Hydroxyapatite: Reduction of the bacterial load on the tooth surface


Caries is still a very serious disease around the world. In addition to cleaning the teeth and using dental floss to clean the interdental spaces, both successes and a decline in caries could be achieved, but still require continuous improvements. One possible approach to this is the use of hydroxyapatite: Historical findings from the Neolithic period show that the detected bacteria as well as nutrition were similar to today, however less caries could be found. One theory is that hydroxyapatite particles were available in the mouth due to constant abrasion of the teeth and the oral microorganisms built up on them. This build-up led to a reduction in the bacterial load on the surface of the teeth. As a result, the biofilms could rarely reach a critical mass and become pathogenic.


What antibacterial and anti-adhesive properties does hydroxyapatite have in a mouthwash compared to a chlorhexidine mouthwash?

Material and methods

In this in situ study, sterilised and polished enamel plates from bovine teeth were inserted into 6 test subjects. Various dilutions of mouthwashes were prepared and given to the test subjects in a random sequence. The test solutions used were a hydroxyapatite mouthwash and a chlorhexidine mouthwash. The sample plates were removed from the test subjects after 6 and 12 hours and prepared for further analysis. After intraoral use, the plates were analysed to determine the entire number of bacteria (DAPI staining) and the live and dead cells (BacLight staining) using fluorescence microscopy. The mouthwashes were also examined in vitro: Streptococcus mutans was incubated for 10 minutes with each solution and the live and dead cells (live/dead staining) quantified. The groups were then examined for statistically significant differences (Kruskal-Wallis test and Mann-Whitney test).


Hydroxyapatite reduces the bacterial build-up in situ. Both the tested product with hydroxyapatite, and hydroxyapatite in an aqueous solution show similar anti-adhesive effects to chlorhexidine. This effect can be detected after 6 and 12 hours.


Hydroxyapatite is an ideal substance for biofilm management particularly due to its anti-adhesive properties. Hydroxyapatite oral care products also show antimicrobial properties and therefore support biomimetic plaque management.

The publication of the study can be found here.

Source: Hannig, C., S. Basche, T. Burghardt, A. Al-Ahmad and M. Hannig (2013). “Influence of a mouthwash containing hydroxyapatite microclusters on bacterial adherence in situ.” Clin. Oral Investig. 17: 805-814.