Objectives: Former investigations have shown that dentin adhesives and other sealants can prevent root surface caries. The aim of the present study was to determine the caries-protective effect of two different desensitizing agents (Controcar, D/Sense 2) on root surfaces in vitro. Methods: The root surfaces of 30 freshly extracted caries-free human molars were thoroughly cleaned, thereby removing the cementum. The teeth were then coated with acid-resistant nail varnish, exposing two rectangular windows. One window served as an untreated control, while the other window was treated with one of the desensitizing agents. All specimens were distributed among the following experimental groups: A: treated with Controcar; AA: untreated control; B: treated with D/Sense 2; BB: untreated control. All specimens were demineralized for 14 days with acidified gel (HEC, pH 4.8, 37 degrees C). From each tooth, two dentinal slabs were cut. The depth of the demineralized areas was determined using a polarized light microscope. Results: All untreated specimens showed uniform lesions with a mean depth of 81 µm (± 17 µm)in group AA and 77 µm (± 18 µm) in group BB. The specimens treated with Controcar showed a mean lesion depth of 2 µm (± 1.5 µm). In group B, treated with D/Sense 2, a mean lesion depth of 45 µm (± 11 µm) was observed. In both groups (A, B) the lesion depth was reduced significantly compared to the untreated control groups (AA, BB) (p Conclusions: It can be concluded that the demineralization of the root surface can be hampered by the application of desensitizing agents in vitro. Palabras clave: dentin, demineralization, root caries, desensitizing agent