Erosive and Mechanical Tooth Wear in Viking Age Icelanders

Article Erosive and Mechanical Tooth Wear in Viking Age Icelanders

Svend Richter * ID and Sigfus Thor Eliasson

Faculty of Odontology, University of Iceland, IS101 Reykjavik, Iceland; [email protected] * Correspondence: [email protected]; Tel.: +354-5254850

Received: 2 March 2017; Accepted: 30 May 2017; Published: 29 August 2017

Abstract: (1) Background: The importance of the Icelandic Sagas as a source of information about diet habits in medieval Iceland, and possibly other Nordic countries, is obvious. Extensive tooth wear in archaeological material worldwide has revealed that the main cause of this wear is believed to have been a coarse diet. Near the volcano Hekla, 66 skeletons dated from before 1104 were excavated, and 49 skulls could be evaluated for tooth wear. The purpose of this study was to determine the main causes of tooth wear in light of diet and beverage consumption described in the Sagas; (2) Materials and methods: Two methods were used to evaluate tooth wear and seven for age estimation; (3) Results: Extensive tooth wear was seen in all of the groups, increasing with age. The ﬁrst molars had the highest score, with no difference between sexes. These had all the similarities seen in wear from a coarse diet, but also presented with characteristics that are seen in erosion in modern Icelanders, through consuming excessive amounts of soft drinks. According to the Sagas, acidic whey was a daily drink and was used for the preservation of food in Iceland, until fairly recently; (4) Conclusions: It is postulated that the consumption of acidic drinks and food, in addition to a coarse and rough diet, played a signiﬁcant role in the dental wear seen in ancient Icelanders.

Keywords: enamel erosion; mechanical tooth wear; Icelandic settlers

1. Introduction Wear is a generic term used in dentistry to describe phenomena of attrition (proximal and occlusal inter-dental friction), abrasion (friction with the intervention of particles) and erosion (chemical dissolution). This terminology suggests that these three phenomena act independently, whereas in fact it is more often the case that they interact simultaneously, which makes the diagnosis more difﬁcult [1]. Dental erosion is tooth surface loss caused by extrinsic or intrinsic forms of acid. Extrinsic erosion is due to a highly acidic diet, while intrinsic erosion is caused by regurgitation of gastric acids [2]. Erosion softens the dental hard tissues, making them more susceptible to attrition and abrasion. Thus, if erosion and bruxism both exist, surface loss due to attrition is faster. The different physiological processes of tooth wear (abrasion, attrition and erosion) usually occur simultaneously and rarely work individually. Therefore, it is important to understand these tooth wear processes and their interactions to determine causes of tooth surface loss [1]. It is the norm to see extensive tooth wear in all ancient societies and is considered a major cause of tooth problems [1]. Tooth wear studies based on skull material from archaeological excavations have mainly been attributed to factors related to diet [3,4]. Acid erosion is hardly ever mentioned as a possible cause of this observed tooth wear [2]. From skeletal remains, evidence for dental health of ancient populations can be provided. The study of the ancient dentition can assist in reconstructing the lifestyle patterns and shed light on dental and general health. Among the conditions considered are ante mortem tooth loss, root abscesses, caries frequency, alveolar bone loss and occlusal tooth wear [5]. Hypo-mineralization of enamel,

