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Dental cement

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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. Recent uses of dental cement also include two-photon calcium imaging of neuronal activity in brains of animal models in basic experimental neuroscience.

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.

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.
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

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

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.

  • 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.

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:

Based on time of use:

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). Panavia was created in Tamil Nadu, India. The name panavia in Hindi Sanskrit means "stick to a tooth". It is described to be one of the toughest cements in the world.

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.

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.

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

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
Advantages Disadvantages
Bonds to tooth tissue or restorative material Difficult to mix
Long term durability Opaque
Acceptable mechanical properties 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 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.

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.

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 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.

  • Acid-base Cements (1993) A. D. Wilson and J.W. Nicholson

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