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Multivariate analysis, specifically principal components analysis (PCA), was carried out on the frequencies of pathologies in the dentition and surrounding bone (see Chapter Four, section 4.9 for method). This was undertaken firstly in order to gauge whether there were any initial groupings of samples based on the inclusion of multiple variates, and secondly, to further illuminate both the similarities in frequencies of pathological lesions and thus samples, as well as the influence of these frequencies on the positions of the sites on the resulting graphs.

Table 6.37 presents the results of correlations of the collective pathological lesions

including caries by tooth count, caries by individual, ADP and AMTL, conducted through the PCA. Caries frequencies by tooth count, ADP by alveoli and AMTL were chosen for inclusion as they proved to have the least correlations to one another,based on the initial run of the model (See Table 6.37). Figures 6.1, 6.2 and 6.3 and Table 6.38 demonstrate results of the altered PCA tests. Some groupings of the samples are clear both by site (Figure 6.3) and by country (Figure 6.4).

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Table 6.37: Correlations (r2-values) of collective pathological lesions (caries by tooth, caries by individual, ADP by alveoli and AMTL) from the Library site sample and European site samples

by principal component analysis

% CT1 % IC1 % AA1 % AMTL1

% CT 1.0000 0.5729 0.1460 0.1141

% IC 0.5729 1.0000 -0.0683 0.5744

% AA 0.1460 -0.0683 1.0000 0.6088

% AMTL 0.1141 0.5744 0.6088 1.0000

CT: caries by tooth; IC: individuals with caries; AA: ADP by alveoli; AMT: ante-mortem tooth loss

1_{indicates r}2_{-value; bold numbers indicate significance; significance is considered as}

values ≤‐0.5 or ≥0.5

Table 6.38: Correlations (r2-values) of pathological lesions (caries by tooth, ADP by alveoli and AMTL) from the Library site sample and European site samples by principal component

analysis

% CT1 % AA1 % AMTL1

% CT 1.0000 0.1160 0.0380

% AA 0.1160 1.0000 -0.2362

% AMTL 0.0380 -0.2362 1.0000

CT: Caries by tooth; AMTL: ante-mortem tooth loss AA: ADP by alveoli

1_{indicates r}2_{-value; bold numbers indicate significance; significance}

is considered as values ≤‐0.5 or ≥0.5

Figure 6.1: Loading plot of collective pathological lesions (caries by tooth, ADP by alveoli and AMTL) from the Library site sample and European site samples by PCA

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Figure 6.2: Score plot of collective pathological lesions (caries by tooth, ADP by alveoli and AMTL) by site from the Library site sample and European site samples by PCA

Figure 6.3: Score plot of collective pathological lesions (caries by tooth, ADP by alveoli and AMTL) by country from the Library site sample and European site samples by PCA

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The Library site sample generally had lower than average frequencies of pathological lesions in the dentition and surrounding bone when compared to the European samples. As Figure 6.2 demonstrates, the Library site sample sits away from the centre of the

diagram and does not appear to be grouped with any other samples, or with its counterpart at Nidaros Cathedral. A number of groupings are notable in Figure 6.2, as indicated by the circles on the score plot. In the second quadrant, the samples from Turku and Vicenne- Campochiaro overlap one another. The second grouping is at the centre of the plot and includes the samples from Wharram Percy, Raunds Furnells, Jutland, Korytiani and Nidaros. Finally, the samples from Eleutherna, Kastella, Messene, Sourtara Galaniou Kozanis and the medieval Iberian Peninsula samples are grouped together in the fourth quadrant. Most of the samples appear to be drawn more to the centre of the plot, but the modern Iberian Peninsula (J) sample is an outlier in the first quadrant.

Figure 6.3 also demonstrates some groupings by country (as circled on the score plot). Three samples from Croatia, two samples from Scotland and the samples from Germany and Crete are all grouped together throughout the plot. Since the samples from Germany, Crete and two of the samples from Croatia (Nova Râca and Ðakovo) were assessed by the same authors, it cannot be discounted that these groupings are related to recording

methods, rather than actual similarities in rates of pathological lesions in the dentition, irrespective of the observer. However, the two samples from Scotland and England were assessed by different observers.

