[Show abstract][Hide abstract] ABSTRACT: Objective: This study compared the mechanical behavior of nickel-titanium instruments with similar geometry, but manufactured by different methods. Material and Methods: Twenty 25/0.06 RaCe files (FKG Dentaire, La Chaux-de-Fonds, Switzerland), 25 mm in length, manufactured with machined conventional NiTi wires; twenty 25/0.06 Twisted File endodontic instruments (TF) (SybronEndo, Orange, CA, USA), 27 mm in length, manufactured by twisting; and twenty 25/0.06 ProFile Vortex endodontic instruments (Dentsply Tulsa Dental, Tulsa, OK, USA), 25 mm in length, manufactured with M-Wire alloy were subjected to flexibility and cyclic fatigue tests. Each group comprised 10 instruments from each manufacturer. Results: Parametric ANOVA revealed significant difference between maximum load values in the following sequence: ProFile Vortex > RaCe > TF (p < 0.01). The rotating-bending test assessed the cyclic fatigue by measuring the time and number of cycles to fracture (NCF). Parametric ANOVA, with significance level set at 1%, revealed that RaCe files had significantly lower resistance than ProFile Vortex which, in turn, had lower values than TF, in terms of time and number of cycles (p < 0.01). Conclusion: TF instruments were more flexible than RaCe which, in turn, presented lower resistance than ProFile Vortex. Regarding the cyclic fatigue test, TF instruments had significantly better performance than the other two instruments tested, particularly in terms of time and NCF.
[Show abstract][Hide abstract] ABSTRACT: Introduction
This article describes 3 cases that presented persistent symptoms after appropriate endodontic treatment. Histopathologic and histobacteriologic investigation were conducted for determination of the cause.
Three cases are reported that presented with persistent symptoms after endodontic retreatment (cases 1 and 2) or treatment (case 3). Periapical surgery was indicated and performed in these cases. The biopsy specimens, consisting of root apices and the apical periodontitis lesions, were subjected to histopathologic and histobacteriologic analyses.
Case 1 was an apical cyst with necrotic debris, heavily colonized by ramifying bacteria, in the lumen. No bacteria were found in the apical root canal system. Case 2 was a granuloma displaying numerous bacterial aggregations through the inflammatory tissue. Infection was also present in the dentinal tubules at the apical root canal. Case 3 was a cyst with bacterial colonies floating in its lumen; bacterial biofilms were also seen on the external apical root surface, filling a large lateral canal and other apical ramifications, and between layers of cementum detached from the root surface. No bacteria were detected in the main root canal.
Different forms of extraradicular infection were associated with symptoms in these cases, leading to short-term endodontic failure only solved by periapical surgery.
No preview · Article · Oct 2014 · Journal of Endodontics
[Show abstract][Hide abstract] ABSTRACT: Introduction: This study compared the flexibility and torsional resistance of two types of instruments manufactured with special NiTi alloys, and one with conventional NiTi. Methods: Twisted File (TF) instruments manufactured with the R-phase of NiTi (SybronEndo, Orange, CA), and ProFile Vortex instruments (Dentsply Tulsa Dental, Tulsa, OK, USA) made of M-Wire NiTi were compared with RaCe (FKG Dentaire, La Chaux-de-Fonds, Switzerland) instruments made of conventional NiTi. Flexibility and torsion assays were carried out using twenty 25/0.06 instruments from each manufacturer. Statistical analysis was performed by ANOVA. Results: The mechanical resistance of the instruments tested was significantly different. TF were the most flexible instruments, followed by RaCe and ProFile Vortex (P < 0.01). In the torsion assay, ProFile Vortex instruments endured the greatest maximum load and maximum torque values prior to fracture, followed by RaCe and TF (P < 0.01). The torsional resistance values of RaCe and TF were not significantly different (P = 0.061). Conclusion: We observed a relationship between flexibility and torsional resistance (maximum torque and maximum angular deflection in torsion). The most flexible instrument (TF) was the least resistant to torsion, while the least flexible (ProFile Vortex) was the most resistant to torsion. RaCe presented intermediate results for both flexibility and torsional resistance.
[Show abstract][Hide abstract] ABSTRACT: This study evaluated the influence of flexibility and reciprocating movement on the fatigue life of endodontic instruments subjected to static and dynamic tests.
The rotary nickel-titanium instruments used in this study were Reciproc and Mtwo. The instruments were initially subjected to a cantilever-bending test and then to static and dynamic fatigue tests. Reciproc instruments were operated in reciprocating movement, whereas Mtwo instruments were worked in continuous rotation.
The means of bending resistance (maximum load in grams) of the instruments were 274.9 for Reciproc and 429 for Mtwo. The mean times (in seconds) to fracture of the instruments subjected to static and dynamic tests were 214.5 (static) and 286.3 (dynamic) for Reciproc and 38.9 (static) and 99 (dynamic) for Mtwo. The Student's t test revealed significant differences in all tests (P < .05).
The results of the present study showed longer fatigue life for instruments with higher flexibility, driven by reciprocating movement, and in the dynamic testing model. These findings reinforce the assumption that use of reciprocating movement is a means to prolong the fatigue life of rotary nickel-titanium endodontic instruments during instrumentation of curved canals.
Full-text · Article · May 2013 · Journal of endodontics
[Show abstract][Hide abstract] ABSTRACT: This study compared the mechanical properties of endodontic instruments made of conventional nickel-titanium (NiTi) wire (K(3) and Revo-S SU), M-Wire (ProFile Vortex), or NiTi alloy in R-phase (K(3)XF).
