Teeth can show fine craze lines that never become a clinical problem. They can also crack through a cusp, under a filling, or down a root. The word crack does not tell a clinician which of those is present. A line in enamel is not the same finding as a tooth that separates when the patient bites on a specific cusp.
Pain from a crack is often inconsistent. It may appear only on release of biting, or only with cold, and then quiet for days. That pattern is a reason to examine the tooth, not a reason to guess. The examination can include drying the tooth, looking under magnification, a bite test, and sometimes removing an old restoration to see the floor beneath it. A radiograph may show nothing, because many cracks do not displace the pieces enough to appear on a film.
Treatment follows what the crack has already done. Observation can be reasonable for a symptom-free craze line. Covering the cusps can limit flex in a tooth that is still one piece. If the pulp is inflamed, root canal treatment may be discussed, and it still does not repair a crack. A tooth that is split into separate mobile pieces, or whose crack reaches far below the bone, may not be restorable.
A crown is not a guarantee that a crack will stop progressing, and extraction is not the first sentence of the visit. The honest account is the depth and direction that can be seen, the symptoms that fit, and the limits of what cannot be seen until the tooth is opened or removed.
