Porcelain inlays and onlays
in Levallois-Perret, near Paris

Inlays, onlays and overlays are three types of partial porcelain restorations, which differ in how much of the tooth surface they cover. An inlay fills an internal cavity between the cusps of the tooth, without touching their tips. An onlay covers one or more cusps as well as the internal cavity, which reinforces the weakened tooth. An overlay covers the entire biting surface, including all the cusps, without encircling the tooth like a crown. The choice between these three options depends on the amount of healthy tissue remaining and the mechanical forces on the tooth to be restored.

The choice between a direct composite filling and a porcelain inlay or onlay depends on how much tissue has been lost and on the area to be restored. Layered composite is well suited to moderate decay and localised cosmetic corrections, in a single appointment in the chair. However, when the tissue loss exceeds 30 to 40% of the crown of the tooth, a porcelain inlay or onlay offers better mechanical strength, better colour stability over time and a more natural look thanks to pressed porcelain. This indirect restoration, made in the laboratory from a precise impression, also allows a fit accurate to the millimetre between the cusps.

A porcelain inlay or onlay is a conservative alternative to a crown when the tooth can still be preserved. Whereas a crown requires the tooth to be prepared all the way around, an inlay or onlay preserves as much healthy tooth tissue as possible by covering only the damaged areas. This approach is part of a biomimetic dentistry that respects the natural anatomy. At Dr Bruno Abehassera's practice in Levallois-Perret, an inlay or onlay is always favoured whenever the clinical conditions allow, with the reversibility and long-term function of the treated tooth in mind.

Yes, inlays and onlays in pressed porcelain (lithium disilicate) are very strong indirect restorations. This material has a flexural strength of between 360 and 400 MPa, which makes it well suited to the forces on the back teeth. Once bonded following a strict adhesive protocol, the inlay or onlay forms a single unit with the tooth, able to withstand significant chewing forces. Strength also depends on the quality of the tooth preparation and the skill of the dental ceramist.

A porcelain inlay or onlay looks very close to a natural tooth. Pressed porcelain has optical properties (translucency, opalescence, fluorescence) that closely mimic tooth enamel. The dental ceramist's work is to reproduce the exact shade of the neighbouring tooth, as well as the characteristics specific to the patient's smile: shade transitions near the gum, surface effects, and incisal mamelons for the front teeth. Cases carried out at the practice can be seen on the Before & After page dedicated to inlays, onlays and overlays.

A correctly indicated and bonded porcelain inlay or onlay has a long lifespan, generally longer than that of a direct composite filling. Its longevity depends on several factors: the quality of the adhesive bonding, the patient's oral hygiene, whether or not there is uncontrolled bruxism, and attending regular check-ups. A yearly visit to the practice makes it possible to check that the bond is intact, that there is no recurrent decay at the margins and whether the biting contacts show any wear. No restoration lasts forever, but a porcelain inlay or onlay remains a very durable option among conservative restorations.

No, inlay or onlay treatment is not painful when carried out in good clinical conditions. The tooth is prepared under local anaesthesia, so the procedure is usually painless or nearly painless. Between the first and second appointments, a temporary restoration is placed to protect the tooth and allow comfortable chewing. The final porcelain inlay or onlay is usually placed at the second appointment without further anaesthesia. Some temporary sensitivity may appear in the days after bonding, but it fades quickly and usually needs no particular treatment.

A porcelain inlay or onlay usually requires two appointments, one to two weeks apart. The first appointment includes the clinical examination, the minimally invasive preparation of the tooth, a digital or conventional impression, and the placement of a temporary restoration. The impression is then sent to the dental ceramist, who makes the custom inlay or onlay in pressed porcelain. The second appointment, about two weeks later, includes the try-in, a check of the fit at the margins, then the final adhesive bonding under rubber-dam isolation. The placement appointment lasts on average 30 minutes to 1 hour.

A root-treated tooth does not always need a full crown. When the tissue loss remains moderate and the remaining walls are sufficient, a porcelain onlay or overlay is enough to protect the tooth against fractures, while preserving as much healthy tissue as possible. This approach avoids the invasive all-round preparation required for a crown, which can further weaken a root already weakened by root canal treatment. The choice between an onlay, an overlay and a crown is made after a precise analysis of the remaining damage, the quality of the root anchorage and the expected forces of the bite.

A porcelain inlay or onlay is cared for exactly like a natural tooth. Thorough brushing twice a day, together with daily use of dental floss or interdental brushes at the contact points between teeth, is enough to keep the bond intact and prevent recurrent decay at the margins. A yearly check-up at the practice makes it possible to check for any leakage, the condition of the bond and any wear of the biting contacts. If bruxism is confirmed, wearing a custom-made night guard is recommended to protect the inlay or onlay from grinding forces.

Unlike a full crown, a porcelain inlay or onlay preserves most of the tooth tissue, which allows some flexibility in treatment if a complication arises. If a fracture at the margin or recurrent decay occurs at the edge of the inlay or onlay, it is usually possible to remove the restoration and replace it with a new custom inlay or onlay, without having to prepare the tooth for a crown. Pressed porcelain, however, cannot be repaired directly in the mouth: it must be replaced entirely in the event of a significant fracture. This relative reversibility is one of the great advantages of an inlay or onlay over a traditional crown.