A washing unit (50) that includes: a handpiece (52) that includes a handle located proximally (92) and a cylindrical body (94) located distally, in which the handle (92) and the cylindrical body (94 ) are pivotally connected to each other, so that the angular orientation of the cylindrical body (94) with respect to the handle (92) can be selectively adjusted； an irrigation tube (54) extending from a source of irrigation fluid (53) to the handpiece (52)； a tip assembly (80) extending forward from the cylindrical body (94) of the handpiece and which is connected to the handpiece (52) to receive from the irrigation tube (54) the irrigation fluid for download； and a pump (388) and an engine (360) arranged in the handpiece (52), the pump (388) configured to pump irrigation fluid from the irrigation tube (54) out through the tip assembly ( 80), and the motor (360) connected to the pump (388) to drive the pump, characterized in that: the pump (388) is arranged in the cylindrical body (94) of the handpiece (52)； the motor (360) is arranged in the handle (92) of the handpiece (52)； and at least one cogwheel (368) is arranged in said handpiece (52) to transfer mechanical energy generated by said motor (360) to said pump (388), said cogwheel (368) being mounted so that it can rotate on said handle (92) or said cylindrical body (94) to rotate about an axis around which the cylindrical body (94) pivots with respect to the handle (92).Una unidad de lavado (50) que incluye: una pieza de mano (52) que incluye una empuñadura ubicada proximal (92) y un cuerpo cilíndrico (94) ubicado distalmente, en la que la empuñadura (92) y el cuerpo cilíndrico (94) están conectados de forma pivotante entre sí, de modo que la orientación angular del cuerpo cilíndrico (94) con respecto a la empuñadura (92) pueda ser ajustada selectivamente； un tubo de irrigación (54) que se extiende desde una fuente de fluido de irrigación (53) hasta la pieza de mano (52)； un conjunto de punta (80) que se extiende h
