Dentistry – Orthodontics – By mouthpiece-type retainer
Reexamination Certificate
2000-01-24
2001-05-15
Manahan, Todd E. (Department: 3732)
Dentistry
Orthodontics
By mouthpiece-type retainer
Reexamination Certificate
active
06231337
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to dental devices comprising a shaped member for mounting on the teeth with a hardenable molding composition. These devices may, for example, treat symptoms of temporomandibular and bruxism disorders or facilitate mandibular advancement and breathing enhancement.
BACKGROUND OF THE INVENTION
A variety of occlusally retained mouthpieces have been developed by dentists for a number of different purposes. These mouthpieces are assembled and fitted to the teeth in several different ways.
There are two basic methods for fabricating an intraoral occlusally retained mouthpiece, either forming the mouthpiece directly on the teeth or indirectly on a model of the teeth.
Indirect methods typically require the dentist to take impression of the teeth from which plaster models are fabricated. These models are then used to make the mouthpiece in a laboratory setting. The increased cost and time delay to the patient in acquiring such a mouthpiece has influenced dentists to pursue direct intraoral methods of fabrication.
When fabricating a mouthpiece directly, conventionally an ethyl or methyl methacrylate acrylic resin is used. When cured in the laboratory, these acrylics are safe, but when cured directly in a patient's mouth they can be highly irritating and caustic. In addition they may burn the gingival tissue due to the heat generated during curing. Further, such use of acrylics is contraindicated when the patient is pregnant.
To directly fabricate such a mouthpiece, typically the dentist either forms a doughy “rope” of acrylic to be molded onto the teeth during the curing state. The rope is placed on a plastic substrate, pressed against the teeth and cured. The acrylic monomer slightly dissolves the surface of the substrate so that when fully cured a seamless and permanent bond is formed between the shaped acrylic and the substrate.
Other resins, such as thermoplastic resins like ethylene vinyl acetate, are sometimes used. However, these must be softened by heat which may have deleterious effects on the teeth and gums. Other resins generally do not bond well to the plastic substrates used in such mouthpieces. If the bond breaks while the device is in use, choking on the separated parts is possible.
Typical of the indirect fabrication method is that described by Thornton in U.S. Pat. No. 5,755,219. To produce a device for improving breathing, two trays are provided. The trays are filled with an ethylene vinyl acetate precursor, heated to about 150° F. and pressed against the upper and lower teeth and the resin is cured. This resin at this high temperature may cause discomfort and injure the gingival tissue.
A mouthpiece or splint intended to treat conditions such as temporomandibular joint disorder is described by Summer in U.S. Pat. No. 5,173,048. An arch is held to the lower teeth by metal clips and is coated on the upper surface with an uncured dental acrylic. The patient bites against the arch, embedding the upper teeth in the acrylic, which is then cured. The acrylic is likely to provide the problems detailed above.
A dental device for snoring and sleep apnea treatment is described by Kidd et al. in U.S. Pat. No. 5,829,441. Arch trays are filled with a thermoplastic material, such as ethylene vinyl acetate. The trays is heated to about 165 to 185° F., placed in the patient's mouth. The patient bites into the material in the trays and waits for the material to cool and harden. The heat from the material is likely to have negative effects on the teeth and gum tissue.
Thus, there is a continuing need for improved dental mouthpiece material that are not toxic or irritating to the teeth or gums, do not contain harmful chemicals that irritate the gingival tissue or produce fumes or require heat that are disturbing and potentially harmful to the patient, will bond well with convenient substrate materials and may be removed from the teeth while still quite flexible but shape retaining to allow undercuts and the like to be cleaned up prior to full cure to a tough but slightly flexible state.
SUMMARY OF THE INVENTION
The above-noted problems, and others, are overcome in accordance with this invention by a method of forming mouthpieces and the like which comprises the steps of providing a dental substrate adapted to being brought into contact with the teeth and a curable resin precursor; namely a Bisphenol-A diglycidyl ether dimethacrylate (BIS
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GMA) resin or a urethane dimethacrylate (UDMA) resin (or mixtures of these resins) which is neither caustic nor irritating to teeth or gingival tissue, applying a quantity of the resin precursor to a mouthpiece substrate, inserting the coated substrate into the patient's mouth and into contact with at least one tooth, partially curing the resin precursor to a flexible, shape retaining state, removing the substrate from the patient's mouth, fully curing the resin to a tough, slightly flexible, state and removing any excess resin from interproximal and undercut areas to make the resulting mouthpiece easy to insert and remove from the mouth.
The resin precursor may be cured by either catalytic means, by high intensity light or a combination thereof. For catalytic curing, the resin precursor is mixed with a catalyst, typically a peroxide. For light curing, a conventional light activating initiator is mixed with the resin precursor. The resin precursor and curing agent can be mechanical mixed and applied or can be mixed though simultaneous application with a dual syringe. The mixture may be applied to a surface of the substrate, with the coated substrate then pressed against the teeth. Or, the substrate may be inserted first and held in place (typically clamped between upper and lower teeth and the mixture applied along the tooth-substrate interface.
BIS-GMA and UDMA will not bond to the conventional dental mouthpiece substrate materials used with acrylic impression material. Therefore, a substrate resin must be selected that will bond. For optimum results, the mouthpiece substrate is formed from the same resin precursor as is applied to the teeth. These resins are entirely non-toxic and non-irritating, will cure to an intermediate, relatively flexible state allowing easy withdrawal from the teeth, then will complete the cure outside the mouth to a tough but somewhat flexible state, ideal for ease of use of the mouthpiece.
These BIS-GMA and UDMA resins have been used for sometime for filling pits, fissures and cavities in teeth, bonding ceramic veneer to teeth and surface restoration of front teeth, etc. They bond very firmly to tooth surfaces and resist wear and breaking when all water has been removed from the tooth surface and the surface has been etched or otherwise treated.
Surprisingly, I have found that these resins will not bond to tooth surfaces if no (or very little) filler is used and if the partially cured resin impression is removed from the mouth while still in a highly flexible state. The normal thin film of water on the teeth also allows release the partially cured resin from the teeth. The prior art involving dental uses for these resins stress the need for drying and treating the teeth, thus pointing away from the use in mouthpieces as claimed in this application.
Typical of BIS-GMA resins that can be cured by a catalyst or high intensity light is that available under the Dual Cure trademark from Nulite Systems International. Typical UDMA resins include Megabond from the Harvey J. Bosworth Company, Prisma VLC Dycal baseline composition and Dyract resin restorative system from Dentsply, and Seal-Rite UDMA pit and fissure sealant from Pulpdent Corporation. They are always filled with hard filler particles such as silica, aluminum, zinc, tin, copper and/or iron to give them the desired color and necessary hardness for long useful life on the teeth. While sold for use with dry, treated, teeth to bond to the teeth, they are highly effective in the manufacture of various mouthpieces in accordance with the methods of this invention.
The mouthpieces made by the method of this inve
Harms Donn K.
Manahan Todd #E.
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