The aim of the present study was to evaluate the influence of irradiation on de- and reminerlization of human dentin in vitro. Therefore, 28 human third molars were bisected into two halves. One half was fractionally (2Gy/d, 5d/week) irradiated up to 60Gy. The other half served as non irradiated control. All irradiated test samples and non-irradiated controls were demineralized for 3 weeks using acidified gel (HEC, pH 4,8). 14 test specimens and 14 controls were remineralized using Bifluorid 12®. Remineralization of the other 14 test and 14 control samples was carried out using elmex® gelée. No statistical significant difference of lesion depths could be observed between irradiated samples and non-irradiated controls after demineralization and remineralization (ANOVA; Bonferroni-Holm correction; p ®, remineralization with elmex® gelée resulted in a significant reduction of lesion depth in all samples (ANOVA; Bonferroni-Holm correction; p <= 0,05).