otherwise, the retention depends on the geometry of the tooth preparation.[5][page needed]
Comparison of cements
Cement type
Brands (Manufacturer)
Indications
Contra-indications
Advantages
Disadvantages
Zinc phosphate
DeTrey Zinc (Dentsply)
Hoffmann's (Hoffmann Dental Manufaktur)
Hy-Bond Zinc (Shofu Dental)
Modern Tenacin (L.D. Caulk)
Zinc Cement Improved (Mission White Dental)
Lining for all filling materials (amalgam, composites)
Cementation of inlays, onlays, crowns and bridges made of precious metal, non-precious metal as well as metal ceramic and all-ceramic (zirconium oxide, aluminium oxide and lithium disilicate ceramic)
Cementation of implant-supported crowns and bridges
Dental cements based on organometallic chelate compounds
Types
Composition
Setting reaction
Advantages
Disadvantages
Applications
Zinc oxide/eugenol cements
Supplied as two pastes or as a powder (zinc oxide) and liquid (zinc acetate, eugenol, olive oil)
A slow chelation reaction of two eugenol molecules and one zinc ion to form zinc eugenolate without moisture. However, setting can be completed fast when water is present.
Bactericidal effect due to free eugenol
Pulpal damage due to production of exotoxins
High solubility in water
Interferes with polymerisation process and leads to discoloration
Mainly used for lining under amalgam restorations
Ortho-ethoxybenzoic acid (EBA) cements
Supplied as a powder (mainly zinc oxide and reinforcing agents: quartz and hydrogenated rosin and liquid o-ethoxybenzoic acid and eugenol)
Similar to zinc oxide/eugenol materials
Higher powder/liquid ratio can be achieved, so the set material can be strong
Lower solubility than zinc oxide/eugenol products
Less retention than zinc phosphate cements
Luting cements primarily
Calcium hydroxide cements
Calcium hydroxide in water (water can be substitute by a solution of methyl cellulose in water or a synthetic polymer in volatile organic solvent)
Calcium hydroxide is usually supplied as two pastes
Chelate compounds are formed and chelation is largely due to zinc ions
Antibacterial properties
Induces formation of secondary dentine layer
Setting may be slow due to low viscosity
Exothermic setting reaction
Relatively low compressive strength
Used as lining material under silicate and resin-based filling materials
Dental cements can be utilised in a variety of ways depending on the composition and mixture of the material. The following categories outline the main uses of cements in dental procedures.
Temporary restorations
Unlike composite and amalgam restorations, cements are usually used as a temporary restorative material. This is generally due to their reduced mechanical properties which may not withstand long-term occlusal load.[3]
Amalgam does not bond to tooth tissue and therefore requires mechanical retention in the form of undercuts, slots and grooves. However, if insufficient tooth tissue remains after cavity preparation to provide such retentive features, a cement can be utilised to help retain the amalgam in the cavity.
Historically, zinc phosphate and polycarboxylate cements were used for this technique; however, since the mid-1980s composite resins have been the material of choice due to their adhesive properties. Common resin cements utilised for bonded amalgams are RMGIC and dual-cure resin based composite.[3]
Liners and pulp protection
When a cavity reaches close proximity to the pulp chamber, it is advisable to protect the pulp from further insult by placing a base or liner as a means of insulation from the definitive restoration. Cements indicated for liners and bases include:
Zinc oxide eugenol
Zinc polycaroxylate
Resin-modified glass ionomer cement (RMGIC)
Pulp capping is a method to protect the pulp chamber if the clinician suspects it may have been exposed by caries or cavity preparation. Indirect pulp caps are indicated for suspected micro-exposures whereas direct pulp caps are place on a visibly exposed pulp. In order to encourage pulpal recovery, it is important to use a sedative, non-cytotoxic material such as setting calcium hydroxide cement.
Luting cements
Luting materials are used to cement fixed prosthodontics such as crowns and bridges. Luting cements are often of similar composition to restorative cements; however, they usually have less filler, meaning the cement is less viscous.
Resin-modified glass ionomer cement (RMGIC)
Glass ionomer cement (GIC)
Zinc polycarboxylate cement
Zinc oxide eugenol luting cement
Summary of clinical applications
Clinical application
Type of cement used
Crowns
Metal
Zinc phosphate, GI, RMGI, self or dual cured resin *
Metal ceramic
Zinc phosphate, GI, RMGI, self or dual cured resin *
All ceramic
Resin cement
Temporary crown
Zinc oxide eugenol cement
3/4 crown
Zinc phosphate, GI, RMGI, self or dual cured resin *
Bridges
Conventional
Zinc phosphate, GI, RMGI, self or dual cured resin *
Resin bonded
Resin cement
Temporary bridge
Zinc oxide eugenol cement
Veneers
Resin cement
Inlay
Zinc phosphate, GI, RMGI, self or dual cured resin *
Onlay
Zinc phosphate, GI, RMGI, self or dual cured resin *
Post and core
Metal post
Any cement which is non-adhesive (NOT resin cements)
Fibre post
Resin cement
Orthodontic brackets
Resin cement
Orthodontic molar bands
GI, zinc polycarboxylate, composite
Composition and classification
ISO classification
Cements are classified on the basis of their components. Generally, they can be classified into categories:
Water-based acid-base cements: zinc phosphate (Zn3(PO4)2), zinc polyacrylate (polycarboxylate), glass ionomer (GIC). These contain metal oxide or silicate fillers embedded in a salt matrix.
