Comparison of Defects in Two NiTi-rotary Systems after Single-used.

Objectives: The purpose of this study was to compare incidence and types of defects which are flexural fatigue and torsional failure, of the two nickel-titanium (NiTi) rotary systems after single use by fourth year student in molar extraction.
Methods: Total of 20 ProtaperGold^® and 20 ProtaperNext^® were new and used by 40 dental students supervised by experienced clinicians following the instructions, using crown-down technique, irrigation and RC prep lubrication. Proglider^® was used as a first rotary instrument for guiding path in both rotary systems.The instruments were single used in extracted molar teeth in simulating head models and were collected, ultrasonically cleaned and sterilized. The instruments were examined by scanning electron microscopy (SEM). All defects and fracture were classified into the following groups (A) unfracture with flexural fatigue (B) unfracture with torsional failure, and (C) fracture. Statistic analysed using One-way Anova test with significant set at p<0.05
Results: The flexural fatigue occurred lower than torsional failure. However, statistical analysis revealed that there was no significant difference. The highest incidence of the instrument fracture were 16% for ProtaperNext (X3) following by 10% of ProtaperGold (F2). ProtaperNext (X3) were statistically significant difference than others.
Conclusions: The results from this study suggest that both NiTi rotary systems can have defects and fracture even after the first time used. Large size of Protaper next (X3) tends to be fractured easily than ProtaperGold.