Endodontic treatment system

Abstract

An endodontic system of shaping instruments, irrigation cannulas, filling instruments and materials designed to safely create specific tapers of root canal preparations and to clean, dry, seal, and restore them. The shaping instruments are a series of reamers, files, and handpiece burs, made of stainless steel, nickel-titanium, or other alloys, which impart several different specifically-tapered apertures in root canals. The instruments have one or more safety features to eliminate perforating curved roots, including shorter flute length as the angle of taper increases and variable sharpness along the length of the flute portion, as well as variable flute pitch along the length of the flute portion to maximize cutting efficiency and resistance to breakage, and a rounded tip to eliminate ledging. The hand instruments have a handle designed to optimize use of the instruments in apically directed, notary cutting motions. The irrigation cannulas, the condensation heat carriers, pluggers, injection needles, and backfillers, and the materials, including drying paper points, filling materials, and restorative post systems, have shapes which match the canal tapers created by the shaping instruments.

Description

[0001]This application is the parent of a Divisional Reissue application Ser. No. 10 / 811,796, filed Mar. 29, 2004.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates generally to endodontic instruments and, more particularly, to root canal files or reamers used in the cleaning of material present in the root canal of a human tooth and for enlarging and shaping the root canal so that it may be prepared for filling and also to the materials necessary to dry, fill and restore the prepared channels.[0004]2. Description of the Related Art[0005]A relatively common but difficult dental procedure is the cleaning, shaping, and filling of the root canal of a patient's tooth. In the performance of a root canal procedure, a hole is first cut in the crown or exposed portion of the tooth, typically either in the biting surface of the tooth, for posterior teeth, or in the side of the tooth on the interior of the jaw for incisor teeth. Small endodontic inst...

AI Technical Summary

Benefits of technology

[0044]Fifth, safety and efficiency when these shaping files are used with rotary cutting motions is gained in the present invention by longitudinally varying the pitch and relative sharpness of cutting flutes. When shaping files are used with rotary cutting motions two primary problems are encountered, potential for breakage and slowness of cutting. This is overcome in the present invention by varying the flute pitch from an in-line reamer-like angle at the shank end of the instrument to a more perpendicular K-type flute angle at the file tip. Instead of, or in addition to the above, the relative sharpness of the cutting flutes is varied along the length of the files, being sharpest at the strong shank end to allow for aggressive cutting by the wider flutes, and dullest near the smaller, more fragile tip of the file so these flutes can easily release from the canal wall during rotation, thereby preventing file breakage which can occur when the tip binds.

[0045]Sixth, functional safety when using tapered shaping files in curved canals is enhanced through the use of the alloy nickel-titanium (Nitinol™. This unusual metal exhibits stress-induced phase-transformation of its crystal lattice structure resulting in characteristics of superelasticity, allowing large-diameter Nitinol files to work around root canal curvatures that would be impossible with stainless steel. Nitinol's elastic memory also allows, in one arrangement of the invention, curvatures to be preset in the file during the manufacturing process. By heating and cooling files made of this metal, different curvatures can be present in the metal so that the desired shape is “remembered”, allowing the file to straighten in the relatively uncurved coronal portion of canals and recurve itself when the file tip moves deeper and encounters apical root canal curvatures. When added to a Hedstrom-fluted taper file, a preset file bend directed toward its safe edge causes the Nitinol version of this shaping instrument to automatically seek the inside of canal curvatures with its non-cutting side, thereby effortlessly preventing lateral perforation.

[0046]The seventh aspect of the present invention involves an improvement in the shape of the handle provided for files of the invention. Standard file handles conventionally have a narrowed waist portion with enlarged diameters at both ends of the handle. This is to accommodate a push-pull action in conventional use of the file. Handles in accordance with the present invention have an end diameter smaller than the waist of conventional file handles, and they taper to a larger-than-conventional diameter near the file shank, where the file is embedded in the handle. Since the file is designed to cut with apically directed rotary forces, the shape of the handle enhances operator comfort and reduces the force necessary to cut the desired shape into the root structure around the original canal. This “pear-shaped” handle also enhances the use of standard ISO K-type files used with apically-directed cutting motions.

[0047]Eighth, one of the most important improvements over existing art is the provision of a coherent system of irrigating cannulas, paper points, filling materials and instruments, and restorative posts which relate to the shapes of corresponding shaping files and thus to the pre-define

Problems solved by technology

A relatively common but difficult dental procedure is the cleaning, shaping, and filling of the root canal of a patient's tooth.

While this feature does add strength to the tips of smaller ground-flute instruments, it creates file tips which are too stiff and inefficient in the larger sizes.

Unfortunately, even twisted-flute #15 files are often not strong enough to withstand the tremendous apical forces which dentists bring to bear when attempting to negotiate calcified canal orifices.

Another problem countered when using negotiation files of small diameters is the relatively large jump in tip diameter between #10 files and #15 files, a change of 50%.

The reason for Jacklich's file design is that ground-flute instruments are not strong enough or stiff enough in the smaller sizes.

Although stainless steel ground-flute files are of acceptable strength in ISO sizes #20 and larger, they are of inadequate strength in size #'s 06, 08, 10 and 15.

Another cause of root perforation is the inadvertent introduction of large engine-driven Gates-Glidden or Peezo burs into the middle third of thin, curved roots.

Quite often, when these burs are new and sharp, the operator will intend to use one of the larger sizes only at the orifice of the canal but will helplessly watch the bur grab the canal walls and pull itself into dangerous depths in the root.

While perforation is probably the worst outcome of mistakes in shaping procedures, there is a more common problem in near-perforations and root weakening caused by overzealous widening of the canal preparation.

However, it is difficult to determine the fine line between creating adequate access and dangerous over-instrumentation, as all of these procedures are accomplished in microscopic root canal systems that are hidden from direct view.

This technique is, at best, a difficult and time-consuming method as the dentist must indirectly gauge the rate of taper in the preparation by the distance interval of step-back of the progressively larger instruments as they fit further back from the canal terminus.

As only the ISO taper of 0.02 mm/mm is currently available in standard sizes to dentists in files, irrigation cannulas, condensation pluggers, heat carriers and injection needles, paper points, filling material, and restorative posts, the current shift to canal preparations of greater taper has created great difficulties for dentists who want to enhance their root canal shaping objectives.

While these variably tapered instruments can create continuously tapered root canal preparations, they are extremely difficult to pull out of the canal by hand because the whole length of the cutting flutes is engaged in the canal, as opposed to standard ISO H

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