Dent. J. 2017, 5, 24; doi:10.3390/dj5030024 www.mdpi.com/journal/dentistry Dent. J. 2017, 5, 24 2 of 12 Dent. J. 2017, 5, 24 2 of 12 enamel,enamel enamel hypoplasia, hypoplasia, appearing appearing as lines as orlines pits, or particularlypits, particularly on incisors, on incisors, can can be anbe an indication indication of ofmalnutrition malnutrition or or infections infections during during tooth tooth formation formation [6]. [6]. Observation of of dental dental wear wear patterns patterns is is one of the most commonly util utilizedized methods of age estimation in in adult skeletal remains in archaeology. The The popularity of of this method arises from the high survival raterate ofof teeth teeth within within archaeological archaeological contexts contexts and and the the relative relative ease ease with with which which dental dental wear wearpatterns patterns can be can observed be observed and scored and scored [7]. [7]. Research by trained dental personnel on dental he healthalth in ancient Icelanders has been almost nonexistent. Archaeologists Archaeologists and and anthropologists anthropologists have, have, however, however, noticed, registered and commented on excessive tooth wear without classifying or categorizing the type of wear [[4,5].4,5]. InIn the years 1931–1939, archaeological and and an anthropologicalthropological research research was was undertaken undertaken at at the the Skeljastadir farm farm in Thjorsardalur in Iceland. Si Sixty-sixxty-six skeletons skeletons were were excavated excavated from from an ancient graveyard: 5 infants,infants, 22 children children and and 59 59 adults adults [8 ,9[8,9]. Volcanic]. Volcanic ash ash from from the mountainthe mountain Hekla, Hekla, dated dated from from1104, 1104, covered covered the skeletons the skeletons [10]. [10]. The skeletonsThe skeletons are preserved are preserved in the in Nationalthe National Museum Museum of Iceland. of Iceland. The purpose of this investigation was to undertakeundertake detailed and thorough odontological investigationinvestigation on on the the skulls skulls to tocast cast light light on ondental dental health health in Viking in Viking Age Icelan Age Icelanders,ders, especially especially in terms in ofterms the prevalence of the prevalence and type and of type tooth of wear. tooth wear.

2. Materials Materials and and Methods Methods The skeletonsskeletons werewere examined examined at theat the stores stores of The of NationalThe National Museum Museum of Iceland of Iceland and are inand relatively are in relativelygood condition. good condition. Of the 66skeletons, Of the 66 51skeletons, skulls could 51 skulls be used could for thebe used general for dentalthe general health dental investigation health investigationand 49 skulls and with 49 915 skulls teeth with could 915 be teeth evaluated could forbe evaluated tooth wear. for tooth wear. The examination of the skulls and teeth was performed blinded by the two authors. Agreement Agreement was on more than 90% of allall measurements.measurements. Wh Whenen there there was a disagreement, an agreement was reachedreached based on re-examination and discussion. Seven methods methods were were used used for for age age estimation, estimation, five five were were based based on tooth on tooth development development [11–15], [11– one15], onone tooth on tooth wear wear [16] [16and] and one one on onectodermal ectodermal suture suture closure closure [17]. [17 ].Gender Gender analysis analysis was was performed performed by by using morphological morphological characteristics characteristics from from the the skull, skull, ma mandiblendible and and in in a a few few instances, instances, pelvis pelvis [5,18–21]. [5,18–21]. Two methods were used to register tooth wear. The fir firstst method was simply to register the wear into fourfour categories:categories: (1)(1) nono wear, wear, (2) (2) wear wear in in enamel, enamel (3), (3) dentin dentin exposed exposed and (4)and exposure (4) exposure of the of pulp the cavity.pulp cavity.The second The second method method was that was developed that developed by Brothwell, by Brothwell, where where wear wear was registeredwas registered into 13into groups 13 groups [22] [22]as shown as shown in Figure in Figure1. The 1. The Brothwell Brothwell method method was was limited limited to to the the skeletons skeletons of of subjects subjects 18 18 yearsyears andand older: 22 22 males, males, 21 21 females females and and one one where where gender gender coul couldd not not be be determined. determined. For For statistical statistical calculations, calculations, thethe scale scale for for the the wear wear stages stages was was modified modified and and numbered numbered from from 0 0to to 12 12 as as shown shown in in Table Table 1.1 .

Figure 1. BrothwellBrothwell classification classiﬁcation of of molar molar wear. wear. White White denotes denotes enamel, black is exposed exposed dentine [22]. [22].

Dent. J. 2017, 5, 24 3 of 12

Table 1. Modiﬁcation of Brothwell tooth wear.

