Patent Application
20070149642
The present invention relates to adherent compositions, and, more particularly, to denture fixative compositions.
Dentures are removable appliances that serve as a replacement for missing teeth and neighboring structures in the oral cavity. Denture fixative compositions are widely used to hold dentures in place, both while the user's mouth is at rest and particularly during mastication. Such denture fixative compositions should also perform their intended function without causing irritation to the mucosal denture surfaces. Ideal denture fixative compositions make the users of dentures confident that their dentures will remain fixed in place while functioning as intended. This is sometimes difficult to achieve particularly where dentures are not fitted perfectly or where the denture fit deteriorates over time due to denture wear or changes in the mucosal denture surfaces.
Denture fixatives come in many forms including pastes, liquids, powders and aerosols. Denture fixatives may also be supplied as liners or adhesive-like strips. In all cases, it is important that good tack is achieved as soon as the dentures are properly positioned in the mouth. It is also important that the fixatives be capable of being readily spread and distributed across the denture-mucosal interface to produce sufficient adhesion to resist the stresses encountered upon mastication. Finally, the fixatives must perform well under the environmental changes typically encountered in the user's mouth such as the temperature changes experienced in drinking very hot or very cold beverages like tea, coffee or cold iced drinks or eating very hot or very cold foods.
Over the years, there have been numerous improvements in denture fixative compositions. Both synthetic and natural polymers and gums have been used alone or in combination with denture fixative compositions and have been combined with various adhesives and other materials in order to achieve such improvements. For example, denture fixative compositions using alkyl vinyl ether-maleic copolymers and salts and derivatives thereof are known to provide good adhesion. U.S. Pat. No. 3,003,988 to D. P. Germann et al., issued Oct. 10, 1961, describes certain synthetic water-sensitized water-insoluble polymeric materials comprising synthetic, hydrophilic, colloidal materials in the form of mixed partial salts of lower alkyl vinyl ether-maleic anhydride-type copolymers, where the mixed partial salts and esters contain both divalent calcium and monovalent alkali cations. U.S. Pat. No. 4,373,036 to Tiang-Shing Chang et al., issued Feb. 8, 1983,relates to improved denture fixative compositions containing a dentally acceptable excipient and a fixative mixture comprising hydroxypropyl cellulose and at least one partially neutralized alkyl vinyl ether-maleic acid or anhydride copolymer, optionally partly crosslinked, a partially neutralized, optionally partly crosslinked polyacrylic acid, or a precursor combination of copolymer or polyacrylic acid, neutralizing agents, and optionally crosslinked agents or polyethylene oxide. U.S. Pat. No. 5,006,571 to Lori D. Kumar et al., issued Apr. 9, 1991, describes improved denture adhesive base compositions comprising a substantially anhydrous mixture of a mixed Na/Ca salts of methyl vinyl ether-maleic acid, sodium carboxymethylcellulose and a trivalent cation.
It is therefore an important object of this invention to provide new and improved denture fixative compositions that resist the stresses at the denture-mucosal interface encountered upon mastication.
It is a further object of the present invention to provide denture fixative compositions that work well immediately after application and retain their fixative properties for prolonged periods of time.
Yet another object of the present invention is to provide denture fixative compositions that perform well in spite of the extreme environmental changes typically encountered in the user's mouth.
Still another object of the present invention is to provide denture fixative compositions that do not cause oral mucosal irritation and further may be used to protect select areas of the gums or other oral surfaces.
These and other objects of the invention will become apparent to those skilled in the art from the following detailed description of the invention.
This invention relates to denture fixative compositions that can be formulated and used in the form of pastes, liquids, powders and aerosols or in making the adherent layers of liners and adhesive-like strips used as denture fixatives. Among these, the paste denture fixative compositions are preferred.
In the practice of the invention, required ingredients taken from each of the three distinct categories described below are combined with adjunct ingredients including conventional vehicles, emollients, flavorants, colorants, preservatives, therapeutic components, etc. to form unique unexpectedly effective denture fixative compositions. The required ingredients include lower alkyl vinyl ether-maleic anhydride copolymers, water-insoluble and water-swelling polymers, and at least one additional adhesive material.
