Comparison of the cyclic fatigue resistance of VDW.ROTATE, TruNatomy, 2Shape, and HyFlex CM nickel-titanium rotary files at body temperature

Objectives@#This study aims to compare the cyclic fatigue resistance of VDW.ROTATE, TruNatomy, 2Shape, and HyFlex CM nickel-titanium (NiTi) rotary files at body temperature. @*Materials and Methods@#In total, 80 VDW.ROTATE (25/0.04), TruNatomy (26/0.04), 2Shape (25/0.04), and HyFlex CM (25/0.04) NiTi rotary files (n = 20 in each group) were subjected to static cyclic fatigue testing at body temperature (37°C) in stainless-steel artificial canals prepared according to the size and taper of the instruments until fracture occurred. The number of cycles to fracture (NCF) was calculated, and the lengths of the fractured fragments were measured. The data were statistically analyzed using a 1-way analysis of variance and post hoc Tamhane tests at the 5% significance level (p < 0.05). @*Results@#There were significant differences in the cyclic fatigue resistance among the groups (p < 0.05), with the highest to lowest NCF values of the files as follows: VDW.ROTATE, HyFlex CM, 2Shape, and TruNatomy. There was no significant difference in the lengths of the fractured fragments among the groups. The scanning electron microscope images of the files revealed typical characteristics of fracture due to cyclic fatigue. @*Conclusions@#The VDW.ROTATE files had the highest cyclic fatigue resistance, and the TruNatomy and 2Shape files had the lowest cyclic fatigue resistance in artificial canals at body temperature.

Comparison of the cyclic fatigue resistance of VDW.ROTATE, TruNatomy, 2Shape, and HyFlex CM nickel-titanium rotary files at body temperature

Objectives@#This study aims to compare the cyclic fatigue resistance of VDW.ROTATE, TruNatomy, 2Shape, and HyFlex CM nickel-titanium (NiTi) rotary files at body temperature. @*Materials and Methods@#In total, 80 VDW.ROTATE (25/0.04), TruNatomy (26/0.04), 2Shape (25/0.04), and HyFlex CM (25/0.04) NiTi rotary files (n = 20 in each group) were subjected to static cyclic fatigue testing at body temperature (37°C) in stainless-steel artificial canals prepared according to the size and taper of the instruments until fracture occurred. The number of cycles to fracture (NCF) was calculated, and the lengths of the fractured fragments were measured. The data were statistically analyzed using a 1-way analysis of variance and post hoc Tamhane tests at the 5% significance level (p < 0.05). @*Results@#There were significant differences in the cyclic fatigue resistance among the groups (p < 0.05), with the highest to lowest NCF values of the files as follows: VDW.ROTATE, HyFlex CM, 2Shape, and TruNatomy. There was no significant difference in the lengths of the fractured fragments among the groups. The scanning electron microscope images of the files revealed typical characteristics of fracture due to cyclic fatigue. @*Conclusions@#The VDW.ROTATE files had the highest cyclic fatigue resistance, and the TruNatomy and 2Shape files had the lowest cyclic fatigue resistance in artificial canals at body temperature.

Radiological assessment of the lateral osteotomy line-lacrimal system distance on three-dimensional models.

AIMS: One of the most commonly performed operations in aesthetic, plastic, and reconstructive surgery is rhinoplasty, the aim of which is to construct an altered nasal shape, either for aesthetic or functional reasons. The lateral osteotomy is the most traumatic step of rhinoplasty, and is generally difficult to perform. The lacrimal system can be damaged during the lateral osteotomy procedure. In this study, we aimed to measure the distance between the lacrimal system and the lateral osteotomy line, and to determine the safe and ideal osteotomy level, which is very important in rhinoplasty procedures. We also evaluated the safe relationship of this osteotomy level with the lacrimal system by constructing a three-dimensional model. MATERIALS AND METHODS: The three-dimensional models were constructed on axial planes using paranasal computed tomographic (CT) images of 40 male and 40 female patients. The 'lateral osteotomy model' was designed in three dimensions. The axial CT images were obtained from the model. On the CT images, the distance between the lateral osteotomy line and the lacrimal system was assessed by measuring three distances. The first was the distance between the anterior lacrimal crest and the lateral osteotomy line. The second was the distance from the midpoint between the anterior lacrimal crest and the inferior meatus to the lateral osteotomy line. The third was the distance between the opening of the lacrimal canal to the inferior meatus and the lateral osteotomy line. RESULTS: No lacrimal system injury was seen on any of the models. The shortest distance was found between the anterior lacrimal crest and the lateral osteotomy line, measured at 4.5 mm and 5.0 mm in the female and male patients, respectively. CONCLUSION: Performing the lateral osteotomy meticulously while paying attention to remaining anterior to the medial canthal ligament will not lead to any lacrimal system injury.