Scales for Wear Stages Brothwell Wear Stages (1981) 1 2 2+ 3− 3 3+ 4 4+ 4 5+ 5++ 6 7 Brothwell Wear Stages (authors modiﬁcation) 0 1 2 3 4 5 6 7 8 9 10 11 12

Tooth wear examination was performed with a dental explorer under good lighting and loupes with 2.8× magniﬁcation (Exam Vision ApS, Samsø, Denmark) and photographs with high resolution (Lester A. Dine Inc., Olympus Digital Camera Model No C-5060, Palm Beach Gardens, FL, USA). Conventional dental and radiographic examinations were performed for analyzing abscesses. A portable X-ray unit for X-ray analysis was used (Sirona, Helio Dent, Bensheim, Germany), as well as digital X-ray technology (Trophy RVG Digital X-ray Systems, Eastman Kodak Company, Rochester, NY, USA). Statistical analyses were made in the Stat View statistical software package (Stat View Software, SAS, Cary, NC, USA). R (The R Foundation for Statistical Computing, Vienna, Austria), RStudio (Rstudio, Boston, MA, USA) and Microsoft Excel (Microsoft Corporation, Redmont, WA, USA) were used for analyzing tooth wear in quartiles and the percentage of the scores, while other statistics were analyzed in Stat View.

3. Results Gender distribution was equal: 24 females, 24 males and 1 of unknown sex. Tooth wear for each tooth number is shown in Table2, where 0 means no detectable wear, 1 is wear in enamel, 2 is wear exposing dentin and 3 is wear exposing the pulp cavity. Table 2. Tooth wear for each tooth number according to the classiﬁcation: 0 no wear, 1 wear in enamel, 2 dentin exposed and 3 exposure of pulp cavity.

Tooth Wear 915 Teeth in 49 Skeletons Number of teeth 18 27 37 33 28 28 19 23 21 18 33 31 33 32 26 20 Highest value 2 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 Lowest value 0 0 1 1 0 0 0 2 2 0 0 0 0 1 0 0 75% 2 2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Median 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 25% 0 1 2 2 2 2 2 2 2 1 2 2 2 2 1 0 Tooth 18 17 16 15 14 13 12 11 21 22 23 24 25 26 27 28 Tooth 48 47 46 45 44 43 42 41 31 32 33 34 35 36 37 38 25% 0 2 2 2 2 2 2 2 2 2 2 2 2 2 2 0 Median 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 75% 2 2 3 2 2 2 2 2 2 2 2 2 2 2 2 2 Lowest value 0 0 1 0 0 0 1 2 2 1 0 1 0 1 1 0 Highest value 2 3 3 3 2 3 3 3 3 3 3 2 3 3 2 2 Number of teeth 25 38 39 31 32 28 28 25 23 32 34 37 26 34 32 24

Distribution of tooth wear for each tooth number according to the classiﬁcation: 0 no wear, 1 wear in enamel, 2 dentin exposed and 3 exposure of pulp cavity, can be seen in Figure2 and in Figure3, which shows the distribution of tooth wear according to Brothwell, 18 years and older. Tooth wear according to age and gender, using the Brothwell method, is shown in Tables3–5, where tooth wear was only measured in skulls of subjects classiﬁed as being aged 18 years and older: 21 males, 21 females and one skull that where gender could not be determined. Tooth wear was higher in the age group 36 and older than for the 18–35 years group (Table4), but no statistical difference between genders was noted (Table5). Tooth wear with cuppings was registered in most molars in the younger age group and in the older age group where enamel was left (Figures 7 and 8). Root abscesses were found in 22 skulls out of 49, or in 45% of the cases. The abscesses were more common in the 36 years and older Dent. J. 2017, 5, 24 4 of 12

Dent. J. 2017, 5, 24 4 of 12 group,showed and signiﬁcantly the highest rate more of commonabscesses in(Table males 7). thanCaries females was almost (Table non-existent,6) and the ﬁrstbeing molar registered showed in the highestjust rate two ofteeth. abscesses (Table7). Caries was almost non-existent, being registered in just two teeth.

FigureFigure 2. Distribution 2. Distribution of toothof tooth wear wear for for each each toothtooth numb numberer according according to tothe the classification: classiﬁcation: 0 no 0wear, no wear, 1 wear1 wear in enamel, in enamel, 2 dentin 2 dentin exposed exposed and and 3 3 exposure exposure ofof pulp cavity. cavity.

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 18 17 16 26 27 28 48 47 46 36 37 38

1 2 3 4 5 6 7 8 9 10 11 12

FigureFigure 3. Distribution 3. Distribution of of tooth toothwear wear accordingaccording to to Brothwell, Brothwell, 18 18years years and and older. older.

