Guidelines for choosing a cleaning silica abrasive
While the science of toothpaste ingredients is largely understood, final toothpaste formulation remains an art. We has identified the following considerations in formulating toothpaste:
Choosing A Cleaning Silica
Formulators choose a cleaning silica system to meet the desired toothpaste performance. Generally, performance is targeted to specific Pellicle Cleaning Ratio (PCR) and Relative Dentin Abrasion (RDA) ranges. The PCR of our cleaning silicas is displayed in the table shown below. This will drive a choice of standard cleaning, high cleaning silica or both. RDA values tend to increase with greater PCR. The absolute concentration of all cleaning silicas is important to achieve PCR/RDA targets and desired mouth-feel. (Often higher silica concentrations lead to better mouthfeel.) ZEODENT® 103 high cleaning silica can be used alone or as a “booster” in conjunction with other Evonik standard cleaning silicas to target higher cleaning/whitening performance. For maximum cleaning, it can be used at 10 to 20 percent loadings (higher, but acceptable RDA levels) with thickener silica to improve the mouth-feel. For lower RDA targets, ZEODENT® 113 at ~20 percent loading or ZEODENT® 124 at ~10 percent loading are usually better cleaning silica choices because of the higher loading level. These help reduce the level of gum necessary to obtain an acceptable rheological profile for toothpaste. Clear gel toothpaste is a special case where the optical properties of the silica must be taken into consideration along with meeting the PCR/RDA targets. ZEODENT® 113 and ZEODENT®124 cleaning silicas deliver greater optical clarity than ZEODENT® 103 high cleaning silica.
Guidelines for Cleaning Silica:
Choose a level of cleaning performance based on target PRC and RDA values
Abrasion (RDA) typically increases with higher cleaning (PCR)
Mouthfeel improves with higher loading levels
Guidelines for choosing a thickener silica
Typically, a 20 percent loading of cleaning silica is used and thickener is added as needed to achieve the desired viscosity build. The mouth-feel problems posed by a low level of cleaning silica are overcome simply by increasing the thickening silica content of the formulation. A formulator typically uses from 20 to 30 percent silica in order to address mouth-feel issues. By addressing performance with the cleaning silica and viscosity by the thickener, great toothpaste can be created. A 12 percent loading of ZEODENT® 124 cleaning silica would be complemented by 10 percent ZEODENT® 165, resulting in a smooth, readily dispersible mouth-feel. Other examples of choices would include 18 percent ZEODENT® 113 plus 6 percent ZEODENT® 165, or 20 percent ZEODENT® 103 plus 8 percent ZEODENT® 165.
Guidelines for Thickener Silica:
Thickener silica has negligible effect on cleaning and abrasion levels
The primary function of thickener silica is rheology control during processing and in the final product
Higher levels of thickener deliver products with higher viscosity (better “stand up”) and enhanced mouthfeel