IE20090415U1 - Use of novel complex fluoro-aluminium ions (F AL2+) for anti-caries activity - Google Patents

Abstract

ABSTRACT This invention ro oses the use of novel com lex fluoro—aluminium cation, FAl2+, in P place of, or as an adjunct to, the use of anionic sources of flouride ion, F-, as an anti- caries agent in dental materials and products.

Description

Use of Novel Complex Fluoro-Aluminium Ions (FAl2") for Anti-Caries Activity The invention relates to the addition of a novel cationic complex fiuoro-aluminium ion, FAI”, in the form of a suitable salt, as a source of fluorine to dental materials for the prevention of dental caries, in place of or as an adjunct to the use of anionic fluoride ion, F‘, normally used for that purpose.

It is now generally accepted that free fluoride ion, F‘, is the principal effective active agent in the prevention of dental caries. In many surface and ground waters, fluoride ion, F‘, occurs naturally and the importance of fluoride as a preventative of dental caries was recognized when it was noticed that people living in areas with naturally occurring fluoride in their drinking water had lower levels of dental decay.

In the absence of naturally occurring fluoride in the surface and ground waters (i.e. the raw waters) that are used as a source of drinking water, it is now common practice to add fluoride during the treatment process for the preparation of drinking water, so that this element is available in the final drinking water to prevent dental caries. In the preparation of drinking water, the fluoride is added in the form of a salt of hexafluorosilicic acid or from the acid itself, H2SiF.;, which is then rapidly completely dissociated to free fluoride ion, F‘, in the solution“). A typical concentration of fluoride ion, F‘, in drinking water is approximately 1.0 mg/l. The addition of a source of fluoride to drinking water is very cost effective in the preventative of dental decay in the general population.

Fluoride is also added to dental materials and products for the prevention of dental caries, in the form of suitable soluble or insoluble salt of hydrofluoric acid or from a suitable soluble or insoluble salt containing complex fluorine containing anions (e.g. fluorophosphates, fluorosilicates, etc.). Fluoride ion, F‘, in the form of soluble (e.g. sodium fluoride, NaF) or insoluble (e.g. calcium fluoride, CaF2) salts of hydrofluoric acid) or other soluble or insoluble sources of fluoride ion (e.g. fluorophosphates, fluorosilicates, etc.) are present in many toothpastes and mouth washes at significant significantly higher concentrations, typically at approximately 1000 mg/g and 1000 mgil as fluoride ion, F‘, respectively.

Although the use fluoride toothpaste is effective in the reduction of dental caries, its use in conjunction with the consumption of fluoridated drinking water increases the effectiveness considerably“). Because of the significantly greater levels of fluoride in toothpaste relative to that present in drinking water, this observation is counter-intuitive.

To date, there has not been any consensus on why the very low levels of fluoride in drinking water are so effective in the protection of the population at large against tooth decay. However, this enhanced performance can only be explained by the chemical speciation of fluoride to a more active form in drinking water.

Specific unit operations in the preparation of drinking water may be responsible for this activation. In the treatment of surface waters for the preparation of drinking water, a number of physical-chemical processes are used to remove contaminants and detritus from the raw water. While these processes are intended for the mentioned purpose, ways. These alterations to the basic chemistry of the water give rise to characteristics that allow activation of the fluorine to a more active form.

As part of the treatment process, aluminium ion, AI“, is added at approximately 50 mg/I is added to the raw water as it arrives in the waterworks. Normally, the aluminium that is observed in the raw surface water that is fed to a waterworks is present as a complex with organic matter and there is very little free ionic aluminium ion, Al“, present in the raw water. When the aluminium ion, AI”, is added to the water, a flocculent blanket is formed in the water. This flocculent blanket that is formed (which consists of a complex matrix of oxy- and hydroxy-aluminum species) has an active surface to which is attracted all the undesirable detritus and organic particulates in the raw water (including viruses and bacteria).

