||This article relies largely or entirely upon a single source. (January 2010)|
||The examples and perspective in this article may not represent a worldwide view of the subject. (April 2011)|
A dental dam or rubber dam is a rectangular sheet of latex used in dentistry, in particular endodontic therapy, to reduce contamination, and where dental composite is being placed, due to the need for the area to remain dry during filling placement. They are also used as a safe sex technique during cunnilingus and other sexual activities.
In dentistry 
A dental dam (sometimes known as a "Kofferdam"--from German), is used mainly in endodontic treatment and when putting fillings into teeth. They are thin squares of latex rubber. Silicone versions are available for those with latex allergies.
The main function is to isolate the tooth being treated from its environment, in particular from the bacteria in the oral cavity. The rubber dam is held over individual teeth or groups of teeth by appropriate rubber dam clamps or threads (ligatures) along the edge of the gum. The tooth crown stands out from the rubber dam through individual holes made by a hole punch. This permits a clean and dry operative field, retracts the lips and cheeks, and enables treatment of the appropriate tooth without contamination from blood or saliva. Another function of the rubber dam is to protect the patient's airway from any materials which may fall into it during treatment.
Routine use of dental dams is not always appropriate because of some difficulties: for instance communication with the patient is significantly reduced and the patient may feel restricted. However for endodontic procedures it is considered mandatory. For adhesive dentistry procedures involving bonding dental composite it is to be encouraged as the operative field must avoid moisture contamination in order to get maximum bond strength from restorative material to tooth substance. Composite is affected by moisture during its setting reaction and thus a rubber dam is considered advisable during placement.
Safe sex 
In safe sex practices, dental dams are recognized for their use during cunnilingus and anilingus to protect against the transmission of sexually transmitted diseases. After lubrication with water-based lubricant an unpunctured dental dam may be held over the vulva or anus, allowing oral stimulation of these areas without transmission of bodily fluids and skin contact.
- "Dental Dams | Sexually Transmitted Infections | Adults | sexualityandu.ca - Your Link to Sexual Well-Being". sexualityandu.ca. 2006-12-15. Retrieved 2010-09-12.