Stannous Compatible Silica Particles for Dentifrice Formulations
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Solution Overview
Problem
Stannous fluoride in dentifrice formulations interacts negatively with silica materials, reducing its effectiveness due to compatibility issues, leading to diminished cavity protection and increased plaque and tooth sensitivity.
Innovation Solution
Development of silica particles with improved stannous compatibility, characterized by specific surface area, pack density, Einlehner abrasion value, and total mercury intrusion pore volume, produced through a process involving alkali metal silicate and mineral acid addition to adjust pH and reduce surface area, resulting in particles that are highly compatible with stannous fluoride.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard silica materials are used in dentifrice formulations, then cleaning and abrasiveness are maintained, but stannous fluoride compatibility deteriorates leading to reduced therapeutic effectiveness
Solution Approach 1:
The patent applies parameter changes by modifying the BET surface area of silica particles to a specific range (5-50 m2/g) and controlling the pore volume (0.3-2.0 mL/g) to optimize stannous fluoride compatibility. This involves adjusting manufacturing parameters such as surface treatment and particle size distribution to achieve the desired surface characteristics that prevent stannous fluoride deactivation while maintaining cleaning efficacy.
Solution Approach 2:
The patent employs composite materials by creating silica particles with specific surface modifications and controlled pore structures that combine cleaning functionality with stannous fluoride stability. The composite structure includes the silica base material with modified surface properties that simultaneously provide abrasiveness and compatibility with stannous fluoride therapeutic agents.
2Reliability
If silica surface area is reduced to improve stannous compatibility, then stannous fluoride stability improves, but cleaning effectiveness may deteriorate
Solution Approach 1:
The patent applies local quality by creating non-uniform pore size distributions within the silica particles, where specific pore size ranges (0.03-2.0 micrometers) are optimized for stannous fluoride compatibility while maintaining overall surface area for cleaning. This involves creating regions with different pore characteristics that simultaneously satisfy both stability and cleaning requirements.
Solution Approach 2:
The patent applies partial action by reducing the BET surface area to a moderate range (5-50 m2/g) rather than minimizing it completely, and by controlling pore volume within specific limits (0.3-2.0 mL/g). This partial reduction is sufficient to improve stannous fluoride stability while preserving enough surface area and porosity to maintain effective cleaning and abrasiveness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting silica particles maintain porosity and abrasiveness within acceptable ranges, enhancing the therapeutic effectiveness of stannous fluoride in dentifrice compositions by improving compatibility and reducing tooth sensitivity and plaque formation.
Implementation Method 1
adding to the mixture an alkali metal silicate and a mineral acid under surface area reduction conditions... to adjust the pH of the mixture to within a range from about 5 to about 8.5
Implementation Method 2
adding to the mixture an alkali metal silicate and a mineral acid under surface area reduction conditions
Implementation Method 3
a total mercury intrusion pore volume in the range from about 0.7 to about 1.2 cc/g
Data Source
AI summary
Silica particles having a BET surface area from 0.1 to 7 m2/g, a pack density from 35 to 55 lb/ft3, an Einlehner abrasion value from 8 to 25 mg lost/100,000 revolutions, a total mercury intrusion pore volume from 0.7 to 1.2 cc/g, and a stannous compatibility from 70 to 99%, are disclosed, as well as methods for making these silica particles.