What Causes a Black Spot on a Tooth That Isn't a Cavity?

You notice a dark mark on a tooth, usually in unforgiving bathroom light, and immediately assume the worst.

Sometimes decay is the answer. Frequently it is not. Several entirely different things produce dark marks on teeth, and they look broadly similar from the outside. What distinguishes them is texture, location, how they respond to a probe, and what shows on a radiograph — none of which can be assessed by looking in a mirror.

The reason it matters is that the treatment differs completely. Some causes are removed in twenty minutes at a hygiene appointment. Others need restoring. And a few dark marks are decay after all, which is why guessing is not a good strategy in either direction.

What are the usual explanations?

Most commonly, external staining from food, drink, smoking or certain mouthwashes; hardened tartar, which can appear dark particularly at the gum line; stained fissures — the deep grooves on back teeth trapping pigment without being decayed; existing restorations, since old amalgam can leave a grey shadow and worn composite can stain at its margins; and less commonly, chromogenic bacterial staining, trauma-related discolouration, or fluorosis. Decay is on the list too, which is why examination matters.

The most frequent cause. Chromogens from coffee, tea, red wine, dark berries, balsamic vinegar, soy sauce and curry bind to the pellicle layer on the tooth surface. Tobacco produces particularly stubborn dark staining. Chlorhexidine mouthwash — often prescribed for short periods after treatment — is well known for causing brown or black surface staining with prolonged use, as can iron supplements.

These stains sit on the surface, feel smooth or slightly rough, and are typically worse in areas that are cleaned less thoroughly. Our article on managing staining with tea and coffee covers this in more detail.

Plaque that is not removed hardens into calculus within a couple of days. It commonly forms just above the gum line on the inner surfaces of the lower front teeth and around the upper molars, and it picks up pigment readily, appearing yellow, brown or black. It is hard, rough to the tongue, and cannot be brushed off — it needs professional removal at a hygiene appointment.

Tartar also drives gingivitis, so a dark deposit at the gum line often comes alongside bleeding gums.

Molars and premolars have deep grooves on their biting surfaces. These can trap pigment and appear as dark lines without any decay being present. Distinguishing a stained fissure from early decay is a genuine clinical judgement, based on whether the surface is hard, whether it catches a probe, and radiographs. Where the fissure is sound but at risk, fissure sealants can protect it.

Old amalgam fillings can leave a grey or dark shadow through the surrounding tooth, sometimes visible from the outside on a tooth you had forgotten was filled. Composite fillings pick up stain at their margins over time, producing a dark outline. Neither is necessarily decay, but marginal staining does sometimes indicate leakage, so it warrants inspection.

A distinctive dark line following the gum contour, caused by particular pigment-producing bacteria. It is seen more often in children, is not associated with poor oral health, and tends to recur after cleaning. It is harmless but frustrating.

A tooth that has been knocked can darken from within, sometimes years later, as the pulp responds or dies. This usually affects the whole tooth rather than producing a spot, and needs assessment because it may require root canal treatment.

Usually white or brown mottling rather than a discrete black spot, but severe cases can include darker pitting. These are formed during tooth development and are permanent, though they can be masked cosmetically.

Enamel is the hard outer layer. Beneath it lies dentine, which is naturally more yellow and, if exposed by wear or enamel erosion, makes the tooth look darker overall. Decay changes the structure of these tissues — the surface becomes soft and catches a probe — whereas staining sits on top of intact enamel.

Location gives clues too. Marks between teeth or beneath the contact point are more concerning and often need radiographs, since decay there is invisible to direct inspection. Marks at the gum line more often relate to tartar or staining. Root surfaces exposed by receding gums are softer than enamel and decay more readily, so dark marks there are treated with more suspicion.

Book an assessment if:

• A dark spot has appeared or is enlarging

• The area feels rough, catches floss or catches your tongue

• You have tooth sensitivity to hot, cold or sweet at that spot

• You have toothache or pain when biting

• Food consistently packs into the area

• A dark line has appeared around an existing filling

• A single tooth has darkened, particularly after past trauma

• You simply want to know what it is

Do not attempt to scrape marks off with anything sharp — this damages enamel and gum and does not remove tartar.

Professional cleaning. Scaling and polishing removes tartar and most surface staining. Air polishing systems using fine powder are effective for stubborn stain and are compared with whitening in our article on air polishing versus teeth whitening.

Whitening. Useful for generalised discolouration within the tooth structure rather than surface deposits, and it does not lighten existing fillings or crowns. Our teeth whitening page explains the process and what it can and cannot address.

Restoration. Where the mark is decay or a failing filling, a white filling restores the tooth.

Cosmetic options. For persistent marks that cleaning and whitening do not resolve, composite bonding or porcelain veneers can mask them. These involve some alteration of the tooth and should be discussed carefully.

Sealants. For deeply grooved but sound back teeth.

• Brush twice daily for two minutes with fluoride toothpaste

• Clean between the teeth daily — most decay and staining starts where the brush cannot reach

• Attend hygiene appointments at the interval recommended for you

• Rinse with water after staining drinks; use a straw for iced coffee and cola

• Limit how often you have sugar rather than only how much

• Do not use chlorhexidine mouthwash long term unless advised to

• Stop smoking, which causes both heavy staining and gum disease

• Keep routine check-ups with radiographs at the recommended frequency

• A dark spot is not automatically decay

• Common non-decay causes are surface stain, tartar, stained fissures and existing restorations

• Stains sit on intact enamel; decay changes the structure and feels soft

• Marks between teeth and on exposed roots warrant more concern

• Radiographs are often needed, since much decay is invisible to direct inspection

• Cleaning removes tartar and stain; whitening addresses internal discolouration, not deposits

• Never scrape at a mark yourself

The NHS page on tooth decay explains how decay develops and how it is treated.

A dark spot on a tooth is worth having looked at, but it is not automatically bad news. A good proportion turn out to be stain or tartar and are dealt with in a single hygiene appointment.

The ones that matter are the ones that are quietly progressing between teeth where you cannot see them — which is the actual argument for having it checked rather than watching it.

To have a mark assessed, book an appointment at 22 Wimpole St, London W1G 8GQ, or call 020 7183 0692.

Dental symptoms and treatment options should always be assessed individually during a clinical examination.

This article is for general educational information only and is not professional dental advice, diagnosis, or a treatment recommendation. Information here is general and cannot replace an in-person assessment by a qualified, GDC-registered dental professional. Symptoms, suitability, fees, timelines, and outcomes vary according to individual clinical circumstances. If you have pain, swelling, or other concerning symptoms, seek prompt professional dental care. Always request a written treatment plan and cost estimate before proceeding with treatment.

Written Date: 1 September 2026 Next Review Date: 1 September 2027