When the handpiece stops inhalation, the present handpiece can prevent the formation of negative pressure in the turbine room caused by the inertial rotation of the impeller that leads to promote the rotary efficiency of the turbine. The handpiece includes a head portion containing a built-in impeller, a neck potion connected to the head portion for the practitioner to hold, a grip portion which communicates with the neck portion, an air supplying pipe which supplies air to drive the impeller. The handpiece includes an exhaust pipe for exhausting the air while the impeller is rotating. The above-mentioned handpiece includes a reflux circuit. An opening functions as a reflux entrance set in the exhaust pipe and the other opening functions as an reflux exit set in the turbine room which form a reflux circuit to exhaust air. The ratio of the diameter of a reflux exit of the reflux circuit divided by the diameter of an air supplying opening of the air supplying pipe is less than 1. The reflux exit is set between the air supplying pipe and the exhaust exit which is near the turbine room.於牙科手機使用完畢停止吸氣之際,防止渦輪葉片因慣性旋轉使得渦輪室內產生負壓,且可提升渦輪的旋轉效率。牙科手機係包含一頭部,內建可自由旋轉的渦輪葉片、一頸部,與頭部相連,可供技術者把持、一握持部,相連設置於頸部的後方;其更包含一供氣管路,供給氣體以驅動渦輪葉片、與一排氣管路,於渦輪葉片旋轉之後以排氣。牙科手機更包含一迴流管路,其一端開口於排氣管路,以作為迴流入口,其另一端係開口於渦輪室,以作為一排氣用之迴流出口。迴流管路之迴流出口的口徑除以供氣管路之供氣口的口徑所得到的值設定為1以下,其中迴流出口係開口於供氣口及排氣出口之間,且靠近供氣口之渦輪室。1...氣動渦輪牙科手機2...頸部3...頭部6...渦輪葉片8...夾盤11...供氣管路12...排氣管路13...噴嘴14...供氣口15...渦輪室16...迴流管路17...迴流出口18...排氣口19...迴流入口A...區域
