Comparison of root surface roughness induced by hand and ultrasonic instrumentation on treated molars:an in vitro study - Ivanovska Stojanovska M, Popovska M, Dimova C, Simjanovska Lj, Spasovski S, Radojkova Nikolovska V, Mitik K, Tasevska A. (Knowledge- International Journal,2018; 26.4: 1335-1340, 2018)