Volume 9 • 2022 • Issue 2

Dr. O’Hagan-Wong says that toothpaste that includes HAP is especially important for young children. “We often don’t want to give small children fluoride toothpaste because we don’t want them to swallow it, which could cause fluorosis,” she says. “But how can we also protect them from caries? HAP toothpaste can be very beneficial for this group.” Dr. O’Hagan-Wong and her co-authors Drs. Joachim Enax, Frederic Meyer and Bernhard Ganss reviewed research into fluoride-free HAP toothpaste in vitro, in situ and in vivo. For the reviewed in vitro experiments, extracted human or bovine teeth were treated with HAP micro- or nanocrystals and then examined with a microscope or tested for hardness. HAP toothpaste performed as well as fluoride in remineralizing enamel and increasing hardness. In situ, researchers were interested in seeing how well HAP toothpaste performed inside the oral cavity interacting with saliva, biofilms and dietary carbohydrates. In one of the reviewed studies, participants wore a fixed appliance that held enamel near their back molars and brushed either with 10% HAP toothpaste or 500 ppm fluoridated toothpaste for 4 weeks. When the enamel was later measured with microradiography, both HAP and fluoride reduced lesion rates and remineralized with similar effectiveness. “One of the surprises for me was discovering that althoughmanyHAP-related studies have been published, it only includes a limited number of clinical trials,” says Dr. O’Hagan-Wong. “We found three clinical trials.” A 1980s study of Japanese school children found that HAP toothpaste was more effective at preventing dental caries compared to a placebo. Further, two clinical trials carried out in Germany and Poland, found that HAP toothpastes performed as well as, or better than, fluoride toothpaste in preventing caries. Studies cited by Dr. O’Hagan-Wong and her colleagues also found that HAP helps prevent bacteria from sticking to enamel. When asked why HAP isn’t more commonly used, Dr. O’Hagan- Wong says, “We already have fluoride, which also works well in many circumstances, and HAP is more expensive.” She would like to see HAP become more readily available for the people it could help the most, including young children and people who are especially vulnerable to caries, who might benefit from using both fluoride and HAP in their oral health routines. Next up for Dr. O’Hagan-Wong and her colleagues is research into adding a protein involved with tooth formation to HAP toothpaste. “The protein is involved with stacking together the particles, consisting of calcium and phosphate ions, that make up the tooth surface,” she says. “So, we will try to find out if using the two together helps keep teeth even healthier.” One of the surprises for me was discovering that although many HAP-related studies have been published, it only includes a limited number of clinical trials. Reference 1. O’Hagan-Wong K, Enax J, Meyer F, Ganss B. The use of hydroxyapatite toothpaste to prevent dental caries. Odontology . 2021 Nov 22. doi: 10.1007/ s10266-021-00675-4. Online ahead of print. A low-pH can cause the dissolution of hydroxyapatite crystals, which is a factor in how dental caries can begin. Remineralization adds new calcium and phosphate ions back into the enamel structure. 29 Issue 2 | 2022 | Issues and People