Working parameters of a sonic scaler influencing root substance removal in vitro.

This study assessed defect depth and volume resulting from root instrumentation using a KaVo Sonic-flex Lux 2000 L sonic scaler with a slim scaling tip (Perio-Tip no. 8) in vitro. Combinations of the following working parameters were analyzed: lateral forces of 0.5 N, 1 N, and 2 N; tip angulations of 0 degree, 45 degrees, and 90 degrees; and instrumentation time of 10 s, 20 s, 40 s, and 80 s. Defects were quantified using a three-dimensional optical laser scanner. Instrumentation time had an almost linear impact on defect depth and volume. Although lateral force (beta-weight 0.55 +/- 0.062) had a greater influence on defect volume than tip angulation (beta-weight 0.29 +/- 0.062), their effects on defect depth were similar (beta-weight 0.43 +/- 0.052 and 0.50 +/- 0.052, respectively). The combination of force and angulation showed synergistic effects resulting in a wide range of defect depths (21.9 +/- 0.96 microns to 174 +/- 28.8 microns, at 40 s) and volumes (0.056 +/- 0.019 mm3 to 0.68 +/- 0.10 mm3 at 40 s). Severe root damage (> 50 microns/40 s) did not occur at any combination of 0.5 N lateral force and/or 0 degree tip angulation. By adjusting lateral force and tip angulation, the efficacy of the assessed sonic scaler may be adapted to various clinical needs.