How to Tell a Baby Tooth From a Permanent Tooth

If a tooth has come out, this matters more than it might seem: never put a baby tooth back in, but put a permanent tooth back in if possible. Getting this wrong is the single biggest mistake in dental trauma first aid. Here’s how to tell the two apart quickly.

Is it a baby tooth or a permanent tooth?

Is the child under 6?
→ Almost certainly a baby tooth. See what to do if a baby tooth is knocked out.

Is the child 12 or older?
→ Usually a permanent tooth by this age. See what to do if a permanent tooth is knocked out.

Between 6 and 12?
→ This is the mixed-dentition stage — children have both baby and permanent teeth at once, so age alone won’t tell you. Check size, colour and the neighbouring teeth below.
→ Still unsure after checking? See “If you’re still unsure” further down.

How to check

Feature	Baby tooth	Permanent tooth
Typical age lost	6–12 (varies by tooth)	Not usually lost at a young age except through injury
Size	Smaller	Noticeably larger
Colour	Whiter, almost milky	More yellow-white
Edges	Smooth, rounded	Often slightly ridged, especially if newly through
Root, if visible	Often already shortened or dissolving	Usually long and fully intact if freshly knocked out
If knocked out	Never replant	Replant if possible — see the permanent tooth guide

A useful clue: what else is in the mouth

Look at the teeth either side of the gap. If the neighbouring teeth are clearly a mix of sizes — some noticeably bigger than others — the child is in the mixed-dentition stage, and you can’t rule out either type on age alone. If every visible tooth looks a similar, larger adult size, a freshly lost tooth is more likely to be permanent.

If you’re still unsure

This isn’t a situation where guessing wrong is a small mistake — but it’s also not a situation to guess your way through. If there’s genuine doubt after checking the above:

Don’t attempt to replant the tooth without professional advice.
Keep the tooth safe, in case a dentist wants to see it.
Have a dentist check the child as soon as reasonably possible — they can confirm which type it is, often just by looking at the socket.

What to do next

If you’ve confirmed it’s a permanent tooth: see what to do if a permanent tooth is knocked out — acting quickly matters here.
If you’ve confirmed it’s a baby tooth, or you’re not sure: see what to do if a baby tooth is knocked out — this is a slower-paced situation, but still needs a dentist to check it.
Either way, if you’re unsure where to get help: see dentist, NHS 111, A&E or 999 — where to get help for a dental injury.

Print this before you need it

A Baby or Permanent Tooth? quick-reference card is coming to the Download Centre — a phone-saveable and printable version of the comparison above. In the meantime, the Knocked-Out Tooth Poster covers the permanent-tooth emergency steps. Download free

References

International Association of Dental Traumatology (IADT), Guidelines for the Management of Traumatic Dental Injuries, 2020 (current as of August 2026)
NHS, Knocked-out tooth, nhs.uk

This guide does not replace assessment by a dentist or emergency service. It reflects current international and UK guidance, reviewed by Dr Yousuf Ibrahim, BDS.