Kijsamanmith K, et al. - Researchers examined how conventional and acidified casein phosphopeptide-amorphous calcium phosphate–containing crèmes (CPP-ACP and ACPP-ACP) affect dentin permeability (DP) before and after acid challenge, using a fluid-flow measuring device and scanning electron microscopic (SEM) examination. From intact human third molars, they prepared 50 dentin discs. they sectioned each tooth 3 mm above and below the cementoenamel junction. The dentin and dentinal tubules were exposed via removing the smear layer. They used and divided 20 specimens into two groups for fluid-flow measurement: (a) CPP-ACP (pH=7) and (b) ACPP-ACP (pH=2). The crème was applied to the dentin surfaces for five minutes daily for two weeks and then using 6% citric acid, an acid challenge was performed. Measurement of DP was done at baseline, five minutes, two weeks, and after acid challenge under simulated pulpal pressure. they prepared the remaining specimens and examined it using SEM for dentinal tubule occlusion. Outcomes revealed that partial occlusion of the dentinal tubules remains after acid challenge. They observed a decrease in DP and partial occlusion of the dentinal tubules, that resisted the acid challenge, when conventional and acid-modified CPP-ACP–containing crèmes were used for two weeks.