Dental compomers, also known as polyacid-modified resin composite, are used in dentistry as a filling material. They were introduced in the early 1990s as a hybrid of two other dental materials, dental composites and

glass ionomer cement A glass ionomer cement (GIC) is a dental restorative material used in dentistry as a filling material and luting cement, including for orthodontic bracket attachment. Glass-ionomer cements are based on the reaction of silicate glass-powder (calc ...

, in an effort to combine their desirable properties: aesthetics for dental composites (they are white and closely mimic tooth tissue, so can camouflage into a tooth very well) and the fluoride releasing ability for glass ionomer cements (helps to prevent further tooth decay).

History

Compomers were introduced in the early 1990s. Previous available restorative materials included

dental amalgam Dental amalgam is a liquid mercury and metal alloy mixture used in dentistry to fill cavities caused by tooth decay. Low-copper amalgam commonly consists of mercury (50%), silver (~22–32%), tin (~14%), zinc (~8%) and other trace metals. ...

, resin modified glass ionomer cement and dental composites.

Composition

Compomers are resin-based materials like dental composites, and the components are largely the same. The setting reaction is similarly a

polymerisation In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many for ...

process of resin monomers (e.g. urethane dimethacrylate) which have been modified by polyacid groups, and is induced by free radicals released from a

photoinitiator A photoinitiator is a molecule that creates reactive species (free radicals, cations or anions) when exposed to radiation (UV or visible). Synthetic photoinitiators are key components in photopolymers (for example, photo-curable coatings, adhesive ...

such as camphorquinone. To induce the release of these free radicals, the

must be exposed to a specific wavelength of light, blue light in the case of camphorquinone. There is a second less significant acid-base setting reaction which takes place after the light-cured polymerisation reaction; this setting reaction occurs as the compomer absorbs water from the oral environment. Also in compomer is fluoroaluminosilicate glass which, when broken down by hydrogen ions through an acid-base reaction, releases

fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts typ ...

. This process requires water absorbed from the oral environment. To aid water absorption and

release, some of the resins in the compomer matrix are more

hydrophilic A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press. In contrast, hydrophobes are no ...

(e.g. glycerol dimethacrylate). The source of the hydrogen ions that break the fluoroaluminosilicate glass particles apart are certain resin monomers that have a carboxyl group attached. Some compomers instead source their hydrogen ions from a methacrylated polycarboxylic acid copolymer that is similarly used in some resin modified glass ionomer cements.

Properties

Aesthetics

Compomers are tooth coloured materials, and so their aesthetics can immediately be seen as better than that of dental amalgams. It has been shown that ratings in various aesthetic areas are better for compomers than resin modified glass ionomer cements.Folwaczny M, Mehl A, Kunzelmann KH, Hickel R. Clinical performance of a resin-modified glass-ionomer and a compomer in restoring non-carious cervical lesions. 5-year results. ''American Journal of Dentistry'', 14(3):153-6, 2001 Jun. Compomers are also available in various non-natural colours from various dental companies for use in deciduous teeth. Compomers and resin-modified glass ionomers have better aesthetics than conventional glass ionomer cements.

Fluoride release

Compomers and glass ionomer cements can release

. This property can be useful in cases where a patient has a higher risk of experience

tooth decay Tooth decay, also known as cavities or caries, is the breakdown of teeth due to acids produced by bacteria. The cavities may be a number of different colors from yellow to black. Symptoms may include pain and difficulty with eating. Complicatio ...

in future.

Fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts typ ...

is a mineral which helps strengthen our teeth and protects them from decay, and it is found in many dental products including

toothpaste Toothpaste is a paste or gel dentifrice used with a toothbrush to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from the teeth, a ...

. Compomers and glass ionomer cements are able to release

over extended periods, and this may help to reduce the risk of a tooth decaying further. However, such a property does not negate the need for excellent

oral hygiene Oral hygiene is the practice of keeping one's mouth clean and free of disease and other problems (e.g. bad breath) by regular brushing of the teeth (dental hygiene) and cleaning between the teeth. It is important that oral hygiene be carried out ...

to prevent oral disease. Compomers are recommended for patients at medium risk of developing

dental caries Tooth decay, also known as cavities or caries, is the breakdown of teeth due to acids produced by bacteria. The cavities may be a number of different colors from yellow to black. Symptoms may include pain and difficulty with eating. Complicatio ...

. There is conflicting evidence regarding the amount of

compomers can release: Powers, Wataha and Chen (2017) state compomers do not release as much

as glass ionomer cements because they have a lower concentration of fluoroaluminosilicate glass particles; there is supporting evidence to suggest compomers only release 10% of that of

. On the other hand, Richard van Noort (2013) states that, due to recent developments, modern compomers are now capable of releasing the same amount of

over the lifetime of the restoration as glass ionomer cements. Emerging evidence has shown that compomers and glass ionomer cements are able to absorb

from the oral environment when their own

stores are depleted, a process described as 'recharging'. The material can then release this stored

when the

concentration in the oral environment falls, thus exposing the teeth to

for longer. This recharging ability is not as effective in compomers as it is in glass ionomers cements. Nevertheless, this can further prevent the risk of

. There is evidence to show compomers have no advantage over an

amalgam Amalgam most commonly refers to: * Amalgam (chemistry), mercury alloy * Amalgam (dentistry), material of silver tooth fillings ** Bonded amalgam, used in dentistry Amalgam may also refer to: * Amalgam Comics, a publisher * Amalgam Digital ...

restoration with a fluoride releasing bonding agent, which releases

mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

and

.Trachtenberg F. Maserejian NN. Soncini JA. Hayes C. Tavares M. Does fluoride in compomers prevent future caries in children? ''Journal of Dental Research'', 88(3):276-9, 2009 Mar.

