Composite Resin in Dentistry

• White fillings. Composite fills a cavity in a front or back tooth and is shaped to the tooth in the mouth. When a filling is needed, and what it involves, is covered on dental fillings.
• Composite bonding. Composite is added to a tooth to repair a chipped or worn edge, close a small gap or change the shape of a tooth. See composite bonding.
• Composite veneers. When the composite covers the whole front surface of a tooth, it is called a composite veneer. It can be shaped in the mouth or made in a laboratory. How veneer materials compare is covered on dental veneers.
• Laboratory-made (indirect) inlays and onlays. For a large cavity in a back tooth, composite can be made outside the mouth to fit the tooth, then bonded in place. See inlays and onlays.
• Fissure sealants. A related use. SCENIHR describes sealants as flowable resins or glass ionomers¹ applied to seal the pits and grooves of permanent (adult) back teeth, to prevent decay.

What it is made of

The SCENIHR opinion describes the main parts:

• The resin (matrix). A mixture of organic monomers that link together into a hard solid as the material sets. Common ones are Bis-GMA, Bis-EMA, TEGDMA and UDMA¹. Two of these, Bis-GMA and Bis-EMA, are based on bisphenol A (BPA), but they are not BPA itself; see "Sensitivity and other risks".
• The filler. Fine inorganic particles, such as silica glass and alumina glass¹. The particles are coated so that they bond to the resin. Some fillers make the composite show up on X-rays.
• Other ingredients. A starter (initiator) that sets the material off when the light is applied, stabilisers, and pigments that give the range of shades¹.

Manufacturers do not always publish their full recipe. In 2015 the committee noted that the full chemical specification of these materials is not always divulged¹. If you want to know what is in a product, ask for its name and manufacturer.

Categories

Composites are usually grouped by the size of their filler particles¹: from macrofill, with the largest particles, down to microfill and nanofill. Hybrid composites mix two particle sizes, so you may see names such as micro-hybrid or nanohybrid on a product.

Composites also differ in how they handle. Some are a firm paste that can be sculpted; others are runnier and are called flowable. Conventional composite is built up in layers. Bulk-fill composites are an alternative to that layering for fillings in back teeth. A 2019 review of 941 back-tooth fillings, followed for 1 to 6 years, found no statistically significant difference in failure³ between bulk-fill and conventional composite. It included both flowable and sculptable bulk-fill types, and its authors called for longer trials. A 2026 review of 12 randomised trials in back teeth looked at fit at the edges, fractures and retention. Up to two years, it found no statistically significant differences⁴.

Composite for inlays, onlays and veneers can also be made in a laboratory (indirect composite). Related resin-based materials reinforced with ceramic particles are known as resin-matrix ceramics.

Shade

Composite comes in a range of shades. The shade is chosen to match the neighbouring teeth, with a shade guide, photographs or a measuring device. Choosing a shade by eye is subjective. In two meta-analyses, selection with digital photography came closer to the target shade⁵ than selection by eye. For spectrophotometers (devices that measure tooth colour) the two disagreed: one found an advantage, the other did not⁶; the studies are few and small.

Whitening will not work on fillings⁷, crowns or veneers, and composite does not change colour when bleached⁸. Next to whitened teeth, it can look darker. A review based mainly on laboratory studies notes that restorations may need to be polished or replaced⁸ after whitening. Polishing deals with the surface; if the shade itself no longer matches, the composite may need replacing. If you are thinking about whitening, raise it before the shade is chosen.

Choosing the material

Which material suits a tooth is decided at an examination, with X-rays where needed. The main questions are:

• Where the tooth is, how large the cavity or the change is, and how much sound tooth is left.
• Your bite, and whether you clench or grind your teeth.
• Your risk of decay. In an analysis of back-tooth composite fillings, failure was more common⁹ in people at high risk of decay. It was also more common in fillings that covered more surfaces of the tooth.
• Whether composite placed in the mouth is enough, or a laboratory-made inlay, onlay, veneer or crown is needed.
• Your health. The 2015 SCENIHR opinion advised that the choice of material be based on patient characteristics. It named whether the tooth is a baby tooth or an adult tooth, pregnancy, allergies to components of dental materials and reduced kidney function¹.

