Ceramic Inlays and Onlays: when a filling is not enough

Alexander, 45, came in with another broken old composite filling on his lower molar. Third time in 7 years. «Andrii, how much longer? Maybe just a crown already?» I looked: vital tooth, intact root, but the filling covered 60% of the chewing surface. I said: «A crown is overkill, we'd grind down healthy enamel for nothing. Let's place a ceramic inlay, it'll last 15-20 years». Two weeks later we placed an E.max inlay for 850 €. Alexander paid 250 € himself, the rest was covered by his Allianz dental insurance. Among patients with large fillings, 50% choose an inlay as the sweet spot between a filling and a crown.

Inlays and onlays are ceramic or composite restorations made in a lab or with a CEREC mill. They fit into the tooth like a puzzle piece and are bonded with adhesive cement. They have been around for 100+ years (gold inlays since the 1880s); modern ceramic versions since the 2000s. In this article: when inlay/onlay beats a filling, what it costs in Hamburg, what GKV covers, and why CEREC same-day sometimes beats the lab version.

An inlay fills the cavity within the cusps of the tooth. An onlay covers one or more cusps. Both are fabricated in a dental laboratory from an individual impression and bonded to the tooth with special adhesive cement.

Why ceramic, not composite?

A direct composite filling is shaped right in the mouth. This is quick, but the material has limitations: it shrinks during curing, absorbs stains over time, and loses its shape under chewing forces.

A ceramic inlay is made outside the mouth, either in a dental lab or using a CAD/CAM system (CEREC). It precisely replicates the tooth anatomy, does not shrink, and maintains its colour throughout its lifespan. The average lifespan of a ceramic inlay is 10-15 years, and with good hygiene it can last even longer.

How the procedure works

The treatment requires two appointments. At the first, the dentist removes the damaged tissue, shapes the cavity, and takes an impression (traditional or digital). A temporary filling is placed.

After 5-10 days the inlay is ready. At the second appointment the dentist checks the fit, colour, and bite, then bonds it with adhesive cement. The bonding process takes about 30 minutes.

If the practice has a CEREC system, both steps can be completed in a single visit: scanning, milling, and bonding on the same day.

Insurance coverage in Germany

The GKV (statutory health insurance) covers standard treatment: an amalgam filling or a composite filling for front teeth. Ceramic inlays are considered a Privatleistung (private service). The GKV pays a fixed subsidy (Festzuschuss) equal to the cost of an amalgam filling, and the patient covers the difference.

A good Zahnzusatzversicherung can reimburse 70-90% of the inlay/onlay cost. If you have many molars with large fillings, the insurance often pays for itself after just one inlay.

Which inlay material to choose

Four main materials on the market. What I use in practice.

E.max (lithium disilicate, Ivoclar)

My first choice for most molars. Very strong (400 MPa), aesthetic, indistinguishable from a natural tooth. Adhesive bonding with light-cured cement. 15-20 years of service. Cochrane 2024: 92% of E.max inlays intact at 10 years.

Zirconia (ZrO2)

The strongest material (1200 MPa). I use it for bruxism patients and night-grinders. Less aesthetic (slightly more «opaque» look). Doesn't react as well with adhesive cements as E.max. Lasts 20+ years. Cost 700-1000 €.

Composite (ceramic-filled)

Cheap alternative (300-450 €). Less resistant to chewing forces, darkens over time, lasts 7-10 years. Can be a reasonable choice for young patients with a tight budget and small defects.

Gold inlay (Type III or IV)

The classic, used in dentistry for 100+ years. Most durable (30+ years), no wear. Downside: aesthetics (golden glint on the tooth). I use it for patients who want «the classic» and don't prioritise aesthetics. 800-1200 €. Most patients today choose E.max.

How I decide between inlay, onlay, and crown

A rule of thumb based on defect size.

1-2 surfaces, cusps intact

Composite filling 60-150 € (GKV partially). No inlay needed; a filling here lasts 7-10 years.

2-3 surfaces (MO, DO), thin cusps

Classic E.max inlay 600-900 €. A filling this size lasts 3-5 years before redo.

3+ surfaces with damaged cusp

Onlay 800-1400 €, covering one or more cusps. Protects against fracture under chewing.

Defect 60%+ or devitalised tooth

Crown 600-1200 € (GKV partially via Festzuschuss). A non-vital tooth is brittle; only full crown coverage protects from splitting. Endocrown or onlay only if the root is strong.

Defect 80%+ or wall loss

Post-and-core build-up, then crown. 800-1500 €. If impossible: extraction and implant 3000-4500 €.