6.7 Discussion

This examination into the oral health of the Library site sample and comparisons to data collected from other European samples aimed to broaden understanding of population health in medieval and early modern Europe. Specifically, examinations of pathological lesions of the dentition and surrounding bone aimed to provide insight into the health of the Library site sample, how the collective health of samples compared to one another, and what social, economic and environmental changes could have affected health in the Library site sample and others.

Whilst typically the Library site sample appeared to have had average or below-average frequencies of pathological lesions when compared to other European populations, some interesting patterns across time and by sex and age were evident when assessing the sample in isolation. In addition, some groupings were evident in statistical assessments of the

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pathological lesions of European samples, particularly in relation to specific countries, whilst a number of samples also demonstrated exceptionally high frequencies of lesions in the dentition.

Any discussion of oral health must firstly be premised with an examination into the teeth and alveoli available for examination. Across the sample, 60.3% of posterior teeth and 16.0% of anterior teeth were retained post-mortem. This is not unexpected, given the trend toward greater preservation of the posterior teeth, due to differences in crown and root morphology and the increased likelihood of post-mortem loss of anterior teeth (Erdal and Duyar 1999, Roberts and Manchester 2007). Given the predominance of posterior teeth in the sample, this may well be skewing the data collected in favour of pathological lesions that occur more commonly in the posterior teeth, such as dental caries. This would also serve to reduce the number of other abnormalities usually apparent in anterior teeth, such as linear enamel hypoplasia, which will be discussed in the following chapter. As Erdal and Duyar (1999) point out, the loss of anterior teeth, which are generally more resistant to caries effectively increases the total caries frequency in a population. However, given the already low frequency of caries within this group, and that the evidence for subsistence in Norway during this period points to a diet fairly typical of this period for Europe,

particularly the reliance on carbohydrates for daily energy intake (Dyer 1983, Gaunt 1998, Orrman 2003, Adamson 2004, Yoder 2010), it seems unlikely that this issue considerably affected carious lesion frequencies in the Library site sample. The presence of calculus on a number of teeth has also served to impede observation for a number of pathological lesions, such as LEH and dental caries.

Examinations of pathological lesions in the dentition and surrounding bone will be discussed below in the context of environmental and social factors, as well as climatic and economic change occurring over the periods from which the European samples are dated. In the case of the Library site sample, large scale social, economic and environmental change occurred from the 13th _{through to the 18}th _{centuries, as has been detailed in Chapter} Two. The impact of these events along with other social variables such as diet, economic status and settlement type will be considered where the evidence suggests an external cause to differing frequencies of lesions in a particular sample population.

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6.7.1 Calculus

The accumulation of calculus on the labial surface of teeth is very common in the archaeological record, and results from the mineralisation of bacterial plaque, partly composed from microorganisms and partly derived from protein in the saliva (Hillson 1986). Those teeth closest to the salivary glands and the lingual and buccal surfaces are the most highly predisposed to supragingival and subgingival calculus (Hillson 1996). A number of factors can be linked to changes in frequencies of calculus; these include the oral environment, cultural practices and diet (Lieverse 1999).

Frequencies of calculus across time at the Library site sample were fairly consistent. The pattern in Phase C was fairly typical, with higher frequencies in older adults when

compared to their younger counterparts. However, in Phase B, in both sexes, frequencies of calculus were far higher in the younger adult groups. This is contrary to the expected trend of increased calculus accumulation with age. This could be linked to the adoption of more effective oral hygiene practices during Phase C. Poor diet quality has also been linked to an increase in calculus deposits (Al-Zahrani et al. 2003) and changes in diet could be affecting frequencies of calculus accumulation in the younger adult groups of Phase B. It is also possible that this difference may be related to post-mortem loss due to curation techniques. However, given that the majority of work undertaken on the teeth has been conducted by a single research group (Beyer-Olsen 1989, Beyer‐Olsen and Risnes 1993, Beyer-Olsen et al. 1994, Beyer-Olsen and Risnes 1994, Beyer-Olsen and Alexandersen 1995), assessing teeth from both phases, it would seem unlikely that this was a considerable factor. Finally, this difference may be the result of selectivity, with individuals dying at a younger age also presenting with higher frequencies of calculus. This would be even more plausible if changes in the dentition, such as the build up of calculus, were linked to poor health. However, given that calculus is generally as a result of diet or hygiene practices, it is difficult to justify such a hypothesis from this result. Having said that, given, as discussed above, that calculus can be linked to poor diet quality, this may be connected to the

shortened life span of these individuals. This will also be discussed in the context of greater frequencies of carious lesions in young adults when compared to old adults.

