[Show abstract][Hide abstract] ABSTRACT: This study evaluated the influence of different features of canal curvature geometry on the number of cycles to fracture of a rotary nickel-titanium endodontic instrument subjected to a cyclic fatigue test.
BioRaCe BR4C instruments (FKG Dentaire, La Chaux-de Fonds, Switzerland) were tested in 4 grooves simulating curved metallic artificial canals, each one measuring 1.5 mm in width, 20 mm in total length, and 3.5 mm in depth with a U-shaped bottom. The parameters of curvature including the radius and arc lengths and the position of the arc differed in the 4 canal designs. Fractured surfaces and helical shafts of the separated instruments were analyzed by scanning electron microscopy.
The Student's t test showed that a significantly lower number of cycles to fracture values were observed for instruments tested in canals with the smallest radius, the longest arc, and the arc located in the middle portion of the canal. Scanning electron microscopic analysis of the fracture surfaces revealed morphologic characteristics of ductile fracture. Plastic deformation was not observed in the helical shaft of the fractured instruments.
Curvature geometry including the radius and arc lengths and the position of the arc along the root canal influence the number of cycles to fracture of rotary nickel-titanium instruments subjected to flexural load.
Full-text · Article · May 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 in vitro study aimed to investigate the antibacterial effects of photodynamic therapy (PDT) with methylene blue (MB) or toluidine blue (TB) (both at 15 microg/mL) as a supplement to instrumentation/irrigation of root canals experimentally contaminated with Enterococcus faecalis.
Seventy extracted teeth had their root canals contaminated with an endodontic strain of E. faecalis for 7 days, instrumented with nickel-titanium instruments and irrigated either with 2.5% NaOCl or with 0.85% NaCl, and then randomly distributed into four experimental groups: MB/NaOCl (PDT with MB and NaOCl as the irrigant), TB/NaOCl (PDT with TB and NaOCl as the irrigant), MB/NaCl (PDT with MB and NaCl as the irrigant), and TB/NaCl (PDT with TB and NaCl as the irrigant). For PDT, the photosensitizer remained in the canal for 2 minutes before exposed to red light emitted from a diode laser for 4 minutes. Samples were taken before and after instrumentation/irrigation and following the specific PDT procedure for each group, plated onto Mitis-salivarius agar and the colony forming units counted.
Regardless of the irrigant used (NaOCl or NaCl), instrumentation significantly reduced bacterial counts in comparison to the baseline (p < 0.001). NaOCl as the irrigant was significantly more effective than NaCl, and this difference persisted after PDT, irrespective of the photosensitizer used (p < 0.05). PDT with either MB or TB did not significantly enhance disinfection after chemomechanical preparation using NaOCl as irrigant (p > 0.05). No significant differences were observed between the two photosensitizers (p > 0.05).
These in vitro results suggest that PDT with either MB or TB may not exert a significant supplemental effect to instrumentation/irrigation procedures with regard to intracanal disinfection. Further adjustments in the PDT protocol may be required to enhance predictability in bacterial elimination before clinical use is recommended.
Full-text · Article · Feb 2010 · Journal of endodontics
[Show abstract][Hide abstract] ABSTRACT: Several irrigation techniques have been recently introduced with the main objective of improving root canal disinfection. This in vitro study aimed at comparing the intracanal bacterial reduction promoted by chemomechanical preparation with 3 different irrigation techniques.
Root canals from extracted teeth were contaminated with Enterococcus faecalis ATCC 29212 for 7 days and then randomly distributed into 3 experimental groups of 20 teeth each: group 1, conventional irrigation with NaviTip needles inserted up to 3 mm short of the working length; group 2, same as group 1, but supplemented with final irrigant activation by the EndoActivator system; and group 3, irrigation with the EndoVac system. NaOCl and ethylenediaminetetraacetic acid (EDTA) were the irrigants used in all experimental groups. The overall preparation time was kept constant for the groups, but the total volume ranged from 20 mL (groups 1 and 2) to 43 mL (group 3). The control group was irrigated with saline solution (total volume, 43 mL). Samples taken before and after chemomechanical procedures were cultured, and the colony-forming units (CFUs) were counted.
Reduction in the bacterial populations was highly significant for all groups. The 3 experimental groups with NaOCl and EDTA as irrigants were significantly more effective than the control group with saline in reducing CFU counts. There were no significant differences between the 3 techniques tested.
There was no evident antibacterial superiority of any of the irrigation techniques evaluated in the present in vitro model.
Full-text · Article · Oct 2009 · Journal of endodontics