“10% hydroxyapatite achieved comparable efficacy with 500 ppm F− in remineralizing initial caries and preventing demineralization. Thus the HAP toothpaste is confirmed to be equal to the fluoride toothpaste in this study.”
“Hydroxyapatite-based gel (15% HAP) was as effective as fluoride-based gel (12,500 ppm F−) in remineralizing initial caries lesion.”
You can use a Hydroxyapatite toothpaste as an adjunct toothpaste alongside Fluoride-Free paste, and a hydrogen peroxide & iodine mouthwash.
https://www.nature.com/articles/s41405-019-0026-8