Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-02-06
2003-12-30
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S204000, C526S208000, C526S217000, C526S321000, C526S323100, C526S323200, C526S328500
Reexamination Certificate
active
06670436
ABSTRACT:
The invention relates to dental materials which contain a thermochromic dye and which display a reversible change of colour in the event of temperature changes.
For aesthetic reasons, tooth-coloured restoration materials are increasingly being used in restorative dentistry. These materials have the disadvantage that they can be visually distinguished from the natural tooth substance only with difficulty, with the result that the removal of excess material and also the reworking and matching for example of fillings is made difficult. The consequence is that, frequently, healthy tooth substance is unnecessarily removed or on the other hand excess dental material is overlooked which can then, as a retention niche, encourage the formation of plaque and lead to parodontal problems. Also, when tooth-coloured fillings are removed, because of the poor visibility of the transition area between filling and tooth substance, it often happens that either too much healthy tooth substance is removed or else remains of the filling are overlooked. Similar problems result when using tooth-coloured fixing materials for the cementing of tooth-coloured restorations.
EP 0 610 072 A2 relates to toothbrushes which contain a thermochromic material and which, during use, show the cleaning time by changing colour.
U.S. Pat. No. 4,957,949 discloses masterbatches which contain wax and a granular thermochromic material homogeneously dispersed therein, which is coated with a high-molecular-weight, hydrophilic substance. The masterbatches are said to be able to be incorporated into thermoplastics even at high temperatures and pressures without loss of the thermochromic properties. The dye-containing thermoplastics are said to be particularly suitable for the manufacture of toothbrushes.
U.S. Pat. No. 5,431,697 discloses compositions on the basis of olefin polymers which contain thermochromic dyes. The dyes are preferably used in a granular form which can be obtained by mixing polymer and dye and then crosslinking the polymer. The obtained granular material is said to be suitable in particular for mixing with thermoplastics, which can then be further processed to give toothbrushes which change colour.
U.S. Pat. No. 3,619,254 discloses multi-layered articles which, in addition to a base layer and at least one protective layer, include a thermochromic layer which contains liquid-crystalline, thermochromic dyes. The articles are said to be suitable in the form of rectangular strips for the measurement of body temperature.
U.S. Pat. No. 4,022,706 discloses thermochromic, liquid-crystalline printing dyes in the form of viscous oil-in-water emulsions which are said to be suitable in particular for the imprinting of films and laminates. The printing dyes are deposited onto the films and not incorporated in them.
Dental materials are disclosed in U.S. Pat. No. 5,162,130, the colouring of which can be set by irradiation with UV light followed by heating. The materials undergo a permanent change of colour and are not suitable for the temporary visualization of colourless or tooth-coloured dental materials.
DE 195 02 751 A1 discloses a process for the manufacture of plastic models for dental engineering, which are characterized by a high-contrast, coloured surface. This is achieved by integration for example of a thermochromic dye into the surface of the model.
Dental materials which contain a thermochromic dye are not known at present.
The object of the present invention is to create a dental material, the colour of which can be temporarily changed in a simple way such that the material can be visually distinguished from the natural tooth substance, and which again assumes its original colour after a period sufficient for the working of the dental material.
This object is achieved by dental materials which, in addition to at least one polymerizable ethylenically unsaturated monomer and at least one initiator for cold, hot and/or photopolymerization, contain at least one thermochromic dye.
By dental materials is meant materials which are suitable for use in the patient's mouth, i.e. for example as a dental restoration, as a constituent of a dental restoration or serve to fix a dental restoration or orthopaedic device in the patient's mouth.
By thermochromic dyes are meant inorganic or preferably organic substances which reversibly change their colour according to the temperature.
According to the invention, thermochromic dyes are preferred which are colourless at a temperature of approx. 37° C. and which change colour upon heating or preferably cooling, i.e. assume a colour that can clearly be distinguished from the natural tooth substance. At a temperature of approx. 37° C. the colour of the dental material is thus determined by its intrinsic colour.
Particularly preferred are thermochromic dyes which change colour at a temperature of 29° C. or less, preferably of 5 to 29° C., in particular 12 to 29° C. and quite particularly preferably 20 to 29° C., or materials which change colour at temperatures of 40° C. or more, preferably 40 to 60° C. and in particular 45 to 55° C.
Furthermore, dyes are preferred which assume a red, blue or black colouring and can thus be distinguished particularly well from the natural tooth substance.
Thermochromic dyes are preferred which contain an electron donor and an electron acceptor, or dyes which contain an acid-responsive component and an acidic component,
Mixtures of an electron-emitting chromogen (electron donor) and an electron acceptor are particularly suitable as thermochromatic dyes on the basis of an electron donor and electron acceptor. Preferred as electron donors are substituted phenyl-methanes, fluoranes, such as for example 3,3′-dimethoxy-fluorane, 3-chloro-6-phenylamino-flourane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethyl-7,8-benzofluorane, 3,3′, 3″-tris(p-di-methylaminophenyl)phthalide, 3,3′-bis(p-dimethyl-aminophenyl)-7-phenylaminofluorane and 3-diethyl-amino-6-methyl-7-phenylamino-fluorane, indolylphthalides, spiropy-ranes and cumarins, as well as mixtures of these substances.
Particularly suitable as electron acceptors are phenols, azoles, organic acids and esters as well as salts of organic acids. Examples that may be cited as phenols are phenylphenol, bisphenol A, cresol, resorcinol, chlorolucinol, phenol, phenol oligomers, &bgr;-naphthol, 1,5-dihydroxynaphthalene, pyrocatechol, pyrogallol, and the trimer of p-chlorophenol formaldehyde condensate. Examples that may be cited as azoles are benzo-triazoles, such as 5-chlorobenzo-triazole, 4-laurylaminosulfo-benzotriazole, 5-butylbenzotriazole, dibenzotrizaole, 2-oxy-benzotriazole, 5-ethoxy-carbonylbenzo-triazole, 5,5′-methylene-bisbenzotriazole, imidazole, such as oxybenzimidazole, and tetrazole. The organic acids comprise for example aromatic and aliphatic carboxylic acids and substituted derivatives thereof. Examples of aromatic carboxylic acids are salicylic acid, methylenebissalicylic acid, &bgr;-resorcylic acid, gallic acid, benzoic acid, p-oxy-benzoic acid, pyromellitic acid, &bgr;-naphthoic acid, tannic acid, toluic acid, trimellitic acid, phthalic acid, terephthalic acid and anthranalic acid. Examples of aliphatic carboxylic acids are acids with 1 to 20 carbon atoms, preferably 3 to 15 carbon atoms, such as for example stearic acid, 1,2-hydroxystearic acid, tartaric acid, citric acid, oxalic acid and lauric acid. Examples of esters are alkyl esters of aromatic carboxylic acids in which the alkyl group contains 1 to 6 carbon atoms, such as butyl gallate, ethyl-p-hydroxybenzoate and methyl salicylate. Examples that may be cited as salts are ammonium and metal salts of the above-named acids. The metal salts comprise for example lithium, sodium, calcium, magnesium, aluminium, zinc, tin, titanium and nickel salts. Particularly preferred electron acceptors are 1,2-hydroxystearic acid, tartaric acid and citric acid. The above-named electron acceptors can be used alone or mixed with one another. Furthermore, the thermochromic materials can be used as such or in microenca
Burgath Armin
Burtscher Peter
Rheinberger Volker
Salz Ulrich
Ivoclar Vivadent AG
Nixon & Peabody LLP
Pezzuto Helen L.
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