Ask which composite product is proposed for each tooth, and why it suits that tooth better than the alternatives.

The steps below are for composite placed directly in the mouth, as for a white filling or bonding. Composite is attached with a bonding system of etchants, primers and bonding resins¹. Most composites are then set with visible light from a curing light¹. Your dentist decides whether a local anaesthetic is needed, depending on the extent of the work. The pages on dental fillings and composite bonding give the details of each treatment.

Laboratory-made composite inlays, onlays and veneers, like porcelain ones, need a laboratory stage between appointments. The tooth is prepared and an impression or scan is taken; the restoration is made in a laboratory and bonded at a later appointment. Ask the clinic where laboratory-made composite restorations are made.

The figures below come from published studies, not from our own records.

Benefits

• Tooth-coloured. The shade can be matched to the neighbouring teeth.
• Little or no drilling for bonding. Bonding can be done with very little tissue removed from the tooth, or none. Composite veneers may require less tooth enamel to be removed² than porcelain ones.
• No laboratory for direct work. A filling or bonding made in the mouth needs no laboratory stage, and a small repair is often finished in one appointment.
• Repairable. Composite is easier to fix than porcelain when it is damaged, and it can often be added to (see "Wear, staining and repair").

Limitations

• Staining and wear. Composite is not as stain- or wear-resistant² as porcelain.
• It cannot be fully undone. The tooth surface is treated so the composite can hold, and tooth removed for a filling does not grow back. Veneers, including composite veneers, are not designed to be removed¹⁰.
• It does not protect the tooth from decay. New decay can start at the edge where composite meets the tooth.
• Large cavities. In 2015 SCENIHR wrote that tooth-coloured materials in back teeth had improved. In its view they were still inferior to amalgam in certain clinical situations¹, such as large cavities and high rates of decay. See "Alternative materials".

How long it lasts

Studies show how groups of restorations fare. They cannot tell you how long your own will last.

• Fillings in back teeth. A 2014 analysis pooled data on 2,816 composite fillings in back teeth, from 12 studies that followed them for at least 5 years. During follow-up, 569 of these fillings failed, mainly because of new decay or fracture⁹.
• Composite veneers. A meta-analysis pooled randomised studies of composite veneers made in the mouth and in the laboratory. With average follow-up of 2 to 8 years, about 88 in every 100 veneers stayed in place¹¹. In a single-practice study of 1,459 veneers followed for up to 10 years, composite needed repair or replacement more often than ceramic. Counting repaired and replaced veneers together, the estimated yearly rate was about 10 in every 100 veneers for composite and about 3 for ceramic¹². These are average rates per year. Because this study was not randomised, it does not show that the difference comes from the material alone.
• Laboratory-made composite veneers. In a ten-year randomised study, survival was 75% for indirect composite and 100% for ceramic¹³. The study was small: 24 veneers of each kind, and all 6 failures were composite. It does not show that ceramic veneers never fail, and its result does not apply to composite shaped in the mouth.
• Large cavities in back teeth. Two reviews compared fillings made in the mouth with laboratory-made composite inlays and onlays. They reached different conclusions¹⁴. One found no significant difference; the other reported fewer failures with direct fillings¹⁵. Both rated the certainty of their evidence as very low.
• Root-filled teeth. At a university clinic, 196 composite veneers made in the mouth were followed for an average of 3.5 years. In this retrospective study, about 5 in every 100 veneers on living teeth failed each year, and about 10 in every 100 on root-filled teeth¹⁶. The main cause was fracture of the veneer. This does not mean that a root-filled tooth cannot be restored with composite.

Staining

Composite stains more readily than porcelain, and staining can appear at the edges over time. Tea, coffee and tobacco can increase staining of composite. A review looked at 17 studies on composite restorations in front teeth. Failures due to colour, shape and surface staining were more common in restorations done for cosmetic reasons¹⁷. Whitening does not lighten composite (see "Shade and material selection").

Wear and chipping

Composite also wears more than porcelain, and it can chip or break. In the same review, the most common reason for failure was fracture of the tooth or the restoration¹⁷. Nail biting and biting on hard objects increase the risk.

