The telescopic sleeve of the present invention is suitable for assembly in a dental handpiece, and the telescopic sleeve includes a first end portion, a second end portion, at least one first support spring, a third end portion and at least one second support spring. Wherein, the first end portion is in a hollow tubular shape, and the top end of the first end portion is detachably coupled to the dental handpiece. The second end is hollow tubular and the top end of the second end is nested by the trailing end of the first end. The first support spring is disposed in the first end portion, and one end of the first support spring abuts against the top end of the second end portion, and the other end of the first support spring abuts against the first end portion. The third end portion has a hollow tubular shape, and the top end of the third end portion is nested by the trailing end of the second end portion. The second support spring is disposed in the second end portion, and one end of the second support spring abuts against the top end of the third end portion, and the other end of the second support spring abuts against the second end portion.本新型之伸縮套管適於組裝在一牙科手機，伸縮套管包括一第一端部、一第二端部、至少一第一支撐彈簧、一第三端部及至少一第二支撐彈簧。其中，第一端部是呈中空管狀，第一端部的頂端是以可拆卸的方式連結牙科手機。第二端部是呈中空管狀，第二端部的頂端被第一端部的尾端所套疊。第一支撐彈簧是設置於第一端部內，且第一支撐彈簧的一端抵靠第二端部的頂端，第一支撐彈簧的另一端抵靠第一端部。第三端部呈中空管狀，且第三端部的頂端被第二端部的尾端所套疊。第二支撐彈簧是設置於第二端部內，且第二支撐彈簧的一端抵靠該第三端部的頂端，第二支撐彈簧的另一端抵靠第二端部。
