A brown spot on a tooth is not always decay that needs a filling. Some brown marks are old decay that has stopped and hardened, some are stain on the surface of the tooth, and some are changes in the enamel that formed while the tooth was developing. Others are decay that is still active. Colour is only part of the picture: how the surface looks and feels, where the spot sits and whether it is changing over time also help a dentist tell these apart.
Colour alone does not tell a dentist much
It seems logical that a darker spot would be worse, but the criteria used to judge decay activity do not rank spots by how dark they are. The Nyvad criteria, described by researchers at Aarhus University in Denmark, separate active from inactive decay mainly by the texture and surface of the lesion. As described in a 2023 review by Abdelaziz in Diagnostics, an active early lesion in enamel is whitish or yellowish, opaque and has lost its lustre, and it feels rough when a probe tip is moved gently across it. An arrested (inactive) enamel lesion may be whitish, brownish or black, may be shiny, and feels hard and smooth. Arrested decay that has formed a cavity into the dentine is mostly dark, with dentine that is shiny and hard on gentle probing.
In other words, a brown, glossy, hard spot matches the description of a lesion that has stopped. A chalky, dull white patch near the gum line can be the more active one.
Decay can stop at any stage
Tooth decay is not a one-way process. The Australian Dental Association's patient site explains that acid made by bacteria dissolves minerals from the enamel, while saliva and fluoride help neutralise the acid and put minerals back. Abdelaziz describes decay activity as reflecting this mineral balance over time, which can mean net loss, net gain or stability. A 1997 review by Nyvad and Fejerskov noted that clinical observations suggest decay can be arrested at any stage of its development, provided the surface is kept clinically free of plaque.
Our article on whether early decay can be reversed explains the remineralisation process in more depth.
Active spots are more likely to get worse
The distinction matters because activity is linked to what happens next. A 2018 review by Nyvad and Baelum in Caries Research reported that active non-cavitated lesions were at higher risk of progressing to a cavity or a filling than inactive non-cavitated lesions.
A 2025 cohort study by Abdalla and colleagues followed 322 adults working at a factory in Belarus for two years. Most early lesions, active or inactive, did not progress. The share of each type of lesion that did progress was:
| Type of early lesion at the start | Share that progressed within 2 years |
|---|---|
| Active, surface intact | 24% |
| Active, with a tiny break in the surface or a shadow underneath | 31% |
| Inactive, intact or with a tiny break or shadow | 15% |
Lesions between the teeth and in the pits and grooves of the teeth were also more likely to progress than those on smooth surfaces. The people in the study had high levels of active decay, and the authors noted that the findings apply to groups with similar characteristics, so the numbers may differ for people at lower risk.
Brown marks that are not decay
Several other things can discolour teeth or leave marks:
- Surface stain. Healthdirect lists tea, coffee, red wine and smoking as things that can stain the outside of the teeth, and lists a clean by a dental professional as one option for stained teeth. Our article on dark stains on front teeth covers this.
- Black stain. Light brown to black dots or dark lines along the part of the tooth nearest the gums, of bacterial origin and more common in children. A 2026 systematic review by Boukhancha and colleagues cited a reported prevalence of 2.4% to 20%, and noted that it often comes back after scaling and polishing.
- Fluorosis. Changes in the enamel that form while teeth are developing. A 2018 report by Mejàre noted that it is in the preschool years that too much fluoride intake may result in fluorosis. In their 1978 study, Thylstrup and Fejerskov found that the visible signs matched the degree of porosity under the enamel surface, and that in more marked cases some surface enamel was lost, probably after the teeth came through. Our article on fluorosis marks explains the grades.
- Silver diamine fluoride. A dentist may use this to help stop early decay in suitable cases. It stains the decayed area black, which is expected. Our post on silver diamine fluoride covers who it suits.
- Old fillings and their edges. Staining around the edge of a filling is hard to interpret. In a 1996 study by Kidd and Beighton, staining at the margins of tooth-coloured fillings did not reliably predict decay underneath; only an obvious carious lesion at the margin did. A dentist or OHT can check the edge of the filling.
What happens at a check-up
The systems used to assess decay, such as the International Caries Detection and Assessment System (ICDAS) and the Nyvad criteria, are based on a tooth surface that has been cleaned and dried, because some early changes are only visible once the surface is dry. The ICDAS descriptions use air drying for about five seconds. The Nyvad criteria combine looking closely at the surface with moving a probe gently across it to feel its texture.
X-rays can help with spots between the teeth, which cannot be seen directly, and with judging how deep decay reaches into the dentine. They have limits for early lesions on biting surfaces. In a 1997 laboratory study of 100 biting surfaces of extracted teeth, Ekstrand and colleagues found that X-rays could not detect decay limited to the enamel, although they were an excellent predictor of softened dentine.
A stopped spot often needs watching, not drilling
An inactive brown spot that is hard, shiny and not breaking down may not need a filling. Abdelaziz notes that even inactive lesions should receive routine care and monitoring, which usually means keeping the area clean, continuing to use fluoride toothpaste and checking it again at future visits. Our article on watching a small cavity or filling it explains how that decision is made.
An active lesion calls for a closer look at what may be driving it, such as diet, how well the area is cleaned and the use of fluoride. Abdelaziz notes that lesions without a cavity may be stopped with fluoride and calcium-based products, or sealed if that does not work, while a cavity with exposed dentine usually needs a filling.