Effect of glide path preparation with PathFile and ProGlider on the cyclic fatigue resistance of WaveOne nickel-titanium files

OBJECTIVES: The aim of this study was to investigate the effect of glide path preparation with PathFile and ProGlider nickel-titanium (NiTi) files on the cyclic fatigue resistance of WaveOne NiTi files. MATERIALS AND METHODS: Forty-four WaveOne Primary files were used and divided into four groups (n = 11). In the first group (0 WaveOne), the WaveOne Primary files served as a control group and were not used on acrylic blocks. In the 1 WaveOne Group, acrylic blocks were prepared using only WaveOne Primary files, and in the PF+WaveOne group and PG+WaveOne groups, acrylic blocks were first prepared with PathFile or ProGlider NiTi files, respectively, followed by the use of WaveOne Primary files. All the WaveOne Primary files were then subjected to cyclic fatigue testing. The number of cycles to failure was calculated and the data were statistically analyzed using one-way analysis of variance (ANOVA) and the Tukey honest significant difference multiple-comparison test at a 5% significance level. RESULTS: The highest number of cycles to failure was found in the control group, and the lowest numbers were found in the 1 WaveOne group and the PF+WaveOne group. Significant differences were found among the 1 WaveOne, PF+WaveOne, and control groups (p 0.05). CONCLUSION: Glide path preparation with NiTi rotary files did not affect the cyclic fatigue resistance of WaveOne Primary files used on acrylic blocks.

The effect of root canal preparation on the surface roughness of WaveOne and WaveOne Gold files: atomic force microscopy study

OBJECTIVES: To examine the surface topography of intact WaveOne (WO; Dentsply Sirona Endodontics) and WaveOne Gold (WOG; Dentsply Sirona Endodontics) nickel-titanium rotary files and to evaluate the presence of alterations to the surface topography after root canal preparations of severely curved root canals in molar teeth. MATERIALS AND METHODS: Forty-eight severely curved canals of extracted molar teeth were divided into 2 groups (n = 24/each group). In group 1, the canals were prepared using WO and in group 2, the canals were prepared using WOG files. After the preparation of 3 root canals, instruments were subjected to atomic force microscopy analysis. Average roughness and root mean square values were chosen to investigate the surface features of endodontic files. The data was analyzed using one-way analysis of variance and post hoc Tamhane's tests at 5% significant level. RESULTS: The surface roughness values of WO and WOG files significantly changed after use in root canals (p < 0.05). The used WOG files exhibited higher surface roughness change when compared with the used WO files (p < 0.05). CONCLUSIONS: Using WO and WOG Primary files in 3 root canals affected the surface topography of the files. After being used in root canals, the WOG files showed a higher level of surface porosity value than the WO files.

Effect of adaptive motion on cyclic fatigue resistance of a nickel titanium instrument designed for retreatment

OBJECTIVES: The aim of this study was to evaluate the cyclic fatigue resistance of the ProTaper Universal D1 file (Dentsply Maillefer) under continuous and adaptive motion. MATERIALS AND METHODS: Forty ProTaper Universal D1 files were included in this study. The cyclic fatigue tests were performed using a dynamic cyclic fatigue testing device, which had an artificial stainless steel canal with a 60° angle of curvature and a 5 mm radius of curvature. The files were randomly divided into two groups (Group 1, Rotary motion; Group 2, Adaptive motion). The time to failure of the files were recorded in seconds. The number of cycles to failure (NCF) was calculated for each group. The data were statistically analyzed using Student's t-test. The statistical significant level was set at p < 0.05. RESULTS: The cyclic fatigue resistance of the adaptive motion group was significantly higher than the rotary motion group (p < 0.05). CONCLUSION: Within the limitations of the present study, the ‘Adaptive motion’ significantly increased the resistance of the ProTaper Universal D1 file to cyclic facture.

