Comparison of Calculus Removal Efficiency and Working Posture Between Ultrasonic and Manual Scalers

Objective: In this study, we compared calculus removal efficiency and dental hygienists’ joint angles when using ultrasonic and manual scalers to assess clinical and ergonomic differences. Methods: Thirty-seven dental hygienists performed scaling on two artificial calculus-coated dentiform models: one with an ultrasonic scaler and the other with a manual scaler. We quantified calculus removal using an image analysis software. We measured the joint angles at the cervical spine, lumbar spine, elbow, and wrist using inertial sensors. We used pairedsample t-tests for statistical analysis. Results: Ultrasonic scalers yielded significantly higher calculus removal across all regions (p<0.001). The lumbar flexion angle was significantly smaller when using the ultrasonic scaler(103.75 °) compared to that when using the manual scaler(108.39 °)(p=0.010), and the elbow flexion angle was closer to neutral(73.97 °; p=0.010). Wrist flexion/extension also decreased with the ultrasonic scaler(p=0.035), indicating a reduced musculoskeletal burden. Conclusions: Ultrasonic scalers improve calculus removal efficiency and promote a more ergonomic posture by reducing lumbar and wrist strain. Our findings support the use of ultrasonic devices for clinical effectiveness and dental hygienists’ musculoskeletal safety.