Female dentition had slightly higher frequencies of calculus, both within and across all phases of the site. Unfortunately, the majority of European samples included here for comparison did not include data on levels of calculus, or if it was included, details of sex or age-specific frequencies of calculus were not specified. The exceptions to this were the

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samples from Eleutherna, Kastella, Germany and Wharram Percy. Frequencies for these samples were published only by individual rather than tooth count, and it was unclear from published information on the samples from Crete how many individuals had teeth

observable for assessment. There was no evidence for sex differentiation in calculus deposits at Wharram Percy. In the samples from Nusplingen and Pleidelsheim, females exhibited a slightly higher frequency of calculus deposits by individual (Jakob 2009). Pooled calculus results also reflected this trend for the German, but not British, samples (Jakob 2009). Males in the Library site sample may have had slightly better oral hygiene practices than females but it seems unlikely that they were markedly different. These differences could also have been due to dietary differences, which will be further explored in relation to dental caries.

6.7.2 Dental caries

Analyses for the presence of carious lesions in the Library site sample and comparisons to European samples revealed a number of expected patterns, such as the high frequency in posterior teeth and greater frequencies in samples subsisting on high carbohydrate diets. However, the unexpected greater frequency of carious lesions in males and young adults during Phase C of the site and the increased frequency of caries over time and differences across geographical locations were of particular interest. These shall be discussed and analysed below.

Patterns of caries in the Library site sample

Across the Library site sample, it is clear that there is a tendency for lesions to occur in the posterior teeth, with no instances of dental caries recorded in the anterior teeth. This is to be expected as caries in molars and premolars are more common generally, with these often beginning in the crevices of the occlusal surfaces (Ortner 2003). Hillson (2001) suggests that in modern populations with high-sugar diets and low frequencies of caries, lesions in the fissures and pits of molar teeth are the most commonly occurring carious lesions, with lesions in the anterior teeth more common in populations with high levels of caries. This is also directly related to reduced occlusal surface wear related to the

consumption of softer and more highly refined carbohydrates, which increases the likelihood of bacteria aggregating in the caries-prone areas of the molars and premolars (Maat and Van der Velde 1987, Hillson 1996, Schollmeyer and Turner 2004). The pattern of caries commonly occurring in the posterior teeth, particularly where there are lower

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levels of wear and a high sugar or soft carbohydrate diet, and an increase in cervical and root caries with wear (and predictably, age) is common in the archaeological record (Powell 1988, Kelley et al. 1991, Larsen et al. 1991, Moore 1993). Therefore, the pattern presented by the Library site sample for higher frequencies in posterior teeth is not unexpected. The effect of sex on dental caries

Males and females within the Library site sample had fairly similar frequencies of carious lesions by tooth count when including adults of unknown age. However, once only aged and sexed individuals were included for statistical comparisons, disparities between the sexes became more obvious. There was a significant difference in the frequencies of caries between males and females across the sample, with males exhibiting a higher frequency of caries. A greater number of male individuals were also affected by carious lesions,

approximately 10.0% more than females. When the data was divided into phases

frequencies between the sexes were similar in Phase B, although the frequency in males was once again higher, but not significantly so. During Phase C, male individuals had a

frequency double that of females, with 51.4% of males affected by carious lesions, compared to 25.7% of females, though the difference by tooth count was not statistically significant (see Table 6.12).

This observed difference is unexpected and unusual in the bioarchaeological record. Most examinations into dental caries in bioarchaeology support the notion that the common pattern is for greater frequencies of carious lesions in females (Kelley et al. 1991, Larsen et al. 1991, Larsen 1998, Roberts and Cox 2003, Lukacs and Largaespada 2006, Lukacs 2008, Malčić et al. 2011, Willis and Oxenham 2013). The pattern of dental caries in modern populations is also consistent with a tendency for higher frequencies in female individuals (Lukacs 2011).

