Silica, as an indispensable key ingredient in modern toothpaste, directly determines the cleaning efficacy, user experience, and safety of the product. This article comprehensively explores the types of silica suitable for toothpaste, analyzes their physicochemical properties, compares the advantages and disadvantages of different silica varieties, and elaborates on their multiple functions in oral care. From abrasive to thickening silica, from gas-phase to precipitation-based production processes, we will delve into how to select the most suitable silica for toothpaste formulations while also examining technological innovations and market trends in this field. This provides professional reference for both consumers and industry practitioners.

History and Current Status of Silica as a Toothpaste Abrasive

The application of silica in toothpaste dates back more than half a century, closely aligned with advancements in oral care science. As early as the 1960s, researchers began exploring silica as a replacement for traditional abrasives (such as calcium carbonate and dicalcium phosphate) in toothpaste formulations. In 1978, Chengdu Toothpaste Factory in China pioneered the use of silica to produce the country's first silica-based toothpaste, "Xiaolidoo," marking the beginning of commercial applications of this material in oral care. However, due to limitations in production technology and consumer awareness at the time, the adoption of silica in toothpaste progressed relatively slowly.

With advancements in materials science and dental medicine, the importance of silica in improving toothpaste quality and protecting teeth has become increasingly recognized. Compared to traditional abrasives, silica offers significant advantages, including strong chemical inertness, excellent compatibility with fluoride, and high stability of the paste. Particularly in the 21st century, rising consumer awareness of oral health and demand for high-quality toothpaste have driven the widespread use of silica in toothpaste. According to market research data, the global market size for toothpaste-grade silica reached 390 million in 2021 and is projected to grow to390millionin2021andisprojectedtogrowto494 million by 2026, with a compound annual growth rate (CAGR) of 4.85%. In the Chinese market, demand for toothpaste-grade silica is expected to increase from 45,000 tons in 2019 to 60,000 tons by 2026, with a market size approaching 800 million RMB.

Today, silica has become the only abrasive choice for transparent and semi-transparent toothpaste. Its advantages lie in its low abrasiveness, excellent fluoride compatibility, and the ability to adjust various physicochemical parameters (such as abrasiveness, oil absorption, specific surface area, water absorption, light transmittance, and refractive index) to meet different formulation requirements. These properties enable silica not only to fulfill basic cleaning functions but also to provide excellent thixotropy, dispersibility, and stability to the paste, making it a core ingredient in modern high-end toothpaste formulations.

Types and Characteristics of Silica Suitable for Toothpaste

Toothpaste-grade silica is primarily divided into two categories: abrasive and thickening. These two types can be further subdivided based on production processes and structural characteristics. Understanding the distinctions and properties of these silica varieties is crucial for toothpaste formulation design and product optimization. From a production standpoint, toothpaste-grade silica mainly includes two preparation methods: precipitation and gas-phase, each with unique performance features and application advantages.

Abrasive silica is a low-structure product, typically with a wet cake moisture content below 70% (around 60%) and moderate oil absorption (100–130 mL/100g) and a large specific surface area (170–220 m²/g). This type of silica has regularly shaped particles with rounded edges, effectively removing plaque and surface stains while minimizing enamel wear. The Relative Dentin Abrasivity (RDA) of abrasive silica is a key safety indicator. High-quality toothpaste-grade silica should have an RDA value between 20 and 70, falling within the low-abrasion range to ensure cleaning efficacy without damaging enamel. Well-known commercial products like SIDENT® 22S precipitated silica are typical abrasive types, usually added at 7–9% to provide excellent cleaning performance and rheological properties.

Thickening silica, on the other hand, is a high-structure product with a wet cake moisture content above 70% and oil absorption typically exceeding 130 mL/100g, along with a relatively small specific surface area. This type of silica primarily functions as a thixotropic agent and thickener in toothpaste, effectively modifying the viscosity index of liquid systems to prevent sedimentation and sagging while improving suspension and dispersion. Hydrophilic AEROSIL® 200 fumed silica is a representative thickening product, featuring extremely low iron content and being particularly suitable for peroxide-based toothpaste thickening, with a recommended addition rate of 3–5%. Fumed silica is produced by hydrolyzing volatile chlorosilanes in a hydrogen-oxygen flame, consisting of high-purity amorphous silica with nanoparticle characteristics and excellent rheological modification capabilities.

From a safety and efficacy perspective, silica offers clear advantages over traditional abrasives. Calcium carbonate, while inexpensive, has large crystalline particles and high hardness during abrasion, which can easily scratch enamel. Additionally, calcium carbonate readily reacts with free fluoride in toothpaste to form insoluble calcium fluoride, significantly reducing anticaries efficacy. Dicalcium phosphate causes less enamel damage and provides moderate cleaning power, but due to phosphate resource limitations and environmental policies, its price now exceeds that of silica. In contrast, silica exhibits excellent fluoride compatibility. Experimental data show that fluoride detection rates in fluoride toothpaste with silica abrasives can reach 100%, far surpassing traditional abrasives like dicalcium phosphate (97%) and aluminum hydroxide (84%). This makes silica the ideal choice for fluoride toothpaste.

Table: Performance Comparison of Different Toothpaste Abrasives

With consumer upgrades and increasing oral health awareness, Grade A toothpaste (priced above 9 RMB per tube) now accounts for 55% of the Chinese toothpaste market, driving demand for high-quality abrasives. In this context, silica, with its comprehensive performance advantages, is gradually replacing traditional abrasives, particularly in the premium toothpaste segment. Manufacturers can select silica with different particle sizes, structures, and surface properties—or combine abrasive and thickening types—to achieve optimal cleaning performance and user experience based on product positioning and efficacy requirements.