It is a small, square shaped rubber which is used to isolate a single or group of teeth.
We always use it during root canal treatments to stop the bacterial contamination of root canals by saliva. It stops the flow of saliva into the working area and makes the treatment easier for both dentist and patient as the patient can swallow and move the tongue freely.
It also stops any chance of swallowing small instruments and chemicals.
With the rubber dam we have also a better isolated and dry environment for a much better work quality.