A dental dam is a medical device which is used by dentists to maintain a sterile work area when they are drilling and filling teeth. Safer sex advocates have also adopted the dental dam, because when used correctly during oral sex, it can prevent the transmission of sexually transmitted infections (STDs). When used as a safer sex tool, a dental dam is sometimes called an oral dam, but the material used and the basic design is the same. Many companies make both types, selling them with different packaging depending on the target market.

A dental dam is usually made from latex, although latex-free varieties are available for people with latex allergies. Usually, a dental dam comes in the form of a small square of material, although some dental supply companies sell dental dam in rolls, so that the dentist can cut off a piece of the appropriate size. The dental dam is designed to be single use, and is usually packaged in sterile material. After one use, the dental dam should be thrown away.

In dental procedures, a dental dam is used to isolate the tooth or area of the mouth being worked on, especially when that tooth is exposed because it has been drilled or the dentist is performing a root canal. Using a dental dam ensures that the sensitive tooth is not exposed to oral bacteria, providing a clean work space for the dentist and reducing the risk of painful infection. The dental dam can be secured in the mouth with bands and clips, and although it can be uncomfortable for the patient, it is an excellent dental safety measure, especially when combined with gloves and other barrier methods in the dental suite.

When used for safer sex, a dental dam should only be used on one area of the body before being discarded, and should never be flipped, because that could result in the exchange of body fluids. Use of a dental dam can also be combined with lubricants for increased sensation, and some companies make flavored dental dams to encourage people to use them. Makeshift dental dams can also be made from condoms and gloves, but if the gloves are talc covered, the talc should be rinsed off before use, as it will irritate mucus membranes. Dental dams are readily available from many drugstores, and some public health departments stock them at low cost as well.