Dental cement

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]

Traditional cements have separate powder and liquid components which are manually mixed to form a viscous liquid. The liquid sets to form a brittle solid after application on the treated surface. More advanced cements, such as GIC, can come in capsules and are mechanically mixed using rotating or oscillating mixing machines.[2]

Ideal cement properties

• Non irritant – many cements are acidic and irritate the pulp. However, on setting there is a rapid increase in pH. Polycarboxylate cement is considered the most biocompatible type due to having the most rapid pH rise.
• Provide a good marginal seal to prevent marginal leakage.
• Resistant to dissolution in saliva, or other oral fluid – a primary cause of cement failure 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.
• Adequate working and setting time.
• Good aesthetics.
• Good thermal and chemical resistance.
• Opacity – for diagnostic purposes on radiographs.
• Low film thickness (ideally 25 microns).
• 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.[3]

Comparison of cements

Cement type	Brands (Manufacturer)	Indications	Contra-indications	Advantages	Disadvantages
Zinc phosphate	Hy-Bond Zinc Phosphate Cement (Shofu Dental) Modern Tenacin (L.D. Caulk) Zinc Cement Improved (Mission White Dental)	Long span bridges Metal Crowns Metal-Ceramic Crowns Feldspathic Porcelain jacket crowns Orthodontic bands Cavity liner	All-ceramic restorations – due to setting expansion Inadequate retention form of tooth preparation	Highest elastic modulus High Compressive Strength Low film thickness Low cost	Acidic – possible pulpal irritation Lack of antibacterial action Brittle Lack of adhesion Low tensile strength Provides only mechanical seal Exothermic during set High solubility (in oral fluids) Low hardness
Zinc polycarboxylate	Hy-Bond Polycarboxylate Cement (Shofu Dental) Tylok Plus (L.D. Caulk) Durelon	Porcelain restorations Orthodontic bands Cavity liner Metal crowns Metal-ceramic crowns	Titanium based restorations (cement discolouration occurs)	Antibacterial Low irritation Adhesive to tooth structure Sufficient compressive strength Higher tensile strength than Zinc Phosphate Low post-op sensitivity	Low pH initially Low resistance to erosion in acidic environment Short working time
Glass ionomer (GI)	Fuji I (GC America) Ketac-Cem (3M/Espe)	Metal and Metal-Ceramic Restorations Porcelain restorations All Ceramic Crowns with high strength cores such as alumina or zirconia Orthodontic bands Cavity liners Restoring erosion lesions	Allergy (rare) Dentine close to pulp (place suitable liner first)	Adhere to teeth and metal Fluoride release Ease of Mixing Good flow Cheap Aesthetic Thermal compatible with enamel Low shrinkage Good resistance to acid dissolution Translucency ??	Soluble in water Rapid set – time limitation especially in cementation of several units. Moisture sensitivity at set Brittle Inherent opacity Low fracture toughness Poor wear resistance Radiolucency Possible pulpal sensitivity
Resin modified glass ionomer (RMGI)	Fuji Plus (GC America) Vitremer Luting (3M/Espe) Advance (L.D. Caulk) Rely X Luting	Cavity liners Core buildups Luting cements Crowns Orthodontic appliances	All-ceramic crowns – due to uptake of water causing swelling and pressure on the crown Veneer – not retentive enough	Dual cure Fluoride release Higher flexural strength than GI Capable of bonding to composite materials	Setting expansion may lead to cracking of all-ceramic crowns Moisture sensitive
Zinc oxide eugenol (ZOE)	Temp-Bond Fynal (L.D. Caulk) Super EBA (Bosworth)	Temporary crowns, bridges Provisional cementation of fixed partial dentures Provisional restoration of teeth Cavity liner	When resin cement to be used for permanent cementation	Neutral pH Good sealing ability Resistance to marginal penetration Obtundent effect on pulpal tissues	Weakest of the cements Low strength   Low abrasion resistance Soluble (in oral fluids) Little anticariogenic action
Resin cements	Panavia 21 (Kurarary) Multilink Automix SG(Vivadent) RelyX Unicem 2 (3M/ESPE) Maxcem Elite (Kerr) TheraCEM (BISCO)	All crown types Bonding fixed partial dentures Inlays Veneers Indirect resin restorations Resin-fiber posts	If a ZOE cement has been used for the previous temporary. Light cured under a metal crown since it would not cure through the metal.	Strongest of the cement – highest tensile strength. Least soluble (in oral fluids) High micromechanical bonding to prepared enamel, dentin, alloys, and ceramic surfaces Neutral pH	Setting shrinkage – contributing to marginal leakage Difficult sealing Requires a meticulous and critical technique Possible pulpal sensitivity Difficult to remove excess cement

