S. D. Aspriello, M. Piemontese, L. Levrini, and S. Sauro, “ Ultramorphology of the root surface subsequent to hand-ultrasonic simultaneous instrumentation during non-surgical periodontal treatments: an in vitro study ”, J Appl Oral Sci, vol. 19, no. 1, pp. 74–81, Feb. 2011, doi: 10.1590/S1678-77572011000100015.