If a stopped brown spot on a front tooth bothers you for how it looks, that is a separate decision. Your dentist can talk through cosmetic options, such as composite bonding, and whether they suit the size and depth of the mark.
For dentists: clean, dry and move the probe gently
Activity calls rest on a clean, dry surface. Abdelaziz notes that the clean and dry for 5 seconds step is not always applied in practice. The ICDAS II summary by Dikmen (2015) states that white spot lesions only visible after air drying are limited to the outer half of the enamel, while a white or brown lesion visible without drying lies somewhere between the inner half of the enamel and the outer third of the dentine. Know where this comes from: it is based on Ekstrand and colleagues' 1995 histological work on the occlusal fossae of 140 extracted third molars. Wet then dry gives a rough indication of depth on occlusal surfaces, not a measurement, and it does not replace radiographs where dentine involvement is suspected.
For texture, the Nyvad descriptors are based on moving the probe tip gently across the surface. Roughness and loss of lustre suggest activity; a hard, smooth, shiny surface suggests arrest. Expect some uncertainty. In the original reliability study by Nyvad and colleagues (1999), carried out in 50 children with high caries experience, inter-examiner kappa values were 0.78 to 0.80 and intra-examiner values 0.74 to 0.85, but 81.6% of all misclassifications involved non-cavitated lesions. Disagreement was more often about whether a surface was sound or had a non-cavitated lesion (about 31%) than about active versus inactive (10.6%), and a non-cavitated active diagnosis was reconfirmed on re-examination 68.7% of the time. Abdelaziz recommends categorising lesions as active or arrested and continuing to monitor their status, so recording the finding and reassessing at later visits adds information a single look cannot.
Common questions about brown spots
Will whitening remove a brown spot?
The NHS notes that whitening can only lighten the colour of natural teeth, and it is not a treatment for decay. Healthdirect advises that whitening is not recommended if you have untreated dental problems or holes in your teeth, so it makes sense to have a brown spot checked first, as the NHS also advises. Whitening also will not change the colour of fillings, crowns or veneers.
Can I scrape a brown spot off at home?
It is best not to. Healthdirect warns that using abrasive home methods such as baking soda or charcoal often may damage your teeth. Having the spot checked tells you what it is before anything is done.
Why does my brown spot look the same as it did years ago?
A spot that has stayed the same in size, colour and texture over several check-ups, and is hard and shiny, is consistent with an inactive lesion. Comparing dental records over time helps a dentist judge this.
Having a spot checked
If you have noticed a brown mark on a tooth, a check-up with a dentist or OHT at our general dentistry practice in Melrose Park can help work out whether it is stain, an old stopped lesion or something that needs treatment. You will usually receive a written treatment plan after the examination, often by email.
Sources
- Abdelaziz M. Detection, diagnosis, and monitoring of early caries: the future of individualized dental care. Diagnostics, 2023. PubMed 38132233
- Nyvad B, Fejerskov O. Assessing the stage of caries lesion activity on the basis of clinical and microbiological examination. Community Dentistry and Oral Epidemiology, 1997. PubMed 9088694
- Nyvad B, Baelum V. Nyvad criteria for caries lesion activity and severity assessment. Caries Research, 2018. PubMed 29506010
- Nyvad B, Machiulskiene V, Baelum V. Reliability of a new caries diagnostic system differentiating between active and inactive caries lesions. Caries Research, 1999. PubMed 10343087
- Abdalla H and colleagues. Caries lesions progression in adults: a prospective 2-year cohort study. Community Dentistry and Oral Epidemiology, 2025. PubMed 39160698
- Ismail AI and colleagues. The International Caries Detection and Assessment System (ICDAS). Community Dentistry and Oral Epidemiology, 2007. PubMed 17518963
- Dikmen B. ICDAS II criteria. Journal of Istanbul University Faculty of Dentistry, 2015. PubMed 28955548
- Ekstrand KR, Kuzmina I, Bjørndal L, Thylstrup A. Relationship between external and histologic features of progressive stages of caries in the occlusal fossa. Caries Research, 1995. PubMed 7656292
- Ekstrand KR, Ricketts DN, Kidd EA. Reproducibility and accuracy of three methods for assessment of demineralization depth of the occlusal surface. Caries Research, 1997. PubMed 9165195
- Kidd EA, Beighton D. Prediction of secondary caries around tooth-colored restorations: a clinical and microbiological study. Journal of Dental Research, 1996. PubMed 9033448
- Thylstrup A, Fejerskov O. Clinical appearance of dental fluorosis in permanent teeth in relation to histologic changes. Community Dentistry and Oral Epidemiology, 1978. PubMed 282114
- Mejàre I. Current guidance for fluoride intake: is it appropriate? Advances in Dental Research, 2018. PubMed 29461106
- Boukhancha O and colleagues. Alternative strategies for managing dental black stains: a systematic review. Dentistry Journal, 2026. DOI 10.3390/dj14100638
- Australian Dental Association. Tooth decay. teeth.org.au
- NHS. Teeth whitening. nhs.uk
- Healthdirect Australia. Teeth whitening. healthdirect.gov.au
This article is general information only and is not a substitute for an in-person assessment by a dental professional.
