A dentist has suggested painting a liquid on your child's cavity instead of filling it, and has mentioned that the tooth will go black.
In silver diamine fluoride (SDF) treatment, a dentist paints a liquid onto a cavity in a milk tooth (a baby tooth) to stop the decay. There is no drill and no injection. The treated decay turns black and stays black until the tooth falls out or is covered with a filling. Healthy parts of the tooth, and the adult tooth underneath, do not stain.
It stops most of the cavities it is used on, not all of them, and it often needs a second coat. Whether it suits your child depends on which tooth, how deep the decay goes, and how your family feels about a black mark.
This page covers what turns black and what does not, how well SDF stops decay, when it is the wrong choice, how it compares with a filling, and what happens at the appointment.
Does silver diamine fluoride turn teeth black?
Yes, but only the decayed part. This is the question parents ask most, so here is exactly what changes colour and what does not.
Before SDF
- The cavity: soft and brown, still spreading
- Healthy enamel around it
- The adult tooth, forming in the gum
After SDF
- The cavity: hard and black, no longer spreading
- Healthy enamel: unchanged
- The adult tooth: not stained
- The decay turns black. The soft, decayed part hardens and darkens, and the dark colour is the sign it has worked. The American Academy of Pediatric Dentistry (AAPD) describes the colour as permanent unless the spot is covered with a filling.
- Healthy enamel does not. SDF darkens decayed and weakened surfaces, not sound ones. That is why the dentist keeps the liquid to the cavity.
- The adult tooth is not stained. The black stays in the milk tooth and leaves with it.
- Skin, lips and gums can mark briefly. If the liquid touches them, a brown mark like henna can appear. It fades within 2 to 14 days on skin, and within one to three weeks on the gums and lips.
- Clothes stain for good. That is why your child wears a bib.
Can the black be covered? Yes. Once the decay has stopped, the tooth can be filled, which improves how it looks.
Is there an SDF that does not stain? Some dentists paint a second liquid, potassium iodide, straight after SDF to lighten the colour. A 2020 review of six studies found the evidence for a real, lasting difference is not strong enough yet.
How do other parents feel about it? In a survey of 120 parents in New York and New Jersey, 67.5% found the black acceptable on a back tooth, but only 29.7% on a front tooth. When the alternative was treatment under general anaesthesia, acceptance rose to 68.5% for back teeth and 60.3% for front teeth. Both kinds of answer are reasonable. Ask to see a photo of a treated tooth before you decide. The AAPD recommends showing one.
What is SDF treatment, and how does it work?
Two ingredients, two jobs. The silver kills the germs inside the cavity. The fluoride hardens the weakened tooth around it. The decay stops spreading, and the spot turns hard and dark.
It does not fill the hole. The cavity is still there, now hard and inactive instead of soft and growing. If the hole traps food, or the shape of the tooth matters, a filling can go over it later.
Does SDF actually stop cavities?
Usually, and more reliably with a second coat. These are the results from trials in young children.
| Study | Children | Cavities stopped |
|---|---|---|
| 2016 review of 8 studies | Milk teeth, 38% SDF | 81% |
| Hong Kong trial, 30 months | 888 children aged 3 to 4 | 75.7% with a coat twice a year, 66.9% once a year |
| Kerala trial, 12 months | 80 children aged 2 to 6, 440 teeth | 78.2% twice a year, 58.4% once a year, 80.5% with four coats in two months |
| Oregon trial, 2 to 3 weeks | 66 preschool children | 72%, against 5% with a look-alike liquid that had no medicine in it |
It does not work on every cavity, and one coat can wear off. The AAPD notes that after a single coat, half the cavities that had stopped at six months were active again two years later. That is why SDF comes with re-checks and, often, a second coat every six months. Cavities on front teeth stop more often than those on back teeth.
When is SDF the right choice, and when is it not?
SDF is not right for every cavity, and a dentist should be able to tell you why it fits this one.
It is usually considered when:
- there is a real hole, with no sign the nerve is involved, and your child cannot manage a filling yet: very young, very frightened, or with a medical or developmental need;
- there are several cavities that cannot all be treated in one visit, and they need stopping while the rest are dealt with;
- the cavity is difficult to treat in the usual way.
It should not be used when:
- the tooth hurts on its own, wakes your child at night, or the gum or face is swollen. These are signs the nerve inside is inflamed or infected;
- the decay has reached the nerve;
- your child is allergic to silver, or has raw or painful sores in the mouth.
