Cement can be defined as a substance that hardens from a viscous state to a solid union between two surfaces; for dental applications, cements act as a base, liner, filling material, root canal sealer, or adhesive to bind devices and prostheses to tooth structure or to each other.
There are various type of cements used in the dental practice. For an easy understanding of the different dental cements, we will group them according to their composition, properties and usage.
Composition
Zinc-oxide based Cements
The zinc oxide group of cements are one of the earliest materials to be used widely in dentistry, although they have become less popular with time. These cements involves an acid-base reaction, that never progresses to completion, and therefore, the hardened cements retain composite structure, consisting of unreacted powder particles in a matrix of reaction products.
Zinc Phosphate Cement
- Formed by the reaction between zinc oxide powder and phosphoric acid liquid.
- Composition : Powder : Zinc oxide and Magnesium oxide. Liquid : Phosphoric acid, water.
- Indication : Cementing metallic fixed prostheses.
Zinc Polycarboxylate Cement
- It was the first dental cement that chemically bonded to tooth, where in the polyacrylic acid forms linkage to the zinc ions of the powder and to the calcium ions of the mineralised tooth.
- Composition : Powder : Zinc oxide and Magnesium oxide. Liquid : Polyacrylic acid, water.
- Indication : Cementing metallic fixed prostheses short spans or crowns.
Zinc oxide Eugenol Cement
- Based on the reaction between zinc oxide and eugenol.
- Composition : Powder : Zinc oxide. Liquid : Eugenol ( in EBA modified ZOE).
- Indications : Pulp protection and temporary cementation.
Zinc oxide Non-eugenol Cement
- These are formed by making some additions to the powder and/or replacement of part of the eugenol liquid with other compounds.
- EBA-modified ZOE : Consists of ortho-ethoxybenzoic acid added to the eugenol liquid and alumina to the powder.
- Polymer-reinforced ZOE : Incorporates a powder containing 20-40 wt% fine polymer particles and zinc oxide particles treated with carboxylic acid.
Glass Ionomer Cement
The glass ionomer cement, also referred as glass polyalkenoate cement can be defined as a cement that sets following an acid-base reaction between fluoroaluminosilicate glass powder and an aqueous-based polyacrylic solution.
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Composition : Powder : Fluoroaluminosilicate glass. Liquid : Polyacrylic acid, Polybasic carboxylic acid, Water.
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Indications : Cementation of crowns (alumina, zirconia metal), metal posts and core restoration.
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It can be classified as:
- Type I : Luting cement for crown, bridges and orthodontic brackets.
- Type II a : Esthetic restorative cements.
- Type II b : Reinforced restorative cements.
- Type III : Lining cements and bases.
Resin Cements
Resin cements are low-viscosity versions of resin-based composites, that consists of a matrix of methacrylate monomers with dispersed fillers.
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These can be grouped further based on the polymerisation mechanism:
- Self-cure resin cements.
- Light-cure resin cements.
- Dual-cure resin cements.
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Indications: Ceramic veneers, maryland bridges, lithium disilicate, alumina, zirconia, cores and posts.
Tri-/Dicalcium Silicate Cement
Dental cements based on tri-/dicalcium silicates have good sealing ability, biocompatibility and bioactivity.
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They are hydraulic cements that need water to set, and are less toxic than glass-ionomer cements or polymeric materials.
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Tricalcium silicate cements include Mineral trioxide aggregate (MTA) and Bioceramic.
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Indications:
- Powder/Liquid systems : Pulpal protection, periradicular contact, endodontic sealing.
- Single component system : Primary tooth pulpectomy, pulp-capping, pulpotomies and endodontic sealing.
Calcium Phosphate Cements
These are formed by combination of dicalcium phosphate dihydrate, dicalcium phosphate anhydrous, tri- and tetracalcium phosphate that are mixed with an aqueous solution saturated with calcium phosphate, an organic acid, or a solution of polymers. e.g., Sankin apatite root canal sealer.
- The cement pastes gradually set and form hydroxyapatite.
- Indication: Suitable for bone-substitute materials (because they are gradually resorbed) and are sometimes used in place of granular hydroxyapatite.
