Meaning of Onlays

If the tooth damage is so great that a smaller filling is not sufficient for treatment, dentists often resort to so-called onlays. These are usually more durable than the standard fillings and often represent the ideal treatment when it comes to replacing larger areas of damaged tooth substance.

  • Unlike an inlay, an onlay (dome filling) includes not only the chewing surface of the corresponding tooth, but also at least one tooth cusp.
  • The greatest advantage over plastic tooth fillings, which are filled into the tooth as a malleable mass, is the significantly longer shelf life of onlays.
  • To ensure that the dome filling looks like the natural tooth, the dental technicians usually make it out of ceramic – but onlays made of gold and composite ceramic are also not uncommon.
  • Statutory health insurances only support the treatment with a fixed allowance, which corresponds to the standard care.

What are onlays?

Onlays differ from other forms of filling mainly in that they include the chewing surface of the natural tooth crown as well as lateral parts of the affected tooth. According to, an onlay is usually used when the damage to the tooth is so extensive that the treating doctor has to include the tooth cusps in the treatment. Unlike plastic fillings, an onlay is made in a dental laboratory. As a result, the dentist cannot insert an onlay directly into the tooth.

Differences to inlays, overlays and partial crowns

The differences between the different types of dentures are sometimes fluid and not immediately understandable, especially for laypeople. Sometimes the terms inlay, onlay, overlay and partial crown are even used as synonyms, although they are not. This is probably due to the fact that all of the mentioned types of dentures represent a partial replacement for an only partially defective tooth. The main distinguishing feature here is above all the extent of the dental prosthesis.

  • An inlay usually only comprises the inner chewing surface and sometimes also the interstitial surfaces of the tooth.
  • An onlay extends not only to the chewing surface, but also to at least one tooth cusp.
  • An overlay is a more extensive covering that also includes the sides of the teeth that are adjacent to the neighboring teeth.
  • A partial crown also has a side portion, which, unlike an overlay, extends to the gum transition.

What are the advantages of onlays?

The main advantage of onlays over conventional fillings is their significantly longer lifespan. Their advantage over partial and full crowns is that more tooth substance is retained with onlays, as the dentist has to grind the teeth less. Oral hygiene has a major influence on the durability of onlays – but this also applies to other forms of dentures.

What materials are available for onlays?

Today dentists mostly rely on ceramic onlays. Many patients choose this mainly because the material enables a very aesthetic result. The material can be adapted to the tooth color, which means that the result resembles a natural tooth. In addition, ceramics are considered to be insensitive to temperature and biocompatible.

Gold dome fillings were the norm in the past. Since they visually stand out very clearly from natural teeth whitening, gold is now rarely used as a material. However, the material is characterized by its high stability and durability. In addition, gold, like ceramic, does not usually cause allergies. So it is very well tolerated by the body.

Composite ceramic onlays are an inexpensive variant that usually consists of ceramic, quartz and plastic particles. Since the durability is significantly lower compared to pure ceramic versions, dentists rarely use composite ceramic onlays.

Onlays: the treatment process at the dentist

To restore a tooth with an onlay, at least two appointments with the dentist are necessary. First, the doctor prepares the tooth to be treated. To do this, he first removes all carious areas, if any. He then grinds the tooth a little to create optimal conditions for filling the dome. Then the doctor takes an impression. This serves as the basis for the dental laboratory to manufacture the onlay. But there are also methods in which a special camera creates a digital image of the tooth.

The patient receives a short-term temporary restoration for the period up to the completion of the dome filling. At the second appointment, the dentist first checks the accuracy of fit of the denture with the help of a try-in. Only then does he insert the onlay into the tooth cavity (cavity).

Does the statutory health insurance company bear the costs for onlays?

The statutory health insurance companies assume the costs of an onlay only proportionally. Patients receive a fixed allowance that corresponds to the costs of the respective standard care. In the case of a molar tooth this would be an amalgam filling and in the case of the front teeth a filling made of composite . The onlay costs depend in particular on the severity of the tooth defect and the material used. Patients should expect an own contribution of around 100 to 600 euros. With an additional dental insurance , the co- payment can be reduced even further.