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Preparation of the apical part of the root canal by the Lightspeed and step‐back techniques
Author(s) -
Isabelle Portenier,
F Lutz,
F Barbakow
Publication year - 1998
Publication title -
international endodontic journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.988
H-Index - 119
eISSN - 1365-2591
pISSN - 0143-2885
DOI - 10.1046/j.1365-2591.1998.00116.x
Subject(s) - root canal , dentistry , orthodontics , materials science , displacement (psychology) , mathematics , medicine , psychology , psychotherapist
This study measured in vitro the displacement of natural canal centres in 18 human teeth before and after shaping by the step‐back or Lightspeed techniques. Experimental roots ( n = 9 per group), embedded in clear plastic, were cross‐sectioned using a 0.1‐mm‐thick band saw at distances 1.25 mm, 3.25 mm and 5.25 mm from the apices. A stereo microscope was used to take 35 mm slides of the cut surfaces of the sectioned roots and canals. The slides of the uninstrumented canals were scanned into a computer and saved. Each sectioned root was then reassembled and the canals shaped by the step‐back or Lightspeed technique. File size 40 and instrument size 50 were selected as the master apical file and master apical rotary for the step‐back and Lightspeed groups, respectively. The 18 prepared canals were photographed, and the 35 mm slides scanned and computer stored as previously. This allowed the positions of the pre‐ and postinstrumented roots to be electronically superimposed for subsequent analyses. Displacements of the root canal centres before and after preparation were assessed in relation to the cross‐sectional diameter of the files or instruments used. In addition, increases in cross‐sectional area of the root canals after preparation were evaluated in relation to the cross‐sectional area of the files or instruments used. Engine‐driven nickel‐titanium Lightspeed instruments caused significantly less ( P < 0.001) displacement of the canal centres, so roots in the Lightspeed group remained better centred than those in the step‐back group. The mean cross‐sectional area after preparation in the Lightspeed group was significantly less ( P < 0.001) than that recorded in the step‐back group. Clinically, this implies less apical transportation and less dentine destruction with the Lightspeed technique than with the step‐back technique.