This water with its flocculant blanket is then fed into the bottom of the clarifier and rises vertically through the clarifier and overflows at the surface. This flocculent blanket falls under the influence of gravity in a clarifier against the upward flow of the water and is removed via hoppers at mid-depth in the tanks, while the clarified drinking water overflows at the top of the clarifier. Although the total concentration of all forms of aluminium (i.e. organically bound aluminium from the raw water and ionic aluminium added as a flocculent) is less in the clarified water than in the raw water, the residual aluminium exists in ionic form (i.e. as aluminium ion, AI3‘). Typically, the concentration of free aluminium ion, AI3‘, is within regulatory limits (i.e. <0.2 mg/l aluminium ion, Al”, in the water within the European Union). However, even at this low concentration, the aluminium ions, Al”, that remain in solution are available as a reagent for further reaction. This change in the speciation of aluminium during the treatment process has significance for its role in altering the reactivity of the water.

Recently, the formation and characterization of the fluoro-aluminium ion, FAl’*, as a complex ion during the analysis of waters and fluids for levels of fluoride at a micro trace levels has been reported‘ . This reported complex fluoro-aluminium ion, FAI“, is deliberately formed quantitatively during the analytical procedure at a pH of approximately 3.0 and its concentration is then determined to measure the level of fluoride in the sample. However, this complex fluoro-aluminium ion, FAI”, can also be formed in the environmental conditions in watenivorks and in distribution systems when free aluminum ion, AI“, and free fluoride ions, F‘, are present and available to interact.

The complex fluoro-aluminium ion, FAI”, is readily formed“) in dilute solutions at a pH of approximately 3.0 at 50°C, where the aluminium ion, Ala‘, is present along with fluoride ion, (F'). The complex fluoro-aluminium ion, FAI”, so formed is in the form of one of its salts (e.g. the nitrate salt of the complex fluoro-aluminium, (FA|2")(NO3')2).

This compound exists only as an ion-pair or as an outer-shell complex in solution.

Although this complex ion is stable enough to be separated by HPLC, it is recommended that it not be isolated, but the solution in which it is formed be used as the base or solvent for further processing, to which other materials are added to form the finished dental product. in the case of the preparation of drinking water, the conditions required for the synthesis of the complex fluoro-aluminium ion, FAI”, are present within the treatment process.

The three requirements are present at the point when the drinking water is leaving the ' waterworks and the fluorosilicilic acid, H2SiF.; is added as the final step in the treatment.

IE 090415 At that point, (a) low levels of aluminium ion, Al“, are present the water (typically at concentrations of approximately 0.05 mg/I), (b) there is high level of acidity immediately surrounding the point of dosing of the hexafluorosilicic acid, H-2SiF;, and (c) fluoride ion, F‘, is available from the rapid dissociation of the hexafluorosilicic acid, H2SiF5. It is unlikely that the formation of the complex fluoro-aluminium ion, FA!” under these conditions is quantitative (based on the concentration of the limiting component available for the reaction: aluminium ion, Al”). Nevertheless, this subtle speciation through the formation of the complex fluoro-aluminium ion, FAI“ at ultra trace levels (approximately 1 to 50 pg/I) is likely and is one possible explanation for the extraordinary effectiveness of the fluoridated drinking water in preventing dental decay.

Taking toothpaste as an example, to date the list of ingredients that make free fluoride ion, F‘, available in the oral cavity, are based on the release of free fluoride ions, F‘, from anions (l.e. negatively charged ions), including soluble (e.g. sodium fluoride, NaF, etc.) or insoluble (e.g. calcium fluoride, CaF2 etc,) salts of hydrofluoric acid or other soluble or insoluble sources of fluoride ion (e.g. fluorophosphates, fluorosilicates, etc.).

The free fluoride ions, F‘, are made available from the complex cations either by direct ionization of the complex salt or by hydrolysis of the parent source ions that are present.

This invention involves the use of the novel complex fluoro-aluminium cations, FM”, (in the form of its salts) as agents for the prevention of dental caries, either directly or as a source of fluoride or as reagents for the supply of fluoride ion, at the surface of the tooth or within the structure of the tooth. This is in contrast-to the negatively charged anions (e.g. fluoride, F‘, fluorosilicate, SiFe2', etc) that are currently used for that purpose. The reactions of this cation at the surface of tooth or within fissures in the tooth will act in a manner different from that ofanions.

