Hard tissue resorption occurs under physiological conditions in deciduous dentition and under pathological conditions in deciduous and permanent dentition. It has been discussed whether there are differences in the resorption mechanisms between physiological root resorption and pathological dental hard tissue resorption. Therefore, we studied different resorption patterns with SEM under physiological and pathological conditions. Teeth extracted for the following reasons, physiological root resorption, chronic periodontitis, acute apical inflammation after root resection and one exhibiting an internal granuloma were dried in acetone, sputtered with gold-paladium and investigated with SEM (Philips XL 30 FEG) at 20 kV beam current. Additionally the tooth with the internal granuloma was decalicified and histological sections were stained with Azan. Physiological root resorption showed a regular resorption pattern with shallow resorption lacunae. The teeth with chronic periodontitis showed irregular resorption patterns especially in areas with cement destruction. The resorption lacunae were distinct and very shallow. In acute inflammation after root resection the resorption appeared to be very aggressive with irregular dissolution of the dentin around the apex. In contrast to all other investigated cases this dentin resorption was globular, no resorption lacunae were found. In the case of the internal granuloma the resorption lacunae were very deep and regular exposing dentin tubules and showing the typical keyhole structure where ranging into the enamel. The crown thickness was reduced and dentin almost completely resorbed. Histological investigation revealed numerous odontoclasts at the pulp dentin border. From these results we conclude that different reasons causing resorption under physiological and pathological conditions lead to different morphologies. Chronic inflammation of the periodont leads to distinct resorption in areas with cement distruction, whereas acute inflammation causes agressive rapid resorption. This might also be of clinical and forensic interest. Keywords: dental hard tissue, resorption, SEM