Combination Cements
These cements are developed by combination of two or more cements by substituting or incorporating ingredients, in order to achieve unique properties such as higher strength, longer working time, etc. These include.
Resin-modified GIC (Hybrid ionomer)
- Contains water-soluble polymerizable monomers in a liquid, usually a water solution of polyacrylic acid, 2-hydroxymethyl methacrylate (HEMA), and polyacrylic acid-modified methacrylate.
- Indications : Metal, lithium disilicate, alumina or zirconia prosthesis, metal posts/core.
Compomer (Polyacid-modified GIC)
- Derived from the terms composite and ionomer, it is a light-cured resin-based composite that consists of a silicate glass filler phase and a methacrylate-based matrix with carboxylic groups.
- It integrates the fluoride-release capability of glass ionomers with the durability of composite resins in a one-paste restorative resin.
- Indications: Cavities in deciduous teeth, cervical cavities in adults, anterior proximal restorations in adults, small load-bearing restorations in adults, temporary restoration.
Calcium aluminate GIC
- It is a self-adhesive-bioactive cement that is formed by the combination of GIC and calcium aluminate cement.
- Indication: Luting of fixed dental prostheses.
Properties and usage
Fluoride-releasing Materials
The fluoride-containing restorative materials and cements have anticariogenic potential due to the ability of fluoride to inhibit demineralisation. These include:
- Glass ionomer cement.
- Resin-modified glass ionomers.
- Polyacid modified composites (compomers).
- Fluoridated varnishes.
Pulp Protectants
After cavity preparation the exposed dentinal tubules provide a communication path to the pulp, for acids and microbes, depending on the remaining dentin thickness, Hence, pulp protection is required when little protection dentin is left after a cavity preparation. The protective cements can be grouped as,
Pulp-capping Materials
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Used when the pulp has been exposed and bleeding is frank. They are in direct contact with the pulp, and their biocompatibility is crucial to the pulp's healing. These include,
- Calcium hydroxide.
- Tri-/Dicalcium silicate.
- Formocresol and Ferric sulfate.
Varnishes
- Used when the remaining dentin thickness is less than 1 mm, to plug and block the dentin tubules exposed in cavity preparation.
- Varnishes are solutions of synthetic resins or natural gums, such as copal or rosins, in an organic solvent (ethanol, acetone, chloroform, or ether).
Cavity Liners
- Are more protective than varnishes and used in thin layers for indirect pulp capping when the remaining dentin is less than 1 mm.
- These include low-viscosity ZOE, glass ionomer (Type III), calcium hydroxide products, and the tricalcium silicates.
Base Materials
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Cement bases are placed farther from the pulp at the bottom of cavity preparations, in thicker layers than liners and provide insulation from the thermal, chemical or galvanic irritants that may occur with restorative materials.
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These include:
- Zinc phosphate.
- Zinc-oxide eugenol.
- Zinc polycarboxylate.
- Fast-setting glass ionomers (Type III)
- Calcium hydroxide.
- Tricalcium silicate cements.
Luting Cements
Can be defined as materials that fills a gap between two surfaces to prevent dislodgement through mechanical retention (luting).
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Traditionally, the term luting refers to the use of non-adhesive materials for retaining prosthesis, and bonding refers to the use of adhesive bonding materials. However, with time the distinction has faded, and the use of adhesive bonding medium is also referred as luting.
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The commonly used luting cements include,
- Zinc phosphate.
- Zinc polycarboxylate.
- Zinc oxide eugenol and non-eugenol cements.
- Glass ionomer cement (Type I).
- Resin cements.
Endodontic Sealers
Endodontic sealers are used in conjunction with an obturation material such as gutta-percha, to fill voids and achieve a close seal between the obturating material and the root canal walls, thus, preventing any transmission of fluid or bacteria from the coronal to the apical region. These include,
- ZOE-based sealers.
- Resin-based sealers.
- Tri-/Dicalcium silicate cements.
References
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[](https://amzn.to/3USt5AE) Phillips' Science of Dental Materials, 13th Edition, Shen, Rawls, Esquivel-Upshaw, Elsevier
*This article is an excerpt from the above mentioned book and Medical Sutras does not make any ownership or affiliation claims.