The dietary behavior of two early medieval individuals with temporomandibular ankylosis

Highlights

• Diet of two medieval individuals suffering from syngnathia is described.

• Both of them consumed diet comparable to contemporaneous population sample.

• Isotopic analysis of dentine was used to discover potential dietary change.

• There was no observable change that could be linked to the occurrence of syngnathia.

Abstract

Objectives

This study aimed to reconstruct the dietary behavior of two early medieval individuals who display gnathic malformation.

Material

Two skeletons affected by temporomandibular ankylosis were analyzed, one from the Great Moravian burial site of Rajhradice (9th century AD, Czech Republic), and the other from the Avar burial site of Schӧnkirchen (8th century AD, Austria).

Methods

Carbon and nitrogen isotopic values were measured from the bone collagen of both individuals. In the Rajhradice case, where the childhood origin of ankylosis is deduced, isotopic analysis of dentine sections was performed.

Results

Both individuals show isotopic values within the range of variation of a contemporaneous population sample. There was no observable dietary change in the Rajhradice individual that could be linked to the occurrence of ankylosis.

Conclusions

Both individuals consumed diets typical for their populations. They appear to not have restricted access to foodstuffs, namely animal protein, which would likely have had to be served in liquid (e.g. milk) or in a highly mashed form to compensate for insufficient mastication.

Significance

This finding provides specific evidence of care provided to these two afflicted members of past populations.

Limitations

Though the proportion of animal protein is an important indicator of the quality of diet, many other aspects of diet – such as micronutrient content – elude stable isotope analysis.

Suggestions for further research

Amino acid compound specific isotope analyses of collagen would provide deeper insight into both the diet and physiology of the affected individuals.

Introduction

Fusion of the temporomandibular joint (TMJ) due to ankylosis is an extremely rare condition. Clinical descriptions of the abnormity are reported only sporadically. According to Kumar et al. (2019), only 20 cases of congenital syngnathia with TMJ involvement have been described. Descriptions of this rare anomaly in historical skeletal series are even more exceptional: from the Central European context, Hyrtl (1877) provided an extended description of a cranium of unknown origin and context from a crypt located in Mödling (Lower Austria). Hořejší and Stloukal (1985) reported and analyzed a severely altered cranium from an old Slavonic burial site at Rajhradice (Czech Republic) dating to the 9th century AD. Pretterklieber et al. (2007), and Schamall et al. (2008) presented fragments of an individual from an 8th-century AD Avar burial ground that were excavated in 1979 at Schönkirchen-Reyersdorf (Lower Austria). The latter two cases are examined in this study.

Etiologically, syngnathia can originate due to both pre-natal aberration and post-natal causes (Cerny et al., 2004; Inman et al., 2013; Tak et al., 2017). In very rare cases, the articulation between the maxilla and mandible is restricted at birth: this results from fusion of the jaws that may range from the consolidation of soft tissues (synechiae) to complete ossification (synostoses) (Maeda et al., 2006; Olusanya and Akadiri, 2020). A coalescence might also be acquired post-partum (Laster et al., 2001) through trauma, chronic inflammation, or neoplasm.

Complete ankylosis of the temporomandibular joint produces almost complete immobility of the lower jaw (Dvořák, 1964). An affected individual cannot open the mouth, chew or receive normal food, and therefore has to ingest only liquid or highly mashed food. Under-nutrition may develop in afflicted individuals, which, occurring during childhood, may cause growth and developmental retardation (Dvořák, 1964). Moreover, the difficult ingestion of food is not the only limitation the individual faces: speech is unclear, and the aberrant shape of the jaw, as well as occlusal deformities, may change facial features (Shah and Desai, 2013). Reconstruction of diet, an important indicator of aspects of daily life, supplies knowledge of lives of severely impaired people.

As a standard, dietary reconstruction for past populations is based on a combination of the isotopic values of carbon (δ¹³C) and nitrogen (δ¹⁵N) in bone or tooth collagen. The carbon isotopic values permit the definition of some basic characteristics of the ecosystem that provided the dietary resources for the individuals under study. They help to distinguish between foods coming from terrestrial, as opposed to marine environments, and to assess the relative importance of C3 versus C4 plants in the diet. Stable nitrogen isotopes enable estimation of the dietary proportion of animal protein. The combination of carbon and nitrogen isotopic values can also provide information about freshwater fish consumption (Lee-Thorp, 2008). The application of an intra-individual sampling strategy enables a description of dietary changes through life, including the process of weaning, which is expressed by a decrease in both δ¹⁵N and to a lesser extent δ¹³C (Fogel et al., 1989; Fuller et al., 2006). Another source of isotopic variation, which affects isotopic values, is nutritional stress. This has been explored in the contexts of eating disorders and pregnancy among modern humans, as well as in a number of controlled-feeding experiments on different animal species (for review see e.g. Reitsema, 2013).

This study aims to explore the impact of temporomandibular ankylosis on the diet of two medieval individuals. Their isotopic values will be discussed in relation to a comparative dataset and inferences about their lives will be made.