Clinical positions, and the criteria behind them

A veneer is declined when the complaint is colour alone and the enamel is intact, because whitening and, if needed, direct composite can address colour without removing sound tooth. It is declined when the teeth are crowded or rotated and the request is to mask the position rather than correct it, because covering a rotation means cutting into the tooth to make room for the covering. It is declined when active wear, untreated gum disease, or an unmanaged grinding habit is present, since those change the surface the veneer would bond to.

The position changes when the enamel is already lost, when a previous restoration has failed and the tooth needs coverage regardless, or when correcting position orthodontically has been offered, understood, and declined by the patient. In that last case the veneer is a compromise made knowingly, which is a different thing from a veneer offered as the first option.

A crown is recommended only when enough tooth structure has already been lost that a partial-coverage restoration cannot be retained or cannot protect the remaining cusps. The test applied is whether an onlay would leave a sound wall standing. If it would, the onlay is used. The reason this matters is that the two options are not far apart in longevity: a systematic review in the Journal of Oral Rehabilitation reported mean survival of 93.5% for onlays against 95.4% for full crowns, both above 90% at five years, while the crown is the one that removes the wall.

A crown is not recommended to change the shape or colour of a structurally sound tooth, and it is not recommended on a tooth that has simply been root treated, since a root filled tooth with intact walls does not automatically need full coverage. Where a crown is genuinely indicated, the preparation is kept to what the material requires and no more.

The default is to keep the tooth. A natural root that can be cleaned, sealed and restored is preferred to removing it and replacing it with something manufactured, because the replacement resets a clock that the original tooth was not running. Extraction is supported when the tooth cannot be restored without violating the biological width, when a vertical root fracture is confirmed rather than suspected, or when keeping it would put a neighbouring tooth at risk.

What does not by itself justify removing a tooth: the treatment being longer, the outcome being less certain than an implant, or the tooth having been treated before. Uncertainty is a reason to stage the work and reassess, not a reason to remove the tooth while it is still asking to be kept.