Fred Barbakow

Effects of Irrigation on Debris and Smear Layer on Canal Walls Prepared by Two Rotary Techniques: A Scanning Electron Microscopic Study

Debris and smear layer were evaluated in canals prepared with either Lightspeed (LS) or ProFile (PF) rotary instruments. Irrigants used were tap water (group A) or alternating 5.25% NaOCl and 17% EDTA (group B). Apical stops were prepared to size 52.5 in the LS and to size 6 (approximately ISO size 36) in the PF techniques. The roots were split longitudinally and examined at apical, middle and coronal levels for debris and the smear layer using a 5-step scale. Using only water, mean debris scores were similar for LS and PF. In contrast, with EDTA/NaOCl, LS- and PF-prepared canals had similar debris scores at the apical and coronal levels, but there was a significant difference at the middle level. Mean smear layer scores were similar in LS- and PF-shaped canals when water was the sole irrigant. In contrast, with NaOCl and EDTA, mean smear layer scores were significantly different at the apical and middle levels, but not at the coronal level. Neither technique was superior in removing debris, but larger canal preparations obtained in this study with LS instruments enabled a more effective removal of the smear layer in the EDTA-NaOCl group.

Wear of nickel-titanium lightspeed instruments evaluated by scanning electron microscopy

Used rotary nickel-titanium instruments require frequent replacing. This laboratory study evaluated defects of Lightspeed cutting tips before and after usage. The instruments were fixed into custom-made holders, the cutting heads photographed in a scanning electron microscope at x120 to x400 magnification at preset points around the cutting tip (90, 180, 270 and 360 degrees) and head-on. Instrument sizes 20 to 32.5, 35 to 60, and 65 to 100 were used in 9, 18, and 36 canals, respectively, and autoclaved after shaping every third root canal. The used instruments were cleaned and then reexamined in a scanning electron microscope as before. The presence of 11 types of conditions was scored from the pre- and postusage photographs. No instruments fractured during the test, but all the cutting heads had one or more imperfections, even before usage. The presence of debris, pitting, and metal strips changed significantly. Imperfections were found on new and used Lightspeed cutting heads, indicating the general difficulty in machining defect-free nickel-titanium rotary instruments. However, high quality should remain a goal to improve instrument efficiency.

Comparing Apical Preparations of Root Canals Shaped by Nickel-Titanium Rotary Instruments and Nickel–Titanium Hand Instruments

This study measured displacement of canal centers in extracted human teeth after preparation by Lightspeed and nickel-titanium K-files. The specimens were divided into two groups (n = 11), after radiographing the roots from the buccolingual and mesiodistal planes with pathfinding files in situ. More strongly and less strongly curved canals were, respectively, assigned to the Lightspeed and nickel-titanium K-file groups. Using a reassembly technique, cross-sections at 1.25 mm, 3.25 mm, and 5.25 mm from the apices were made of the experimental roots embedded in clear plastic. Stereomicroscopic 35-mm slides were taken of the uninstrumented sectioned canals. The sections were reassembled and then prepared to size 50 Master Apical Rotary and size 40 Master Apical Files, for the Lightspeed and K-file groups, respectively. Similar 35-mm slides of the instrumented canals were taken and electronically superimposed over their uninstrumented counterparts. Displacements of root canal centers after preparation and increases in cross-sectional areas of the prepared root canals were evaluated at specific levels. No significant differences in displacement of canal centers or between the mean cross-sectional areas of the instrumented root canals were recorded between the Lightspeed and K-file groups. Both types of instruments produced similar displacement of canal centers after preparation.

An in vivo comparison of gradient and absolute impedance electronic apex locators

Two electronic apex locators based on the gradient (Apit) and absolute (Odontometer) impedance principles were evaluated. Distances of file tips to apical foramina were determined in vivo with the electronic apex locators and subsequently verified after extraction. Mean differences between file tips and apical foramina were +0.14 +/- 0.27 mm and -0.36 +/- 0.71 mm for the Apit and Odontometer, respectively. These differences were statistically significant (p < 0.001). the Apits and Odontometers results ranged from +0.85 to -0.65 mm and from +0.35 to 2.45 mm from the apical foramen, respectively. Ninety-three and 73% of the findings for the Apit and the Odontometer, respectively, were within the +/- 0.5 mm range, whereas 100% and 86%, respectively, were within the +/- 1.0 mm range. Thirty-three and 43% of the results for the Apit and the Odontometer, respectively, were 1.0 mm or less coronal to the apical foramen. The Apit tended to yield the more reliable results because of the narrower range.