Dento‐alveolar pathologies: caries, ante mortem tooth loss, abscesses, calculus, alveolar resorption and tooth wear were analysed in two composite skeletal series from Croatia's eastern Adriatic coast (Dalmatia). The first consists of 103 skeletons from seven Late Antique (3rd–6th century AD) sites, the second of 151 skeletons from three Early Medieval (7th–11th centuries AD) sites. As recent bioarhaeological studies (Šlaus) showed a significant increase of disease loads and trauma frequencies in Dalmatia during the Early Medieval period, the aim of this study was to investigate whether dental health was equally adversely affected by the Late Antique/Early Medieval transition. The results of our analyses show that the frequencies of carious lesions, ante mortem tooth loss, abscesses and alveolar resorption increased significantly during the Early Medieval period, as did the degree of heavy occlusal wear on posterior teeth. These data suggest a change in alimentary habits, with a significantly higher dependence on carbohydrates and a greater reliance on hard, fibrous foods requiring vigorous mastication in the Early Medieval diet. The combination of higher calculus and lower caries rates in the Late Antique series similarly suggests more protein in the Late Antique diet and is, therefore, also consistent with the hypothesised change in alimentary habits. In general (the two exceptions are male caries and female alveolar resorption frequencies) lesion frequencies increased uniformly in both sexes suggesting that the deterioration of dental health during the Early Medieval period equally affected males and females. Cumulatively, the collected data suggest that the political, social, economic and religious changes that characterised the Late Antique/Early Medieval transition in Dalmatia resulted in a clear discontinuity, not only from the cultural, but also from the biological point of view with an evident deterioration of oral health during the Early Medieval period. Copyright © 2010 John Wiley & Sons, Ltd.