Title: Slow-release disposable elastomeric buccal devices
United States Patent: 6,326,022
Inventors: Katz; Harry S. (785 Pleasant Valley Way, W. Orange, NJ 07052)Appl. No.: 433893
Filed: November 4, 1999Low-cost disposable elastomeric devices are conveniently insertable to grip between teeth and are easily removable. The devices contain substances such as odorants or medications which slowly permeate into the mouth. The preferred embodiment has a mushroom shaped head, containing the active substance, with a stem that engages between teeth to hold the device in place.
DESCRIPTION OF PREFERRED EMBODIMENTS
My invention involves the use of rubber or elastomeric
polymers that are filled or formulated with substances, which may be
liquid or solid, that will permeate out when the molded device is within
the mouth. In essence, the device may be considered as a combination of an
active substance within a polymer matrix. The active substance may be a
liquid odorant that will provide a pleasing breath odor for the wearer, or
a drug that will provide a medical benefit. The active substance may also
be a solid filler, which will be dissolved by the permeating saliva, and
will then permeate into the mouth. Conditions within the oral cavity
include exposure to saliva and a temperature of about 98.6 F. When my
devices are exposed to the conditions within the oral cavity, the active
substance will exude or permeate out at a rate that will be influenced by
a number of factors. Among these factors are the shape of the device, the
surface area to volume ratio of the device, the concentration of the
active substance and permeation characteristics of the polymer matrix.
There are many different rubbers and elastomer polymers that are non-toxic
and can be used as the matrix. An example of polymers that have been used
in the mouth are the acrylic polymers that are molded as dentures or
composite tooth fillings and these have an established history of safe
long term use. Other polymers have been used to manufacture athletic
mouth-guards. Polymers that are preferred for my invention are rubbers or
elastomers.
The American Society for Testing and Materials (ASTM), Philadelphia, Pa.,
has a Compilation of Standard Definitions in which film permeability is
defined as "the measure of the rate at which chemical reagents
penetrate a film". Permeation rate may be considered as the rate at
which a liquid substance will penetrate or diffuse through a non-porous
polymer. Polymers have different permeation rates that depend on the
molecular structure of the polymer. This is often an important factor in
the choice of a polymer film for specific applications, such as food
packaging. Polyvinylidene chloride ( Dow Chemical's Saran) film usually
has a much lower permeation rate than most packaging films and, therefore,
is often selected for critical food packaging and food wrap applications
where it is desirable to have substances such as water retained within the
package.
Polyethylene tubes are often used for packaging toothpaste, but flavor
ingredients can penetrate the tube wall at a relatively fast rate so that
special "barrier coatings" are applied to the polyethylene
tubes. The main point of this discussion is that the polymer matrix must
be carefully selected in order to provide the optimum rate of diffusion of
the active substance for each application of my devices. In some
applications, silicone rubber will be the best matrix because active
substances will permeate at a relatively high rate. There are many
publications that present a good description of permeation factors for
polymers and an example is the book titled, PERMEABILITY OF PLASTIC FILMS
AND COATINGS, Edited by H. B. Hopfenberg and published by Plenum Press,
New York, 1974. The information in this publication shows that there is a
wide choice of polymers, and each provides characteristic permeation rates
and other properties.
There are many different candidate non-toxic rubbers and elastomeric
polymers that can be selected and tested for use in my slow release
devices. Among the preferred choices are RTV silicone rubber, elastomeric
thermoplastic olefins, flexible methacrylate polymers and co-polymers and
ethylene vinyl acetate polymers.
The following is a partial list of some specific materials that have been
molded as trial devices for my invention.
Company Trademark Product No.
Dow Corning Corporation Sylgard RTV Silicone 186
Rubber
Dynaflex Kraton D2122
Dynaflex Kraton 7431-1
Dynaflex Kraton 7820-1
Dynaflex Kraton 7980-1
Dynaflex Kraton CL-40
Advanced Elastomeric Systems Vistaflex 671N
The following is a partial list of some of the odorants that have been used to make devices per my invention:
Product
Company Trademark No.
Virginia Dare Lemon-Lime RA54
Virginia Dare Peppermint Oil HD30
Virginia Dare Fruit Gum MN75
Virginia Dare Spearmint Oil HF40
Crompton & Knowles Spearmint Oil DP501527
As mentioned above, a convenient and good matrix for fabrication of my devices is Room Temperature Vulcanizing (RTV) silicone rubber. There are many grades of RTV, produced by companies that include Dow Corning Corporation and General Electric Co. When using this type of product, about 10% by weight of a liquid catalyst is mixed with the silicone rubber viscous polymer and the catalyzed mixture will then cure to a solid rubber within a relatively short period of time. The cure time, appropriate curing temperature and final hardness of the rubber can be predetermined and controlled as a result of experience with the selection and formulation of many ingredients for this family of rubber products. In the preparation of trial quantities of my devices, small batches of about 10 grams to 30 grams of Dow Corning's Sylgard 164 were mixed and placed into a plastic syringe. The mixture was then injected into a three cavity "mushroom" mold. For injection molding of large quantities, the mold cavities can be increased to any desirable size. The "mushroom" design is described later in this disclosure. The mold was then placed into an oven set at 180 F. for a period of time to convert the liquid mix to a rubbery solid. A higher temperature can be used to reduce the curing time. Alternatively, the mold was kept at room temperature for about 30 hours to convert the mix to a solid. After the cure cycle, the mold was opened to remove the rubber "mushrooms". Devices were made by either including the active substance in the mixture before molding, or by exposing the molded device to the active liquid ingredient in an enclosure so that the active ingredient permeated into the device. The final device was packaged in an aluminum foil laminate so that the active ingredient is contained upon long term storage prior to use. The end user opens the package and places the device in the mouth between two teeth as shown later in this disclosure.