TableTable 3. Tooth 3. Tooth wear wear according according to toBrothwell Brothwell modification, modiﬁcation, 18 18 years years and and older. older.

Brothwell, 18 Years and Older Brothwell, 18 Years and Older 337 Teeth in 44 Skeletons Number 337of teeth Teeth 19 in 4426 Skeletons 36 31 24 16 Highest value 9 11 12 11 11 6 Number of teeth 19 26 36 31 24 16 Lowest value 0 1 3 3 1 0 Highest value 9 11 12 11 11 6 75% 3 7 10 9 6 3 Lowest value 0 1 3 3 1 0 Median 2 5 9 7 6 2 75% 3 7 10 9 6 3 25% 1 2 6 6 2 0 Median 2 5 9 7 6 2 Tooth 18 17 16 26 27 28 25% 1 2 6 6 2 0 Tooth 48 47 46 36 37 38 Tooth 18 17 16 26 27 28 25% 1 3 6 6 4 1 Tooth 48Median 47 1 6 46 8 8 365 2 37 38 25% 175% 3 3 8 6 10 10 67 2 4 1 Median 1Lowest value 6 0 1 8 3 1 81 0 5 2 75% 3Highest value 8 9 12 10 12 11 1010 7 7 2 Lowest value 0Number of 1teeth 23 38 3 39 32 132 21 1 0 Highest value 9 12 12 11 10 7 Number of teeth 23 38 39 32 32 21 Dent. J. 2017, 5, 24 5 of 12

Table 4. Tooth wear in 18–35 years and 36 years and older according to Brothwell.

Age 18–35 ≥Age 36 Age Groups 121 Teeth in 13 Skeletons 207 Teeth in 31 Skeletons Number of teeth 7 9 9 11 10 7 11 16 26 19 13 8 Highest value 2 3 8 9 6 1 9 11 12 11 11 6 Lowest value 0 1 2 3 1 0 1 1 5 4 1 0 75% 1 2 6 7 4 1 6 8 10 10 7 5 Median 0 1 5 6 2 0 3 6 9 8 6 3 25% 0 1 4 4 1 0 2 6 8 7 6 2 Tooth 18 17 16 26 27 28 18 17 16 26 27 28 Tooth 48 47 46 36 37 38 48 47 46 36 37 38 25% 0 1 5 5 1 0 2 6 7 7 5 2 Median 1 3 6 6 3 0 4 7 9 10 6 2 75% 1 4 6 7 5 1 6 9 10 10 8 5 Lowest value 0 1 3 3 1 0 1 2 5 4 3 1 Highest value 3 5 8 9 5 2 9 12 12 11 10 7 Number of teeth 12 13 12 10 11 10 10 25 26 21 21 11

Table 5. Tooth wear for males and females according to Brothwell modiﬁcation.

Males 18 Years and Older Females 18 Years and Older Gender 163 Teeth in 21 Skeletons 143 Teeth in 22 Skeletons Number of teeth 12 14 17 15 10 8 4 10 16 13 11 6 Highest value 9 11 12 10 11 6 5 10 11 11 7 6 Lowest value 0 1 3 3 1 2 0 1 4 4 1 0 75% 4 7 10 9 6 2 3 6 9 8 6 4 Median 2 6 9 7 5 2 2 4 7 6 6 1 25% 1 2 6 6 1 1 1 2 6 6 3 0 Tooth 18 17 16 26 27 28 18 17 16 26 27 28 Tooth 48 47 46 36 37 38 48 47 46 36 37 38 25% 0 3 5 7 3 1 1 4 6 6 4 0 Median 1 6 8 9 6 2 2 5 7 7 5 1 75% 5 7 10 10 8 4 3 9 10 10 7 2 Lowest value 0 1 3 3 1 0 0 1 5 4 1 0 Highest value 6 12 11 11 10 7 9 11 12 11 9 2 Number of teeth 9 18 17 15 16 12 11 18 19 14 14 7

Table 6. Prevalence of root abscesses according to age and gender.

Gender Age n Skeletons n with Abscesses % with Abscesses % Abscesses 35 years and below 11 2 18 Female 36 36 years and above 14 7 50 35 years and below 6 2 33 Male 54 36 years and above 18 11 61 35 years and below 17 4 24 Both Sexes 45 36 years and above 32 18 56

Table 7. Number of root abscesses per tooth.

