1 INTRODUCTION

Of all the diseases found globally, untreated dental caries in permanent teeth currently constitutes the most prevalent condition, and in deciduous teeth, it is the 10th most prevalent condition (Kassebaum et al., 2015). Even if there is strong evidence of a decline in dental caries in many western countries since the middle of the last century, the disease is still prevalent, and a shift in the burden of caries from children to adults has been observed (Norderyd et al., 2015). Dental caries has been affecting mankind since time immemorial, but the caries prevalence has shifted in pattern and severity. In literature, historical data are often presented as case reports. Larger findings of skeletal remains from Scandinavian populations are more common from the Medieval period and onwards (Olsson & Sagne, 1976; Varrela, 1991) but more uncommon from earlier times.

Even if the caries distribution found in remains of early historical Scandinavian populations has varied, a frequently reported figure for caries prevalence is around 10% of all examined teeth (Lingström & Borrman, 1999; Olsson & Sagne, 1976; Varrela, 1991). However, a notable higher caries prevalence at individual level, of 40–60%, has been found in remains from medieval times (Varrela, 1991). Explanations of these differences could be related to technical aspects, such as the occurrence of post mortem defects, and number of missing teeth. The population itself may play a role, where factors such as heterogeneity of the studied individuals, general standard of living and variation in diet, are important factors (Vehkalahti, Rajala, Tuominen, & Paunio, 1983; Lingström & Borrman, 1999). In an Icelandic study of dentitions from the Viking era, only “a few” caries lesions were found (Richter & Eliasson, 2008).

The island of Gotland in the Baltic Sea in Sweden is known for its old history and played a central role during the Viking Age as an important area for trading goods. On site Kopparsvik, archaeological excavations in 1964 and 1965 resulted in an assemblage that has been thoroughly examined, including some osteological examinations of the skeletons found (Pettersson, 1966; Mälarstedt, 1979; Carlsson, 1983; Larje, 1985; Westholm, 1989; Thunmark‐Nylén, 2000, 2004a, 2004b; Arcini, 2005, 2010; Sten & Mellström, 2011; Sten, 2015; Toplak, 2016; Margaryan, 2017, Ytterman, Brynnel, Sandström, & Sten, 2017; Ahlström Arcini, 2018; Mühlemann et al., 2018). The graves of the individuals examined in this work are dating back to the Viking Age (900–1150 AD). However, only limited attention has been paid to dental conditions in these prehistoric individuals.

Little is known about the dietary intake among the study population. The Swedish Vikings lived in farm communities, and their primary source of protein was meat from the farm animals; beef, pork, sheep, and horse. Fish and sea birds were a major part of the diet, explained by the proximity to water. Carbohydrates included grains, root crops, and bread. Mead was drunk, and the sweeteners used was honey or natural berries. Dried fruit, hazelnuts, and mushrooms were also consumed during this period (Wickerts, 2013).

In this article, dental health has been analysed from a number of individuals with special reference to dental caries. The dental examination of a selected number of individuals from the population was to be carried out before a research team from Centre for GeoGenetics at the Natural History Museum of Denmark, Copenhagen, took DNA samples of teeth in the project entitled Population Genomics of Vikings, which meant that analysed teeth would be destroyed (Margaryan, 2017; Mühlemann et al., 2018).

The aim of this study was to study the caries and dental health prevalence in a sample of dentitions from the Viking Age from a limited, but well‐defined, region of Gotland.