The present composition does not cause oral mucosal irritation and-may also be used to protect oral mucosal surfaces. For example, it may be coated onto canker sores to protect those areas from irritation while healing proceeds.
The present invention is a denture fixative composition comprising a combination of ingredients from three distinct categories that can be used in the form of pastes, liquids, powders and aerosols or in the adherent layers of liners and adhesive-like strips used as denture fixatives. Among these, the paste denture fixatives are preferred and illustrated in the formulations and examples described below.
A denture fixative composition comprising a combination of these three ingredients resists the stresses at the denture-mucosal interface encountered upon mastication. This combination also works well immediately after application and retains its fixative properties for prolonged periods of time. Additionally, denture fixatives with these three ingredients perform well under the environmental changes typically encountered in the user's mouth.
The three categories of ingredients that make up the fixative composition are:
A. lower alkyl vinyl ether-maleic anhydride copolymers and derivatives thereof;
B. water-insoluble and water-swelling polymers; and
C. at least one additional adhesive material.
Lower Alkyl Vinyl Ether-Maleic Anhydride Copolymers and Derivatives thereof
The lower alkyl vinyl ether-maleic anhydride copolymers useful in the invention dissolve slowly in the mouth and contribute adhesive properties as they take up water. These lower alkyl vinyl ether-maleic acid polymers may be obtained by polymerizing a lower alkyl vinyl ether monomer, such as methyl vinyl ether, ethyl vinyl ether, divinyl ether, propyl vinyl ether and isobutyl vinyl ether, with maleic anhydride to yield the corresponding lower alkyl vinyl ether-maleic anhydride polymer which is readily hydrolyzable to the acid polymer. Salt forms are also commercially available and can be used. For example, salt forms of the polymers may be used in which the cationic ion is a monovalent, bivalent, or trivalent cation. Also, combinations of such salts may be used. Sodium and calcium forms of the polymer salts and mixtures of such salt forms may be used.
For example, International Specialty Products of Wayne, N.J. provides GANTREZ MS-955 salt which is particularly suitable in the practice of this invention. This copolymer is a mixed sodium and calcium salt supplied as a powder. The copolymer is slowly soluble in water resulting in amber-colored solutions with high viscosity and adhesion. The divalent calcium ion lightly crosslinks the material through ion bridges to reduce its solubility and increase its cohesive strength and viscoelasticity. It is believed that the repeating units may be represented as:
The approximate average molecular weight of GANTREZ MS-955 is 1,000,000 and its Brookfield viscosity (mPa. S (11.1% solids aq.)) is 700-3000.
The lower alkyl vinyl ether-maleic anhydride copolymers should comprise from about 10% to about 55%, preferably from about 20% to about 40%, and yet more preferably 27% to about 31% of the dental fixative composition.
Water-Insoluble and Water-Swelling Polymers
This category of the above tripartite combination of ingredients is believed to be previously unknown in dental fixative applications. When the appropriate levels of water-insoluble and water-swelling polymers along with ingredients from the other two categories are used unexpectedly effective denture fixative compositions are obtained.
These polymers must be water-insoluble at ambient temperatures and preferably will be water-insoluble at temperatures below about 60° C. Useful water-insoluble and water-swelling polymers include low-substituted hydroxypropyl ether of cellulose, croscarmellose sodium, carboxymethylcellulose calcium, agar and mixtures thereof. Low-substituted hydroxypropyl ether of cellulose (which may also be referred to by the chemical name cellulose, 2-hydroxypropyl ether (low-substituted) (CAS 9004-64-2)) has the structural formula:
We refer to this material below as L-HPC.
L-HPC is a low-substituted hydroxypropyl ether of cellulose in which a small proportion of the three hydroxyl groups contained in the β-o-glucopyranosyl ring of the cellulose is etherified with propylene oxide. L-HPC does not dissolve in water, rather it swells when wetted.
