ABSTRACT
The aim was to investigate the cyclic fatigue life of two novel rotary compactors produced for MTA compaction and produced for gutta-percha compaction. Two-type of nickel-titanium rotary compactors were used (n = 20). A static model was preferred for this study due to simulating the clinical application of compaction and to obtain a baseline repository data of this type of instruments. OrthoMTA Compacter (25/0.02) and Revo Condensor (30/0.04) instruments were operated speed of 250 and 4,800 rpm, respectively at 35°C until fracture occurred. The time to fracture was recorded, and the length of the fractured fragments was registered. The independent t-test was performed (p < .05). The fractured instruments were evaluated with a high-resolution field emission scanning electron microscope to allow visualization of the surfaces under several magnifications (×100 and ×10,000). OrthoMTA Compacter (3679.27 NCF), was extremely different in the mean number of cycles to failure when compared with Revo Condensor (1269.48 NCF) (p < .0001). The mean length of the fractured tip of OrthoMTA Compacter and Revo Condensor were 4.87 mm and 4.51, respectively (p < .0001). The surfaces of the instruments shown typical features of cyclic fatigue failure, involving crack origins, fatigue regions, and an overload region. This is the first study in the literature to date evaluating the cyclic fatigue life of Revo Condensor and OrthoMTA Compacter. OrthoMTA Compacter presented higher cyclic fatigue life compared with Revo Condensor.
ABSTRACT
To investigate the cyclic fatigue resistance of novel ROTATE instruments and to compare with the same size of One Curve, TF adaptive, and Mtwo instruments using a root canal simulation model. Four-type of 25/0.06 instruments were used: ROTATE, Mtwo, One Curve, TF adaptive. Instruments were divided into two subgroups: Distilled water and 2.5% sodium hypochlorite (n = 20). Instruments were operated at 35°C. The time to fracture and the length of the fractured fragments were compared One-way analysis of variance (ANOVA) followed by Tukey's multiple comparison tests (p < .05). Descriptive analysis was performed for the elemental composition of instruments by Energy-dispersive X-ray spectroscopy. ROTATE demonstrated the lowest Ni content and SD values. ROTATE had significantly higher NCF values than other groups (p < .0001). Sodium hypochlorite was decreased the mean NCF values. This is the first study in the literature on the cyclic fatigue of ROTATE. ROTATE presented higher cyclic fatigue life than One Curve, TF Adaptive, and Mtwo.
ABSTRACT
PURPOSE: The actual reciprocating angles of endodontic motors might differ from the manufacturers' set values. This study analyzed the effect of clinical usage on the kinematics of reciprocating endodontic motors with 2 different reciprocal modes. METHODS: 1 new and 3 used reciprocating endodontic motors (X-Smart Plus, Dentsply Maillefer) with 2 different reciprocating modes, WaveOne mode (W-mode) or Reciproc mode (R-mode), were analyzed. An angle measurement disc was inserted into a contra-angle. Reciprocating motions were recorded with a high-speed camera at 1,200 fps and analyzed on a computer. The following kinematic parameters were calculated: duration of each reciprocating motion, engaging and disengaging angles, cycle rotational speeds, engaging and disengaging rotational speeds, net cycle angle, total cycle angle, and number of cycles to complete full rotation. One-way ANOVA and Kruskal-Wallis test followed by multiple comparison tests were used for statistical analysis (p = 0.05). RESULTS: In W-mode, the actual engaging angles of all used and new motors were different from the manufacturer's set values (p<0.0001), whereas there was no difference between actual engaging angles among the motors (p>0.05). In R-mode, the actual engaging angles of all used and new motors were similar to the manufacturers' set values (p>0.05). There was no difference between the actual engaging angles among motors (p>0.05). Both the W-mode and R-mode showed statistically different values of actual disengaging angles for all used and new motors when compared with the manufacturers' set value (p<0.0001). CONCLUSIONS: This study confirmed that the actual kinematics of reciprocating endodontic motors differ from the manufacturers' set values. Some kinematic parameters were influenced by the clinical usage of the motors.
