Dental cements are a group of materials with a wide range of Dental & 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 are presented as separate power & liquid components, manually mixed to form a viscous liquid, which then sets to form a brittle solid after application on the required treatment surface. More advanced cements, such as GIC, can also be presented in capsule form and are mechanically mixed using rotational or oscillating mixing machines.
Video Dental cement
Dental Applications
Dental cements can be utilised in a variety of ways depending on the composition & 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
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-1980's 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 & 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
Maps Dental cement
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)
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.
Zinc Polycarboxylate Cements
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
Zinc Oxide Eugenol (ZOE) Cements
Zinc oxide eugenol use in dentistry has been reported as far back as 1858.
It can be used as a luting cement, dental impression material, lining material or as a temporary restorative material.
Indications for use:
- Temporary restorations
- Sedative dressing
- Base/liner
- Luting cement
- Impression material
Advantages:
- Good dimensional stability
- Tooth coloured
- Sedative
- Bactericidal
- Good and long history of use
Disadvantages:
- Difficult to handle
- High solubility in oral fluids
- No bond to tooth tissues
- Weak in thin section
- Incompatible with resin materials
- Pulpal inflammation when in direct contact with the pulp
Zinc oxide eugenol can be reinforced with 2-Ethoxybenzoic acid (EBA), making it more crystalline in structure. This reinforcement overcomes some of its high oral solubility, increase its strength, both compressive and tensile, and increases working time.
Requirements
The requirements for dental cements are that they should:
- Be non irritant to pulp and gingiva (gums) and should not support the growth of secondary caries. (This last property is called cariostatic or anticariogenicity).
- Form a strong bond with enamel and dentin.
- Provide good marginal sealing to prevent marginal leakage.
- Be resistant to dissolution in saliva, or in any oral fluid.
- Have good aesthetics and good thermal and chemical resistance. (Opacity to X-rays is also preferred for diagnostic purposes).
- Be translucent.
- Have a low film thickness (ideally 25microns).
References
3. Acid-base Cements (1993) A. D. Wilson and J.W. Nicholson
Source of the article : Wikipedia
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