Number of Abscesses 1 9 3 2 1 1 1 1 5 1 Tooth 18 17 16 15 14 13 12 11 21 22 23 24 25 26 27 28 Tooth 48 47 46 45 44 43 42 41 31 32 33 34 35 36 37 38 Number of Abscesses 1 6 1 1 2 1 1 3 5 1 Dent. J. 2017, 5, 24 6 of 12

4. Discussion

Dent. J.Previous 2017, 5, 24 studies of tooth wear have used clinical scoring systems [23–26] similar to this study.6 of 12 There is no universally accepted scoring system in the literature [1] and as a result, the use of different clinical indices prevents the direct comparison of different populations [1]. [1]. Generally, these clinical indices are quick, simple, and convenient with with good good reliability, reliability, since they usually have well-defined well-deﬁned criteria with careful calibration amongst examiners [[27–29].27–29]. Tooth wear is seen in archaeologicalarchaeological material from all over the world.world. This wear is generally far more extensiveextensive thanthan can can be be seen seen in currentin current living livi populations.ng populations. Ancient Ancient people people consumed consumed a more a course, more course,rough and rough unprocessed and unprocessed diet, resulting diet, resulting in extensive in extensive occlusal occlusal tooth wear. tooth This wear. wear This has wear been has shown been shownto gradually to gradually increase increase with age with [3,5]. age Usually [3,5]. theUsually wear the was wear most was dominating most dominating on molars, on starting molars, in startingocclusal in enamel occlusal and enamel gradually and gradually reaching intoreaching dentin. into Even dentin. though Even the though wear the reached wear wellreached into well the intodentin, the thedentin, teeth the appeared teeth appeared to remain to functional, remain func sincetional, the since odontoblastic the odontoblastic activity prevented activity prevented the wear thefrom wear reaching from intoreaching the pulpal into the cavity pulpal because cavity of because secondary of secondary dentin formation dentin formation [22] (Figure [22]4). (Figure 4).

36 46

Figure 4. SecondarySecondary dentin dentin formation formation seen seen in in tooth tooth 46, 46, while while tooth tooth 36 36 has excessive wear with pulp exposure.

The amount of wear can by graded by several methods.methods. The simplest scoring of tooth wear is using only four categories: no no wear, wear, wear in enamel, wear into dentin and wear exposing the pulp cavity. WhenWhen more more detailed detailed grading grading is preferred,is preferred, several several systems systems are available. are available. The Brothwell The Brothwell method wasmethod elected was toelected be used to be in theused present in the present study [22 study,30] (Figure[22,30] 1(Figure). Tooth 1). wear Tooth of we eachar toothof each type tooth can type be canseen be in seen Table in2 .Table The third 2. The molars third havemolars the have least the wear least and wear the and first the molars first themolars most, the with most, the with second the secondmolars inmolars between. in between. The amount of wear of the first first molar molar indicates indicates six six years years of of wear wear when when the the second second molar molar erupts. erupts. When the third molar erupts, the first first molar has a approximatelypproximately twelve years of wear, and the second molar, six years of wear. Figure 5 5a,b,a,b, showsshows wornworn dentitiondentition fromfrom twotwo angles.angles. DifferentDifferent eruptioneruption timestimes for the molars are, therefore, the basis for the age estimation. If, for example, the second molar shows that it has been in the mouth for 12 years and the third for six years, it is likely that the individual was about 24 24 years years old. old. If Ifthe the second second molar molar shows shows 18 18years years of wear, of wear, it is itlikely is likely that thatthe individual the individual was wasaround around 30 years 30 years old. old.Most Most of adulthood of adulthood can can be bedetermined determined in inthe the same same way. way. The The study study by by Miles indicated small small differences differences in in the the wear wear rate rate between between the the three three molars. molars. He He found found the the first first molars molars to wearto wear fastest, fastest, with with a decreasing a decreasing rate ratein the in posterior the posterior direction. direction. Thus, Thus,he showed he showed that it took that the it took second the molarssecond 6.5 molars years, 6.5 and years, the third and themolars third 7 years, molars to 7 wear years, the to same wear amount the same as amount the first as molars the first in 6 molars years [30].in 6 yearsThese [30 wear]. These differences wear differences are seen in are Figure seen in 5, Figure explaining5, explaining the age theestimation age estimation method method by Miles. by SomeMiles. studies Some studies have reported have reported similar similar wear weardifferenti differentialsals [31] but [31] others but others have have reported reported equal equal rates rates of wearof wear [32]. [32 The]. The Miles Miles method method was was one one of ofthe the method methodss used used for for age age estimation estimation in in the the present present study. study. Many investigators have confirmedconfirmed the usefulness of tooth wear for age estimation [[32–34].32–34].