Modifications of the substituent content and particle size of L-HPC cause changes in the binding characteristics as a result of subtle changes in physical properties. Therefore, the choice of the L-HPC used is of great importance. In the practice of the present invention, it has been found that the choice of L-HPC with the following properties is key:
Preferred L-HPC includes LH 21, LH 31 and LH B1 available from Shin-Etsu Chemical Company. Combinations of these preferred L-HPC ingredients or of any of the noted water-insoluble and water-swelling polymers can be used.
Other water-insoluble and water-swelling polymers that may be used in the practice of the present invention include croscarmellose sodium, carboxymethylcellulose calcium and agar, as described below.
Croscarmellose Sodium
Croscarmellose sodium, which may also be referred to by the chemical name, cellulose, carboxymethyl ether, sodium salt, crosslinked (CAS 74811-65-7), is insoluble in water, although it swells to 4-8 times its original volume on contact with water. Croscarmellose sodium is commercially available under the trademark of Ac-Di-Sol (FMC BioPolymer, Newark, Del., USA), Primellose (DMV International GmbH, Veghel, The Netherlands) and Kiccolate ® (Asahi Kasei Chemicals Corp, Tokyo, Japan)
Carboxymethylcellulose Calcium
Carboxymethylcellulose calcium, which may also referred to by the chemical name, cellulose, carboxymethyl ether, calcium salt (CAS 9050-04-8), is insoluble in water, but swells to twice its volume to form suspension. Carboxymethylcellulose calcium is commercially available under the trademark of ECG 505 (Nichirin Chemical Industries Ltd., Hyogo, Japan)
Agar
Agar is a biopolymer found in the cell walls of seaweed, and is thought to have a structural functionality, as well as ion exchange and membrane dialysis functionality. Agar is a mixture of a neutral dominating polysaccharide called “agarose” and a charged polymer called “agaropectin”. The agarose skelton is composed of alternating D-galactopyranose units beta (1-4) and 3,6-anhdro-L-galactopyranose units liked alpha(1-3). It is insoluble in cold water but swells, and it is soluble in boiling water. The agaropectin has the same repeating units as agarose but approximately every tenth D-galactopyranose subunit occurs a substituted sulfate, methyl, pyuvic or acetyl functional group. Agar is widely commercially available and has long been used as a food ingredient. It is also currently used in the biochemical industry.
The water-insoluble and water-swelling polymers should comprise from about 1 to 60%, preferably 1% to 30%, and yet more preferably from about 1% to about 13% by weight of the denture adhesive composition. Most preferably, the water-insoluble and water-swelling polymers will comprise about 4-7% by weight of the denture adhesive composition.
Additional Adhesive Materials
The additional adhesive materials will be chosen from the following: natural gums, synthetic polymeric gums, karaya gum, guar gum, gelatin, algin, sodium alginate, tragacanth, chitosan, polyethylene glycol, acrylamide polymers, carbopol, polyvinyl alcohol, polyvinylpyrrolidone, cellulose derivatives and mixtures thereof. Alternatively, the additional adhesive materials may be chosen from the following: methylcellulose, sodium carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyl propylmethylcellulose, carboxymethylcellulose, and mixtures thereof.
Among the above additional adhesive materials, sodium carboxymethylcellulose is currently preferred. This material is a powder that when moistened becomes hydrated and tacky or gummy thereby providing additional adhesive functionality to the dental adhesive composition. The carboxymethyl cellulose gums are water-soluble, anionic long chain polymers whose properties vary to some extent depending on the number of carboxymethyl groups that are substituted per anhydroglucose unit in each cellulose molecule. Combinations of different water-soluble adhesive polymers can be used.
The additional adhesive materials should comprise from about 1% to 35%, preferably from about 10% to about 30%, and yet more preferably from about 19% to about 22% by weight of the dental adhesive composition.
Dental fixative creams may include as additional ingredients emollients such as petroleum jelly, mineral oil and other hydrocarbons suitable for use as emollients. The emollients may be present in the fixative composition at a level of from about 10 to about 50% by weight of the composition.
