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.
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.
- 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.
| Cement type | Brands | Indications | Contra-indications | Advantages | Disadvantages |
| Zinc phosphate | Hy-Bond Zinc Phosphate Cement Modern Tenacin Zinc Cement Improved | 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 Low hardness |
| Zinc polycarboxylate | Hy-Bond Polycarboxylate Cement Tylok Plus Durelon | Porcelain restorations Orthodontic bands Cavity liner Metal crowns Metal-ceramic crowns | Titanium based restorations | 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 | Fuji I Ketac-Cem | 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 Dentine close to pulp | 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 | Fuji Plus Vitremer Luting Advance 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 | Temp-Bond Fynal Super EBA | 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 Little anticariogenic action |
| Resin cements | Panavia 21 Multilink Automix SG RelyX Unicem 2 Maxcem Elite TheraCEM | 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 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
Dental Cements Based on Organometallic Chelate Compounds
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
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
Luting cements
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
Composition and classification
ISO classificationCements are classified on the basis of their components. Generally, they can be classified into categories:
- Water-based acid-base cements: zinc phosphate, Zinc Polyacrylate, glass ionomer. 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.
- Phosphate
- Polycarboxylate
- Phenolate
- Resin
Resin-based cements
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
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.
Zinc polycarboxylate cements
Composition:
- Powder + liquid reaction
- Zinc oxide + poly acid = 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 acid, itaconic acid and maleic acid.
- Zinc polycarboxylate cements adhere to enamel and dentine by means of chelation reaction.
- 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 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 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
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, with positive outcome from patients.