Optimization of Functional Toothpaste Formulation Containing Nano-Hydroxyapatite and Birch Extract for Daily Oral Care

Published In: Materials
Publication Year: 2023

Study Design

This is a laboratory-based experimental study involving in vitro assessments of toothpaste formulations. It evaluated the ability of various nano-hydroxyapatite (nHAP) and birch extract combinations to remineralize enamel and inhibit oral bacteria.

Funding Sources

This research was funded by The Ministry of Research, Innovation, and Digitization, Romania, under Project No. 186 of the PN-III-P4-ID-PCE-2020-1910 Program.

PICO Framework - what was studied and how?

Population:
Artificially demineralized enamel slices from healthy extracted human third molars (n = 84 slices)

Intervention:
Daily application of experimental toothpaste formulations containing nano-hydroxyapatite (HAP, HAP-5%Zn, or multi-substituted HAPs) and birch extract

Comparison:

• Natural enamel (untreated)

• Demineralized enamel (no treatment)

• Toothpastes with only nHAP or only birch extract

Outcomes:

• Enamel surface remineralization (measured by Atomic Force Microscopy surface roughness, Ra)

• Antibacterial activity against Streptococcus mutans, Porphyromonas gingivalis, Enterococcus faecalis, Escherichia coli, and Staphylococcus aureus

In Paragraph Form:
This study examined how experimental toothpaste formulas containing different types of nano-hydroxyapatite (pure and ion-substituted) and birch extract impact enamel remineralization and antibacterial activity. Enamel slices from extracted human teeth were treated over 10 days and analyzed using atomic force microscopy and agar disk diffusion testing against common oral pathogens.

Inclusion and Exclusion Criteria

Inclusion Criteria:

• Extracted healthy third molars

• No cracks, cavities, or prior dental work

• Standardized demineralization protocol

Exclusion Criteria:

• Teeth with visible defects or prior treatment

• Non-molar teeth

Demographics and Study Design

• Total enamel samples: 84 from 21 molars

• Control groups:

  • Ctrl: Untreated enamel (n = 6)

  • NC: Demineralized enamel, no treatment (n = 6)

• Intervention groups: 11 total toothpaste formulas (P1–P11), each applied to 6 enamel slices

Primary Outcome Variables and Results

Outcome 1: Enamel Surface Roughness (Ra)

• Best remineralization observed in P2 (pure HAP)

• Ra values were statistically similar to natural enamel for P2

• Ra ranking (lower is better): Ctrl ≈ P2 ≈ P3 > P4 > P1 > NC

• p-values:

  • Ctrl vs NC: p < 0.001

  • Ctrl vs P2: p > 0.05 (not significant)

  • NC vs all treated: p < 0.001

Outcome 2: Antibacterial Activity

• Assessed via agar disk diffusion test

• Best antibacterial performance seen in P11 (1.3% birch extract only)

• Best balance of remineralization and antibacterial performance seen in P5 (HAP-5%Zn + 1.3% birch extract)

Simple Chart: Enamel Remineralization and Antibacterial Effectiveness

Conclusions

• P5, combining HAP-5%Zn and birch extract, showed the best dual performance: strong enamel remineralization and broad antibacterial activity.

• Birch extract alone showed powerful antibacterial effects (especially in P11), but lacked enamel restoration capabilities.

• Nano-hydroxyapatite (nHAP), particularly pure and zinc-substituted forms, effectively repaired demineralized enamel.

• Birch extract enhanced antibacterial effects against Streptococcus mutans and Staphylococcus aureus even at low concentrations.

Discussion: Strengths and Limitations

Strengths:

• Use of Atomic Force Microscopy for precision analysis

• 11 toothpaste variants allowed detailed formulation comparison

• Broad-spectrum bacterial testing enhanced relevance

Limitations:

• In vitro design may not reflect real-life brushing conditions

• No clinical trial data or long-term outcomes

• Remineralization was only measured over 10 days

Citation

Florea AD, Dobrota CT, Carpa R, et al. Optimization of Functional Toothpaste Formulation Containing Nano-Hydroxyapatite and Birch Extract for Daily Oral Care. Materials. 2023;16(22):7143.

https://pubmed.ncbi.nlm.nih.gov/