Composite is also used to repair worn front teeth. A meta-analysis pooled 6 studies of such repairs, with 141 patients followed for 5 months to 10 years. Over 2 to 10 years, 88 in every 100 restorations stayed in place, and 68 met the researchers' stricter success criterion¹⁸. The differences between the studies are very large. The authors recommend telling patients that these restorations will need monitoring, repair or replacement in the long term.

Repair

Composite is easier to fix if damaged² than porcelain. Small chips can be repaired; sometimes a new veneer is needed¹⁹. A filling with a defect can sometimes be repaired instead of being replaced in full. Studies comparing the repair of defective fillings with their replacement found no significant difference²⁰ in the risk of failure. Only 3 studies were included; the risk of bias was high and the certainty of the evidence very low. Ask your dentist whether a repair is possible, and if not, why not.

Sensitivity after treatment

After a filling, the tooth may be sensitive to hot and cold for a while. If enamel has been reshaped for bonding, the tooth may also be more sensitive. Tell your dentist if it does not settle or keeps getting worse. Pain that starts on its own, lingers after something hot or cold, or wakes you at night is more than simple sensitivity: see a dentist. The NHS website for England advises seeing a dentist for toothache that lasts more than 2 days²¹, or that painkillers do not ease.

The nerve of the tooth

In a deep cavity, the nerve may be exposed while the decay is removed. A 2026 European guideline covers deep decay in a tooth with no symptoms, or only brief sensitivity. It suggests removing the decay selectively or in two stages²². In these approaches, some softened decay next to the nerve is left in place; this is a weak recommendation. If the nerve cannot recover, root canal treatment or having the tooth out is discussed.

Allergy and the chemicals in composite

Reactions to dental materials are uncommon. In its 2015 opinion, SCENIHR looked at local reactions in the mouth to dental materials in general, including allergic reactions. It reported that they occur at an incidence below 0.3% and are usually readily managed¹. Allergies to some substances in these materials have been reported, both in patients and in dental personnel¹. If you have had a reaction to a dental material before, tell your dentist before treatment.

Some of the resins used, such as Bis-GMA, are based on bisphenol A (BPA), but they are not BPA itself. Some dental materials can release BPA. A separate 2015 SCENIHR opinion concluded that release of BPA from some dental materials was associated with only negligible health risks¹. The committee also noted that a similar risk assessment had not been done for other compounds released from these materials. It found information on their toxicity very limited¹. A 2021 Cochrane review compared composite and amalgam fillings in randomised trials. It found no consistent or clinically important harms²³ from either, but that evidence was of very low certainty.

If you are pregnant or breastfeeding, tell your dentist before any filling is planned. In its 2015 opinion, SCENIHR advised that caution should be exercised when considering the placement of any dental restorative material in pregnant women¹. Of resin-based filling materials such as composite, it wrote that, as with amalgam, their use in pregnant women is discouraged¹. The American College of Obstetricians and Gynecologists, a US body, says that urgent dental care may be managed at any time during pregnancy²⁴. It adds that delaying treatment may result in more complex problems²⁴. Ask your dentist which treatment is urgent and which can wait until after the birth.

• Brush twice a day with a fluoride toothpaste, and clean between your teeth every day, including where the composite meets the gum.
• Tea, coffee and tobacco can increase staining of composite.
• Do not bite hard objects such as ice, pens or your nails, and do not use your teeth as tools.
• If you clench or grind your teeth, tell your dentist; they may recommend a night guard.
• Keep up regular check-ups. National guidance in England (NICE) says the interval between check-ups should be set for each person according to their risk²⁵.
• If composite needs adjusting or repairing later, tell the dentist it is composite and, if you know them, the product and shade.

When to see a dentist

• A chip or break in the composite, or a sharp edge that catches your tongue
• Composite that comes loose or comes off (keep the piece and do not try to stick it back yourself)
• Your bite feels high or uneven
• Sensitivity that does not settle, or keeps getting worse
• Pain that starts on its own or wakes you at night
• Staining, roughness or a dark line at the edge of the composite, or bleeding from the gum around it

If pain keeps increasing, or you have facial swelling or a high temperature, see a dentist without waiting for the clinic's reply. In England, if you have no dentist or cannot get an emergency appointment, the NHS says to call 111 or use 111 online²⁶. Elsewhere in the UK, check the urgent dental care route where you live.

