My tooth has taken a knock: what should I do?

The same impact can lead to four different things: the tooth comes out of its socket completely (avulsion), it is displaced or becomes loose (luxation), it breaks, or nothing shows from the outside at all and the tooth changes colour weeks later. All four differ in how urgent they are and in what needs to be done. The first is the only picture in which minutes genuinely decide the outcome.

When a tooth comes out completely, what makes it possible to put it back is not the tooth itself but the living cells of the thin layer of connective tissue covering the root surface. These cells die once they dry. The IADT's 2020 guideline divides teeth into three groups: in a tooth put back at the scene immediately, or within about 15 minutes, the cells are most likely alive; if the tooth has been kept in a suitable fluid and the total dry time is under 60 minutes, the cells may be damaged but still alive; if the total dry time has gone past 60 minutes, then whether or not the tooth was kept in a fluid, the cells are most likely no longer alive.

The same guideline sets out one further threshold: after 30 minutes of dry time, most of the cells on the root surface lose their viability. That is why the first thing the dentist asks is how long the tooth was dry.

The order of preference for the fluid is settled. The IADT gives it as milk, a special storage solution called HBSS, the patient's own saliva (spat into a cup) and saline. Milk comes first because it can be found anywhere and its salt concentration is balanced in a way that will not burst the cells. Water is a poor medium: its low concentration makes the cells break down quickly. Even so, the guideline says that water is better than leaving the tooth to dry in the air.

Even when the dry time has gone past 60 minutes, the tooth is usually still put back. The IADT's reasoning is this: not putting a tooth back is a decision that cannot be undone. A tooth that is put back gives appearance and function back for at least a while, preserves the height and width of the jaw bone, and can be taken out later if need be. Replantation, in other words, keeps the later options open.

Baby teeth fall outside this rule. The IADT's guideline on injuries to baby teeth says that a baby tooth which has come out should not be put back. The reason is that the tip of a baby tooth root and the permanent tooth bud beneath it are very close neighbours, and the procedure can damage that bud. The child is still taken to a dentist the same day.

Breaks and looseness are more common and less urgent, but they are pictures that have to be followed up. Bringing the broken piece in without letting it dry is worth doing; at the front of the mouth in particular, your own enamel can be bonded back on. Do not try to push a loose or displaced tooth yourself. MedlinePlus also warns against touching the root of the tooth, letting it dry, rubbing it, or cleaning it with alcohol or hydrogen peroxide.

A tooth that has taken a knock can also cause trouble months, and sometimes years, later. The most familiar sign is the colour going darker: if the blood supply has been damaged, the pulp can lose its vitality and the tooth turns grey. Another is the tooth fusing to the bone. That is why a tooth that has taken a knock stays under review even after the pain has gone.

The distinction below decides what you do at the scene. The first list covers the situations in which you should try to put the tooth back. In the second, either the tooth is not put back, or, even if it is, the long-term result stays limited.

The sequence below sets out the steps to take at the scene. None of them calls for special equipment; all you need is a glass of milk, and not to rush.

1. 1

   First look at the person's general condition

   If there is loss of consciousness, persistent vomiting, a severe headache or uncontrolled bleeding, the priority is A&E. MedlinePlus writes that being unable to bring your teeth together can point to a broken jaw and needs emergency medical help. The tooth comes second.

2. 2

   Look for the tooth on the ground and hold it by the white part

   Hold the tooth by the crown, that is, the white part you see in the mouth. Do not touch the root, the thin yellowish surface; the cells that will hold the tooth in place are there. If the tooth cannot be found, tell the dentist that it may have been swallowed.

3. 3

   If it is dirty, rinse it gently with milk, and never rub it

   If the tooth has fallen on soil, rinse it for a few seconds with milk, saline or the patient's saliva. Do not brush it, do not rub it, and do not use soap, alcohol or hydrogen peroxide. Trying to clean the root surface scrapes away the very cells that would save the tooth.

4. 4

   If you can, put the tooth back into its socket

   Place the tooth back into the socket the right way round, slowly, and do not force it. Once it is seated, have the patient hold it still by biting on a piece of gauze, a clean handkerchief or a napkin. This single action at the scene is the step that changes the tooth's long-term chances the most.

5. 5

   If you cannot put it back, carry it in the right fluid

   The order of preference is milk, HBSS solution, the patient's own saliva (spat into a cup) and saline. If none of these is to hand, water can be used; it is a poor medium, but better than leaving the tooth to dry in the air. Do not wrap the tooth in a tissue, put it in a pocket or throw it in the freezer.

6. 6

   See a dentist the same day, and ask these questions

   Tell your dentist how long the tooth was dry and which fluid it was carried in; the treatment decision turns on this. Things to ask: how long the splint will stay on, whether root canal treatment will be needed, and whether your tetanus vaccination is up to date. The IADT recommends that the patient be referred for their tetanus status to be assessed.

What needs doing depends on the type of injury. Below are the four pictures seen most often and what each of them calls for, and where things stand if the tooth has been lost.

We set these out so that you do not act on the wrong reflex in an emergency. Each one of them can cost you a tooth that could have been saved.

The sequence below is the care and review schedule the guideline recommends for a tooth that has been put back. With a break or slight looseness the timescales are shorter, but the logic of the follow-up is the same.

1. The first two weeks

   For this period the guideline recommends a soft diet for up to two weeks, brushing with a soft brush after every meal, and using a 0.12% chlorhexidine mouthwash twice a day for two weeks. You need to stay away from contact sports. The splint comes off at the end of the second week.

2. After the splint comes off

   On the day the splint comes off, a certain amount of movement in the tooth is normal, and the patient is told about this beforehand. The bite is checked, and if necessary the tooth is held for another week.

3. The first year

   In a tooth whose root tip has closed, checks are made at two weeks, four weeks, three months, six months and one year; in a young tooth with an open root tip, checks at one month and two months are added within the first year. At every check the dentist looks at the colour of the tooth, how mobile it is, the sound it makes when tapped, and the state of the root surface on the X-ray.

4. The longer term

   The guideline recommends that follow-up continues once a year for at least five years. Two things are being looked for: root resorption driven by inflammation, and the tooth fusing to the bone. In a growing child, a fused tooth falls behind its neighbours; the decision is made according to how the child is growing.

We do not give a single figure on this page, because the same accident ends with a single-session filling in one patient, with replantation and root canal treatment in a second, and with the loss of the tooth in a third. These are the items that determine the scope:

The type of injury

A break, looseness, a tooth coming out completely and a late presentation are entirely different procedures. The decision only becomes clear after an examination and X-rays.

Whether root canal treatment is needed

In a tooth whose root has finished forming, root canal treatment is part of the plan after replantation. In a young tooth with an open root tip the tooth is watched first, and this item may never come into play.

How long the follow-up lasts

The guideline recommends at least five years of follow-up. The number of checks, the X-rays to be taken and any procedures in between all affect the total.

What will replace the tooth if it is lost

The solutions that buy time while growth continues and an implant placed once growth is complete are not the same sum. How many teeth are affected also changes the plan.