Ceramic Inlays and Onlays in Ukraine

Inlays, onlays and overlays replace the damaged part of the tooth's crown, not the whole crown. An inlay sits within the chewing surface between the cusps and does not cover them. An onlay covers one or more cusps. An overlay covers the whole chewing surface while keeping the tooth's own side walls. A separate option is the endocrown, a one-piece restoration for a root-treated tooth that anchors in the access cavity instead of using a post and core.

The difference from a filling lies in how it is made. A filling is built up directly in the mouth, and as the composite sets, its shrinkage pulls the tooth walls inwards; an inlay is made outside the mouth, on a model or digitally, so shrinkage affects only the thin layer of cement. In large cavities this gives a more accurate contact point with the neighbouring tooth, better cusp anatomy and a smoother margin where less plaque collects.

The difference from a crown lies in how much tooth is removed. For an all-ceramic crown the tooth is reduced all the way round; measurements on extracted teeth show this removes about two thirds of the crown's hard tissue. Partial restorations remove roughly half as much, and an inlay only a few per cent more than decay has already destroyed. For a vital tooth this matters: the more dentine is left, the lower the risk of pulp inflammation and root fracture.

The indications depend on the extent of the damage. A practical guide is the width of the cavity and the thickness of the walls: when the cavity spans more than half the distance between the cusps and a cusp wall is thinner than 1.5–2 mm, an ordinary filling is very likely to lead to a fracture. Typical situations include large cavities on the biting and contact surfaces with a lost marginal ridge, replacing an old amalgam or bulky composite filling, cracks in enamel and dentine, a worn biting surface, and root-treated back teeth with enough wall structure left.

Inlays are not needed for a shallow cavity: an ordinary filling is enough, and paying for an indirect restoration makes no sense. Nor are they made when almost no walls are left or the edge of the cavity runs deep under the gum: the area cannot be isolated with a rubber dam, and without a dry field adhesive bonding does not hold, so a crown is considered instead. Relative limitations include uncontrolled bruxism, active decay in several teeth at once, poor oral hygiene, and use of the tooth as a bridge abutment. MediUkraine is a treatment search and coordination service, not a clinic: we select the clinic and the doctor, agree dates and support you, while the dentist decides on the type of restoration after an examination and an X-ray.

An inlay sits within the chewing surface: it fills the cavity between the cusps, rests on the floor and walls, but does not cover the cusps. It is used when the tooth walls are intact and thick enough, and the only problem is that the cavity is too large for a reliable filling. The minimum thickness of ceramic at the narrowest point is about 1.5 mm: a thinner layer chips under chewing load, so the dentist would rather deepen the cavity by a fraction of a millimetre than accept a thin restoration.

An onlay covers one or more cusps and takes the load off a weakened wall. The rule of thumb is simple: a cusp thinner than 1.5–2 mm, or undermined from within by caries, is covered rather than left to bear load. The same applies to teeth after root canal treatment: once the marginal ridge is lost, the tooth loses rigidity and the risk of a wall fracturing during chewing increases many times over. An overlay is the next step: it covers the whole chewing surface but does not touch the side walls, so it suits worn teeth when the height of the tooth needs restoring without grinding it down all the way round.

For root-treated teeth there is a separate option, the endocrown. The restoration has an extension that reaches a few millimetres into the access cavity and acts as the retaining element, so a post and core are no longer needed. This preserves the dentine around the canal openings; drilling it away for a post used to account for a significant share of vertical root fractures. An endocrown works well on molars with enough cavity height; on premolars with a narrow pulp chamber the decision is made case by case.

The most common material is lithium disilicate. It is a glass ceramic with a flexural strength of about 350–400 MPa that etches well with hydrofluoric acid and therefore forms a strong chemical bond with the cement. It is translucent, so it suits both the smile zone and the back teeth; long-term studies show a high proportion of restorations lasting more than ten years. The downside is the thickness it needs, 1.0–1.5 mm on the biting surface; any thinner and the material is working at its limit.

