Writing in two separate international patents, Colgate-Palmolive detailed oral care formulations it had developed using sodium silicate and potassium silicate as active ingredients – both salt compounds providing a gentle whitening effect on teeth. Avoiding use of oxidizing agents, Colgate-Palmolive said the formulas were instead “novel abrasive systems” boosted by the incorporation of these metal silicates.
The formulations could be used to make a range of whitening oral care products, it said, including toothpastes, dental gels, tooth powders, tooth strips, mouthwashes and even gummies or lozenges.
Metal silicates for whitening that is ‘gentle on tooth enamel’
Colgate-Palmolive said there remained “a significant market need” for teeth whitening products that offered something different to traditional products and treatments already on the market.
“A growing number of consumers are expressing a desire for whitening regimens that are gentle on tooth enamel; and are shying away from more extreme and expensive professional treatments. Instead, they seek a safe and easy, inexpensive and effective option, for example, in a toothpaste,” Colgate-Palmolive wrote in its two patent filings.
The metal silicate formulations outlined in the two patents, it said, aimed to plug these needs.
Both formulations targeted extrinsic tooth stains – typically removed through the mechanical action of an abrasive system in a toothpaste in combination with the brushing action of the toothbrush. This abrasive system was formed by blending a primary active silicate – either sodium or potassium –with a “core shell silica particle” that was etched with a second metal silicate. Ideally, Colgate-Palmolive said the second metal silicate would be sodium and/or potassium – whichever was not used as the primary silicate, resulting in a formulation that contained both.
Controlled release of the metal silicate active formula
“The term ‘etched’ means that a surface of the silica core is dissolved, and the metal silicate is formed adjacent to the silica core,” Colgate-Palmolive said. The goal was to ensure the core shell particle comprised “a plurality of metal silicate layers” – as many as 64 monolayers – and that the silicate represented up to 90% of the total silica core weight.
It was also important that the span of the core shell silica particles did not exceed the mean diameter of the human dentin tubule, so the particles could enter and work on any damaged areas of the tooth exposed due to enamel breakdown. It also meant particles could plug or block any holes in the enamel. Release of these active ingredients could be controlled by embedding the first metal silicate and/or core shell silica particle into the gel matrix, Colgate-Palmolive said.
The personal care major said several additional actives could be added to the formulations, including odour-controlling agents, anti-bacterial agents at levels of up to 1.5% by weight, and acceptable antioxidants, among others. Flavours, sweeteners, colourants and mouth-feel agents could also be used to enhance the overall feel of the composition whilst maintaining a pH of between 8-10.
Colgate-Palmolive said by binding the second silicate to the core shell silica particle, the concentration of free metal ions in the formula was reduced; avoiding high concentrations of free metal ions that could lead to a poor taste profile.
Colgate-Palmolive whitening toothpaste innovation
In January this year, the personal care major launched its ‘Smile for Good’ vegan-certified toothpaste range – one for protection and one for whitening. Both toothpaste formulas contained hydrated silica or what Colgate-Palmolive described as ‘high cleaning silica’.
The personal care major also published a patent for teeth whitening in July 2020 that outlined use of natural, plant-based abrasives derived from walnut tree bark and branches for improved polish and shine.
It said a blend of these abrasive ingredients exhibited “relatively greater whitening efficacy than conventional whitening compositions”.
WIPO International Patent No. WO/2020/226876
Published on: November 12, 2020. Filed on: April 17, 2020.
Title: “Oral care compositions”
Inventor: Colgate-Palmolive – S. Tang, L. Fei, S. Chopra, H. Strotman and P. Kulkarni
WIPO International Patent No. WO/2020/226765
Published on: November 12, 2020. Filed on: March 24, 2020.
Title: “Oral care compositions”
Inventor: Colgate-Palmolive – P. Kulkarni, L. Fei, S. Chopra, H. Strotman and S. Tang