Partway through a root canal or a filling, your dentist may fit a small square of stretchy material over your mouth so that only the tooth being treated pokes through. That sheet is a dental dam, also called a rubber dam. It looks odd the first time you see it, but it does two useful jobs: it keeps the tooth dry and clean, and it stops small instruments and liquids from ending up in your throat.
Most people who are nervous about it beforehand find it far less bothersome than they imagined, and some find it more comfortable than having cotton rolls and suction in their mouth.
A tooth on its own island
The dam is a thin sheet of latex or a latex-free material. The dentist punches one or more holes in it, slips it over the tooth or teeth being treated, and holds it in place with a small clamp around the tooth. A light frame outside the mouth keeps the sheet taut. The result is that the treated tooth sits above the sheet while your tongue, cheeks and the rest of your mouth are underneath it.
It is not a new idea. A 2009 review in the International Endodontic Journal (Ahmad) noted that the rubber dam had then been available for more than 140 years and is universally taught and recommended by professional organisations.
Saliva and modern materials do not mix
Saliva carries bacteria and moisture, and both cause problems during treatment. Inside a tooth having root canal treatment, the goal is to clean out bacteria and seal the canals. Letting saliva in while the canals are open works against that.
Fillings have a similar issue. Tooth-coloured composite fillings are bonded to the tooth, and the bonding step is sensitive to contamination from saliva or blood. Cotton rolls and suction can control moisture for a while, but the dam keeps the area dry for the whole procedure.
How much difference does it make to how long fillings last? The evidence is less clear than many people assume. A 2021 Cochrane review (Miao and colleagues) found low-certainty evidence that using a rubber dam may lower the failure rate of direct fillings compared with cotton rolls at six months, while results at later time points were very uncertain. The reviewers called for better research. For root canal treatment, the case rests strongly on infection control and safety as well as on outcomes.
Keeping files and fluids out of your airway
Root canal treatment uses very fine metal files and disinfecting solutions that are flushed through the canals. These solutions taste unpleasant and can irritate the soft tissues. Without a barrier, there is a small risk that a file or fragment could be swallowed or breathed in. Ahmad's review describes treating teeth without a dam as placing the patient at risk of swallowing or aspirating materials and instruments, and links it to poorer treatment outcomes.
The dam also keeps your tongue and cheeks away from sharp instruments, which means you do not have to work at holding them still.
Where you are likely to meet one
You will most often see a dam during root canal treatment, where it is part of standard technique. Many dentists also use one for fillings, particularly on back teeth or where a bonded material needs a dry field, and sometimes for bonding work on front teeth. It is not used for check-ups, cleans or X-rays, because there is nothing to isolate. If you want to know more about the root canal process itself, our root canal treatment guide walks through each visit.
How it feels in the chair
The dam usually goes on after the local anaesthetic has taken effect, so the clamp should not hurt. You may feel some pressure around the tooth and the sheet resting on your lips and chin. Some dentists put a little lubricant on your lips first to stop the material pulling.
You can breathe normally through your nose throughout. The sheet covers your mouth but not your nose. You can also swallow, and saliva can be removed with a small suction tip placed under the sheet. If you need a break, raise your hand and the dentist can pause.
Once the treatment is finished, the frame, sheet and clamp come off together in a few seconds.
Latex allergy, a blocked nose, or feeling closed in
Latex allergy. Tell the practice when you book and again on the day. Latex-free dam sheets are available and work the same way.
A blocked nose. If you have a cold or find it hard to breathe through your nose, mention it. The dentist may cut a small breathing hole in the sheet, adjust its position, or reschedule if needed.
Feeling closed in. Some people feel uneasy with anything over their mouth. Saying so before you start lets the dentist explain each step, agree on a stop signal and show you the dam first. If dental anxiety is more than mild unease, ask about sedation. Happy gas (relative analgesia), oral sedation and IV sedation are available at Lumi, and our IV sedation page explains how that option works.
Questions we are often asked
Does a dental dam hurt?
It should not. The tooth is usually numb before the clamp goes on, and most people find the sheet itself is something they stop noticing after a few minutes.
Can I still breathe and swallow?
Yes. Your nose is not covered, and you can swallow normally. The dentist or assistant can remove saliva with suction if needed.
Can I ask not to have one?
You can always discuss it. For root canal treatment, the dentist is likely to explain why the dam is strongly recommended for your safety and for the quality of the treatment, and to look for ways to make it more comfortable rather than leave it out.
Sources
- Ahmad IA. Rubber dam usage for endodontic treatment: a review. Int Endod J. 2009. PubMed 19825034
- Miao C, et al. Rubber dam isolation for restorative treatment in dental patients. Cochrane Database Syst Rev. 2021. PubMed 33998662
If you have a filling or root canal coming up and want to know what to expect, the team at Lumi Dental is happy to talk it through before your visit. New patient offers are on our current deals page, and more about everyday care is on our general dentist page.
