Hydroxyapatite cavity prevention and remineralization - here - (meta-analysis, more studies in resources section of this paper)

Fluoride Toxicity - here, here, here, here, here, here,

Xylitol cavity prevention and oral health benefits - here and here

Xylitol cavity prevention (meta-analysis)- here

Baking soda for whitening and stain removal - here

Baking soda for plaque removal - here