In vitro comparison of the cyclic fatigue resistance of HyFlex EDM, One G, and ProGlider nickel titanium glide path instruments in single and double curvature canals

OBJECTIVES: It was aimed to compare the cyclic fatigue resistances of ProGlider (PG), One G (OG), and HyFlex EDM (HEDM) nickel titanium glide path files in single- and double-curved artificial canals. MATERIALS AND METHODS: 40 PG (16/0.02), 40 OG (14/0.03), and 40 HEDM (10/0.05) single-file glide path files were used in the present study. Sixty files were subjected to cyclic fatigue test by using double-curved canals and 60 files by using single-curved canal (n = 20). The number of cycles to fracture (NCF) was calculated and the length of the fractured fragment (FL) was determined by a digital micro-caliper. Twelve pieces of fractured files were examined with scanning electron microscope to determine fracture types of the files (n = 2). The NCF and the FL data were analyzed using one-way analysis of variance and post hoc Tukey test using SPSS 21 software (p < 0.05). RESULTS: In all of the groups, NCF values were significantly lower in double-curved canals when compared to single-curved canals (p < 0.05). For both of single- and double-curved canals, NCF values of HEDM group in apical and coronal curvatures were found to be significantly higher than NCF values of PG and OG groups (p < 0.05). In both of single- and double-curved canals, NCF value of PG group was found significantly higher than OG group (p < 0.05). CONCLUSIONS: Within the limitations of this study, HEDM glide path files were found to have the highest cyclic fatigue resistance in both of single- and double-curved canals.

The effects of autoclave sterilization on the cyclic fatigue resistance of ProTaper Universal, ProTaper Next, and ProTaper Gold nickel-titanium instruments

OBJECTIVES: It was aimed to compare the cyclic fatigue resistances of ProTaper Universal (PTU), ProTaper Next (PTN), and ProTaper Gold (PTG) and the effects of sterilization by autoclave on the cyclic fatigue life of nickel-titanium (NiTi) instruments. MATERIALS AND METHODS: Eighty PTU, 80 PTN, and 80 PTG were included to the present study. Files were tested in a simulated canal. Each brand of the NiTi files were divided into 4 subgroups: group 1, as received condition; group 2, pre-sterilized instruments exposed to 10 times sterilization by autoclave; group 3, instruments tested were sterilized after being exposed to 25%, 50%, and 75% of the mean cycles to failure, then cycled fatigue test was performed; group 4, instruments exposed to the same experiment with group 3 without sterilization. The number of cycles to failure (NCF) was calculated. The data was statistically analyzed by using one-way analysis of variance and post hoc Tukey tests. RESULTS: PTG showed significantly higher NCF than PTU and PTN in group 1 (p < 0.05). Sterilization significantly increased the NCF of PTN and PTG (p < 0.05) in group 2. PTN in group 3 had significantly higher cyclic fatigue resistance than PTN group 4 (p < 0.05). Also, significantly higher NCF was observed for PTG in group 2 than in groups 3 and 4 (p < 0.05). CONCLUSIONS: PTG instrument made of new gold alloy was more resistant to fatigue failure than PTN and PTU. Autoclaving increased the cyclic fatigue resistances of PTN and PTG.

Incidence of apical crack formation and propagation during removal of root canal filling materials with different engine driven nickel-titanium instruments

OBJECTIVES: To determine the incidence of crack formation and propagation in apical root dentin after retreatment procedures performed using ProTaper Universal Retreatment (PTR), Mtwo-R, ProTaper Next (PTN), and Twisted File Adaptive (TFA) systems. MATERIALS AND METHODS: The study consisted of 120 extracted mandibular premolars. One millimeter from the apex of each tooth was ground perpendicular to the long axis of the tooth, and the apical surface was polished. Twenty teeth served as the negative control group. One hundred teeth were prepared, obturated, and then divided into 5 retreatment groups. The retreatment procedures were performed using the following files: PTR, Mtwo-R, PTN, TFA, and hand files. After filling material removal, apical enlargement was done using apical size 0.50 mm ProTaper Universal (PTU), Mtwo, PTN, TFA, and hand files. Digital images of the apical root surfaces were recorded before preparation, after preparation, after obturation, after filling removal, and after apical enlargement using a stereomicroscope. The images were then inspected for the presence of new apical cracks and crack propagation. Data were analyzed with χ2 tests using SPSS 21.0 software. RESULTS: New cracks and crack propagation occurred in all the experimental groups during the retreatment process. Nickel-titanium rotary file systems caused significantly more apical crack formation and propagation than the hand files. The PTU system caused significantly more apical cracks than the other groups after the apical enlargement stage. CONCLUSIONS: This study showed that retreatment procedures and apical enlargement after the use of retreatment files can cause crack formation and propagation in apical dentin.