Emergencies. With a suspected dental abscess, the NHS says the following need urgent medical help²⁶. In the UK, call 999 or go to A&E.

• It is hard to breathe, speak, swallow or open your mouth
• A swollen or painful eye, or sudden problems with your eyesight
• A lot of swelling inside your mouth

Composite is one of several options. The right one depends on the tooth, the size of the cavity or change, your bite and what you expect of the appearance. Our page on dental materials gives an overview.

• Amalgam (silver-coloured fillings). The NHS website for England says white fillings are available on the NHS when clinically necessary²⁷, for example in front teeth. For a back tooth, it says a silver-coloured (amalgam) filling may be a more effective option²⁷. A 2021 Cochrane review combined two trials in children with fillings in back teeth. It found that composite fillings may have almost double the failure rate²³ of amalgam. Composite had a much higher risk of new decay at the edge, but no more fractures. The certainty of this evidence is low, and composites have improved since those trials.
• Amalgam rules in Great Britain. In England, Scotland and Wales, the UK version of the EU regulation on mercury applies²⁸. Under it, amalgam is not to be used for baby teeth, for children under 15, or for pregnant or breastfeeding women²⁹. The exception is when the dentist judges it strictly necessary because of the patient's specific medical needs. Northern Ireland follows the EU regulation instead, with separate arrangements for amalgam²⁸ that this page does not set out. We have not found a source for the rules on amalgam in Turkey; ask whether the clinic places amalgam fillings, and for whom.
• Glass ionomer. A tooth-coloured filling material that binds chemically to the tooth¹. If it is proposed, ask why it suits that tooth and how long it is expected to last.
• Ceramic. Porcelain, lithium disilicate and zirconia are used for laboratory-made inlays, onlays, veneers and crowns. Ceramic is more resistant to stains and wear than composite²; composite is easier to repair. See porcelain and dental ceramics and porcelain veneers.
• Gold. Gold fillings are usually made in a dental laboratory to fit your tooth, and need 2 appointments³⁰. Gold is sometimes used for molars.

For changes to the look of healthy teeth, a material is not always needed. If colour is the only concern, whitening may suit you better; orthodontic treatment moves crooked teeth instead of adding to them.

Composite and all of these alternatives are also available from dentists in the UK. A UK dentist can give you an independent opinion before you decide.

Ask for these details in writing before treatment.

• Which material is planned for each tooth: composite placed in the mouth, laboratory-made composite or another material, and why.
• The product name of the composite and its manufacturer.
• For laboratory-made composite, where it will be made.
• What the clinic's written terms say if composite chips, stains or comes off, including after you are back in the UK.
• Whom you should contact if that happens, and who pays for the repair and any travel.

Bring home for your UK dentist. Ask for a written record showing which teeth received composite and on which surfaces, with the material, product and shade. A dentist in the UK can then match a repair. Ask for copies of any X-rays as well. Turkey's health tourism regulation entitles international patients, on request, to free copies of the records of the materials used, the tests and the imaging³¹.

Aftercare. Problems that appear later are usually first seen by your own dentist in the UK. The General Dental Council suggests speaking to your own dentist³² before you consider treatment abroad; ask whether they will see you afterwards. The NHS website for England says the NHS is not liable for negligence or failure of treatment³³ when you have treatment abroad. It also says most travel insurance policies will not cover you for planned treatment abroad³³. That guidance is for England. Scotland, Wales and Northern Ireland run their own health services, with their own rules, which this page does not cover; if you live there, ask your dentist.

Your choice. Composite fillings and bonding are also available from dentists in the UK, and a UK opinion gives you something to compare. You can say no, or ask to stop, at any stage. Once a tooth has been prepared, that step cannot be undone. The questions the GDC and the NHS suggest you ask before treatment abroad are answered on composite bonding.