Glycerin (99.5 percent) and sorbitol (70 percent) are the primary liquids used for the humectant system. Their preference is based on compatibility with the water, cleaning silicas and thickeners, rheology functionality and cost effectiveness. The primary functions of the humectant system are to avoid water separation (stability), reduce evaporation of the water (which leads to “crusting” at the tube orifice), provide a smooth and glossy appearance and provide a consumer friendly homogenous delivery system for all of the ingredients. Organic hydrocolloids are used to prevent phase separation during storage and, in conjunction with thickener silica, provide the desired rheological properties. They are water-soluble polymers which modify the rheology of the continuous phase and thereby of the toothpaste itself. The most commonly used are cellulose gum (CMC or sodium carboxymethyl cellulose), carrageenan and xanthan gum. These products are available from CP Kelco, a subsidiary of the J.M. Huber Corporation (for more information, contact CP Kelco at cpkelco.com or call 1-678-247-7300). Formulation experience now becomes the guide in deciding which silica and gum system to use. In general, gum levels should be minimized because silica is more cost effective at building viscosity and excessive gum levels lead to negative product aesthetics.
A balance must be achieved between the amount and type of gum, amount and type of silica thickener and the amount and composition of the humectant system. A proper balance will result in toothpaste with a desirable rheology and appearance. “Starter formulations” are available from Huber upon request. Formulation changes can then be made to modify the appearance/ rheology of the toothpaste and evaluate the cost performance of the components. Today’s marketplace includes toothpaste applications that serve therapeutic market segments for sensitive teeth, for gum protection, for tartar control, for anti-caries and for children, not to mention formulations that offer multiple benefits. Once the humectant and cleaning silicas are selected, the formulator will choose from an array of ingredients to satisfy the needs of the target market.
- Polyphosphates enhance cleaning, control tartar and provide buffering
- Therapeutic actives can provide bacterial, tartar and caries control (e.g., NaF). Level of these actives is usually determined by regulatory requirements, but the bioavailability of the active is influenced by the formulation
- Preservatives protect the formulation from biological degradation during shelf-life
- Surfactants, color, sweetener and flavor enhance aesthetic properties