Dentistry – Apparatus – Having intra-oral dispensing means
Reexamination Certificate
2000-06-07
2003-10-28
Lucchesi, Nicholas D. (Department: 3764)
Dentistry
Apparatus
Having intra-oral dispensing means
Reexamination Certificate
active
06638064
ABSTRACT:
FIELD OF THE INVENTION
The invention is an apparatus and method for use in dental applications. In particular, the invention is an apparatus and method for use in endodontic or root canal procedures.
BACKGROUND
Endodontics or root canal therapy is a well-known dental procedure wherein the crown of a diseased tooth is opened to permit the canal (or canals) of the tooth to be cleaned and filled. In general terms, a root canal proceeds as follows. The crown of the tooth is opened to expose the root canal. Typical root canals have a non-linear central axis, i.e., they are curved, and the curve of the canal can be quite severe. During an endodontic procedure, a series of very delicate, flexible, rotary driven or finger-held instruments or files are used to extirpate or clean out and shape the root canal. These files typically possess contoured or rough outer surfaces to enable the endodontist to break up and loosen tissue as well as remove infected dentin from the canal walls within the root canal. Examples of such files are discussed in U.S. Pat. No. 5,713,736 to Heath et al. The endodontist usually rotates and reciprocates the file to bring loose tissue and debris out of the root canal.
The files, however, are incapable of removing all of the necessary tissue and debris, especially tissue and debris trapped in the smaller lateral canals extending off the main canal. Thus, Endodontists remove this tissue and debris by injecting a fluid (typically a disinfecting agent or chelating agent) into the canal to irrigate the canal. The typical disinfecting fluid is a dilute solution of sodium hypochlorite. Ethylenediaminetetraacetic acid (EDTA) is a typical chelating agent.
Fluid injection is accomplished by means of a hollow needle or syringe. As used herein, the term needle will generally refer to the elongate, typically metal shank traditionally associated with medical injections. The term needle and shank may be used interchangeably herein unless the context of the description or claims requires otherwise. The term syringe is used to encompass both a needle and other elements necessary to discharge a fluid from a needle such as a fluid reservoir and plunger. The injection and removal of the solution is referred to as “irrigating” or “aspirating” the canal.
After irrigation, the cleaned, disinfected and vacant root canal is then obturated or filled, typically with a waxy, rubbery compound known as gutta percha. A set of rod-like pluggers similar to the files used to extirpate the canal force the gutta percha down into the canal. After the canal is filled, the crown of the tooth is repaired thereby completing the procedure.
The non-linear structure of root canals presents several problems for endodontists. The canal must be cleaned and disinfected but the integrity of the canal must be maintained. If a stiff file or plugger is used, the distal end of the tool may pierce the sidewall of the canal and destroy the tooth. If a flexible file or plugger is used, it must maintain enough rigidity to accomplish the task of removing or inserting material. For many years, a suitable material for making files and pluggers did not exist and endodontists compensated by creating larger entry holes in crowns and using the best materials at hand.
In the late 1980's and early 1990's, nickel-titanium alloys possessing superelastic and suitable shape memory properties became available. Instrument companies began manufacturing files and pluggers made from these alloys. The nickel-titanium files and pluggers allowed the endodontist to reach the bottom of the root canal without excessive risk of puncturing the side of the canal.
Although nickel-titanium files and pluggers improved portions of the root canal procedure, problems remain with respect to the irrigation, aspiration and disinfection of the canal. Presently, the irrigation solutions used to clean, disinfect, and remove debris in the canal are delivered using rigid irrigation needles. These needles are typically made of stainless steel and possess blunt ends. The distal end of the needle typically possesses slits or other structural components to ensure that the solution is distributed both axially and radially within the canal.
The rigid nature of a stainless steel irrigation syringe prevents an endodontist from reaching the bottom of a root canal with a syringe. Accordingly, an endodontist cannot directly irrigate the distal end of the root canal adjacent the apical foramina or a large portion of the complex network of fine lateral fissures, tubules and canals that extend from the main canal. The bottom of the root canal and the fine web of fissures may act as a breeding ground for bacteria that may later lead to a serious infection resulting in failure of the endodontic treatment and loss of the tooth. Using current syringes, the endodontist must try to force the solution, through exertion of hydraulic pressure, to the bottom of the canal and into the fine fissures and canals or make geometric adjustments to the insertion angle. If too much pressure is exerted, the solution may exit the root canal seriously damaging underlying tissue. Geometric adjustments to the insertion angle to extend the insertion distance may damage the crown. In short, complete irrigation and proper disinfection of the canal cannot be ensured using known instruments.
Accordingly, a need exists for an endodontic instrument that allows an endodontist to inject irrigation, disinfecting, and debris removal solutions adjacent the distal end of a root canal. Such an instrument must also be compatible with the physical and geometric constraints imposed by structure of the root canal.
OBJECT AND SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved endodontic instrument and method for use in root canal therapy. A further object of the invention is to provide an improved endodontic instrument and method for irrigating and disinfecting root canals during endodontic procedures. A still further object of the invention is to provide an improved endodontic instrument and method that allows for the injection of irrigating and disinfecting solutions at the distal end of a root canal adjacent the apical foramina.
The above and other objects and advantages of the present invention are achieved in the embodiments illustrated herein by the provision of an endodontic instrument adapted for use in performing root canal therapy on a tooth. The endodontic instrument according to the invention is particularly useful for irrigating a root canal possessing a non-linear central axis. In one embodiment, the endodontic instrument according to the invention comprises an elongate shank having a first end and an opposite second end and an enclosed axial channel extending the length of the shank for providing fluid communication between the first end and the second end. The enclosed axial channel delivers fluids to areas external to the second end of the shank (i.e., the wall of a root canal). The instrument also comprises at least one radial orifice positioned adjacent the second end for providing radial dispersion of fluid from the orifice. The instrument is further defined as possessing a shank having a flexibility sufficient to substantially traverse the entire length of a root canal having a non-linear central axis and position the second end of the shank adjacent the distal end of the curved root canal and the apical foramina.
In a further embodiment, the invention is a method for irrigating a root canal possessing a non-linear central axis. The method according to the invention comprises transferring a fluid by way of a needle from the crown of the tooth along the non-linear central axis of a root canal to a discharge point adjacent the apical foramina. Thereafter, the method comprises discharging a fluid from an orifice at the distal end of the needle such that a portion of the fluid is discharged along a vector that is substantially perpendicular to the openings of the side canals and tubules extending from the main root canal and adjacent the apical forami
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