This study aimed to compare the cross-sectional shape of two nickel-titaniu
m rotary instruments, namely Profile and Quantec files, both ISO 25, 0.06 t
aper, and sought to relate this to the chips produced by cutting dentine. A
limited comparison was made with stainless steel engine reamers. First, fi
ve files of each type were sectioned transversely at 12 mm, 8 mm and 4 mm f
rom the tip and examined by scanning electron microscopy. The cutting angle
s were assessed by a direct measurement technique which allowed for the inc
lination of a cutting edge to the root canal. Second, eight samples of cutt
ing debris were collected from instrumentation by each type of nickel-titan
ium file and four samples from the engine reamers. The major and minor axis
, area and roundness of the dentine chips in each sample were measured usin
g computerized par-tide analysis. The results demonstrated that all files h
ad a negative cutting angle which varied at the different levels (ProFiles
range 69.4 degrees to 58.4 degrees and Quantec range 74.8 degrees to 56.8 d
egrees). The consistency within files of the same type was good as demonstr
ated by low standard deviations, except for Quantec files at the 4 mm level
where higher standard deviations of 4.1 degrees and 5.5 degrees for the tw
o blades were found. The chip analysis showed significant differences betwe
en chips produced by Profile and Quantec files (P<0.05). The latter were la
rger and rounder. The chips from the Profile and the engine reamer chips we
re similar in dimension (P>0.05). No simple relationship existed between fi
le geometry and the dentine chips produced during instrumentation.