I have noted that the addition of a fine particle size microporous filler, with interconnecting pores such as diatomaceous earth fillers, when added in concentrations of from 5 to 25% by weight to the polymer matrix, usually provide a matrix with improved capability to retain the active ingredient so that it exudes at a slower rate. However, my devices also perform satisfactorily without this type of additive.
A convenient laboratory machine for molding small thermoplastic parts is the Mini-Max Molder that is available from CSI, Cedar Knolls, N.J. This equipment permits molding or mixing and molding plastic materials or thermoplastic composites in batches as small as two to four grams. Thus, one batch is suitable for trial moldings that were made in a 3-cavity "mushroom" mold. In a typical trial run, about 3 grams of Elastomeric Systems's Vistanex polymer pellets were placed into the machine chamber, which had been heated to 185oC. After rotating the rotor for several minutes to obtain a uniform melt of the polymer, it was injected into the mold. The mold was then cooled to room temperature, and the molded mushrooms removed. As indicated above, there are many ways for including the active ingredient within the matrix polymer. A main procedure is to include the active ingredient within the molding compound. This is my preferred method when the base polymer in my device is an RTV silicone rubber as described in the preceding paragraph. When the device is manufactured by use of a thermoplastic elastomer, it is necessary that the polymer will be subjected to heat during the molding procedure. The heat may adversely effect the active ingredient or may volatilize it so that the concentration will be below the optimum level. Therefore, I have found it effective to treat molded thermoplastic devices with an active ingredient in liquid form, by placing them within an enclosure at room temperature or slightly elevated temperature for a period of time that will be adequate for a sufficient quantity of active ingredient to permeate into the device. The outer surface of the device is then wiped clean and packaged in an impermeable aluminum foil laminate container.
A typical preparation for a single device that was molded from RTV silicone rubber, was to place it onto aluminum foil, add two to three drops of the active ingredient, such as Virginia Dare Peppermint Oil HD30 or Spearmint Oil HF40 and then fold over the foil with double folds on each open edge. This closed container was allowed to remain overnight; the package was opened and excess liquid was quickly wiped off the device by use of a paper towel. The treated device was immediately repackaged in another sheet of aluminum foil. It was noted that the treated device could be stored in an enclosure of aluminum foil or foil laminate for weeks without loss of any significant amount of the active odorant. Indications are that the foil laminate packages will retain the activity of these devices for many years. When the package was opened and placed into the mouth, a pleasant odor of the active ingredient persisted on the user's breath for over 3 hours.
It was noted in trials with the thermoplastic elastomers mentioned above, that some of the active ingredients will result in a significant weakening of the tensile strength of the polymer, such that the stem will break when stretched beyond about 50% elongation. Also, that some polymers, such as Vistoflex 671N has the characteristic of retaining most of its elongation upon stretching, rather than returning to the original length that is the usual behavior of a true rubber. In spite of that characteristic, the Vistoflex polymer has generally better resistance to loss of strength upon exposure to the typical odorants that were used, and had sufficient tendency to increase in thickness after release of the stretching force, so that it proved to be a good matrix for this application. However, the results of many tests that involved permutations of polymer matrices and active ingredients makes it apparent that for each application there must be a judicious selection of matrix, form of active ingredient, processing method and packaging material.
The preferred elastomer matrices for my invention are the RTV silicone rubbers and thermoplastic elastomers that have FDA approval for dental and/or medical applications. Among the characteristics of these materials is the capability of being stretched to decrease the thickness and then relaxed to return partially or completely to the original shape or thickness. Thus my invented device is easily placed into position between two teeth and when the stretching tension is removed, the device stem will increase in thickness and be locked in place. Then the active ingredient will permeate slowly into the mouth. The active ingredient can be an odorant that will provide a pleasant smelling breath for the user, or nicotine or a nicotine simulant as a means for stopping the smoking habit, or a medication for various patient needs.
The wearer of my device has a number of obvious choices in the exact manner to be used. The device can be inserted between any two teeth with the usual small gap between teeth. Experiments have proven that a preferred location is between an upper central incisor tooth and the adjacent lateral incisor. Another common choice is between the upper lateral incisor and the canine tooth. Another choice relates to the wearer's tolerance for the slight protrussion of the thin soft stem against the inside of the lip. It has proven safe to use a small scissors to snip off the stem close to the outer surface of the tooth so that the remaining short stem does not exert any pressure upon the inside of the lip.
Claim 1 of 13 Claims
I claim:
1. A device for slow release of substances into the oral cavity
comprising:
a stretchable permeable elastomer polymer matrix containing an active
ingredient which can permeate out when the device is inserted into the
oral cavity, said matrix including a head extending laterally over
adjacent teeth, and
a stretchable stem of said elastomer polymer extending longitudinally from
said head and having a stretchable thickness fitting and insertable
between adjacent teeth, the thickness of said stem being decreased upon
stretching and insertion between said teeth and returning to the original
thickness upon relaxation for holding said device in position between the
teeth.
____________________________________________
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