Mehmet Emin Kaval

Comparison of the Cyclic Fatigue Resistance of 5 Different Rotary Pathfinding Instruments Made of Conventional Nickel-Titanium Wire, M-wire, and Controlled Memory Wire

INTRODUCTION This study compared the cyclic fatigue resistance of current nickel-titanium rotary path-finding instruments. METHODS Five types of nickel-titanium rotary pathfinding instruments were used in steel canals with a 90° curvature and a curvature radius of 3 mm (n = 10) and 5 mm (n = 10). The cyclic fatigue of the following instruments was tested at 4 mm from the tip: PathFile (#16 and a .02 taper; Dentsply Maillefer, Ballaigues, Switzerland), G-File (#12 and a .03 taper; Micro-Mega, Besançon Cedex, France), Scout Race (#15 and a .02 taper; FKG Dentaire, La Chaux-de-Fonds, Switzerland), HyFlex GPF (#15 and a .02 taper; Coltene-Whaledent, Allstetten, Switzerland), and ProGlider (#16 with a mean taper of .04125 and a .02 at the first 4 mm from the tip, Dentsply Maillefer). The length of the fractured parts was measured, and the number of cycles to fracture (NCF) was calculated. The data were statistically analyzed using Kruskal-Wallis and Mann-Whitney tests (α = .05). After Bonferroni correction, the new P value was set as .005. RESULTS The difference in the cyclic fatigue of all the files at both curvatures was statistically significant (P values from .0035 to less than .0001). The ranking of the instruments from the highest to the lowest NCF was as follows: HyFlex GPF, G files, ProGlider, PathFile, and Scout Race. The length of the fractured part of the instruments was similar in all the groups (P > .05). All the tested instruments had a lower NCF at a curvature radius of 3 mm when compared with a curvature radius of 5 mm (P < .0001). CONCLUSIONS Within the limitations of this study, the cyclic fatigue resistance of the HyFlex GPF instrument was the highest, and the curvature radius had a significant effect on the fatigue resistance.

Effect of novel restoration techniques on the fracture resistance of teeth treated endodontically: An in vitro study

The aim was to evaluate the effects of fiber-reinforced composite restorations and a bulk-fill resin composite on the fracture strength of mandibular premolars treated endodontically. Standard mesio-occluso-distal (MOD) cavities were prepared in 48 mandibular premolars. Following root canal treatment, teeth were assigned to four groups: Group 1, nano-hybrid resin composite; Group 2, polyethylene woven fiber plus nano-hybrid resin composite; Group 3, short fiber-reinforced resin composite plus nano-hybrid resin composite; and Group 4, bulk-fill resin composite plus nano-hybrid resin composite. Then, the teeth were subjected to the fracture toughness test. The data were analyzed statistically using one-way ANOVA, followed by Tukeys post-hoc test. The fiber-reinforced groups had better results than the nano-hybrid and bulk-fill composites (p<0.05), while the bulk-fill and nano-hybrid composite restorations gave similar results (p>0.05). Fiber-reinforcement improved the fracture strength of teeth with large MOD cavities treated endodontically. Bulk-fill composites can be used reliably as well as nano-hybrid composites.

Surface roughness and bond strength of zirconia posts to a resin cement after various surface pretreatments.

OBJECTIVE The purpose of this study was to investigate the influence of post surface conditioning methods on the surface roughness and microtensile bond strength (μTBS) of zirconia posts to a resin cement. BACKGROUND DATA Debonding at the post-adhesive interface is a major problem for zirconia posts. METHODS A total of 25 zirconia posts (n=5) were prepared as follows: untreated (control, group C), airborne-particle abraded (group AA), silica coated (group SC), Nd:YAG laser irradiated (group N), and Er:YAG laser irradiated (group E). Prior to application of a dual-cured resin cement on the posts, roughness values of the post surfaces were detected with a profilometer. Specimens were then sectioned to obtain rectangular sticks for μTBS. After sticks were stored in distilled water at 37°C for 24 h, μTBS values were determined in a universal testing machine at a crosshead speed of 1 mm/min until failure. Furthermore, scanning electron microscopic (SEM) analysis was performed for one specimen of each group to evaluate the post surface morphology. One-way ANOVA and post-hoc comparison tests (α=0.05) were performed on all data. RESULTS All surface treatment groups demonstrated significant higher μTBS values than the control group (p<0.001). The highest mean force value was observed in group SC. In addition, similar bond strength results were detected between group SC and group E (p=0.669). None of treatment groups resulted in significant improvement in roughness values of the post (p<0.05), except group N. CONCLUSIONS All surface treatments were found to be effective methods to achieve a durable bond between zirconia posts to resin cement.