The fixative composition may also include silicon dioxide at a level of about 0.1 to about 9.0% by weight of the composition. It may also include flavorants, colorants, preservatives, and mixtures thereof, as desired.
Finally, the denture composition may include a therapeutic component selected from the group consisting of medically acceptable anti-bacterial agents, anti-fungal agents, anti-inflammatory agents and mixtures thereof.
The following examples are presented in order to illustrate the present invention, but should not be taken as limiting the scope thereof.
The efficacy of the compositions of the present invention was demonstrated in a series of tests using experimental formulations as listed below.
In selected tests, the following commercially-available and experimental dental fixative compositions were used.
The adhesive strength of Formulations #1-16 was evaluated using a Tinius Olsen multipurpose test stand 10 with an upper rod 12 and lower sample plate arranged as illustrated in
The adhesive strength of the samples was measured by:
a. first filling the holding area with the test composition with any excess material being removed.
b. Both the upper rod and the filled lower plate were then attached to the Tinius Olsen multipurpose test stand.
c. The upper rod was advanced to a depth of 0.25 mm below the surface of the test material in the lower sample plate. d. The filled lower sample plate with the penetrating rod were placed in the 37° C. water bath to soak the entire sample area.
e. At the end of about five minutes, the upper rod was withdrawn from the sample of a rate of 0.5 mm per minute. A first adhesive force was registered by the Tinius Olsen gauge and recorded.
f. Immediately following the recordal of Tinius Olsen gauge reading, the upper rod was placed in the same position at a depth of 0.25 mm below the surface of the test material in the lower sample plate, while the sample was continuously hydrated.
g. The penetration and decompression (pulling) and associated Tinius Olsen gauge readings were taken until the readings approached zero force.
h. The readings of the entire cycle were recorded and plotted graphically in
We turn now to a discussion of the test results as reflected in
This Figure provides a comparison of the adhesiveness over time of a base composition (Formulation #1) free of water-insoluble and water-swelling polymer to test compositions using three different L-HPC products (Formulations #3, #4 and #5) and a second base formulation containing water soluble hydroxypropyl cellulose (Formulation #2) as a reference. As can be seen from the graph of adhesive force vs. time of this Figure, the formulations containing L-HPC generally have markedly higher adhesiveness overall and the superior adhesiveness is maintained over time.
The graph in this Figure provides a comparison of the adhesiveness over time of a base composition (Formulation #1) free of water-insoluble and water-swelling polymer to five test compositions containing different croscarmellose sodium products (Formulations #6, #7 and #8), carboxymethylcellulose-calcium (Formulation #9) and agar (Formulation #10).As can be seen from the graph of adhesive force vs. time of this Figure, the formulations containing croscarmellose sodium, carboxymethylcellulose-calcium and agar generally have better early adhesiveness and comparable adhesiveness over time to the base formulation free of water-insoluble and water-swelling polymer.
In this Figure, compositions of the present of invention containing L-HPC (Formulation #4) and croscarmellose-sodium (Formulation #6) were compared with the commercially available compositions, Product-A and Product-B. The results obtained demonstrate that the compositions of the present invention have substantially greater maximum adhesiveness than any of the commercial products tested and also superior adhesiveness over time as compared to Product-A and Product-B.
The graph in this Figure reports adhesiveness vs. time for a series of test formulations with varying levels of L-HPC. The formulations tested contain the following level of L-HPC:
The test results show generally substantially superior adhesiveness for all of the formulations containing insoluble swelling polymers, in comparison to formulations without insoluble swelling polymer. Additionally, Formulation #16 showed superior early adhesiveness, Formulations #14 showed superior maximum adhesiveness, and all of the formulations containing L-HPC showed superior adhesiveness over time in comparison to the formulation free of water-insoluble and water-swelling polymer.
If desired, denture fixatives in the forms of liquids, powders, aerosols, and even liners or adhesive-like strips may be formulated using compositions as set forth above, substituting appropriate types and levels of the adjunct ingredients required to formulate such compositions. The identity and appropriate levels of these ingredients are well-recognized by those skilled in the art.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. It should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the invention.