Dent. J. 2017, 5, 24 7 of 12 Dent. J. 2017, 5, 24 7 of 12 Dent. J. 2017, 5, 24 7 of 12

(a) (b) (a) (b)

FigureFigure 5. (5.a )( aIncreasing) Increasing tooth tooth wearwear accordingaccording to to time time of oferuption, eruption, with with pulp pulp exposure exposure in tooth in 16.tooth (b) 16. (b) Figure 5. (a) Increasing tooth wear according to time of eruption, with pulp exposure in tooth 16. (b) RootRoot abscess abscess in in tooth tooth 16 16 due due toto tooth wear.wear. Root abscess in tooth 16 due to tooth wear. BrothwellBrothwell used used material material from from many British British archaeological archaeological investigations investigations when when he examined he examined the the Brothwell used material from many British archaeological investigations when he examined the teethteeth of youngof young people people and and found found that toothtooth wear wear had had changed changed little little from from Neolithic Neolithic times times(4000 B.C.)(4000 B.C.) teeth of young people and found that tooth wear had changed little from Neolithic times (4000 B.C.) to to theto thelate late middle middle ages ages (16th (16th century). century). TheseThese findi findingsngs helped helped him him to develop to develop a chart a chart estimating estimating tooth tooth the late middle ages (16th century). These ﬁndings helped him to develop a chart estimating tooth wearwear and and age age at atdeath death for for these these populations [22,30] [22,30] (Figure (Figure 6). 6). wear and age at death for these populations [22,30] (Figure6).

Figure 6. Estimated correspondence between adult age at death and molar wear phases for British material from Neolithic to medieval periods [35]. FigureFigure 6.6. EstimatedEstimated correspondencecorrespondence between adult age atat deathdeath andand molarmolar wearwear phasesphases forfor BritishBritish materialmaterialTooth fromfrom wear NeolithicNeolithic that is so toto excessive medievalmedieval that periodsperiods it opens [[35].35]. into the pulp cavity, as well as the effects on tooth physiology and pathology, need to be considered. Tooth wear is the cumulative loss of enamel and dentinToothTooth and wearwear it thatthatis considered isis soso excessiveexcessive natural thatthat that itit opensteethopens we intointoar throughout thethe pulppulp cavity,cavity, life. Us asasually, wellwell astheas the theodontoblasts effectseffects onon toothtooth physiologyphysiologycompensate and for pathology, pathology, this wear needwith need new,to to be be reactive, considered. considered. secondary Tooth Tooth dentin wear wear beingis the is the laidcumulative cumulativedown inside loss loss theof enamel pulp of enamel and cavity, making the teeth functional and healthy [30]. Therefore, many investigators have used anddentin dentin and andit is it considered is considered natural natural that that teeth teeth we wearar throughout throughout life. life. Us Usually,ually, the odontoblastsodontoblasts secondary or tertiary dentin as a foundation for developing methods for age estimation. These compensatecompensate forfor this this wear wear with with new, new, reactive, reactive, secondary secondary dentin dentin being being laid downlaid down inside inside the pulp the cavity, pulp makingmethods the are teeth based functional on radiographic and healthy measurements [30]. Therefore, of the formation many of investigators new dentin and have the used shrinkage secondary cavity,of the making pulp cavity the [15,36].teeth functional and healthy [30]. Therefore, many investigators have used or tertiary dentin as a foundation for developing methods for age estimation. These methods are secondarySeveral or tertiaryteeth in thisdentin investigation as a foundation had wear exposurefor developing into the methodspulp cavity. for Jon age Steffensen, estimation. who These basedmethodsexcavated on radiographicare basedand originally on radiographic measurements investigated measurements ofthis the bone formation material, of the offound formation new only dentin one of and newdefinite thedentin shrinkagecase andwhere the ofbone shrinkage the pulp cavityof thechanges [pulp15,36 indicatedcavity]. [15,36]. scurvy or more likely vitamin D deficiency [3], although scurvy was known to be a SeveralSeveralcommon teeth disease in in thisin this Iceland investigation investigation until the had19th had wearcentur wear exposurey exposure[4,37]. Pindborg, into into the the pulpsupported pulp cavity. cavity. by Jonother Steffensen, Jon authors, Steffensen, who whoexcavatedstated excavated that and scurvy originally and originallycould investigatedharm investigatedthe odontoblasts, this bone this le bonematerial,ading material, to irregular found found onlydentin one only formation definite one deﬁnite that case possibly where case where bone bonechangeswears changes indicated at a faster indicated ratescurvy [38]. scurvy or Furthermore, more or more likely likelyBrothwell vitamin vitamin statedD deficiency D that deﬁciency in some [3], [ althoughinstances,3], although toothscurvy scurvy wear was could was known known be to be to so much and so fast that the normal odontoblastic activity is not enough to compensate for the wear, bea common a common disease disease in inIceland Iceland until until the the 19th 19th centur centuryy [4,37]. [4,37]. Pindborg, Pindborg, supported supported by by other authors, statedstated thatthat scurvyscurvy couldcould harmharm thethe odontoblasts,odontoblasts, leadingleading toto irregularirregular dentindentin formationformation thatthat possiblypossibly wearswears atat aa fasterfaster raterate [[38].38]. Furthermore,Furthermore, BrothwellBrothwell statedstated thatthat inin somesome instances,instances, toothtooth wearwear couldcould bebe soso muchmuch andand soso fastfast thatthat thethe normalnormal odontoblastic activity is not enough to compensate for the wear,

