Effect of palm oil alone or associated to stannous solution on enamel erosive-abrasive wear: A randomized in situ/ex vivo study

•Lipid-rich AEPs has been suggested to be more resistant to acid challenges.•Palm oil previously protected against initial erosive demineralization in vitro.•Palm oil associated or not with stannous protect enamel against erosion or abrasion.•Palm oil presented similar anti-erosive effect to stannous solution.•Deionized water presented higher enamel loss than palm oil and stannous solution. Palm oil has demonstrated preventive potential against initial erosive demineralization in vitro. This in situ study evaluated the effect of palm oil alone or associated with stannous-containing (Sn) solution on preventing enamel loss from an erosive/abrasive challenge. This single-blind, randomized, crossover in situ/ex vivo study was developed in four phases (one per group of five days) with sixteen volunteers. Enamel blocks (n = 256) were allocated to groups according to the treatment: Palm oil; Palm oil plus Sn solution; Sn solution – positive control; and Deionized water – negative control. Half of the enamel blocks of each group was subjected to erosion and the other half to erosion + abrasion. The daily ex vivo protocol consisted of four citric acid immersions (2 min). Before the first and third acid exposure, the blocks were treated with the test solutions (1 drop/block) for 1 min followed by acid immersion and abrasive challenge (toothpaste was applied on all blocks and half were brushed for 15 s/block). Enamel loss was quantified profilometrically and data were analyzed by two-way ANOVA and Tukey’s test (p