Smile Simulation & AI
The prepared tooth under a translucent restoration shifts the final colour — and most briefs never mention it. Here is the stump shade problem, the ND1–ND9 guide, and how to photograph it so the case comes back right.
Simulated preview — a visualization aid, not a guaranteed outcome.
The stump shade — the colour of the prepared tooth — shows through translucent ceramics and shifts the final result, yet most cosmetic briefs never record it, which is why technically perfect restorations come back too grey or too dark at the neck. The ND1–ND9 guide exists precisely to communicate this, and a single good photograph does more than any letter code. Here is the stump shade problem in plain terms, and how to solve it before the case ever leaves the room.
The stump shade is the colour of the prepared tooth — the “stump” left after the dentist reduces it for a crown or veneer. It matters because modern all-ceramic restorations are translucent to look lifelike, and translucency means the substrate underneath is a partner in the final colour, not a hidden foundation. Two identical restorations placed over two different stumps will look different in the mouth. The stump shade is the missing variable that explains why a case built to the right target shade can still come back wrong: the ceramist matched the target but never knew what was underneath.
ND1–ND9 is Ivoclar's Natural Die shade guide, a set of nine tabs representing prepared-tooth colours from light (ND1) to dark (ND9). It gives the dentist and ceramist a shared vocabulary for the stump specifically, separate from the tooth-shade guides used for the target. Holding the ND guide against the prepared tooth and recording the closest match tells the ceramist how light or dark the substrate is, which in turn drives the opacity decision. It is a small, cheap tool that closes one of the most expensive information gaps in cosmetic dentistry.
Because light passes into a translucent restoration, interacts with the substrate, and comes back out carrying the substrate's influence. A bright, healthy stump reflects light cleanly and supports a vital, natural result. A dark, discoloured, or non-vital stump absorbs and greys the light, dragging the restoration down in value and warmth no matter how skilfully it was layered. The restoration is not the whole optical system — the stump is half of it. Ignoring the stump shade is like judging a stained-glass window without knowing whether it is backlit by sun or by shadow.
Because a photograph carries information a letter cannot. A note that says “ND5” tells the ceramist a category; a photo of the ND tab held against the actual prep, in natural light, shows the true colour, its distribution, any dark spots or discoloured cores, and how sharply it varies across the tooth. It also lets the ceramist calibrate your lighting and camera against a known reference. The photo turns an approximate label into an accurate picture, and accuracy on the substrate is what prevents the value remake. One good stump-shade image is among the highest-value things you can put in a case.
Do it immediately after preparation, before the tooth dehydrates or bleeding obscures it, and before the isolation dries everything to a false brightness. Hold the closest ND tab edge-to-edge with the prepared tooth so the two colours sit in the same plane and light. Use natural light where you can, avoid direct flash glare that washes out the true value, and take both a close view and one showing the prep in context. If the stump is uneven — a dark core, a discoloured area — capture that explicitly, because those are exactly the spots the ceramist needs to mask. A careful thirty-second photo here saves a fortnight later.
The ceramist chooses opacity blind. They will make a reasonable assumption — often that the stump is average — and if it is not, the case comes back wrong: grey at the cervical, low in value, or dark where a post or core bled through. The dentist sees a beautiful shade match to the target and cannot understand why it looks dull in the mouth; the answer is the substrate no one documented. Skipping the stump shade is not saving a step; it is deferring a remake. The related shade failures are catalogued in why cases come back the wrong shade.
They are two ends of one decision. The stump shade tells the ceramist how much substrate influence they are fighting, and the opacity code — HT, LT, MO, HO — is how they fight it. A light ND stump can carry a translucent HT ingot; a dark ND stump or a metal core points toward MO or HO to mask it. Send the stump shade and the ceramist can pick opacity confidently; withhold it and even a master ceramist is guessing. The opacity side of the story is in the e.max opacity guide.
A preview handles the target — the look the patient approved — and has nothing to say about the stump, which is a clinical measurement the dentist takes. The two are complementary: the preview aligns everyone on the aesthetic destination, and the stump-shade photo tells the ceramist how to reach it over this particular substrate. A preview is a visualization aid, not a guarantee, not a substitute for stump documentation, and it never prints a stump shade or an opacity. Keeping the aesthetic and the clinical inputs in their own lanes is what makes the whole case predictable.
Six habits eliminate the value remake.
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