A surgical instrument (10, 110) comprises a shaft (12, 112) extending axially between a proximal end and a distal end, said shaft including a vibration conversion mechanism； and an ultrasonic tip (16, 116) coupled to the distal end of said shaft (12, 112) and configured for delivering at least torsional vibration to a target site, said ultrasonic tip having a head portion (32, 132) extending axially along an axial axis (37, 137) to a distal end (38, 138), said head portion including a plurality of teeth (34, 134) separated by a plurality of slots (36, 136) extending between inner and outer circumferential surfaces, Each tooth (34, 134) comprises a side cutting edge (40, 140) having a positive rake angle, said side cutting edge (40, 140) defined between said outer circumferential surface of said head portion (32, 132) and a side surface of said slot (36, 136), said side surface of said slot (36, 136) extending between said inner and outer circumferential surfaces of the head portion (32, 132).
