Operative dentistry aje qualtrough, jd satterthwaite la morrow, pa brunton

Fig. 3.6
Typical files used in endodontics, Hedström (top) and K-file (bottom).
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FlexoFiles
• Using computer-assisted grinding technology, it has been possible
to fabricate these files from a round blank, similar to the K-type file.
• These files have sharper flutes to increase their cutting efficiency
and have a deeper space between flutes to transport dentine shav-
ings more efficiently but they are more prone to fracture.
Greater taper (GT) hand files
• These files are constructed from nickel titanium. They are non-ISO
files and are available in four sizes with varying taper, increasing
from 0.06, 0.08, 0.10 to 0.12; all have a size 20 tip (i.e. 0.20 mm).
Gutta-percha cones are available in the same range of tapers,
though the terminology used is often (confusingly) different: 0.06
taper is termed fine, 0.08 is fine-medium, 0.10 is medium and 0.12 is
medium large.
• GT files are designed to be active in a counter-clockwise direction.
• The most apical extent of a GT file should never engage dentine,
rather it should passively follow the canal direction.
Rotary instruments
Gates Glidden drills
The six instruments in this series are made from stainless steel. Each
instrument has a long shaft and a flame-shaped cutting head. Gates
Glidden drills are ideally used to cut dentine on the withdrawal
stroke. They are confined to the straight section of the canal and are
used serially and passively in a step-back manner, such that each 
successively larger drill is worked shorter than the preceding smaller
one. They may also be used in a step-down manner. Used properly,
these drills are inexpensive, safe and beneficial. However, they must
be used with care as they may separate and over-aggressive use may
result in perforation of the canal wall.