From novel approaches to tooth whitening to biofilm prevention, these patents are at the cutting edge of oral care technology
1. Oral care compositions
US Patent 10,363,210
Application No 15/723,730
Granted 30 July 2019
The patent describes oral care compositions that are stable during long term storage and remain effective to clean and whiten teeth. The oral care compositions comprise a whitening complex of crosslinked polyvinylpyrrolidone with hydrogen peroxide.
The compositions may also contain one or more humectants, a thickener, polyethylene glycol, an abrasive, flavourings, sodium lauryl sulfate, stannous fluoride and sodium monoflurophosphate.
The accompanying table (below) is an illustrative formula. It is important for the stability of the composition that water content is minimal. By exposure to aqueous environments, as in the oral cavity, the PVP-H2O2 dissociates into PVP polymer and H2O2.
The PVP-H2O2 complex generally comprises about 80% by weight polyvinylpyrrolidone and 20% by weight H2O2. Calcium pyrophosphate particles serve to break up the stain during the act of brushing and peroxide whitens both extrinsic surface stains and intrinsic stains below the surface of enamel through a chemical reaction in which the unsaturated bonds in coloured stain molecules are oxidised by peroxide to become colourless.
The patent includes test protocols for measuring tooth whitening and product stability for the illustrative formula plus formulations and test results for teeth whitening gels containing 1% hydrogen peroxide.
2. Dentifrice compositions comprising zinc oxide and zinc citrate
US Patent 10,342,750
Application No 15/106,280
Granted 9 July 2019
The applicants stated that there is a need for agents in oral care products that provide enhanced benefits including antibacterial, anti-cavity, enamel erosion prevention and breath freshening.
They claim to have surprisingly and unexpectedly discovered that a specific ratio of zinc oxide to zinc citrate provides a high level of efficacy in the reduction of biofilms in the oral cavity and increased antimicrobial effect.
This ratio is two parts zinc oxide to one part zinc citrate, and the patent describes an oral care composition comprising about 1% zinc oxide and about 0.5% zinc citrate in an orally acceptable carrier having synergistic antibacterial effects.
The carrier may comprise abrasives, thickening agents, humectants, polymers, colourants, viscosity modifiers, foam modulators, emulsifiers, pH modifying agents, diluents, mouth feel agents, sweetening agents, flavour agents, preservatives, suitable cosmetic or therapeutic actives, and combinations thereof.
Optional ingredients include whitening agents such as peroxide compounds, chlorine dioxide, chlorites and hypochlorite, titanium dioxide and hydroxyapatite.
One or more whitening agents are optionally present in a tooth-whitening effective total amount, and the whitening agent may be separated from the aqueous carrier by encapsulation of the whitening agent.
Although the composition of the carrier does not appear to be an essential part of the patent it is of interest because it lists by function most additives likely to be found in a mouthwash, toothpaste or gel.
3. Single layer tooth whitening system
US Patent 10,307,348
Application No 15/545,434
Granted 4 June 2019
Assignee Koninklijke Philips
The use of varnish compositions by painting or other spreading techniques to administer oral care ingredients to teeth has several advantages.
However, wetting of the outer surface of the varnish can cause the oral care agents to leak into the mouth or to be soft and easily washed away. The deposited varnish composition may also have a rough surface that can irritate the lips and other soft tissues, or the deposited composition may have an undesirable appearance in terms of a rough surface, poor colour or undesirable reflectance properties.
To overcome these disadvantages the patent describes a varnish composition comprising a hydrophilic oral care agent, such as a peroxide material, dispersed in a solution of a film-forming hydrophobic polymer in a non-polar solvent.
The hydrophobic polymer and the non-polar volatile solvent are of a different phase than the dispersed hydrophilic agent. The applicants suggest that after application the non-polar solvent will migrate towards the surface carrying both the hydrophobic polymer and the dispersed hydrophilic agent.
As the solvent evaporates the concentration of the hydrophobic polymer increases and starts to form a solid polymer film. This has the dual effect of enhancing the sealing of the agent from the aqueous environment of the mouth, and to effectively increase the concentration of the agent on the teeth.
The hydrophilic oral care agents are either present in the form of aqueous solutions, or in the form of hydrophilic particles. Representative examples include solutions of hydrogen peroxide in water or solid peroxides, such as carbamide peroxide and polyvinylpyrrolidone hydrogen peroxide adduct.
Other examples of hydrophilic oral care agents include remineralisation agents, fluoride agents and desensitising agents.
The preferred hydrophobic polymer is a clear, linear triblock copolymer based on styrene and ethylene/butadiene with a styrene content of about 30-35%, available as Kraton polymers from the Kraton Corporation.
Preferred solvents include alkanes, isoalkanes, isoparaffins and siloxanes, fluorinated hydrocarbons, and mixtures of these solvents. Isopentane is included in a solvent mixture to reduce cure time and isoparaffin is an alternative to the alkanes.
After sufficient time to effect treatment the varnish layer is removed by peeling it away from the teeth or by brushing.
4. Dual phase mouthwash compositions
US Patent 123,951
Application No 15/329,123
Granted 13 November 2018
The patent describes a packaged mouthwash composition comprising an aqueous phase and an oil phase as separate layers in a single container. An essential part of the patent is one or more silicone oils, present in either or both the oil and the aqueous phase.
The preferred silicone oils are a linear polydimethylsiloxane and a cyclic polysiloxane. A polyoxyethylene sorbitan ester such as polysorbate-20 is also present and found in the aqueous phase.
The aqueous phase may also contain one or more humectants, phosphate salts, sweetening agents, preservatives, colourants, whitening agents, anti-sensitivity agents, zinc salts, tin salts, antibacterial agents, fluoride ion sources, water-soluble or water-dispersible polymers, ethanol and tartar control agents.
The oil phase is a mineral oil and may also contain colourants, flavourings and oil-soluble active ingredients. Examples of each of these optional ingredients are listed and make up the bulk of the patent.
Interesting additives are bicarbonate salts to impart a clean, fresh feel to the mouth, food acids as saliva stimulating agents to combat dry mouth and tarter control agents such as phosphates, polycarboxylate polymers and polyvinyl methyl ether/maleic anhydride (PVM/MA) copolymers.
The silicone oil is present at a maximum of 0.1% by weight and it is suggested that it suppresses foam formation when the dual composition is agitated or shaken, thereby contributing to a rapid separation of the two phases.
The aqueous phase may be between 65% and 95% by weight of the total composition, with the balance being the oil phase, which forms the top layer.