Precipitation hardenable stainless steel endodontic instruments and methods for manufacturing and using the instruments

Abstract

Precipitation hardenable stainless steel endodontic files and methods for their manufacture, wherein the most preferred precipitation hardenable stainless steel is 17-4PH and aging is preferably not one of the manufacturing steps. Precipitation hardenable stainless steels used in embodiments of this invention are iron-chromium-nickel grades that have the desired properties of flexibility, strength, hardness, wear resistance, stiffness, resistance to permanent deformation, resistance to variable torque, and biocompatibility for endodontic files.

Description

[0001] 1. The Field of the Invention[0002] The present invention relates generally to endodontic file instruments and methods for their manufacture. More specifically, the present invention relates to precipitation hardenable stainless steel endodontic instruments and methods for their manufacture that preferably do not include heat treatment.[0003] 2. Relevant Technology[0004] To preserve a tooth with a pulp that is diseased or is potentially diseased, it is generally necessary to remove as much of the pulp material as is possible from the pulp canal of the tooth, to shape the root canal(s) without excessively weakening the root canal walls, to prevent or minimize the presence of bacteria through the use of irrigants and dressings, and lastly, to clean the walls of the root canal(s) by removing the smear layer created during instrumentation of the root canal(s). These steps are all done to prepare the root cavity for sealing or obturation which involves filling the root canal with ...

AI Technical Summary

Benefits of technology

0092] Once the PH stainless steel endodontic file has been appropriately shaped it is then ready for use. As indicated above, conventional techniques teach that such stainless steel alloys are aged by thermal treatment to increase their hardness. However, it has been discovered in the co

Problems solved by technology

As a result, it becomes increasingly difficult for the files to adjust to or to follow the contours of the perimeter surfaces of the root canal.

This reduced flexibility also increases the likelihood that the files will fail to contact some portions while removing too much of the surrounding dentin in some areas through excessive abrasion and resulting in overthinning of the walls.

Not only is the completeness effected by the use of a set of files wherein each file is more rigid than the preceding file but the ability to safely move the file within the canal is also limited.

More particularly, the increasing rigidity results in decreased ability to negotiate the curves in the canal.

Significant problems that can result from inserting increasingly rigid files and also from initially inserting a file all the way down to the apex includes laceration and transportation of the apical foramen, as well as misdirection and perforation of the wall.

Another problem is the formation of ledges.

Ledges can occur when a practitioner attempts to insert a file as far as the apex and the file is too inflexible to properly curve with the root canal or move around a protrusion.

Such ledges are difficult to bypass; and if the ledge occurs very close to the apex, the ledge may give the practitioner the mistaken impression that the apex has been reached.

One example of the operational deficiency of the crown-down method lies in its association with instruments made of nickel/titanium (Ni/Ti).

Additionally, it has been asserted that such files are more likely to stay in the center of the root canal, thereby decreasing the likelihood of ledging or perforating the root canal walls.

Moreover, because nickel/titanium files are more flexible than steel files, they tend to follow the path of least resistance and therefore cannot be used, in the same way as steel files, to be applied actively and intentionally by the operator.

As a result, even when the operator knows the thickness of a particular portion, such as an interference or obstruction which the operator desires to rectify or straighten, the operator lacks the freedom to aggressively drive the file as needed and clean the portions that are difficult to reach.

Accordingly, when a nickel/titanium file is used to clean a non-cylindrically shaped root canal, the file moves only at the center of the canal and/or the area of least resistance and fails to remove all of the necrotic tissue.

Problems, such as overthinning of root canal walls, perforation of a root canal wall, excessively weakening of the walls of the tooth and a failure to fully contact all of the canal walls, can be easily caused by the passive, self-guiding use of nickel/titanium files with progressively larger tapers in the transition from the first instrument to

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