Inlays.
An indirect inlay restores within the cusps without covering them. Where a cavity is too wide for a predictable direct restoration but the cusps are sound, it is the conservative answer.
Indirect over direct
The arguments for taking a cavity indirect are contour, contact and polymerization. A laboratory-processed restoration achieves proximal contact and anatomical form far more predictably than a large direct composite, and it polymerizes fully outside the mouth rather than shrinking against the cavity walls.
Polymerization shrinkage in a large direct restoration produces stress at the bonded interface, which is a contributor to post-operative sensitivity and to marginal breakdown over time.
The threshold is a matter of judgement, but a wide isthmus, a deep proximal box, or a restoration that will carry meaningful occlusal load all point toward indirect.
When an inlay is not enough
If a cusp is undermined, cracked, or thin enough that it will flex under load, an inlay leaves the problem in place. An intracoronal restoration wedges the cusps apart under function rather than holding them together.
Assess cusp thickness and look for existing crack lines before committing. Where a cusp is questionable, cover it — the restoration becomes an onlay and the tooth is considerably better protected.
The decision is set out in onlays.
Preparation
Divergent walls, so the restoration has a path of insertion. Rounded internal line angles, because sharp angles concentrate stress and are where ceramic cracks. A defined margin the laboratory can read unambiguously around its full circumference.
Margins should sit clear of occlusal contact where possible — a margin under a contact point is loaded exactly where it is most vulnerable. Proximal margins should be accessible for finishing and for cleaning.
Adequate isthmus width matters for the material's own strength, and it is one of the dimensions most often left too narrow.
Material
Lithium disilicate is the usual ceramic choice, bonded, where its adhesive interface contributes real structural support. Indirect composite is kinder to the antagonist and repairable. Cast gold remains the most durable and the most conservative in thin section.
The Rx form carries all three routes — IPS e.max, Tescera or Cristobal+, and full metal with the alloy specified.
Choose on isolation as much as on aesthetics. If the field cannot be controlled, a bonded ceramic inlay is the wrong selection.
Contacts and contour
Proximal contact is where indirect inlays earn their keep and where they most often need chairside adjustment. A contact established against an incompletely captured adjacent tooth will be wrong however well the restoration is made.
Capture the adjacent teeth in full, and specify the contact you want — the Rx offers normal, broad or point, with tightness normal or tight. A broader contact is more resistant to food packing than a point contact and takes longer to open if the teeth drift.
Marginal ridge height and embrasure form matter too. An inlay built with a low marginal ridge invites food impaction regardless of how tight the contact is.
What to put on the prescription
State that the restoration is an inlay rather than leaving it to be inferred, name the material and mark the tooth and surfaces on the design chart.
Give the shade with the guide named for anything tooth-coloured, the antagonist, and the interproximal contact form and tightness you want. Note the occlusal relief if you have a preference.
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