Abstract: An automatic cleaning device for delivering a cleaning fluid to a vacuum hose of a dental suction system is provided which automatically dispenses a measured amount of cleaning fluid into the vacuum hose each time that a dental instrument is changed. The automatic cleaning device includes a housing having a first end and a second end. The first end of the housing is adapted to releasably receive a hollow dental instrument, such as a suction tube. The second end of the housing is coupled to the vacuum hose. The housing of the automatic cleaning device includes a cavity which extends from the first end to the second end and a reservoir is disposed within the housing, the reservoir containing a cleansing fluid. A hollow piston is disposed within the housing and coupled to the first end of the housing such that receipt of the hollow dental instrument in the first end of the housing causes a forward-backward longitudinal movement of the hollow piston.