Zirconia is stronger: from 1,000–1,200 MPa in the opaque generations to 550–800 MPa in the more translucent ones made for aesthetics. It allows a thinner restoration, from 0.5–1.0 mm, so it is chosen for bruxism and where vertical space is short. The trade-off is more complex bonding: zirconia does not etch with hydrofluoric acid, so the surface is sandblasted with aluminium oxide and a primer containing the phosphate monomer MDP is applied. Another feature is hardness: monolithic zirconia with an unpolished surface wears the enamel of the opposing tooth faster than glass ceramic, so after fitting the restoration is always polished rather than left rough.

Composite CAD/CAM blocks and hybrid ceramics with a polymer matrix are an intermediate option. They are softer, absorb impact better, are easier to adjust directly in the mouth and cost less, but over time they wear more and change colour. They make sense as a temporary or medium-term solution: for young patients whose bite is still developing, for heavy grinding or clenching where ceramic is too risky, or as an interim stage before definitive prosthetic work. For smaller cavities, a direct composite filling placed in the chair remains a valid option: it is cheaper and can be repaired.

The tooth is recorded with a digital scanner or a conventional impression. Intraoral scanning takes a few minutes, needs no impression tray and immediately shows on screen any areas where the preparation margin is unclear, so the dentist can correct this before you leave. From there, there are two routes. The first is milling at the clinic: the restoration is cut from a block in 10–20 minutes, crystallised in the furnace, glazed and bonded the same day. The second is the laboratory: the technician presses or mills the restoration and applies stains and glaze, which takes 3–10 working days, during which the tooth is protected by a temporary inlay.

The success of the work depends more on bonding than on the material. The tooth is isolated with a rubber dam, the ceramic surface is etched with hydrofluoric acid and treated with silane, the enamel and dentine with phosphoric acid and adhesive, after which the restoration is seated on a dual-cure or light-cure composite cement. Excess is removed before curing, the margin is polished, and the bite is checked with articulating paper at rest and during sideways jaw movements. Glass ceramic must not be fitted with conventional cement: it stays in place precisely because it is bonded to the tooth tissue.

It is also worth understanding the limits of the method. A partial restoration has to rest on the tooth's own walls, so when practically none are left, when the edge of the defect runs more than 1–2 mm under the gum and the field cannot be isolated, or when the tooth has to serve as an abutment for a bridge, a crown is chosen, sometimes after crown lengthening. This is not a failure but a different tool: a crown encircles the tooth and is held mechanically, so it does not need a perfectly dry field.

No one can predict how long a particular restoration will last without an examination: the outcome depends on the amount of remaining tissue, the state of the pulp, the nature of the bite and hygiene. A realistic conversation with the dentist starts not with promises but with what, in this particular tooth, speaks for and against a partial restoration.

In the first days after bonding the tooth may react to cold and to biting. This is a normal response to preparation and adhesive treatment of the dentine and usually fades within one to two weeks. If sensitivity has not eased after a month, gets worse, or pain appears for no reason, book an extra check-up rather than wait.

Pain only when biting usually means the restoration is slightly high, a fraction of a millimetre taller than it should be. The adjustment takes a few minutes: the dentist finds the spot with articulating paper, removes the excess and polishes the area. Do not put it off, because overloading a single cusp can lead to a crack.

The result can be fairly judged after about two weeks, once you stop noticing the tooth and your tongue has got used to the new shape. Until then, a feeling that "something is in the way" is normal even if the bite is correct. The colour of glass ceramic is stable from the start: unlike composite, it does not darken from coffee and wine, although plaque forms at the edge of the restoration just as it does on natural enamel.

You can usually chew on that side from the next day; for the first 24 hours, avoid very hard food while the cement reaches full strength. After that the restrictions are the usual ones for any restoration: do not crack fruit stones, ice or nuts in their shells, and do not open packaging with your teeth. Use floss as usual, but rather than snapping it upwards out of the gap, pull it out sideways.

A check-up is usually booked after a month, then every six months alongside professional cleaning. The dentist checks the restoration margin with a probe and on an X-ray, and assesses the surrounding gum and the bite, which changes over time. These check-ups catch secondary caries at the margin while refinishing and polishing are still enough.

Lifespan is best discussed as a range rather than a single figure. Clinical studies of ceramic partial restorations show that most of them last more than ten years, but some need attention sooner because of chipping, debonding or decay next to the restoration. The dentist can only estimate how long it will last in your case after an examination, taking into account the condition of the neighbouring teeth, the bite and hygiene.