Cyclic Fatigue Resistance of Novel Glide Path Instruments with Different Alloy Properties and Kinematics

Introduction The aim of the present study was to evaluate the cyclic fatigue resistance of the WaveOne Gold Glider (Dentsply Maillefer, Ballaigues, Switzerland), R‐Pilot (VDW, Munich, Germany), and ProGlider (Dentsply Maillefer) glide path instruments. Methods Ten instruments from each glide path system were included in the study. A stainless steel artificial canal with a 90° angle and a 3‐mm radius of curvature was used for the testing process. The working lengths of the instruments were fixed at 19 mm, and the instruments were operated using an endodontic motor (X‐Smart Plus, Dentsply Maillefer) at recommended setting for each. A digital camera (Sony HDR‐XR260; Sony Corporation, Minato, Tokyo, Japan) was positioned on the top of the cyclic fatigue test device, and the time to fracture was recorded in seconds by means of the video camera. For each instrument, the number of cycles to failure was calculated, and the length of the fractured fragment was measured. The data were analyzed using 1‐way analysis of variance followed by the post hoc Tukey test. Results Statistically significant differences in the number of cycles to failure values were observed across the tested groups; the ranking of the instruments was as follows: WaveOne Gold Glider > R Pilot > ProGlider (P < .05). There was no significant difference in the mean length of the fractured fragment of the instruments (P > .05). Conclusions Within the limitations of the present study, it can be concluded that improved alloy properties and reciprocating motion could enhance the cyclic fatigue resistance of glide path instruments. HighlightsThe current study is the first to compare the cyclic fatigue resistance of the WaveOne Gold Glider, R‐Pilot, and ProGlider glide path instruments.Improved alloy properties could enhance the cyclic fatigue resistance of glide path instruments.Reciprocating motion achieved higher cyclic fatigue resistance compared with rotation movement.

Radiopacity of Esthetic Post Materials: Evaluation with Digital Analysis Technique.

PURPOSE To evaluate the radiopacity of five post materials using a digital image analysis method. MATERIALS AND METHODS Twelve specimens from each post type (two zirconia and three fiber based) of 2 mm in thickness were obtained using a diamond blade mounted on a cutting machine, and digital radiographs were taken along with aluminum step-wedge and dentin discs under standard exposure conditions. The mean gray-values of specimens were measured using a computer graphics program. Data were analyzed using one-way ANOVA followed by Holm-Sidak multicomparison test (p = 0.05). RESULTS The highest radiopacity was observed in custom zirconia (5.842 millimeters of equivalent Al [mmAl]), and the lowest value was detected with FRC-Postec (Ivoclar Vivadent) (1.716 mmAl). Significant differences were revealed between the radiopacity values among all groups (p < 0.05), except the Zr post materials (p = 0.56). CONCLUSIONS All tested post materials had higher radiopacity than dentin. Further studies will be required to clarify optimum radiopacity properties of the post materials to provide a precise clinical observation.

Endodontic management of immature teeth with spontaneous apical closure and periapical lesions: case series and review of the literature.

Spontaneous apical closure in non-vital immature teeth has been rarely encountered and outcome of non-surgical endodontic treatment of related teeth associated with periapical lesions has not yet been adequately elucidated. The aim of this article was to report endodontic management of spontaneous apical closure of infected untreated immature teeth with periapical lesions and to review previously proposed mechanisms for the development of spontaneous hard tissue barrier. Three patients were referred at different time intervals to the endodontic clinic for treatment of their maxillary anterior incisors with acute or chronic apical periodontitis. Dental histories indicated that related teeth had been subjected to trauma approximately 12-18 years previously. Radiographically, the involved teeth exhibited incomplete root formation with spontaneous apical closure and were associated with an apical radiolucency. After biomechanical preparation, calcium hydroxide paste was applied and was changed once or twice within 3 months. All canals were then filled with gutta-percha and AH Plus and the follow-up period was 16-50 months; both clinical and radiographic examinations revealed adequate function, the absence of clinical symptoms and significant healing of the periapical radiolucency.