IADR Abstract Archives
Improved Anhydrous Toothpaste Thickening System
Objectives: Anhydrous toothpastes are used to protect water-labile active ingredients and there are currently relatively few rheology modifiers capable of adequately structuring anhydrous toothpastes. Carbomer (crosslinked polyacrylic acid- CPA) is widely used to structure anhydrous toothpastes but its viscoelastic properties in the absence of water are poor. As a result, toothpastes made with CPA typically exhibit poor ribbon stand-up, stringiness, syneresis and are difficult to scale-up. The aim of this study was to improve the viscoelastic properties and process robustness of an anhydrous toothpaste by incorporating polymers that are synergistic with CPA.
Methods: Toothpaste formulations were made at the lab scale using conventional toothpaste manufacturing methods. Except for the thickening system, all formula ingredients and levels were held constant. Toothpaste viscosities were measured using a Brookfield DV2T viscometer fitted with a TD spindle and toothpaste rheology parameters were measured using an AR-G2 rheometer (TA instruments) fitted with parallel plates. Toothpaste ribbon stand-up was evaluated visually and with a Cuban rack. A stannous fluoride, anhydrous toothpaste formula incorporating Carbomer Homopolymer Type B was used as the control.
Results: The addition of very low levels of a strongly swellable, lightly to moderately crosslinked polyvinylpyrrolidone (PVP) to the control formula provided enhanced (synergistic) viscosity, higher viscoelasticity and thixotropy, improved toothpaste ribbon stand-up, reduced stringiness, improved stability and improved process robustness, compared to the control formula. Linear and more highly crosslinked grades of PVP, used at the same level, were not effective at improving toothpaste rheology and physical characteristics.
Conclusions: The addition of a small amount of a strongly swellable, lightly to moderately crosslinked PVP to a stannous fluoride, anhydrous toothpaste thickened with Carbomer Homopolymer Type B improved the following toothpaste attributes: rheology, physical characteristics and esthetics, processing and, stability. This polymer could be a useful ingredient to add to anhydrous toothpaste formulations thickened with carbomer.
Methods: Toothpaste formulations were made at the lab scale using conventional toothpaste manufacturing methods. Except for the thickening system, all formula ingredients and levels were held constant. Toothpaste viscosities were measured using a Brookfield DV2T viscometer fitted with a TD spindle and toothpaste rheology parameters were measured using an AR-G2 rheometer (TA instruments) fitted with parallel plates. Toothpaste ribbon stand-up was evaluated visually and with a Cuban rack. A stannous fluoride, anhydrous toothpaste formula incorporating Carbomer Homopolymer Type B was used as the control.
Results: The addition of very low levels of a strongly swellable, lightly to moderately crosslinked polyvinylpyrrolidone (PVP) to the control formula provided enhanced (synergistic) viscosity, higher viscoelasticity and thixotropy, improved toothpaste ribbon stand-up, reduced stringiness, improved stability and improved process robustness, compared to the control formula. Linear and more highly crosslinked grades of PVP, used at the same level, were not effective at improving toothpaste rheology and physical characteristics.
Conclusions: The addition of a small amount of a strongly swellable, lightly to moderately crosslinked PVP to a stannous fluoride, anhydrous toothpaste thickened with Carbomer Homopolymer Type B improved the following toothpaste attributes: rheology, physical characteristics and esthetics, processing and, stability. This polymer could be a useful ingredient to add to anhydrous toothpaste formulations thickened with carbomer.
