This study aimed to evaluate the influence of scaler tip wear and different working parameters, i.e., lateral force, power setting and tip angulation, on the roughness of root surfaces following treatment with piezoelectric ultrasonic scaling devices.Twenty piezoelectric ultrasonic scaler inserts (10 worn/10 new) were selected to examine the erosion ratio (ER) under atomic force microscopy (AFM). A total of 160 root samples were prepared and instrumented by new (n = 80) and worn inserts (n = 80) at different working parameters (tip angulation, power setting, lateral force). Roughness change (Rc) on root surfaces after instrumentation was examined by a contact profilometer.Statistically significant differences were found between the mean ERs of new and worn tips (p < 0.0001). The various combinations of the assessed working parameters showed synergistic effects resulting in a wide range of root surface roughness. The present study found the higher Rc in the group with a 45° angulation, (P10) high power setting and 1.0 N lateral force (subgroup 8) when compared to other groups. Among the groups, the worn scaler tips subgroup 8 showed a higher Rc (5.692 ± 0.81) when compared to new scaler tips subgroup 8 (4.798 ± 0.51; p < 0.001).The findings of the present study highlighted that scaler tip wear strongly influences the root surface roughness when used at higher tip angulation, lateral force and power settings. Hence, ultrasonic scaler tip wear should be periodically evaluated and should be considered as much as the other working parameters.