Evacuating the oral cavity of excessive moisture is a common part of dental treatment, but it's essential that it be done properly so as not to compromise the patient's health. Many clinicians use a device called a saliva ejector - a straw-like, perforated suction tube that sucks out moisture from your mouth. The saliva ejector is a narrow tubular device providing suction to draw saliva, blood, and debris from the mouth of a dental patient in order to maintain a clear operative field.