A dental turbine driven by pressurized air comprises a head housing (1) with a turbine chamber (2) and a rotor shaft (3) mounted using an anti-friction bearing (8a) with a non-rotatably mounted turbine wheel (13). The outer race (10a) of the anti-friction bearing (8a) extends into the turbine chamber (2) in axial direction. The turbine wheel (13) comprises an annular web (16a) that is arranged concentrically to the outer race (10a) of the anti-friction bearing (8a) and, together with the outer race (10a), forms a gap seal (17a). This gap seal (17a) extends in axial direction between outer race (10a) and annular web (16a) and prevents the sucking-in of liquids and dirt particles into the turbine chamber (2) during inertial rotation of the turbine wheel (13).

A dental handpiece includes a barrel, an air turbine, a central shaft, a bearing and a seal. The barrel includes an axial open end. The air turbine is rotatably provided in the barrel. The central shaft is secured to the air turbine to rotate with the air turbine. The bearing is mounted in the barrel and supports the central shaft for rotation. The seal is trumpet-shaped and arranged between the open end of the barrel and the bearing. The seal includes a sealing portion sleeved over an outer cylindrical surface of the central shaft. The sealing portion is deformable to separate from the outer cylindrical surface of the central shaft or closely contact the outer cylindrical surface of the central shaft depending on a pressure difference between interior and exterior of the barrel.

A dental handpiece includes a barrel, an air turbine, a central shaft, a bearing and a seal. The barrel includes an axial open end. The air turbine is rotatably provided in the barrel. The central shaft is secured to the air turbine to rotate with the air turbine. The bearing is mounted in the barrel and supports the central shaft for rotation. The seal is trumpet-shaped and arranged between the open end of the barrel and the bearing. The seal includes a sealing portion sleeved over an outer cylindrical surface of the central shaft. The sealing portion is deformable to separate from the outer cylindrical surface of the central shaft or closely contact the outer cylindrical surface of the central shaft depending on a pressure difference between interior and exterior of the barrel.

A method of preventing suckback of a dental handpiece and a dental handpiece system having a bypass injection structure are capable of effectively blocking a suckback phenomenon that occurs at the moment a rotating impeller stops. The method of preventing suckback includes bypassing air pumped from an air pump in a state where a flow path of an air supply pipe is blocked at the moment the impeller stops rotating and halts inside a head casing and injecting the air into the head casing through an air discharge pipe to block the suckback phenomenon.

A dental handpiece includes a body and a head. The body includes a supply tube configured to supply air to the head. The head includes a housing, a rotor, and a holding portion configured to rotate a cutting tool with rotation of the rotor. The housing includes: an air supply port configured to supply the air supplied from the supply tube to the inside; an air discharge port disposed on a side closer to a tip end of the cutting tool than the air supply port and configured to discharge the air from the inside; a diffuser portion configured to change a flow direction of a part of the air supplied from the air supply port so as to direct the part of the air toward the rotor; and an air-retaining portion configured to retain the part of the air supplied from the air supply port.