Mechanisms of Oral Malodor Removal by Diatom Toothpaste

Physicochemical Properties of Diatomaceous Earth

Diatomaceous earth (DE), the core functional ingredient in diatom toothpaste, provides the fundamental mechanisms that enable efficient removal of oral malodor. From a physical perspective, DE possesses an exceptionally well-developed porous architecture. Its microstructures appear in disk-shaped, sieve-like, tubular, and rod-like forms, with silica surfaces covered by a highly ordered network of micropores. This unique morphology gives DE strong adsorption capacity; studies demonstrate that it can absorb 1–4 times its own weight in water and 11–15 times its weight in oils.

Chemically, DE consists primarily of amorphous silica, generally above 80% purity, and can reach 90% in high-grade deposits. Trace components include Al₂O₃, Fe₂O₃, CaO, MgO, K₂O, Na₂O, P₂O₅, and organic matter. Its pH of 6.0–9.0 (weakly acidic to neutral) supports stable oral acid–base balance.

The isoelectric point of DE is 1.8–2.0, while the oral cavity maintains a physiological pH of 6.5–7.0; diatom toothpaste typically has a pH around 6.8. Under these conditions, DE particles carry a negative surface charge, which attracts positively charged pathogenic bacteria. The resulting electrostatic interactions disrupt bacterial membranes and lead to inactivation—one of the major antibacterial mechanisms of DE.

Core Mechanisms for Removing Oral Malodor

The odor-removal effects of diatom toothpaste operate through three synergistic mechanisms: physical adsorption, chemical neutralization, and biological antibacterial action.

1. Physical Adsorption (Primary Mechanism)

DE exhibits strong adsorption toward key odorants responsible for malodor, such as indole and dimethyl sulfide. Measurements using electronic nose analysis and UV–Vis spectrophotometry confirm that toothpastes formulated with different DE particle sizes effectively remove these odorants—with 800-mesh DE showing the highest adsorption efficiency.

The extensive porous network of DE traps and immobilizes volatile odor molecules, resulting in a pronounced deodorizing effect.

2. Chemical Neutralization

DE contains natural mineral constituents capable of regulating oral pH, creating conditions less favorable to odor-producing bacteria. Additionally, its surface features abundant silanol groups and hydrogen-bonding sites, which can react with odor molecules, enhancing odor-neutralizing performance.

3. Biological Antibacterial Activity

Diatomaceous earth demonstrates broad-spectrum antibacterial effects, inhibiting harmful oral bacteria such as Streptococcus mutans, Staphylococcus aureus, and Escherichia coli. Inhibition rates exceed 99%, and brushing with diatom toothpaste for 2 minutes reduces oral bacterial load to 0.01%. This significantly decreases the microbial sources of malodor.

Synergistic Actions of Auxiliary Ingredients

Diatom toothpaste formulations commonly include multiple complementary ingredients:

• Natural Plant Extracts

Examples include pine needle extract, green tea extract, and peppermint.

• Pine needle extract contains flavonoids and vitamins with antibacterial, anti-inflammatory, antioxidant, and anti-allergic effects.

• Green tea polyphenols exhibit strong antibacterial and antioxidant activity.

• Enzymes

Advanced formulations incorporate proteases, amylases, and lysozyme.

• These enzymes break down food residues and dental plaque.

• Lysozyme specifically disrupts bacterial cell walls.

• Functional Oral-Care Ingredients

Hydroxyapatite, active calcium, and xylitol are often included.

• Hydroxyapatite and active calcium strengthen enamel and reduce acid erosion.

• Xylitol prevents caries and prolongs the sensation of freshness.

These components work synergistically with DE to achieve comprehensive deodorizing, whitening, anti-caries, and gum-protection benefits.

Summary

The superior deodorizing performance of diatom toothpaste is derived from the unique properties of diatomaceous earth—its >80% amorphous silica content, 90% porosity, and 50–2000 m²/g surface area, enabling exceptional adsorption. DE’s isoelectric behavior, pH compatibility, and electrostatic antibacterial effects contribute to efficient and sustained malodor reduction.

Core mechanisms include:

• Physical adsorption (primary): 800-mesh DE shows optimal adsorption of indole and dimethyl sulfide.

• Chemical neutralization: pH regulation plus silanol–odor molecule reactions.

• Biological antibacterial action: >99% inhibition of pathogenic bacteria; 2-minute brushing reduces bacteria to 0.01%.

Additional plant extracts, enzymes, hydroxyapatite, and xylitol provide synergistic benefits, making diatom toothpaste a multi-functional oral-care solution.