Clinical study from Japan proves the efficacy of hydroxyapatite in caries prophylaxis


Cleaning the teeth is part of daily oral hygiene and is often practiced as a group at school after lunch. In addition to other ingredients, hydroxyapatite is used more frequently in toothpastes. In the past, hydroxyapatite was only known as bone replacement material or as a filler for artificial tooth roots. The strong similarity of hydroxyapatite to natural enamel led to the idea of the substance being used in toothpastes. As well as remineralizing the teeth, hydroxyapatite is also known for inhibiting the formation of plaque.


How prevalent is caries among children who use hydroxyapatite toothpaste?

Material and methods

This study was conducted over a time period of three years at Japanese schools. Here, it was common for the children to clean their teeth together after lunch under observation of a teacher. A total of 181 children were recruited, equally distributed between both genders. At the beginning of the study, all children were in year four at a Japanese school. The observation period was three years. One group was given a hydroxyapatite toothpaste, while the second group was given the same toothpaste without hydroxyapatite as a control. At the beginning of the study, the tooth status of the children (DMFT [decayed missing filled teeth]) was recorded and examined twice a year throughout the study. Both groups were examined for statistically significant differences using a chi-square test.


The DMFT index of both groups (toothpaste with hydroxyapatite vs. toothpaste without hydroxyapatite) proved to be significantly different at the end of the study. The DMFT index was at 0.29 in the hydroxyapatite group and 0.96 in the control group (toothpaste without hydroxyapatite). This data was used to measure caries inhibition by hydroxyapatite in toothpastes compared to the control group: This was 35.9% for the boys and 55.9% for the girls. There was also a significant difference between the two groups in the teeth that were not broken through at the start of the study: After three years, 1.6% (boys) and 5.0% (girls) of the children that cleaned their teeth with a toothpaste with hydroxyapatite developed caries. These values were significantly higher in the children who cleaned their teeth with a normal toothpaste without hydroxyapatite: 9.2% (boys) and 15.6% (girls) developed caries.


Hydroxyapatite is effective in the long-term prevention of caries. Children who clean their teeth with a hydroxyapatite toothpaste develop significantly fewer caries than children who use a normal toothpaste.

The publication of the study can be found here.

Source: Kani, K., Kani, M., Isozaki, A., Shintani, H., Ohashi, T., & Tokumoto, T. (1989). Effect of apatite-containing dentifrices on dental caries in school children. J. Dent. Health, 19, 104-109.