Cyclic fatigue comparison among endodontic instruments with similar cross section and different surface coating.
BACKGROUND
The aim of this study was to analyze the influence of rotary instruments' geometry and surface titanium-nitride (TiN) treatment on the fatigue fracture, through the comparison of cyclic fatigue resistance of two endodontic systems that have similar cross-sectional design and different surface coating.


METHODS
In this study 130 Mtwo (10/.04; 15/.05; 20/.06; 25/.06; 30/.05; 35/.04; 40/.04) and Easy Shape (15/.04; 20/.05; 25/.06; 30/.05; 35/.04; 40/.04) were tested for cyclic fatigue resistance. Time to fracture (TtF) was determined by counting the seconds of continuous rotation until final fracture in an artificial canal with 60° angle and a 5 mm radius of curve. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). Data were subjected to one-way analysis of variance (ANOVA) and Tukey post-hoc tests.


RESULTS
Mtwo perform a significantly (P<0.001) higher number of cycles to fracture (NCF) compared with Easy Shape of the same size and taper. The comparison between Mtwo and Easy Shape instruments with the same taper showed higher TtF values of Mtwo files than the Easy Shape ones (P<0.001) while there were no differences among Mtwo and Easy Shape instruments with the same tip, (P>0.05).


CONCLUSIONS
Mtwo exhibit a higher NCF thanks to the smaller metal volume contained in their core. Titanium-nitride coating does not influence the performance of Easy Shape instruments on static test of cyclic fatigue.
Department of General Surgery and Surgical-Medical Specialties, University of Catania, Catania, Italy.
Eugenio
E
Pedullà
Department of Endodontics, Sapienza University of Rome, Rome, Italy.
Gianluca
G
Plotino
Department of General Surgery and Surgical-Medical Specialties, University of Catania, Catania, Italy.
Mauro
M
Scibilia
Department of Endodontics, Sapienza University of Rome, Rome, Italy.
Nicola M
NM
Grande
Section of Oral and Maxillofacial Surgery, Department of Surgical Sciences, Dentistry, Gynecology and Pediatrics, University of Verona, Verona, Italy - daniele.desantis@univr.it.
Daniele
D
De Santis
Section of Oral and Maxillofacial Surgery, Department of Surgical Sciences, Dentistry, Gynecology and Pediatrics, University of Verona, Verona, Italy.
Alessia
A
Pardo
Department of Endodontics, Sapienza University of Rome, Rome, Italy.
Luca
L
Testarelli
Department of Endodontics, Sapienza University of Rome, Rome, Italy.
Gianluca
G
Gambarini
D003430:Cross-Sectional Studies; D003722:Dental Alloys; D003762:Dental Instruments; D004867:Equipment Design; D004868:Equipment Failure; D008422:Materials Testing; D009532:Nickel; D018915:Root Canal Preparation; D013499:Surface Properties; D014025:Titanium
D003722:Dental Alloys; D009532:Nickel; D014025:Titanium