What 50 years of research says about hydroxyapatite
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Time to read 6 min
In 2021, a team of researchers from the University of Toronto and the Dr. Wolff Group published a narrative review in Odontology, one of dentistry's leading peer-reviewed journals, examining the full body of scientific evidence on hydroxyapatite (HAP) toothpaste.[1] It covered in vitro laboratory studies, in situ clinical conditions, and randomised controlled trials. The findings are worth understanding.
What is hydroxyapatite, exactly?
Hydroxyapatite (Ca₅(PO₄)₃(OH)) is a calcium phosphate mineral. It is, notably, the primary inorganic component of human dental enamel, making up approximately 97% of enamel's structure. [1] The review describes how HAP crystals form compact enamel rods extending from the dentin-enamel junction to the outer tooth surface, contributing to enamel's ability to withstand force and resist microbial attack.
Tooth decay begins when oral bacteria metabolise carbohydrates, producing lactic acid that drops mouth pH below 5.5, the threshold at which enamel begins to demineralise, losing calcium and phosphate ions to the surrounding environment. [1] Early lesions ("white spot lesions") are porous, non-cavitated, and theoretically capable of remineralisation if the process is arrested early enough.
"One major limiting factor in remineralisation has been identified as calcium and phosphate ion availability."
— O'Hagan-Wong et al., Odontology, 2021
HAP toothpastes address this directly. The review notes that HAP particles "have been shown to bind to the damaged enamel surface and fill in the porous surface irregularities in order to restore the surface integrity." [1] The rationale is grounded in biomimetics — using a material that mirrors the tooth's own mineral composition.
What laboratory evidence shows
Under scanning electron microscopy (SEM), the review reports that brushing demineralised teeth with HAP toothpaste resulted in HAP crystals binding to and restoring the tooth surfacem visually filling in pitted areas — while fluoride toothpaste at 1,040 ppm "produced very little surface remineralisation and failed to repair any of the enamel surface irregularities." [1]
A key study by Tschoppe et al. (2011), cited in the review, used transverse microradiography (TMR), a high-resolution technique for quantifying mineral content changes and found that HAP toothpaste formulations produced "a similar degree of remineralisation in both enamel and dentin lesions which was significantly higher than that produced in the fluoridated toothpaste group." [1]
On surface hardness, a proxy for mineral content, a study by Poggio et al. found HAP toothpaste produced increases in enamel hardness "comparable to that of regular fluoride (1,450 ppm) containing toothpastes." [1] The review acknowledges some conflicting in vitro evidence exists, and notes more research is needed on dentin specifically.
Clinical Trial Results
The review identified three prospective clinical studies. The earliest followed 181 Japanese schoolchildren from 1983 to 1986. Children using a 5% HAP toothpaste showed a caries inhibition rate of 35.86% in boys and 55.93% in girls compared to non-HAP controls. [1]
A more recent German multi-centre randomised controlled trial by Schlagenhauf et al. (2019) — conducted across five university hospitals — compared HAP toothpaste to a high-strength fluoride formula (1,400 ppm AmF/SnF₂) in orthodontic patients over 168 days. The conclusion: HAP demonstrated non-inferiority to fluoride in preventing caries in this high-risk population. [1]
A 2021 one-year RCT by Paszynska et al. in young children found that 72.2% of children using HAP toothpaste showed caries progression, compared to 74.2% in the fluoride control group — a statistically equivalent outcome. [1]
"The results of this one-year randomised clinical trial suggest that HAP is as efficacious as fluoridated toothpaste in treating dental caries in young children."
— Paszynska et al. (2021), cited in O'Hagan-Wong et al., Odontology
On sensitivity: a double-blind RCT cited in the review found participants reported significantly lower dentinal hypersensitivity after two to four weeks of HAP use compared to fluoride controls. [1] Microscopy confirmed HAP particles physically occluding exposed dentinal tubules. A network meta-analysis (Hu et al., 2019) suggested nano-HAP toothpastes may be superior to multiple other desensitising toothpaste types including fluoride, potassium-containing, and strontium-containing formulas. [1]
On biofilm: studies show HAP reduces adhesion of pathogenic bacteria including Streptococcus mutans to enamel surfaces, while — importantly — not killing bacteria outright as chlorhexidine does. The review suggests this may have the advantage of "preserving the normally occurring oral flora" while still reducing pathogen colonisation. [1]
The Safety Profile
The review is direct on this point: "Thus far in the literature, there have been no reports of adverse dental or systemic effects of HAP-containing toothpastes because HAP has an excellent biocompatibility." [1] Accidentally ingested calcium phosphate particles dissolve in stomach acid into ionic form with no adverse effects under realistic doses. Calcium phosphate is a naturally occurring mineral in teeth and bones, with no reported adverse environmental effects.