The test instruments were subjected to mechanical tests to evaluate resistance to bending (flexibility), cyclic fatigue, and torsional load in clockwise rotation. Data were statistically evaluated by the analysis of variance test and the Student-Newman-Keuls test for multiple comparisons.
In the bending resistance test, flexibility decreased in the following order: K(3)XF > Revo-S SU > ProFile Vortex > K(3). The ranking in the fatigue resistance test was the following: K(3)XF > K(3) > ProFile Vortex > Revo-S SU. In the torsional assay, the angular deflection at failure decreased in the following order: K(3)XF > Revo-S SU > K(3) > ProFile Vortex. For the maximum torque values, the ranking was K(3) > K(3)XF > ProFile Vortex > Revo-S SU.
The results showed that the K(3)XF instrument, which is made of NiTi alloy in R-phase, had the overall best performance in terms of flexibility, angular deflection at failure, and cyclic fatigue resistance. In addition to the alloy from which the instrument is manufactured, the design and dimensions are important determinants of the mechanical performance of endodontic instruments.
Full-text · Article · Apr 2013 · Journal of endodontics
[Show abstract][Hide abstract] ABSTRACT: This study compared the mechanical properties of 3 pathfinding endodontic instruments.
The test instruments were subjected to mechanical tests to evaluate resistance to bending (flexibility), buckling, cyclic fatigue, and torsional load in clockwise rotation. Data were statistically evaluated by analysis of variance and the Student-Newman-Keuls test for multiple comparisons.
In the buckling resistance test, the highest values were observed for C-Pilot files (VDW, Munich, Germany) and the lowest for Scout RaCe (FKG Dentaire, La Chaux-de-Fonds, Switzerland) instruments. In the bending resistance test, the lowest flexibility was observed for the C-Pilot instrument, and no significant difference was observed between Scout RaCe and PathFile (Maillefer/Dentsply, Ballaigues, Switzerland) instruments. The ranking in the fatigue resistance test was the following: PathFile > Scout RaCe > C-Pilot, with statistically significant differences observed in the number of cycles to fracture between all the instruments. In the torsional assay, the angular deflection to fracture decreased in the following order: Scout RaCe > PathFile > C-Pilot. As for the maximum torque values, the ranking was as follows: C-Pilot > PathFile > Scout RaCe.
Findings revealed that the stainless-steel C-Pilot instrument showed increased resistance to buckling but decreased flexibility and cyclic fatigue resistance when compared with nickel-titanium pathfinding instruments. PathFile instruments showed the highest resistance to cyclic fatigue, and Scout RaCe files exhibited the highest angular deflection to fracture. The different mechanical behavior of the instruments indicates that the combined use of stainless steel hand instruments and rotary nickel-titanium instruments during the exploration of narrow curved canals may be necessary to exploit the best performance of each pathfinding instrument.
Full-text · Article · Oct 2012 · Journal of endodontics
[Show abstract][Hide abstract] ABSTRACT: This study compared the buckling resistance of the following endodontic pathfinding instruments: C-Pilot file (VDW, Munich, Germany), C+ file (Maillefer/Dentsply, Ballaigues, Switzerland), and PathFile (Maillefer/Dentsply).
The test instruments were subjected to a devised buckling resistance test, which consisted of the application of an increasing load in the axial direction of the instrument by using a universal testing machine. The maximum load required to generate a lateral elastic displacement of 1 mm was recorded for each instrument.
The results indicated that the buckling resistance decreased in the following order: C+ file > C-Pilot file > PathFile. The difference was statistically significant (P < .05).
The stainless steel instruments (C+ and C-Pilot) were more resistant to buckling than the nickel-titanium instrument (PathFile). Considering that buckling resistance may influence the performance of instruments during the negotiation of constricted canals, the C+ files showed significantly better results than the other instruments tested.
Full-text · Article · Mar 2012 · Journal of endodontics
[Show abstract][Hide abstract] ABSTRACT: This article describes a case of recurrent post-treatment apical periodontitis and late failure after endodontic retreatment performed in a single visit.
The patient presented with a tooth exhibiting inadequate endodontic treatment and a large periradicular lesion that extended laterally to the root. Retreatment was performed in a single visit and involved chemomechanical preparation using 5.25% NaOCl as the irrigant and root canal obturation by Schilder's vertical compaction technique. A large lateral canal was radiographically revealed after obturation. After 2 years, the lesion was no longer radiographically discernible, a condition that was confirmed 9 years after retreatment procedures. Nonetheless, after 12 years, radiographs revealed recurrent disease. Apical surgery was performed, and the root apex, including the area of the large lateral canal, was resected with care to maintain the lesion attached to it. The biopsy specimen was subjected to histopathologic and histobacteriologic analyses.
Longitudinal sections of the apical root specimen revealed a heavy dentinal tubule infection surrounding the area of the lateral canal. Bacteria were not found in any other area of the specimen. No other possible reason for the inflammatory periradicular lesion, such as root fracture, coronal leakage, or foreign-body reaction, was evident.
A persistent intraradicular infection caused by bacteria located within dentinal tubules is the most reasonable explanation for resurgence of the apical periodontitis lesion. This case report stresses the importance of attaining proper disinfection of the root canal system for a predictable long-term outcome of the treatment.
Full-text · Article · Feb 2012 · Journal of endodontics