Dent. J. 2017, 5, 24 8 of 12 therebyDent. resulting J. 2017, 5, 24 in an exposure into the pulp cavity [22]. Excessively worn dentition is8 shown of 12 in FigureDent.4, whereJ. 2017, 5, tooth 24 number 36 has an exposure into the pulp cavity, while visible secondary8 of dentin12 thereby resulting in an exposure into the pulp cavity [22]. Excessively worn dentition is shown in formation has still compensated for the wear of tooth number 46. It is doubtful that vitamin C or D therebyFigure 4, resulting where tooth in an number exposure 36 has into an the exposure pulp ca intovity the [22]. pulp Excessively cavity, while worn visible dentition secondary is shown dentin in deficiency has resulted in exposure in only one first molar, although uneven wear is a possibility. Figureformation 4, where has still tooth compensated number 36 hasfor thean exposure wear of tooth into the number pulp cavity,46. It is while doubtful visible that secondary vitamin Cdentin or D Rootformationdeficiency abscesses hashas stillresulted were compensated found in exposure in almostfor inthe only wear half one of first tooth the molar, skulls. number although Since 46. It the isuneven doubtful caries wear rate that is was avitamin possibility. very C low or Dfor the population,deficiencyRoot it abscesses cannothas resulted explain were in foundexposure the highin almost in rootonly half abscessone of first the incidence.molar,skulls. althoughSince A the likely unevencaries explanation rate wear was is verya possibility. is low that for excessive the wearpopulation, in someRoot instancesabscesses it cannot were reached explain found intothe in high thealmost pulp root half cavity.abscess of the This incidence.skulls. explanation Since A thelikely caries is explanation supported rate was isvery by that the low excessive fact for thatthe first molars,population,wear which in some showed it cannotinstances the explain highestreached the scoreinto high the ofroot toothpulp abscess cavity. wear incidence. (TableThis explanation2), A also likely had explanationis thesupported greatest is by that frequency the excessive fact that of root abscesseswearfirst molars, (Tablein some 7which). instances showed reached the highest into the score pulp of cavity. tooth wearThis explanation(Table 2), also is hadsupported the greatest by the frequency fact that first molars, which showed the highest score of tooth wear (Table 2), also had the greatest frequency Theof root processed abscesses soft (Table Western 7). diet of today usually produces minor tooth wear. Recently, however, of root abscesses (Table 7). enamel erosionThe processed caused soft by Western excessive diet consumption of today usuall ofy acidicproduces beverages, minor tooth mainly wear. softRecently, drinks, however, fruit juices enamelThe erosion processed caused soft byWestern excessive diet consumptionof today usuall ofy acproducesidic beverages, minor tooth mainly wear. soft Recently, drinks, fruit however, juices and sport drinks, has become an epidemic among young people in Iceland [39], Figure7. enameland sport erosion drinks, caused has become by excessive an epidemic consumption among ofyoung acidic people beverages, in Iceland mainly [39], soft Figure drinks, 7. fruit juices and sport drinks, has become an epidemic among young people in Iceland [39], Figure 7.