Non-aqueous/oil base acid-base cements: zinc oxide eugenol and non-eugenol zinc oxide. These contain metal oxide fillers embedded in a metal salt matrix.
Resin-based: acrylate or methacrylate resin cements, including the latest generation of self-adhesive resin cements that contain silicate or other types of fillers in an organic resin matrix.
Cements can be classified based on the type of their matrix:
These cements are resin-based composites. They are commonly used to definitively cement indirect restorations, especially resin bonded bridges and ceramic or indirect composite restorations, to the tooth tissue. They are usually used in conjunction with a bonding agent as they have no ability to bond to the tooth, although there are some products that can be applied directly to the tooth (self-etching products).
There are three main resin-based cements:
Light-cured – required a curing lamp to complete set
Dual-cured – can be light cured at the restoration margins but chemically cure in areas that the curing lamp cannot penetrate
Self-etch – these etch the tooth surface and do not require an intermediate bonding agent
Resin cements come in a range of shades to improve aesthetics.[8]
Mechanical properties
Fracture toughness
Thermocycling significantly reduces the fracture toughness of all resin-based cements except RelyX Unicem 2 AND G-CEM LinkAce.
Compressive strength
All automixed resin-based cements have greater compressive strength than hand-mixed counterpart, except for Variolink II.[9]
Zinc polycarboxylate cements
Zinc polycarboxylate was invented in 1968 and was revolutionary as it was the first cement to exhibit the ability to chemically bond to the tooth surface. Very little pulpal irritation is seen with its use due to the large size of the polyacrylic acid molecule. This cement is commonly used for the installation of crowns, bridges, inlays, onlays, and orthodontic appliances.[10]
Soluble in mouth particularly where stannous fluoride is incorporated in the powder
Relatively inexpensive
Difficult to manipulate
Long and successful track record
ill-defined set
Zinc phosphate cements
Zinc phosphate was the very first dental cement to appear on the dental marketplace and is seen as the “standard” for other dental cements to be compared to. The many uses of this cement include permanent cementation of crowns, orthodontic appliances, intraoral splints, inlays, post systems, and fixed partial dentures. Zinc phosphate exhibits a very high compressive strength, average tensile strength and appropriate film thickness when applies according to manufacturer guidelines. However, issues with the clinical use of zinc phosphate are its initially low pH when applied in an oral environment (linked to pulpal irritation) and the cement's inability to chemically bond to the tooth surface, although this has not affected the successful long-term use of the material.[10]
Composition:
Phosphoric acid liquid
Zinc oxide powder
Formerly known as the most commonly used luting agent, zinc phosphate cement works successfully for permanent cementation. It does not possess anticariogenic effects, is not adherent to tooth structure, and acquires a moderate degree of intraoral solubility. However, zinc phosphate cement can irritate nerve pulp; hence, pulp protection is required but the use of polycarboxylate cement (zinc polycarboxylate or glass ionomer) is highly recommended since it is a more biologically compatible cement.[11]
Known contraindications of dental cements
Dental materials such as filling and orthodontic instruments must satisfy biocompatibility requirements as they will be in the oral cavity for a long period of time. Some dental cements can contain chemicals that may induce allergic reactions on various tissues in the oral cavity. Common allergic reactions include stomatitis/dermatitis, urticaria, swelling, rash and rhinorrhea. These may predispose to life-threatening conditions such as anaphylaxis, oedema and cardiac arrhythmias.
Eugenol is widely used in dentistry for different applications including impression pastes, periodontal dressings, cements, filling materials, endodontic sealers and dry socket dressings. Zinc oxide eugenol is a cement commonly used for provisional restorations and root canal obturation. Although classified as non-cariogenic by the US Food and Drug Administration, eugenol is proven to be cytotoxic with the risk of anaphylactic reactions in certain patients.
Zinc oxide eugenol constituents a mixture of zinc oxide and eugenol to form a polymerised eugenol cement. The setting reaction produces an end product called zinc eugenolate, which readily hydrolyses, producing free eugenol that causes adverse effects on fibroblast and osteoclast-like cells. At high concentrations localised necrosis and reduced healing occurs whereas for low concentrations contact dermatitis is the common clinical manifestation.
Allergy contact dermatitis has been proven to be the highest clinical occurrence usually localised to soft tissues with buccal mucosa being the most prevalent. Normally a patch test done by dermatologists will be used to diagnose the condition. Glass ionomer cements have been used to substitute zinc oxide eugenol cements (thus removing the allergen), with positive outcome from patients.[12]
^Dean, Jeffrey A. (2015-08-10). McDonald and Avery's dentistry for the child and adolescent. Dean, Jeffrey A. (Jeffrey Alan), Jones, James E. (James Earl), 1950-, Vinson, LaQuia A. Walker,, Preceded by (work): McDonald, Ralph E., 1920- (Tenth ed.). St. Louis, Missouri. ISBN9780323287463. OCLC929870474.{{cite book}}: CS1 maint: location missing publisher (link)
^Deshpande A N, Verma S, Macwan C. January 2014. Allergic Reaction Associated with the use of Eugenol Containing Dental Cement in a Young Child. Research Gate.
Acid-base Cements (1993) A. D. Wilson and J.W. Nicholson
