Dentistry – Method or material for testing – treating – restoring – or... – Endodontic
Reexamination Certificate
1998-11-12
2001-01-30
Wilson, John J. (Department: 3732)
Dentistry
Method or material for testing, treating, restoring, or...
Endodontic
C433S102000
Reexamination Certificate
active
06179617
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
This invention relates to microbrushes, and, in particular, to brushes which are used during an endodontic or root canal procedure to more predictably clean the root canal system prior to obturation.
Following tooth maturation, the dental pulp is harbored within the structural elements of the tooth. Frequently, and for a variety of reasons, the pulp is irreversibly injured, resulting in inflammatory and infectious conditions which often adversely affect the tooth, its supporting structures, and the patient's health. Clinically, as an alternative to extraction, root canal treatment is performed and ideally directed towards the elimination of pulp, bacteria, and related irritants from the root canal system, followed by three-dimensionally filling the root canal space with an inert, biocompatible, dimensionally stable, filling material, such as gutta percha. The obturation procedures will fill not just the main canal, but the fins, webs, cul-de-sacs, lateral canals, and all portals of exit between the root canal system and the tooth's attachment apparatus.
Root canal procedures are common. In 1994 alone, some 40 million root canal procedures were performed in the United States. Central to a successful endodontic treatment has been the use of chemicals to enhance canal debridement during cleaning and shaping procedures to facilitate the preparation and complete cleaning of the root canal system. The chemicals used to enhance canal debridement during cleaning and shaping procedures potentially reach all aspects of the root canal system. The most popular chemicals currently used during canal preparation to actively assist in cleaning include bleach, hydrogen peroxide, and chelating agents. Often, a 2%-5% solution of a clear, pale, greenish-yellow strongly alkaline solution of sodium hypochlorite (NaOCI) is used.
During canal preparation, the sodium hypochlorite solution is liberally irrigated into the root canal space where its solvent action facilitates the digestion and removal of pulp and bacteria and the destruction and removal of viruses, spores, endotoxins and other irritants generated by the microorganisms in the canal system as the solution penetrates into all aspects of the root canal system. However, studies have shown that even the most thorough use of sodium hypochlorite does not remove all the material from the root canals. The root canals are defined by millions of dentinal tubules per square millimeter, and the irritants can find their way into the tubules of the root canal systems. Thus, after cleaning and shaping procedures, the root canal is still covered with a film of debris, frequently described in the literature as a “smear layer.” This “smear layer” includes dentinal mud and/or organic debris, including the irritants noted above.
The smear layer or film compromises the sealing of the root canal system with gutta percha and root canal sealer. If obturation is incomplete then the root canal space is predisposed to leakage and failure. Post-treatment failures attributable to leakage are common and require endodontic retreatment of the tooth. Thus, for a complete and thorough cleaning, this smear layer or film should be removed. Once the existence of this smear layer was discovered, practitioners began using a weak acid or surfactant, such as 17% EDTA ethyldiamine-tetraacetic acid), in an effort to remove the smear layer. Typically, the root canal is flushed with EDTA to accomplish this. Some practitioners have been known to use root canal instruments or files to enhance the performance of the EDTA. The files may be manually used or may be mounted in a rotary or vibratory handpiece. Even when files are used, it is difficult to ensure that the file is brought into contact with the complete surface of the root canal, and hence it is difficult to ensure that substantially all of the smear layer has been removed. Additionally, the use of files, especially with a handpiece, leads to iatrogenic events, such as broken instruments, ledges in the wall of the root canal preparaion, or even perforation of the root canal system. Thus, it is desirable to provide a tool which can remove the smear layer without the associated possibility of iatrogenic events associated with the use of files and other hard instruments.
BRIEF SUMMARY OF THE INVENTION
Briefly stated, a micro-brush is provided which can be used to reach into the root canal to brush and make intimate contact with normal root canal irregularities that exist even after optimal canal preparation procedures. This brushing action facilitates removing the smear layer which remains in the root canal after the pulp and irritants have been mechanically and chemically removed from the root canal using files and sodium hypochlorite. The brush is used in association with an intracanal irrigant such as EDTA, to remove the debris or smear layer or film, from the root canal.
The brush includes a shaft or shank and a tapered brush section depending from the shank. The brush section includes a plurality of bristles extending radially from a central wire base. The bristles are made from a material which is sufficiently stiff so that it will have good rubbing action against the root canal wall to remove the smear layer, which is sufficiently pliable so that it can bend and flex to reach the normal irregularities in the root canal wall, and which is sufficiently soft so that the use of the brush will not form gouges or ledges in the root canal wall (i.e., will not substantially change the normal morphology of the root canal system). The bristles can be formed in a reverse thread pattern so that rotation of the brush in the root canal will pull the contents of the smear layer coronally. The shank can be provided with a handle for manual use or can be adapted to be received in a rotary or vibratory (sonic and ultrasonic) handpieces to impart rotational or vibratory motion to the micro-brush.
The brush section has a diameter of between about 0.2 mm and about 0.5 mm at a tip end and a diameter of between about 1 mm and 2 mm at its coronal end. The brush section is about 16 mm long, and thus has a taper of between about 0.06 mm/mm and about 0.12 mm/mm.
A finishing technique that enhances the cleanliness of a root canal preparation utilized before packing or obturation procedures during an endodontic procedure on a living patient includes the steps of preparing an access cavity to expose the orifice(s) to the root canal beneath the pulp chamber of the tooth crown; mechanically preparing and chemically eliminating the soft tissue, bacteria, and related irritants from the root canal system; flushing the root canal after it has been debrided with a chelating agent; and agitating the chelating agent in the root canal with the brush.
REFERENCES:
patent: 717594 (1903-01-01), Miles, Jr.
patent: 5899693 (1999-05-01), Himeno et al.
D. Keir et al., “Effectiveness Of A Brush In Removing Postinstrumentation Canal Debris” pp. 323-327, Journal Of Endodontics, vol. 16, No. 7 (Jul. 1990).
Polster Lieder Woodruff & Lucchesi
Wilson John J.
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