Promising, not yet fluoride-level settled. The best nHAP toothpaste studies usually find hydroxyapatite non-inferior to fluoride for early lesion remineralization or short-term caries outcomes. The catch: fluoride has decades of population-level evidence; nHAP has a smaller, newer, and more heterogeneous literature.
01Evidence Snapshot
02Most-Cited Studies That Tested nHAP Effectiveness
Tschoppe et al., 2011, Journal of Dentistry
438 OpenAlex citations
In vitro bovine enamel and dentine lesion model; nHAP toothpastes compared with amine fluoride toothpaste.
nHAP toothpastes produced higher remineralizing effects than amine fluoride in dentine and broadly comparable trends in enamel. Strong mechanistic signal, but lab conditions do not equal daily caries prevention.
In vitro | Compared with fluoride | Positive for nHAP
Source
Amaechi et al., 2019, BDJ Open
164 OpenAlex citations
Double-blind, randomized crossover in situ study; 10% HAP children's toothpaste vs 500 ppm amine fluoride.
Both toothpastes remineralized early lesions and prevented demineralization; HAP was statistically non-inferior to fluoride. The microradiographs suggested HAP remineralization was more evenly distributed through the lesion body.
Human in situ | Non-inferior | 30 completers
Source
Najibfard et al., 2011, Journal of Clinical Dentistry
153 OpenAlex citations
Randomized, double-blind, crossover in situ study; 5% and 10% nHAP dentifrices vs 1100 ppm fluoride.
All active arms significantly reduced mineral loss and lesion depth. Percent mineral gain did not differ significantly among 5% nHAP, 10% nHAP, and fluoride, supporting nHAP as a plausible fluoride alternative in this model.
Human in situ | Crossover | Comparable to fluoride
Source
Souza et al., 2015, Caries Research
75 OpenAlex citations
Randomized, double-blind crossover in situ study; experimental nano-HA plus fluoride paste compared with fluoride and placebo controls.
The nano-HA plus fluoride paste was the only treatment that significantly reduced dentine demineralization and improved enamel remineralization versus placebo. Useful, but it tests nHAP as a fluoride-containing enhancer, not a fluoride-free replacement.
Human in situ | nHAP + fluoride | Mixed but favorable
Source
Schlagenhauf et al., 2019, Journal of Investigative and Clinical Dentistry
73 OpenAlex citations
Randomized, controlled 6-month clinical trial in orthodontic patients at high caries risk; fluoride-free microcrystalline HAP dentifrice vs 1400 ppm fluoride.
The HAP dentifrice was not inferior to the fluoride toothpaste for enamel caries progression. This is one of the more clinically persuasive papers because orthodontic patients are a realistic high-risk test case.
Clinical trial | High-risk group | Non-inferior
Source
03The Strongest Critique
Wierichs et al., 2022, Clinical Oral Investigations
Source
This systematic review and meta-analysis concluded that the low number of clinical studies, short follow-up, risk of bias, and artificial study conditions did not allow firm evidence statements that nHAP enhances remineralization or prevents demineralization.
Why this matters clinically
nHAP's best studies often ask whether it is non-inferior in controlled settings. Fluoride's advantage is not that every head-to-head study beats nHAP; it is the volume, duration, and public-health consistency of fluoride evidence.
04Important Context
Newer trials strengthen the case
Paszynska et al. 2021 found microcrystalline HAP non-inferior to fluoride in early childhood caries over 336 days, and Paszynska et al. 2023 found 10% HAP non-inferior to 1450 ppm fluoride in adults over 18 months. These were not in the top five by citations yet, but they are highly relevant.
Negative lab evidence exists
Comar et al. 2013 found experimental nano-HAP pastes, with or without added fluoride, did not reduce demineralization in a bovine pH-cycling model, while fluoride paste did. This is a useful reminder that formulation and model conditions matter.
05Practical Takeaway
Takeaway
nHAP toothpaste is not fringe. It has repeated in vitro, in situ, and clinical evidence suggesting it can remineralize early lesions and perform similarly to fluoride in several head-to-head trials. But the most defensible wording is still: nHAP is a credible alternative when fluoride is undesirable, not a proven superior replacement for fluoride across the general population.
Sources
- Tschoppe et al. 2011 - nHAP toothpastes vs amine fluoride, in vitro.
- Amaechi et al. 2019 - HAP vs 500 ppm fluoride, randomized crossover in situ study.
- Najibfard et al. 2011 - nHAP dentifrice vs 1100 ppm fluoride, randomized crossover in situ study.
- Souza et al. 2015 - nano-HA plus fluoride paste, randomized crossover in situ study.
- Schlagenhauf et al. 2019 - HAP dentifrice vs 1400 ppm fluoride in orthodontic patients.
- Wierichs et al. 2022 - critical systematic review and meta-analysis.
- Paszynska et al. 2021 - early childhood caries RCT.
- Paszynska et al. 2023 - 18-month adult RCT.
- Comar et al. 2013 - negative/critical pH-cycling study.
- Pawinska et al. 2024 - updated systematic review and meta-analysis supporting HAP caries prevention.
