Scientific Article Review:

Benign Shift in the Oral Flora Induced by Nano-hydroxyapatite

Published In: International Association for Dental Research (Abstract Submission)
Publication Year: 2021

Study Design

This study employed a prospective clinical trial design, focusing on the effects of nano-hydroxyapatite (nHAP) on oral microbial flora.

Funding Sources

The research received support from SANGI Co., Ltd., with contributions from various academic institutions in Japan, including Nihon University School of Dentistry and the National Institute of Infectious Diseases, Tokyo.

PICO Framework - what was studied and how?

Population:

• Adults with high oral mutans streptococci (MS) concentrations, indicating a higher caries risk (19 participants).

Intervention:

• Application of a nano-hydroxyapatite paste using a retainer tray for 5 minutes daily for 6 days.

Comparison:

• A placebo paste containing dicalcium phosphate dehydrate.

Outcomes:

• Reduction in the ratio of mutans streptococci (MS) in oral flora.
• Increase in lactobacillus (LB) count, associated with a decrease in caries risk.

In Paragraph Form:
This clinical trial studied 19 adults with elevated mutans streptococci (MS) levels to evaluate the effect of nano-hydroxyapatite (nHAP) paste compared to a placebo (dicalcium phosphate dehydrate). Outcomes included changes in the MS ratio and lactobacillus (LB) count over time to assess the potential for reducing caries risk.

Inclusion and Exclusion Criteria

Inclusion Criteria:

• Participants with high baseline levels of mutans streptococci.
• Consent to adhere to a controlled oral hygiene routine during the trial.

Exclusion Criteria:

• Individuals using antibiotics or antimicrobial oral care products.
• Participants with systemic health conditions affecting oral flora.

Demographics and Study Design

The study involved 19 participants, divided into:

• nHAP intervention group (n=10)
• Placebo group (n=9)

The study included a structured protocol:

• Daily application of the assigned paste for 5 minutes using a retainer tray for 6 days.
• Saliva sampling at multiple intervals: baseline, after treatment, and monthly follow-ups for up to 3 months.

Primary Outcome Variables and Results

Outcome Variables:

1. Change in mutans streptococci (MS) ratio.
2. Change in lactobacillus (LB) count.

Key Results:

• In the nHAP group, MS ratios decreased significantly, with a trend of linear regression showing consistent reductions: $$Y = -2E-07x + 0.0026 \quad (\text{p-value < 0.05})$$
• LB counts in the nHAP group increased: $$Y = 3E-04x + 4.5878 \quad (\text{p-value < 0.05})$$
• The placebo group showed an increase in MS ratios and no significant change in LB counts.

After an additional round of nHAP treatment at 3 months, further improvements were observed, confirming the sustained effects of nHAP.

Conclusions

The study concluded that nano-hydroxyapatite (nHAP):

• Reduces the ratio of mutans streptococci (MS), indicating a lower caries risk.
• Increases lactobacillus (LB) levels, supporting a healthier oral flora.
• Suggests optimal treatment intervals of 2–3 months to maintain beneficial effects.

Discussion

Strengths:

• Longitudinal sampling allowed tracking of microbial shifts over time.
• Clear statistical analyses highlighted significant differences between groups.
• The study design addressed practical application methods.

Limitations:

• Small sample size (19 participants).
• Short follow-up period for placebo participants.
• Limited to a single type of placebo without additional control comparisons.

Citation

Fujimaru T, Ishizaki T, Hayman R, Suzuki H, Kono Y, Senpuku H. Benign Shift in the Oral Flora Induced by Nano-hydroxyapatite. IADR Abstracts. 2021. 

Visual Aids

Simple Chart: Changes in Oral Microbial Ratios