Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-10-05
2001-03-06
Szekely, Peter A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S117000, C523S118000, C524S432000, C524S433000, C524S547000, C524S556000, C524S832000, C524S300000
Reexamination Certificate
active
06197846
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to root canal filling, retrofilling, and perforation materials. More particularly, the present invention relates to a sealer paste and core material for root canal filling, retrofilling, and perforation.
Endodontic therapy (also identified as root canal therapy) involves the removal of all tooth pulp space contents, potentially infected and diseased tissue and their by-products from the root system of a tooth. Once these materials are removed from the root system, the root canal is shaped to facilitate filling. The root canal is then filled.
While there are many techniques for root canal filling, the most widely used technique uses a combination of gutta percha cones and a zinc oxide-eugenol based sealing material. This technique has also been used with retrograde root canal filings following apicoectomy (also referred to as retrofillings) and for the repair of tooth root perforations.
A critical factor in the long-term success of endodontic therapy involves eliminating leakage around and through a root canal filling, a retrofilling, or a perforation repair. Intimate adaptation of the filling material to the root canal typically plays an important role in eliminating leakage. However, attaining intimate adaptation is difficult.
Johnson, U.S. Pat. No. 5,372,759, and Fujisawa et al., U.S. Pat. No. 4,931,096, describe using warm vertical condensation of gutta percha to reduce leakage around and through the root canal filling. Takubo, U.S. Pat. No. 4,657,592, describes using a filling material that remains semi-solid at body temperature but which is softened by heating during the filling process.
One variation in endodontic sealers is to replace the aromatic compound eugenol with carboxylic acids that react with zinc oxide. For example, Molnar, U.S. Pat. No. 3,028,247 describes using caprylic acid (also known as octanoic acid) and lauric acid (also known as dodecanoic acid) as reactants.
Dainippon Toryo KK, Japanese Patent No. 3,027,309, describes using a sealer that adheres to the gutta percha cone to reduce leakage through the root canal filling material. However, potential problems that are associated with leakage at the margins with dentin are still experienced.
Kahn, U.S. Pat. No. 4,526,544, discusses using cyanoacrylate adhesives to bond both to dentin and gutta percha. A drawback of the cyanoacrylate adhesives is that they chemically break down in biological environments, such as are present in the mouth.
In an article entitled, A New Dental Cement, 125 British Dental J. 381 (1968), Smith describes mixing an aqueous solution of poly(acrylic acid) with zinc oxide. This adhesive was identified as zinc polycarboxylate or zinc polyacrylate cement.
It has also been described to use poly(acrylic acid) or a closely related co-polymer with aluminosilicate glass powders to produce translucent dental cement. Wilson et al., 132 British Dental J. 133 (1972). Wilson et al. indicates that the polymer is either in aqueous solution or a dry powder, which is mixed with water.
Combe et al., U.S. Pat. No. 5,141,560, discloses a calcium hydroxide pulp-capping material that is prepared from a non-aqueous cement that contains dry poly(acrylic acid). Adhesion to dentin was achieved through moisture from the tooth structure being absorbed into the cement. This absorption results in partial dissolution of the polymer.
The prior art root canal obturation materials generally fall into three general groups. The first group is gutta percha cone with zinc oxide-euaenol paste. The second group is glass ionomer. The third group is calcium hydroxide.
These root canal filing materials each typically exhibit good dimensional stability, are radiopaque, and do not provoke an immune response. These materials are also bacteriostatic, sterilizable, non-mutagenic, and non-carcinogenic.
Several drawbacks of the gutta percha cone and zinc oxide-eugenol paste technique are that these materials do not form a hermetic seal. The gutta percha/zinc oxide-eugenol material also tends to irritate periapical tissues and is porous to moisture. Additionally, the gutta percha/zinc oxide-eugenol material is degraded by long-term exposure to tissue fluids that are typically present in the mouth.
It is difficult to form a hermetic seal of the root canal using glass ionomer. Glass ionomer is not impervious to moisture and is not non-porous. Another drawback of glass ionomer is that it is difficult to remove the glass ionomer when it is necessary to retreat the root canal. Yet another drawback of glass ionomer is that glass ionomer irritates periapical tissue.
The calcium hydroxide technique has a very limited working time before setting. It is also difficult to form a hermetic seal with the calcium hydroxide filling material. The calcium hydroxide filling material is degraded by long-term exposure to tissue fluids that are typically present in the mouth. This material is also not impervious to moisture.
BRIEF SUMMARY OF THE INVENTION
The present invention is an endodontic sealer paste that contains: (a) a dry poly(carboxylic acid), a precursor transformable into the dry poly(carboxylic acid), or a dry cation-crosslinkable polymeric acid containing on average one phosphonic acid group per one to three backbone carbon atoms; (b) zinc oxide, magnesium oxide, calcium oxide, zinc hydroxide, magnesium hydroxide, calcium hydroxide, hydroxyapatite, or a combination thereof; and (c) an aliphatic acid in the series CH
3
(CH
2
)
n
COOH, a branched chain aliphatic acid, a fatty acid triglyceride, an aromatic compound capable of reacting (b), or a combination thereof.
The present invention also includes an endodontic core material that contains (a) a pliant polymer, (b) a dry poly(carboxylic acid), a precursor transformable into the dry poly(carboxylic acid), or a dry cation-crosslinkable polymeric acid containing on average one phosphonic acid group per one to three backbone carbon atoms; and (c) zinc oxide, magnesium oxide, calcium oxide, zinc hydroxide, magnesium hydroxide, calcium hydroxide, hydroxyapatite, or a combination thereof.
DETAILED DESCRIPTION
The present invention is a sealer paste and a core material for use in conjunction with root canal filling, retrofilling, and perforation repair. When the core material and the sealer paste of the present invention are used in endodontic obturation, there is an adhesive continuum that is attained through commonality of adhesive constituents between the sealer paste and the core material. Therefore, an impervious bond is formed between the sealer paste and the dentin and between the sealer paste and the core material. The adhesion between the elements is continually replenished because the sealer paste and the core material are non-aqueous and because there is an excess concentration of poly(carboxylic acid) in the sealer paste and the core material.
Because of these characteristics, the sealer paste and the core material prevent or significantly reduce apical leakage when produced and used according to the present invention. By preventing or significantly reducing apical leakage, the sealer paste and core material of the present invention significantly enhance the long-term success rate of the root canal filling, retrofilling, or perforation repair.
Further advantages of the sealer paste and the core material of the present invention are that these materials do not shrink or change form after insertion into the root canal. The materials also provide ample time for working before setting. Additionally, the materials do not provoke an immune response, are non-mutagenic, and non-carcinogenic. The present invention is also bacteriostatic, sterilizable, radiopaque, impervious to moisture, and non-porous. The sealer paste and the core material are removable when it is desired to retreat the root canal.
The sealer paste preferably contains poly(carboxylic acid), zinc oxide, and an aliphatic acid. The sealer paste also preferably includes a radiopaque material, viscosity and consistency modifiers, and biologically active agents. The
Combe Edward C.
Reeh Ernest S.
Kinney & Lange , P.A.
River Valley Endodontics, P.A.
Szekely Peter A.
LandOfFree
Dental root canal filling, retrofilling, and perforation... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dental root canal filling, retrofilling, and perforation..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dental root canal filling, retrofilling, and perforation... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2454976