Historically, bioarchaeologists and clinicians have contextualised these differences in terms of behavioural modifications such as dietary habits, differential consumption of nutrients, access of males to higher status foods, such as meat, and the role of women in preparing food and thus, their greater access to certain foodstuffs (Kelley et al. 1991, Larsen 1998, Roberts and Cox 2003, Lukacs 2011). While dental caries is classified as an infectious disease, there are also a number of biological factors that can effect occurrence and frequency of carious lesions, such as inadequate salivary flow, presence of bacteria, host susceptibility, developmental defects of enamel, genetic factors and risk factors in-utero (Seow 1998, Peres et al. 2005, Selwitz et al. 2007). The role of saliva and the salivary

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secretory Immunoglobulin A (IgA) is well known, with the antibody providing immune defence against caries and the saliva buffering against acids, clearing away fermentable carbohydrates and assisting in re-mineralisation of the teeth (Seow 1998, Gussy et al. 2006). In addition, developmental defects of the teeth have also been connected to increased caries risk. The study conducted by Nicolau et al. (2003) somewhat supported the idea that dental caries experience is 'biologically programmed' in that a mother's health, birth weight, premature birth and so on can affect the an individual's predisposition to dental caries in later life.

A number of biological factors are now also considered important in discussions of the sex distribution of caries. Such biological factors predisposing women to caries include genetic differences, such as the relationship between X chromosome genes with saliva flow and diet preference, a less protective oral environment in females and physiological and biological factors, including the early eruption of female teeth, the menstrual cycle, hormones and pregnancy (Legler and Menaker 1980, Larsen et al. 1991, Rugg-Gunn and Nunn 1999, Hillson 2001, Lukacs 2008, Ferraro and Vieira 2010, Oxenham and Domett 2011, Willis and Oxenham 2013). However, the evidence for increased caries rates in females due to early eruption of the teeth does not appear so unequivocal (Hillson 2001, Ferraro and Vieira 2010).

Lukacs and Largaespada (2006) point to a considerable quantity of recent research that indicates that the biochemical composition and flow rate of saliva varies significantly between sexes, and that oestrogen levels play a prominent role in oral health. The authors quote numerous studies that have demonstrated a positive correlation between oestrogen and carious lesions, with the same not being true for androgen (Lukacs and Largaespada 2006). Oestrogen has also been posited as an important factor in caries risk, due to its effect of reducing salivary flow (Percival et al. 1994). This is particularly seen with the onset of pregnancy having a negative effect on oral health. Research by Eliasson et al. (2006) found a significant decrease in mean saliva secretion rates in pregnant women, thus potentially leading to increased suscepbtibility to caries. Thus, the fluctuation of oestrogen during this period can result in changes to the environment of the mouth (Hillson 2001, Ferraro and Vieira 2010). Ferraro and Vieira (2010) have also utilised the research of Deeley et al. (2008) to discuss the role of the Amelogenin gene on the X chromosome as a factor contributing to increased in caries in females. The enamel matrix of teeth consists of 90% of amelogenin protein, so a deletion or mutation in the gene could lead to disruption of enamel formation and thus, increased caries risk.

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For these reasons, the sex distribution of caries in the Library site sample was unforeseen. In archaeological samples, greater frequencies of caries in females are commonly expected, whilst the converse is considered to be rare in adult individuals (Lukacs and Largaespada 2006, Lukacs 2008, Larsen 2015). However, within the European comparison samples alone, a number of populations had no sex difference or greater levels of carious lesions in males. The samples from Raunds Furnells, Vienna, Vilarnau d'Amont, Smörkullen and the medieval sample from the Iberian Peninsula all lacked any obvious sex differences in relation to frequencies of carious lesions (Powell 1996, Esclassan et al. 2009, Meinl et al.

2010, Lopez et al. 2012, Liebe‐Harkort 2012a). Male individuals from the Eleutherna sample exhibited a higher level of caries when compared to females (Bourbou 2003). In the Spanish samples, the frequencies of carious lesions between the sexes remained fairly constant until the modern period, when it is hypothesised that social changes, including the greater power of the Catholic church in excluding women from dental care, contributed to heightened frequencies amongst females (Lopez et al. 2012).

In the case of the Library site sample, subsistence is one factor that may be influencing the frequency of caries in the male population. Jakob (2009) has suggested that in the