a therapeutic gum irrigator is provided for subgingival periodontal irrigation with a chemotherapeutic fluid . the irrigator includes a housing surrounding at least a portion of the irrigator , a reservoir connected to the housing to retain the fluid , and a cannula configured for subgingival periodontic insertion in fluid communication with the reservoir . the irrigator further includes a neck connected to the housing and separating the reservoir from the cannula . a pump in fluid communication with the reservoir and the cannula includes a displacing element movable between first and second positions and a biasing element that biases the displacing element to the first position . a lever connected to the housing can mechanically move the displacing element to the second position , expelling a predefined volume of the fluid through the cannula . the biasing element causes the displacing element to return to the first position upon release of the thumb lever by the user .