The complex fluoro-alumimum cation, FAI”, that is used in this invention is used in the form of one of its salts of various inorganic and organic acids, including but not limited to the chloride, nitrate, sulphate, fluoride, or of the range of ortho—, meta- or poly- phosphate salts or of the salts of the wide range of organic acids including the polymeric organic acids that are in regular use in dental materials.

The active cationic reagent (i.e. the fluoro-aluminium complex ion, FAI”) to prevent dental caries may be added at trace levels, in place of or as an adjunct to the use of free fluoride ion, F‘, to a wide range of dental materials and products, including but not limited to (a) toothpaste, (b) dentifrice, (c) gels used in dentistry, (d) polishing abrasives, (e) mouth washes and mouth rinses, (f) oral hygiene agents, (g) materials for fillings, (h) liners for fillings, (i) fluoride release agents and polymers, (5') crowns, (k) veneers, (l) caps, (m) fissure sealing agents, (n) dental cements and adhesives, (0) dental prosthetics, including plates, crowns, bridges, etc. The cationic reagent (i.e. the fluoro- aluminium complex ion, FAI”) may be incorporated in a form to be released (a) directly from the material (b) from a slow release matrix in the dental material or (c) as a result of the wear of the dental material.

Example 1 A typical formula for a toothpaste containing the complex fluoro-aluminium as its nitrate salt, (FAl2")(N03')2), may be prepared according to the following ‘formula.

IEOQO415 Approximately 1 gram of this toothpaste is used each time when brushing the teeth.

The formula is by weight.

Secondary calcium phosphate 45.0 Sodium carboxymethyl cellulose 1.0 Glycerin 20.0 Sodium lauryl sulphate 1.0 Flavourant (Perfume) 1.0 Sodium Saccharin 0.2 Monofluoro-aluminium nitrate, (FAI2")(NO3‘)2), 0.01 to 0.1 Sodium fluoride 0.05 to 0.5 Made up to 100 with water Example 2 A typical formula for a mouthwash containing the complex fluoro-aluminium as its nitrate salt, (FAI2*)(NO3')2), may be prepared according to the following formula.

Approximately 10 ml of this mouthwash is used for each rinse. The formula is by weight.

Ethanol 20.0 Sodium Saccarin 0.1 Flavourant (Perfume) 1.0 Fatty Acid ester of sucrose ' 0.5 Monofluoro-aluminium nitrate, (FA|"')(NO3')2), 0.001 to 0.01 Sodium fluoride - 0.005 to 0.05 Made up to 100 with water References Cited: . Urbansky, Edward Todd: Chem. Rev. 2002, 102, 2837-2854. DOII .1021lcr020403c.

. Discussions after lecture on fluoridation of drinking water at IADR PEF Dental Conference Trinity College Dublin, 13"‘ to 16"‘ Sept 2006.

. Maria Montes Bayon. Ana Rodriguez Garcia, J Ignacio Garcia Alonso, Alfredo Sanz-Medelz Analyst, 1999, 124, 27-31.

Claims (1)

1. Claims The use of a salt of the complex fluoro-aluminium ion, FAI” (e.g. nitrate, (FAl’*)(N03')g or sulphate, (FAl2")(S042')). as an component of any dental material from which it may be released into the oral cavity for the prevention of dental decay is claimed. The use of a salt of the complex fluoro-aluminium ion, FAI”, (e.g. nitrate, (FA|2")(NO3')2 or sulphate, (FAI’*)(SO42')). as claimed in claim 1, as a component of toothpastes at low concentration as an anti-caries agent is claimed. The use of a salt of the complex fluoro-aluminium ion, FAl"”, (e.g. nitrate, (FAl2“)(N0;a,')z or sulphate, (FAl2*)(S04")), as claimed in claim 1, as a component in mouth washes at low concentration as an anti-caries agent is claimed.