Single dark tooth — why one tooth turns grey and how internal bleaching works

Key facts

• Trauma and nerve damage are the most common causes
• A grey tooth should always be checked with X-rays
• Internal bleaching is for teeth with a sound root canal filling
• Crowns or veneers suit heavily filled or broken teeth
• Swelling or a gum bump needs prompt assessment

Why one tooth changes colour

The most common cause is trauma, sometimes years earlier. A blow to a front tooth can cause bleeding inside the pulp, and the blood breakdown products seep into the dentine, giving a pink, grey or brown tint. If the nerve dies, the tooth often becomes progressively greyer. Other causes include old root canal treatments where material left in the crown of the tooth stains it, dark metal fillings showing through, internal resorption, and decay. Occasionally a tooth turns yellow because the pulp chamber gradually fills with hard tissue after an injury, making the tooth more opaque.

Is a grey tooth a dead tooth?

Not always, but a grey tooth should always be checked. The dentist tests how the tooth responds to cold and other stimuli, looks at it on an X-ray for signs of infection at the root tip, and asks about past injuries. Some teeth darken after trauma but stay alive and even lighten a little over time. Others have a dead nerve that can become infected without causing pain at first. Warning signs include swelling of the gum, a small pimple-like bump near the root, tenderness when biting or a bad taste. These need prompt assessment, as root canal treatment may be required before any cosmetic step.

How internal bleaching works

Internal bleaching, sometimes called walking bleach, is used on teeth that have already had a sound root canal treatment. The dentist opens a small access cavity from the back of the tooth, seals the root filling with a protective barrier, and places a whitening agent inside the crown of the tooth. The opening is closed with a temporary filling, and the agent works from the inside out over several days. The process may be repeated once or twice until the shade is close to the neighbouring teeth, and then the access cavity is sealed with a tooth-coloured filling. Internal bleaching often works well on a dead tooth that has been properly root treated, although colour can relapse over the years.

Internal bleaching vs crown or veneer

Internal bleaching is conservative because it keeps the natural tooth structure. A veneer or crown may be the better option when the tooth is heavily filled, broken, very dark despite bleaching, or when its shape also needs improving. Veneers cover the front surface and need some enamel preparation, while crowns cover the whole tooth and are often suggested for root-filled back teeth or weakened front teeth. Sometimes internal bleaching is done first to lighten the base colour so a thinner veneer can mask it more naturally. External whitening of all teeth may also be planned so the final shade matches.

Treatment for a single dark tooth in Dubai at Manhal

At Manhal Medical Center in Dubai, Dr. Fariba Alnoory, a general dentist with more than 14 years of experience, assesses a discoloured tooth with a clinical examination, vitality tests and X-rays. She explains whether the nerve is healthy, whether root canal treatment is needed first, and whether internal bleaching, a crown or a veneer is likely to give the most natural match. If a more complex restoration is needed, the clinic’s team can coordinate it. You receive a written treatment plan and aftercare advice, including protecting front teeth during sports. Consultations are available in English and Arabic.

Professional whitening uses dentist-controlled gels to break down stains inside the enamel. It lifts discolouration from coffee, tea, tobacco and age, and is checked first to make sure gums and fillings are healthy.

Prepared by the Manhal Medical Center editorial team · Updated: 2026-10-18 · Treating specialist: Dr. Fariba Alnoory

This page is general information and does not replace a consultation. Suitability, risks and results vary between patients.