Unilever patents teeth whitening kit with photosensitiser film and actinic light source

In its international patent, Unilever wrote that it had developed an oral care whitening kit that contains a film that can be applied directly to the teeth and a source of actinic light. The personal care major said the invention provides consumers with a simple and efficient means to whiten teeth at home and built on some of his existing inventions to meet the increasing demands of this market.

“Consumers have a strong desire for whiter teeth and some people are unhappy with the inherent color of their teeth or with the stains. This desire for whiter teeth has led to a growing trend in whitening products ranging from toothpastes to mouthwashes to chewing gum, ”Unilever wrote in its patent application.

Although there have already been a number of whitening toothpastes and kits on the market, including many under its own brands, Unilever said there was a need to move away from compositions and methods that involve bleach as they involve the release of free radicals – “sometimes disliked by consumers because they believe that free radicals can be harmful to the body under certain conditions”.

There was also a need to make home teeth whitening as “easy to use” and efficient as possible for consumers.

Beyond bleach and “messy” gels – single-use film strips.

Back in 2018, Unilever filed a patent for an aqueous tooth whitening gel composition made using photosensitizer ingredients – the same composition that was incorporated into the films for this invention.

“The present inventors have sought to improve the effectiveness of such types of compositions and, after extensive experimentation, have arrived at the present invention,” Unilever wrote in its current patent application.

“… In the present invention, the film is applied to the tooth surface and then illuminated with actinic light. The present invention has the advantage over the previous invention that it eliminates the need for gels which have to be subsequently removed from the mouth by rinsing, which some users may find somewhat messy. The present invention involves simply peeling off the film after use and throwing it away. “

However, it was “not easy” to ensure the desired effectiveness and diffusion of the ingredients onto the teeth in film form.

Photosensitizing formulation “locked” into the film format using polymers.

Unilever said it included the gel composition, which contained at least one photosensitizer selected from a class of xanthene dyes, using two different types of polymers: a polysaccharide or modified polysaccharide and a water-soluble film-forming synthetic polymer.

These ingredients were dissolved in water to form a premix and then poured into a film, preferably a “dry” film that had no noticeable wetness to the touch.

Unilever explained how this composition then worked to whiten teeth: “Conventional compositions containing a bleaching agent are believed to cause photosensitizers to accelerate the dispersion of light energy when exposed to actinic light, thus leading to photochemical activation of the oxidizing agent within the composition. In the case of the present invention, however, when the photosensitizer is exposed to actinic light, it generates reactive excited species which in turn interact with the stains on the teeth to thereby lighten the stains. The film matrix, which is formed as a combination of the two polymers used in the composition according to the invention, enables effective contact of the dye molecules with the surface of the teeth. It also prevents unwanted quenching of the radicals formed, which increases the effectiveness of the dye concentration used. This leads to better whitening of the teeth. “

“Appropriate” light source is also important for lightening.

The company said it was important to ensure the use of an “appropriate source of actinic light” – any that emits light at a wavelength or wavelengths appropriate to photosensitize the photosensitizer present in the composition. Unilever said it would emit light “preferentially in the visible” from a number of potential sources, including halogen lamps, LED or plasma arc lamps, laser or LED photo-curing devices.

The aim is for consumers to use the light source for less than ten minutes in shorter series of one to four minutes so that the application can be repeated as often as desired – up to two or three times a day.

WIPO International Patent No. WO / 2021/094156.
Published on: May 20, 2021. Filed on: November 11, 2020.
Title: “A film and a kit for whitening teeth”
Inventor: Unilever IP Holdings BV, Unilever Global IP Limited, Conopco Inc. – SK. Barne et al.

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