It is not needed when the mark is a chalky white patch with no hole. Fluoride varnish is the usual choice there.
It is your call when the cavity is on a front tooth and a black mark is not acceptable to your family. There are other ways to treat it.
Before you agree, these are fair questions to ask:
- Is this a hole, or a white patch with no hole?
- How close is it to the nerve? Has it hurt on its own?
- Is there a photo of a treated tooth to look at first?
- How often will it need another coat, and when is the re-check?
- Can it be filled later, to cover the black?
If you are weighing whether a milk tooth is worth treating at all, which milk teeth stay until nine to twelve is the place to start.
SDF or a filling?
SDF is not a filling. It stops the decay where it is. A filling removes the decay and rebuilds the tooth.
| Question | SDF | Filling |
|---|---|---|
| What it does | Stops the decay where it is | Replaces the decayed part of the tooth |
| Drill or injection | No | The decay is usually removed first |
| How it looks | Black on the treated spot | The tooth is rebuilt |
| What comes next | A re-check, and often another coat | Routine checks |
Studies that compare the two do not show one clearly ahead. In a New York trial in 48 schools, 1,668 children aged 5 to 13 were analysed: 38.3% of SDF-treated surfaces and 45.5% of surfaces with a simple hand-placed filling had decay come back, a difference too small to be sure of. A 2026 review of eight trials in milk teeth found no clear difference in how many cavities stopped, and warned that the studies varied too much to call them equal.
You do not always have to choose. SDF can stop the decay now, and a filling can go on later, which also covers the black.
If a filling is the right plan but your child cannot manage it awake, laughing gas or general anaesthesia are the other routes. In the survey above, most parents facing general anaesthesia preferred SDF, even on a front tooth. The full range of treatments for cavities in children is on the treatment page.
How much does SDF treatment cost?
There is no single price to quote, because the fee depends on how many teeth are treated and how many coats they need over the following months. The AAPD describes SDF as inexpensive: the material costs little, and each coat takes only a short time in the chair. It also notes that SDF may prevent or delay the need for bigger and more expensive treatment.
Questions worth asking about the fee:
- Is it charged per tooth or per visit?
- Are the re-check and a second coat included, or charged again?
- If a filling goes on later to cover the black, what does that add?
Is silver diamine fluoride safe for kids?
The evidence in young children is reassuring.
- The AAPD reports that trials covering more than 4,000 young children found no deaths and no whole-body side effects at the recommended amounts.
- In a Hong Kong trial of 888 preschool children, parents reported no illness. Within a week of treatment, 6.6% reported some tooth or gum pain, 2.8% gum swelling and 4.7% a whitish patch on the gum.
- An Oregon trial of 66 preschool children found no harms.
It can taste metallic or bitter, which is gone by the next day. If the liquid touches the gum it can cause soreness, which settles within 48 hours.
It is not for children who are allergic to silver or who have raw or painful sores in the mouth. For a child who cannot sit for any dental treatment, special needs dentistry explains the other options.
Does SDF treatment hurt?
No drill and no injection are involved, and the liquid is painted on. That does not mean nothing is felt. In the Hong Kong trial, parents of 6.6% of children reported some tooth or gum pain in the week after treatment.
What happens at the appointment, and after?
- The tooth is checked. An X-ray may be taken to see how deep the cavity goes.
- The lips and nearby gum are protected, and the tooth is kept dry with cotton.
- The liquid is painted on the cavity only, ideally for about a minute, often less with very young children.
- It is dried with a gentle puff of air.
Afterwards:
- Eating and drinking. The AAPD says eating straight away is acceptable. Many trials asked children to wait 30 to 60 minutes. Follow what your dentist tells you.
- Brushing. As normal, with fluoride toothpaste.
- The re-check. The AAPD suggests one two to four weeks after the first coat, to see whether the spot has turned dark and hard.
- Another coat. Common. In the Hong Kong trial, a coat twice a year stopped more cavities than once a year.
When is it worth booking a visit?
SDF is one of the cavity treatments used at Tooth Tales in Greater Noida. You do not need to book an appointment because you read this page. These are the things worth acting on.
- A dentist has offered SDF and you want a second opinion. Take the questions above with you.
- You can see a dark spot or a hole in a milk tooth.
- A tooth hurts on its own, wakes your child at night, or the gum is swollen. Book soon. This is not a situation for SDF.
- Your child has had SDF and, at the re-check, the spot is not dark and hard, or new soft spots have appeared.
If none of these apply, the next routine check is the right time to ask about any mark you have noticed.