| CPC A61F 9/00745 (2013.01) [B06B 1/0614 (2013.01); B06B 2201/76 (2013.01)] | 8 Claims |

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1. An ultrasonic handpiece assembly comprising:
a horn elongated along a longitudinal axis, the horn including a rear end, a front end opposite the rear end, and a horn lumen extending axially through the horn;
a rear mass attached to the rear end of the horn, the rear mass having a rear mass lumen extending axially through the rear mass and communicating with the horn lumen;
a plurality of piezoelectric elements arranged coaxially about the horn in a stack; and
an L-T spring arranged coaxially about the horn axially behind the stack of piezoelectric elements;
wherein the horn includes a low gain section axially in front of the stack of piezoelectric elements and a high gain section axially in front of the low gain section, wherein the high gain section has a transverse cross-sectional area less than a transverse cross-sectional area of the low gain section;
wherein the low gain section of the horn includes a circumferential groove;
wherein the ultrasonic handpiece assembly has a first L-T mode at a first resonant frequency, a T mode at a second resonant frequency, a second L-T mode at a third resonant frequency, and an L mode at a fourth resonant frequency; and
wherein the circumferential groove is arranged at an axial location corresponding to a vibrational node of the first L-T mode.
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