ABSTRACT
Abstract: Among the most common problems within dental professionals, is the fracture of rotary instruments of nickel and titanium root canal files (NiTi), when performing a procedure on a patient. Therefore, the objective of this work is to compare the in vitro resistance to cyclic fatigue of K3XF and TFA rotatory instruments, in continuous rotation and adaptive motion. For this, a static and cyclic fracture test was used and a fracture pattern was searched. The numbers of cycles until the fracture and the length of the fragments were determined. Of all the groups evaluated, K3XF-A exhibited the best resistance to cyclic fatigue. In future research, it will be performed an autoclaving and immersion cycles in sodium hypochlorite to be able to determine the separation causes of the rotary instruments. As a recommendation, the operator could significantly influence the decrease in resistance to cyclic fatigue due to the misuse of rotary instruments.
Resumen: Entre los problemas más comunes entre los profesionistas dentales, es la fractura de los instrumentos rotatorios de limas de canales radiculares de níquel y titanio (NiTi), cuando se lleva a cabo el procedimiento al paciente. Es por eso, que el objetivo de este trabajo es el comparar la resistencia in vitro de la fractura cíclica entre los instrumentos rotatorios K3XF y TFA, en rotación continua y movimiento adaptativo. Para esto, se utilizó la prueba de fractura cíclica y estática y el patrón de fractura fue evaluado. El número de ciclos hasta la fractura y la longitud de los fragmentos fue determinado. De todos los grupos evaluados, K3XF-A presentó la mejor resistencia a la fractura cíclica. Como trabajo a futuro, se utilizará ciclos de inmersión en hipoclorito de sodio y autoclaveado, para ser capaces de determinar las causas de separación de los instrumentos rotarios. Como recomendación, el operador puede influenciar significativamente la disminución de la resistencia a la fractura cíclica utilizando de una manera errónea el dispositivo.
ABSTRACT
Aims: The aim of this study was to evaluate the number of intracanal bacteria extruded apically during root canal preparation using rotary ProTaper, K3XF, twisted, and hand K‑file system. Subjects and Methods: Seventy extracted single‑rooted human mandibular premolar teeth were used. Access cavities were prepared and the teeth were mounted in glass vials. Root canals were then contaminated with a pure culture of Enterococcus faecalis (ATCC 29212) and incubated at 37°C for 24 h. The contaminated roots were divided into four experimental groups of 15 teeth each and one control group of 10 teeth. Group 1: ProTaper; Group 2: K3XF; Group 3: Twisted file; Group 4: Hand K‑file; Group 5: Control group. Bacteria extruded from the apical foramen during instrumentation were collected into vials. The microbiological samples were incubated in culture media for 24 h. Colonies of bacteria were counted and the results were given as number of colony‑forming units (CFU)/ml. Statistical Analysis Used: The obtained data were analyzed using the Kruskal–Wallis one‑way analysis of variance and Mann–Whitney U‑tests. Results: There was a significant difference between the rotary and hand instrumentation system related to the apically extruded intracanal bacteria. Conclusions: Both the rotary and hand instrumentation systems extruded intracanal bacteria through the apical foramen. K3XF file system showed least bacterial extrusion amongst all instrumentation groups.