An oral irrigator (also called a dental water jet) is a home dental care device. It uses a stream of pulsating water to remove plaque and food debris between teeth as well as below the gumline. The oral irrigator improves gingival health.
The first oral irrigator was developed in Fort Collins, Colorado, in 1962, by dentist Gerald Moyer and engineer John Mattingly; this gave rise to the company eventually renamed as Waterpik.
Since that time, oral irrigators have been evaluated in more than 50 scientific studies and have been tested (and proven effective) on people in periodontal maintenance, and those with gingivitis, diabetes, orthodontic appliances, crowns, and implants.
A 2008 meta-analysis of whether or not oral irrigation is beneficial as an adjunct to tooth brushing concluded that "the oral irrigator does not have a beneficial effect in reducing visible plaque" but suggests it may be beneficial to gingival health in addition to regular oral hygiene measures. A study at the University of Southern California found that a 3 second treatment of pulsating water (1,200 pulses per minute) at medium pressure (70 psi) removed 99.9% of plaque biofilm from treated areas.
An oral irrigator, while having a specific intended purpose, is just a device to produce a pulsating jet of water, and can be and has been used for other purposes. It has been recommended to remove "tonsil stones" in those subject to them.