A flossing device having internal floss feed in which floss is advanced from a storage chamber inside the handle of the device, through feed gears, to a pair of spaced apart tines. Spent floss is returned through the return gears, the return drive gear having a greater diameter than the feed drive gear, thus ensuring the floss remains taut between the tines. An integral cutter allows the spent floss to be cut off and discarded. The cover over one or both sets of gears may be open at the top and bottom to allow cleaning of the gears. A flexible tile may be included over the aperture through which the floss exits the storage chamber to prevent water incursion therein. A floss advance lever advances the floss by a single action when pressed forward, which creates and maintains sufficient tension on the floss resulting in taut and snug floss between the tines. Optionally, the flossing head has a vibratory device to aid in the flossing action.