Cements Based on Phosphoric Acid

Types	Composition	Setting reaction	Disadvantages	Advantages	Applications
Zinc phosphate cements	Usually a powder (Zinc Oxide with other metallic oxides, e.g. Magnesium oxide) and liquid (aqueous solution of Phosphoric acid) Zinc Oxide or Aluminium Oxide buffer (up to 10%) mixed by hand	3ZnO + 2H3PO4 +H2O →Zn3(PO4)2 4H2O	May irritate dental pulp, especially when used in cavity lining.	small amounts of fluoride salt, in the cement can leak out to provide protection to surrounding tooth substance non-opaque set material because of unconsumed zinc oxide	Widely used as lute applications
Silicophosphate cements (obsolete)	Supplied as a powder (zinc oxide and aluminosilicate glass mixture) and liquid (aqueous solution of phosphoric acid with buffers)	forms unconsumed cores of zinc oxide and glass particles enclosed by matrix of zinc and aluminium phosphates.	releases F^− ions irritates dental pulp	stronger and less soluble than phosphate cement aluminosilicate glass particles contain fluoride, anti-cariogenic for surrounding tooth substance	Mainly temporary filling materials not used anymore
Copper cements (obsolete)	Supplied as a powder (zinc oxide and black copper oxide) and liquid (aqueous solution of phosphoric acid)	Similar to zinc phosphate	black color caused by copper poor durability	bactericidal effect	rarely used

[4]

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 interfere 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 induce 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

[4]

Dental applications

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.[2]

• GIC – Glass Ionomer cement
• Zinc Polycarboxylate cement
• Zinc Oxide Eugenol cement
• RMGIC
• "dentsply cement

Bonded amalgam restorations

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.[2]

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
• 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.

• RMGIC
• 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 bases 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:

• Phosphate (zinc phosphate, silico phosphate)
• Polycarboxylate (zinc polycarboxylate, glass ionomer)
• Phenolate (Zinc oxide–eugenol and EBA)
• Resin (polymeric)[5]

Resin-based cements

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 3 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.[6]

Mechanical Properties

1. Fracture Toughness
   • Thermocycling significantly reduces the fracture toughness of all resin-based cements except RelyX Unicem 2 AND G-CEM LinkAce.
2. Compressive Strength
   • All automixed resin-based cements have greater compressive strength than hand-mixed counterpart, except for Variolink II.[7]

Zinc polycarboxylate cements

Zinc polycarbonate 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 instillation of crowns, bridges, inlays, onlays, and orthodontic appliances.

[8]

Composition:

• Powder + liquid reaction
• Zinc oxide (powder) + poly(acrylic) acid (liquid) = Zinc polycarboxylate
• Zinc polycarboxylate is also sometimes referred to as zinc polyacrylate or zinc polyalkenoate
• Components of the powder include zinc oxide, Stannous fluoride, magnesium oxide, silica and also alumina
• Components of the liquid include poly(acrylic) acid, itaconic acid and maleic acid.

Adhesion:

• Zinc polycarboxylate cements adhere to enamel and dentine by means of chelation reaction.

Indications for use:

• Temporary restorations
• Inflamed pulp
• Bases
• Cementation of crowns[6]

Advantages	Disadvantages
Bonds to tooth tissue or restorative material	Difficult to mix
Long term durability	Opaque
Acceptable mechanical properties	Soluble in moth 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 manufacture guidelines. However the issues with the clinical use of zinc phosphate is its initially low PH when applied in an oral environment (this linked to pulpal irritation) and the cements inability to chemically bond to the tooth surface although this hasn’t affected the successful long term use of the material.[8]

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 effect, not adherent to tooth structure, 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, glass ionomer) is highly recommended since it is a more biologically compatible cement.[9]

Known contra-indications 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, uticaria, 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 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.[10]

References

1. "dental cement". TheFreeDictionary.com. Retrieved 2017-11-21.
2. J., Bonsor, Stephen (2013). A clinical guide to applied dental materials. Pearson, Gavin J. Amsterdam: Elsevier/Churchill Livingstone. ISBN 9780702031588. OCLC 824491168.
3. Jack L Ferracane, 2001. Materials in Dentistry Second Edition. Colombia
4. McCabe, J. F. (John F.) (2008). Applied dental materials. Walls, Angus. (9th ed.). Oxford, UK: Blackwell Pub. ISBN 9781405139618. OCLC 180080871.
5. According to ISO 9917-1:2007 Dental cements classified as: a. Luting cements, b. Bases or lining, c. Restoration Spiller, Martin S. (2000). "Composite materials". Doctorspiller.com. Archived from the original on 2008-07-30. Retrieved 2008-08-11.
6. Bonsor, Stephen; Pearson, Gavin (2013). A Clinical Guide to Applied Dental Materials. Elsevier. pp. 167, 168 and 169.
7. Sulaiman, Taiseer A.; Abdulmajeed, Awab A.; Altitinchi, Ali; Ahmed, Sumitha N.; Donovan, Terence E. (June 2018). "Mechanical properties of resin-based cements with different dispensing and mixing methods". The Journal of Prosthetic Dentistry. 119 (6): 1007–1013. doi:10.1016/j.prosdent.2017.06.010. ISSN 1097-6841. PMID 28967397.
8. MSEd, AEGIS Communications, By Mojdeh Dehghan, DDS, Ashanti D. Braxton, DDS, James F. Simon, DDS. "An Overview of Permanent Cements | ID | aegisdentalnetwork.com". www.aegisdentalnetwork.com. Retrieved 2019-01-23.
9. 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. ISBN 9780323287463. OCLC 929870474.
10. 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