Abstract: A water purification apparatus includes a water inlet; a medicine mixing device in fluid communication with the water inlet; and a water outlet interconnected to the medicine mixing device and a dental treatment center. The medicine mixing device includes a medicine storage for storing antiseptic solution, a mixing unit interconnected to the water inlet, the water outlet, and the medicine storage, and a controller interconnected to the water inlet and the medicine storage. The controller includes a sensor and a microprocessor. The controller sends the antiseptic solution from the medicine storage to the mixing unit and controls a volume of water flowing from the water inlet to the mixing unit. The microprocessor instructs the controller to control a volume of the antiseptic solution supplied from the medicine storage to the mixing unit based on a signal sensed by the sensor.