Polymerisation shrinkage

Compomers undergo some shrinkage during the setting reaction, and the extent of this

shrinkage is similar to that of dental composites.

Water uptake

Compomers absorb water more rapidly than dental composites due to the addition of

resin monomers within the matrix (see ''Composition'' section above). As such, water equilibrium is reached within days rather than weeks, months or even years in the case of dental composite materials. This property has the advantage of compensating for the polymerisation shrinkage during the setting reaction, thus reducing any gap that develops at the cavity margins. However, it can also cause fracture of all-ceramic crowns when compomer is used as the luting cement. Therefore, it is not recommended to use the luting version of compomer for cementing all-ceramic crowns. More information on luting compomer can be found below.

Mechanial properties

Compomers have poorer mechanical properties than dental composites, with a lower

compressive In continuum mechanics, stress is a physical quantity. It is a quantity that describes the magnitude of forces that cause deformation. Stress is defined as ''force per unit area''. When an object is pulled apart by a force it will cause elon ...

, flexural and

tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...

. Therefore, compomers are not an ideal material for load bearing restorations. In terms of

wear resistance Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical (e.g., erosion) or chemical (e.g., corrosion). The study of wear and related processes is referred to as tribology. Wear in m ...

, compomers wear less quickly than glass ionomer and resin modified glass ionomer cements, but do not perform as well as dental composites.

Clinical application

Handling

Handling and ease of use of composites is generally seen as good by dental professionals. Compomers are available in both normal and flowable forms, with the manufacturers of the flowable compomers claiming that they have the ability to shape to the cavity without the need for hand instruments.

Adhesion to tooth tissue

It is important to note that compomers do not bond to

tooth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

tissue like glass ionomer cements; this is the same issue with dental composites. It is therefore essential to use bonding agents to aid adhesion of the compomer to tooth.

Finishing and polishing

The process of finishing and polishing compomers is similar to that of dental composites. After finishing and polishing, compomers have a similar surface roughness to dental composites.

Indications for use

As a restorative material, compomers are limited to low-stress bearing situations (proximal and cervical restorations) due to their mechanical properties and wear resistance as detailed in the ''Properties'' section above. Compomers can be used as a cavity lining material to provide pulpal protection. Compomers are notable used in

Paediatric dentistry Pediatric dentistry (formerly pedodontics in American English or paedodontics in Commonwealth English) is the branch of dentistry dealing with children from birth through adolescence. The specialty of pediatric dentistry is recognized by the Ameri ...

. Possible uses include: * As a restorative material, particularly for Class I and II cavities (see ''Green Vardiman Black Classification'' section on the Wiki page for

Dental Restoration Dental restoration, dental fillings, or simply fillings are treatments used to restore the function, integrity, and morphology of missing tooth structure resulting from caries or external trauma as well as to the replacement of such structure sup ...

) * Fissure sealants * For cementation of

orthodontic Orthodontics is a dentistry specialty that addresses the diagnosis, prevention, management, and correction of mal-positioned teeth and jaws, and misaligned bite patterns. It may also address the modification of facial growth, known as dentofacial ...

bands

Survival rate

Studies have shown compomers to have high survival rates 2-4 years following placement. Some issues that were identified 2-3 years after placement include discolouration around the restoration margins and loss of marginal integrity.

Compomer luting cement

Composition

A powder and liquid are mixed together to form the luting cement. The powder contains fluoroaluminosilicate glass particles, sodium fluoride, and self-cured and light-cured initiators. The liquid contains poly-acid modified monomers and water. The carboxylic acid groups in the methacrylate-carboxylic acid monomer help with adhesion.

Properties

The advantages of compomer luting cement are listed below: * Retentive * High

bond strength In chemistry, bond energy (''BE''), also called the mean bond enthalpy or average bond enthalpy is the measure of bond strength in a chemical bond. IUPAC defines bond energy as the average value of the gas-phase bond-dissociation energy (usually a ...

* High

compressive strength In mechanics, compressive strength or compression strength is the capacity of a material or structure to withstand loads tending to reduce size (as opposed to tensile strength which withstands loads tending to elongate). In other words, compre ...

* High

flexural strength Flexural strength, also known as modulus of rupture, or bend strength, or transverse rupture strength is a material property, defined as the stress in a material just before it yields in a flexure test. The transverse bending test is most freque ...

* High

fracture toughness In materials science, fracture toughness is the critical stress intensity factor of a sharp crack where propagation of the crack suddenly becomes rapid and unlimited. A component's thickness affects the constraint conditions at the tip of a c ...

* Low

solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...

* Sustained

release with the potential to act as a fluoride reservoir (recharges when it becomes depleted of fluoride, see 'Fluoride release' in ''Properties'' section above for more details) The compressive and tensile strength of compomer cements are comparable to that of glass ionomer, resin-modified glass ionomer, and zinc polycarboxylate cements.

Indications for use

The use of the luting version of compomer is not recommended for all-ceramic crowns, nor as a core or filling material. See 'Water uptake' in ''Properties'' section above for more details. Compomer luting cement can however be used for cast alloy and ceramic-metal restorations.

References

{{Reflist Composite materials Dental materials __FORCETOC__

History

Composition

Properties

Aesthetics

Fluoride release

Polymerisation shrinkage

Water uptake

Mechanial properties

Clinical application

Handling

Adhesion to tooth tissue

Finishing and polishing

Indications for use

Survival rate

Compomer luting cement

Composition

Properties

Indications for use

See also

References