The present invention relates to a disposable dental instrument used by dental professionals to polish a patient's teeth. The dental instrument can be connected to a hand motor used to rotate a prophy cup with a plurality of grinding wings that rub against the patient's teeth as a predetermined amount of tooth cleaning fluid is discharged directly on the patient's teeth through a drain hole within the prophy cup. The tooth cleaning fluid is discharged from a tube that is assembled in a tube room of the dental instrument. The tube is a flexible bladder similar in function and form to a tube of toothpaste. The tube is made of a flexible polymer material that allows it to be squeezed when pressure is applied to it. A roller is assembled within the tube room and on top of the tube. As the roller is pushed forward with a finger, the tube is squeezed to discharge the tooth cleaning fluid directly on the patient's teeth.