Effects of clinical use of NiTi reciprocating instruments on cyclic and torsional resistance, and on roughness

Abstract

The aim of the present study was to evaluate the cyclic fatigue, torsional resistance and surface roughness of Reciproc R25 instruments in four different situations, namely as new instruments and as instruments tested after clinical preparation of one, two or three maxillary molars with four root canals. The total time required to perform each root canal preparation was recorded. Cyclic fatigue resistance was determined by the time to fracture using a customized testing device (n = 10 per group). The torsional test evaluated the torque and angle of rotation to failure according to ISO 3630-1 (n = 10 per group). The roughness of the working parts of new and used instruments was evaluated with a profilometer (n = 5 per group). Statistical analysis was performed using one-way ANOVA and Tukey's test. The level of significance was set at 5%. No fractures or deformations were observed after clinical use. Higher preparation time was needed during the third use of the instruments for all root canals (p < 0.05). There were no significant differences among the groups in regard to either cyclic fatigue or torsional resistance (p > 0.05). Regarding the roughness measurements, groove depth was higher on new and one-versus two-or three-maxillary-molar-prepared instruments (p < 0.05). It can be concluded that the clinical use of Reciproc instruments increased preparation time and decreased surface roughness. However, clinical use did not affect the cyclic fatigue or torsional resistance of the Reciproc instruments.

Surface roughness and cyclic fatigue resistance of reciprocating and novel rotary instruments after use in curved root canals

“…Interestingly, although profilometry analysis revealed a change in instrument roughness after their use, this difference was significant only in the XPS group, but the values of roughness parameters generally increased after the first and decreased after the second use in all groups. These observations are partly in accordance with the results published by Moreira et al [9], who concluded that the clinical use of Reciproc decreased the surface roughness. In some previous studies, using optical profilometry, the roughness values of reciprocating instruments increased after their use [6, 15].…”

“…The overall incidence of file separation is 2.27%, with a higher incidence associated with rotary motion (2.43%) than with reciprocating motion (1.0%) [3]. The surface wear and fracture resistance of various instrumentation systems have been investigated by analysing the surface roughness and cyclic fatigue (CF) resistance of both intact and used NiTi instruments [4][5][6][7][8][9]. At the same time, with advances in manufacturing methods and new alloys, the fatigue life, centring ability and canal transportation of the NiTi files have been improved [10][11][12].…”

Cyclic Fatigue Resistance of Nickel–Titanium Rotary Instruments after Simulated Clinical Use

“…It is important to emphasize that the cost can be decreased with repeated use of the instruments. In contrast, as the number of uses increases, the chance of instrument fracture and the average time required for the instrumentation of the canal will increase, as the file will experience reduced surface roughness, fatigue, and cutting efficiency, as confirmed by other studies as well [ 26 , 27 ].…”