Dental handpiece with angular contact ball bearings

A dental handpiece comprising:

• a burr sleeve for detachably holding a dental treatment tool therein;
• upper and lower ball bearings for rotatably supporting said burr sleeve, wherein said upper and lower ball bearings are angular contact ball bearings each having a bearing cage, said bearing cage having apertures for supporting balls of said ball bearings therein, said apertures being located substantially in the middle of said bearing cage in a thrust direction;
• a rotor fixed to said burr sleeve between said upper and lower ball bearings and rotated by compressed air for rotatably driving said burr sleeve;
• and
• a dust controller including a rotary protruding member fixed on an outer surface of said burr sleeve and rotating integrally with said burr sleeve, and a stationary protruding member attached to a stationary part of said handpiece;
• wherein said stationary protruding member has a radially inner end portion extended radially inwardly beyond the inner ring of the lower ball bearing, said radially inner end portion having a surface facing to said rotary protruding member to define a gap there between, said gap being located outside of said lower ball bearing;
• and
• wherein said burr sleeve has an outer surface substantially flush with an outermost surface of said rotary protruding member.