Objective: To evaluate the anti-erosive effect of solutions containing ??-tricalcium phosphate (??-TCP) nanoparticles functionalized with fluoride or with fluoride plus stannous on enamel and dentin. Methods: ??-TCP nanoparticles were synthesized and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Sixty enamel and dentin specimens were randomly allocated into the groups (n=10): Control (water); F (NaF, 225 ppm F???); F+Sn (NaF+SnCl2, 800 ppm Sn2+); F+??-TCP (F+40 ppm ??- TCP); F+Sn+??-TCP (F+Sn+40 ppm ??-TCP); F+Sn+100??-TCP (F+Sn+100 ppm ??-TCP). Specimens underwent erosion-remineralization cycling (5 min immersion into 1 % citric acid solution and 60 min exposure to artificial saliva, 4??/day, 5 days). Immersion in the test solutions was performed for 2 min, 2??/day. Surface loss (SL, in ??m) was determined by optical profilometry at the end of cycling. Data were analyzed using one way- ANOVA and Tukey???s tests (??=0.05). Results: XRD confirmed the ??-TCP phase. TEM micrographs showed differences between the bare nanoparticle and the ??-TCP functionalized with F and Sn. All enamel groups presented lower SL than the control, with F+Sn, F+Sn+??-TCP, and F+Sn+100??-TCP showing the lowest values. For dentin, all the groups had lower SL than the control. F+??-TCP presented the lowest SL, significantly differing from all the other groups. Conclusion: ??-TCP nanoparticles functionalized with fluoride showed improved anti-erosive effect compared to the fluoride solution on dentin. There was no significant effect of the ??-TCP nanoparticles functionalized with fluoride plus stannous in both substrates. Clinical Relevance: ??-TCP nanoparticles are a promising agent to be added to oral health products to improve the protective effect of fluoride against dentin erosion.Conselho Nacional de Desenvolvimento Cient??fico e Tecnol??gico (CNPq)Funda????o de Amparo ?? Pesquisa do Estado de S??o Paulo (FAPESP)CNPq: 141068/2018-3FAPESP: 15/15629-7