Date of Award

Spring 1999

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)



First Advisor

Gaffney, Joseph

Second Advisor

Kniaz, Avrom

Third Advisor

Austin, B. P.


Endodontic preparation of root canals have traditionally involved the use of stainless steel files and reamers. Conventional endodontic files have now been developed using nickel - titanium. This change in metallurgy from stainless steel to nickel titanium has altered the face of endodontics today. Initially the nickel-titanium files were thought to possess all the qualities of an endodontic file with minimal flawed characteristics. One of the characteristics of nickel-titanium files that has proven to be advantageous is its increased flexibility. It has been shown that nickel-titanium files possess a 2-3 fold increase in flexibility over stainless steel. In the early use of these nickel-titanium files one unforeseen was instrument separation. Instrument separation with stainless steel files can, in most instances, be avoided by careful and frequent observation of the file for unwinding, bending or other permanent deformation. In the case of nickel-titanium files, even upon close examination, deformation is rarely seen before separation. This makes it difficult to determine when a file is to be reused or discarded. When the nickel titanium files are used in a rotary system the problems are compounded because they are not as frequently withdrawn from the canal using the recommended techniques. Manufacturers learned quickly that by increasing the taper of the file from the traditional 0.02mm/mm to a larger taper of 0.03, 0.04, 0.05 or even 0.06 mm/mm the files would be somewhat more resistant to separation under larger stress loads. With the increase in bulk of the instrument the much sought after characteristic of flexibility is now being questioned. The use of nickel-titanium files has increased so much over the last few years and at such a rapid pace that there have been no new standards set forth to guide manufacturers or to inform practitioners which instruments are currently needed and how they are to be used. ADA specification 28 was designed for stainless steel files hand files. The specifications don't take into consideration that nickel titanium instruments are mostly being used in a rotary handpiece, that the material has changed, and that the taper of the files has increased from .02 mm/mm to as high as .12 mm/mm. My hypothesis is: as nickel titanium files increase in taper (tapers >.02mm/mm) the behavior of the files will begin to mimic stainless steel in torsional force and in rotations to failure. The nickel titanium files of greater taper (.02, .03, .04, .05, & .06mm/mm) will be tested at 1, 2, 3, 4, & 5mm from the Do in a clockwise rotational manner to confirm or dispute this hypothesis.



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