This contrasts with the documented risk profile of fluoride, which the review notes includes dental fluorosis, potential developmental neurotoxicity, and gastric irritation in excess — risks that are of particular relevance when considering toothpaste for young children who regularly swallow it. [1]
The Reviews Conclusion
"HAP is a biomimetic oral care agent, and its caries prevention has been tested in vivo, in situ, and in vitro with a high safety profile and no risk of fluorosis... HAP-containing oral products can be considered as an alternative in young children where fluorosis is a concern."
— O'Hagan-Wong et al., Odontology, 2021
REFERENCES
References cited in this article
[1] O'Hagan-Wong K, Enax J, Meyer F, Ganss B. "The use of hydroxyapatite toothpaste to prevent dental caries." Odontology. 2021 Nov 22;110(2):223–230. doi: 10.1007/s10266-021-00675-4. PMCID: PMC8930857. Read on PubMed Central →
[2] Schlagenhauf U et al. "Impact of a non-fluoridated microcrystalline hydroxyapatite dentifrice on enamel caries progression in highly caries-susceptible orthodontic patients." J Investig Clin Dent. 2019;10:e12399.
[3] Paszynska E et al. "Impact of a toothpaste with microcrystalline hydroxyapatite on the occurrence of early childhood caries: a 1-year randomized clinical trial." Sci Rep. 2021;11:2650.
[4] Tschoppe P et al. "Enamel and dentine remineralization by nano-hydroxyapatite toothpastes." J Dent. 2011;39:430–437.
[5] Vano M et al. "Reducing dentine hypersensitivity with nano-hydroxyapatite toothpaste: a double-blind randomized controlled trial." Clin Oral Investig. 2018;22:313–320.
https://pmc.ncbi.nlm.nih.gov/articles/PMC8930857/
This article is an editorial summary of publicly available peer-reviewed research. It does not constitute dental or medical advice, and makes no therapeutic claims about any specific product. The research summarised was conducted independently of Peg Paste. Individual results may vary. Always consult a qualified dental professional for personal oral health advice. Peg Paste Pty Ltd, Noosa Heads QLD Australia.
WHAT IS HYDROXYAPATITE?
Hydroxyapatite is a restorative mineral that occurs naturally in teeth and bones. Hydroxyapatite works to repair, remineralise and strengthen the tooth’s outer layer, acting as a buffer to help prevent mineral loss, tooth erosion, tooth sensitivity and plaque.
HOW DO PREBIOTICS SUPPORT ORAL HEALTH?
Prebiotics support oral health by promoting the growth of beneficial bacteria, which can help maintain a balanced environment in the mouth. It is important to maintain good oral hygiene so harmful bacteria does not take over potentially leading to bad breath, cavities and disease.
WHERE IS PEG PASTE MADE?
Peg Paste is made and manufactured in Australia.
DO YOU USE MICRO-HYDROXYAPATITE OR REGULAR HYDROXYAPATITE?
We use micro-hydroxyapatite in our toothpaste and ensure that it fully complies with current SCCS (Scientific Committee on Consumer Safety) and Australian oral care and cosmetic regulations. We are aware of the European Union’s upcoming ban on nano-materials in cosmetics starting November 2025. The reason for this ban is still unclear, but reports suggest potential risks if nano-hydroxyapatite is used in high concentrations or in sprayable products, where inhalation could be a concern. Since our toothpaste is not a spray and is formulated with concentrations that are within safe guidelines, we remain confident in its safety and effectiveness.
IS PEG PASTE SUITABLE FOR CHILDREN?
Absolutely. Prevention is key when it comes to oral health, so why not instil healthy habits early. Children’s toothpaste normally consists of a lower level or no fluoride because of the greater risk of potential fluoride toxicity. Given Peg Paste is a natural, fluoride-free formulation, it is safe for junior toothypegs. We recommend children use a pea size amount and brush under adult supervision.
I HAVE SENSITIVE HEALTH, IS THIS PRODUCT SUITABLE FOR ME?
Science shows that Hydroxyapatite helps ease tooth sensitivity by filling in microscopic pathways to the nerves in the teeth. With fewer pathways exposed, the less sensitivity and discomfort you should feel to touch, food and temperature. Remember to always consult your dental professional for oral health advice and before trying new products.
I SUFFER FROM DRY MOUTH, IS THIS PRODUCT SUITABLE FOR ME?
Peg Paste does not contain Sodium Lauryl Sulfate or SLS, a common ingredient that acts as a thickener in toothpaste products. SLS can have negative, degenerative effects that can contribute to, or worsen serious oral health issues such as dry mouth, mouth ulcers, mouth irritation and bad breath. Changing to an SLS free toothpaste can make a difference if you’re experiencing these symptoms. Remember to always consult your dentist or dental hygienist for oral health advice and before trying new products.
