Dental dams or rubber dams are rectangular sheets of latex used in dentistry, specifically endodontic therapy. They are also used during sexual activities as a safe sex technique.
A dental dam, also known in Europe as a "Kofferdam" (from German), is used mainly in endodontic treatment and when putting fillings into teeth. They are thin squares of latex rubber. For those with latex allergy, they are also available in silicone.
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 rubber dam is to protect the patient's airway from any materials which may fall down there during treatment.
Routine use of dental dams is not always appropriate because of some difficulties: for instance communication with the patient is strongly 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. Glass ionomer cement is affected by moisture during its setting reaction and thus rubber dam is considered advisable during placement.
In regards to safe sex practices, dental dams are most commonly recognized for their use during cunnilingus and analingus, to protect against the - transmission of sexually transmitted diseases. An unpunctured dental dam may be held over the vulva or anus, allowing oral stimulation of these areas without transmission of body fluids.
The term rubber dam is also used in dam and hydraulic engineering. Rubber dams are long tubular-shaped fabrics placed across channels, streams and weir crest to raise the upstream water level when inflated. The membrane is a multi-layer fabric made of synthetic fibre which may be rubberised on one or both sides, and possibly coated with plastic film. The fabric is quite flexible and yet exhibits very large resistance characteristics. The inflatable flexible membrane dams (IFMD, or rubber dams) were developed in the early 1950s. In open channels, they are used to divert water for irrigation, for raising existing dams, for flood controls. Other applications include remedy measure to prevent dam overtopping and control of chemical spills in streams. Inflatable dams can be filled with water, air or both. The present trend suggests an increased use of air-filled membranes because they can be deflated or inflated more rapidly, and they are little affected by freezing conditions. Characteristic dimensions cover typically lengths of about 100 m with specially-made membranes up to 200-m wide, dam heights usually less than 5-m but some special designs might be up to 10-m high. The membrane is usually deflated for large overflows. It is however common practice to allow small spillages over the inflated dam. During overflows, vibrations might result from fluid-structure interactions (e.g. OGIHARA and MARAMATSU 1985), and the instabilities might damage and destroy the rubber membrane. Several failures were experienced (e.g. CHANSON 1996). In practice, a deflector (i.e. fin) is installed on the downstream face of the rubber dam to project the nappe away from the membrane, hence preventing rubber membrane vibrations.
 CHANSON, H. (1996). "Some Hydraulic Aspects during Overflow above Inflatable Flexible Membrane Dam." Report CH47/96, Dept. of Civil Engineering, University of Queensland, Australia, May, 60 pages (ISBN 0 86776 644 1).  CHANSON, H. (1998). "Hydraulics of Rubber Dam Overflow : a Simple Design Approach." Proc. 13th Australasian Fluid Mech. Conf., Melbourne, Australia, 13-18 December, M.C. THOMPSON & K. HOURIGAN Ed., Vol. 1, pp. 255-258.  OGIHARA, K., and MARAMATSU, T. (1985). "Rubber dam : Causes of Oscillation of Rubber Dams and Countermeasures." Proc. 21st IAHR Congress, Melbourne, Australia, pp. 600-604.
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