Drug – bio-affecting and body treating compositions – Dentifrices – Ferment containing
Patent
1993-11-29
1995-07-18
Griffin, Ronald W.
Drug, bio-affecting and body treating compositions
Dentifrices
Ferment containing
106 35, 10628716, 4332171, 433226, 433229, 424 49, 424 52, 424400, 514835, 556 27, 556 40, 556 28, A61K 6093, C09D 400, C09D18302
Patent
active
054339413
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a sol gel composition for use in producing glassy coatings, to a process for producing a glassy coating using the composition, to a method for cosmetic colouring of teeth using the process and to a method for prophylactic protection of teeth using the process.
BACKGROUND OF THE INVENTION
Fissure sealants have been demonstrated as effective in reducing incidence of tooth decay and inhibiting decay even after it has started, but have not gained universal acceptance in general practice. These fissure sealants are understood to have relatively low durability, adhering to the tooth with a rather short half-life (5 years).
Sol-gels would not be considered for dental use, since the curing of sol gels is typically undertaken in a slow furnace, which would pose clinical difficulties. Japanese Patent Publication 1083671 (published 29 March 1989), in the name of Kobe Steel, proposes a calcium phosphate sol gel, but for coating artificial teeth to be subsequently embedded in the human body.
DESCRIPTION OF THE INVENTION
According to the present invention, a sol gel, xerogel or heat-consolidated gel composition comprises a hydrolysable silicic ester (such as silicon tetrahalide or tetraalkoxysilicon), a solvent (alcoholic or non-alcoholic), and alkoxides of a GpIA metal (e.g. sodium), and of any one, two or all of aluminium, zirconium and of a Gp VB or GpIVB metal (preferably titanium). Part of the silicic ester can be substituted by appropriate compounds of other non-metallic glass formers. Some of these compositions have been found to be usefully stable. The composition may further comprise water, which may however be supplied otherwise, e.g. by exposure to air. Preferred combinations of metal alkoxides are: (i) Al, Ti, Na; and (ii) Zr, Na. The metals (not counting Na) are preferably present in amounts up to 20%. Solid oxides e.g. fine neodymium oxide powder may be dispersed into the sol gel.
Preferably, the sol gel composition synthesis was characterised by an ageing step, during which moisture was admitted to the composition at a rate under 1% of the rate in free air. This controls the rate of hydrolysis and consequently of `polymerisation` of the molecules of the composition without destabilisation, which rate can in principle be monitored via an increase in viscosity of the composition, or e.g. by infra-red spectroscopy, by differential scanning calorimetry, by thermogravimetric analysis, by nuclear magnetic resonance or by electron spin resonance.
Preferably, the sol gel, xerogel or heat-consolidated gel composition comprises a filler, such as laponite, zeolite, kaolinite or vermiculite, or preferably a filler In the form of flat plates such as talc or mica, or a mixture, optionally coated (preferably by chemical vapour deposition) with for example titanium dioxide, chromium oxide or ferric oxide or a mixture, the filler preferably comprising up to 30% by weight of the composition. Such materials are harmless if swallowed in the small quantities in which they might spall off. Other coating methods may also be used, alternatively or in addition, such as deposition of silane. This can promote adhesion and enhance mechanical properties. As silanising agents, compounds containing a glycidoxy organic group and a trimethoxysilyl group may be used, such as Dow Corning Z6040 (trade mark), ##STR1## The mean filler particle size is preferably up to 3 .mu.m (e.g. 0.1 to 2 .mu.m) in one dimension and 5-100 .mu.m in the other two dimensions. Where the latter dimensions are 5-20 .mu.m, the filler preferably comprises from 20 to 30% by weight of the composition (i.e. before curing), and where those dimensions are 10-60 .mu.m, the filler preferably comprises 10-20% by weight of the composition. Cross-laid fibres may be used. In the case of xerogel, which is 90 volume % air, a platey filler will improve its mechanical properties such that It could be used as an insulating material, or the cavities can be used as drug reservoirs, which will slowly release, on a tooth or otherwise.
The filler reduces
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British Technology Group Limited
Griffin Ronald W.
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