Dentistry – Method or material for testing – treating – restoring – or... – Endodontic
Reexamination Certificate
2001-05-03
2003-07-01
Shaver, Kevin (Department: 3732)
Dentistry
Method or material for testing, treating, restoring, or...
Endodontic
C433S102000
Reexamination Certificate
active
06585513
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention is related to the field of endodontistry. More particularly, the invention is related to systems and operating methods for the preparation of root canals for obturation and the subsequent obturating of the root canals. The systems and methods involve the use of instruments which are dedicated to preparing apical portions of root canals for obturation.
2. The Relevant Technology
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 biocompatible materials, such as gutta percha, before the pulp cavity is sealed, thereby promoting the healing and functional recovery of the tooth. This procedure is referred to as root canal therapy.
As indicated hereinabove, root canal preparation involves pulp removal, cleaning of the root canal walls and shaping of the canal walls. This is typically achieved through a guided procedure with the use of instruments which are moved either manually, mechanically or by combinations thereof These instruments are files or bits that are configured to bore and/or cut. Mechanical instrumentation can be achieved through the use of endodontic handpieces coupled to instruments such as files. The endodontic handpieces can impart rotational motion to a file, reciprocal motion by alternately rotating a file clockwise and counterclockwise, sonic movements or ultrasonic movements.
With regard to operating procedures, there are two basic methods from which all of the canal-preparation techniques can be derived. These methods have been interpreted by various authors in an operational context and also in terms of the instrumentation. The primary conventional systems and methods for removing pulp material from the root canal of a tooth are the apico-coronal (step-back) technique and the corono-apical (crown-down) technique. Although these conventional cleaning techniques both rely generally on sequential increases in the diameter of instruments inserted into the root canal. The step-back technique involves the sequential use of instruments by first inserting an instrument all the way down to the apex of the root canal and then using progressively larger and shorter files to clean the root canal. So the step-back technique involves cleaning the root canal from the apex toward the crown. The crown-down technique uses a set of files that are inserted sequentially further and further into the root canal until reaching the apex and then instrumenting along the entire length of the root canal after the apex has been reached. Each technique has its own unique benefits and disadvantages.
Regardless of which system is utilized, they both rely on ISO dimensions in terms of length, tip diameter and taper. In accordance with ISO, 0.02 is the standard taper of instruments used in cleaning the apical portion. What this means is that for every 1 mm of length, the instrument diameter increases by 0.02 mm. After the apical portion has been cleaned, then one or more soft, resilient, needle-like inserts known as gutta percha points are inserted in each root canal branch in order to at least partially seal and fill the root canal. These gutta percha points are also manufactured in accordance with ISO and have a 0.02 taper like the instruments used to shape the apical portion.
The term “gutta percha” refers to a rubbery material derived from natural rubber, typically blended with zinc oxide. This particular rubbery material is preferred because it is compressible, flexible and relatively soft so that it can be used to fill voids within the exposed root canal. The gutta percha points are typically impregnated with other materials such as radiopaque solids, zinc oxide, for its medicinal properties, and other passive or active ingredients as desired.
The gutta percha point or cone is used to seal the apex of the root canal. In order to ensure that the apex has been adequately sealed, a “tug back” seal is formed. That is, the gutta percha cone is first inserted and then removed. If it can be removed with little or no force, the gutta percha point is trimmed to yield a larger diameter tip and reinserted into the ape. This process is repeated until there is “tug back,” thus indicating that the fit between the gutta percha point and the apex is sufficiently tight to adequately seal the apex. However, in some instances the “tug back” may occur above the apex. When this occurs, the apex is not sealed and fluids may enter into the root canal through the apex. This can lead to discomfort and in some instances to failure of the procedure.
To overcome this problem, what is needed in the art of endodontic procedures are methods and system which improve the ability of an endodontic point such as a gutta percha point to seal a root canal at the apex of the root canal.
It would be an additional improvement in the art to provide methods and systems that result in a more thorough cleaning of the apical portion of the root canal to ensure that the “tug back” does not occur during the procedure before the apex has been reached.
SUMMARY AND OBJECTS OF THE INVENTION
An object of the present invention is to provide, methods and systems which improve the ability of an endodontic point such as a gutta percha point to seal a root canal at the apex of the root canal.
It is also an object of the present invention to provide methods and systems that provide for a more thorough cleaning of the apical portion of the root canal to ensure that the “tug back” does not occur during the procedure before the apex has been reached.
An additional object of the present invention is to provide methods and systems which enable the apical portion to be cleaned with files having tapers larger than standard instruments having an ISO taper after the portion above the apical portion has been cleaned and shaped.
Finally, it is an object of the present invention is to provide methods and systems that shape the apical portion of a root canal in a manner that enables a narrow cannula to reach as far as need to deliver adhesive resins for use in filling and/or sealing the root after the gutta percha point has been positioned in the root canal.
Some of the features of the invention which enable these objects to be achieved are summarized hereinbelow.
An apical portion instrument is provided that enables an apical portion of a root canal to be cleaned in a manner than enables an endodontic point, such as a gutta percha point to be easily received in the apical portion of the root canal to seal the apex. It is optimal to utilize a set of instruments. Each instrument in the set has a file that is long enough to extend to the apex of the root canal. At least one of the files in the set of instruments has an abrading portion with a taper that is greater than 0.02. Since conventional gutta percha points have a taper of about 0.02, like conventional instruments used to clean the apical portion of root canals, cleaning the apical portion with an abrading portion of a file that has a taper that is greater than 0.02 enables the gutta percha point to encounter significantly less obstacles or resistance when compared with prior art methodologies.
All of the instruments may have files with abrading portions that have the same taper, such as about 0.025. However, as long as the last file used to clean the apical portion is larger than 0.02 then the others can have any suitable taper. In one embodiment, several of the smaller files have abrading portions with tapers that are 0.02 while the larger files have abrading portions
Bumgarner Melba
Shaver Kevin
Ultradent Products Inc.
Workman & Nydegger & Seeley
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