(a) (b) (a) (b) FigureFigure 7. Similar 7. Similar characteristics characteristics ( a(a)) asas seenseen in in erosion erosion in in young young people people today today (b). (b). Figure 7. Similar characteristics (a) as seen in erosion in young people today (b). ManyMany teeth teeth in thein the present present study study showed showed similarsimilar wear wear patterns patterns to tothose those seen seen in young in young people people Many teeth in the present study showed similar wear patterns to those seen in young people todaytoday that that suffer suffer from from dental dental erosion. erosion. Figures Figures7 7 and and8 8 show show strikingstriking similarities similarities between between tooth tooth wear wear today that suffer from dental erosion. Figures 7 and 8 show striking similarities between tooth wear in medievalin medieval teeth teeth and and in youngin young people people today today withwith occlusal cupping. cupping. Cupping Cupping on tooth on tooth cusps cusps and and infissures medieval is used teeth as anda criterion in young to discriminate people today lesions with occlusalon enamel cupping. and dentin Cupping caused on by tooth dental cusps erosion and fissures is used as a criterion to discriminate lesions on enamel and dentin caused by dental erosion fissuresfrom abrasion/attrition is used as a criterion worn toflat discriminate wear facets lesions[3,4,40]. on enamel and dentin caused by dental erosion from abrasion/attrition worn flat wear facets [3,4,40]. from Figureabrasion/attrition 8 shows clearly worn that flat the wear buccal facets and [3,4,40]. lingual enamel surfaces show little or no tooth wear. FigureThis Figuresuggests8 shows 8 showsthat clearly the clearly observed that that the tooththe buccal buccal wear and andwas lingual lingualnot caused enamel enamel by gastricsurfaces surfaces reflux, show show even little little though or no or tooth nolifting tooth wear. and wear. This suggestsThisother suggests heavy that work that the mightthe observed observed have caused tooth tooth wear problemswear waswas such not ca causedasused hiatus by by hernia, gastric gastric whichreflux, reflux, could even even leadthough though to gastric lifting lifting acidand and otherotherreaching heavy heavy work the work mouth might might haveand have causing caused caused this problems problems typical suchsuch patte as rn hiatus hiatus of tooth hernia, hernia, erosion. which which couldAlthough could lead lead totooth gastric to erosion gastric acid acid reachingreachingassociated the mouth the with mouth andgastric causingand reflux causing this disease typical this is typical now pattern quit patte ofe common toothrn of erosion.tooth in Iceland,erosion. Although andAlthough has tooth a typical erosiontooth erosionclinical associated withassociatedappearance, gastric reflux with the diseaseprevalencegastric reflux is nowof thisdisease quite in th ise common medievalnow quit inperiode common Iceland, is not in andknown Iceland, has [41]. a and typical has a clinical typical appearance,clinical appearance, the prevalence of this in the medieval period is not known [41]. the prevalence of this in the medieval period is not known [41].

(a) (a) Figure 8. Cont.

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Dent. J. 2017, 5, 24 9 of 12 Dent. J. 2017, 5, 24 9 of 12

(b) Figure 8. Similar appearance between the wear(b of) medieval teeth (a) and the erosion with occlusal FigurecuppingFigure 8. Similar in 8. youngSimilar appearance peopleappearance today between between (b). the the wearwear of medieval teeth teeth (a) ( aand) and the the erosion erosion with with occlusal occlusal cuppingcupping in young in young people people today today (b ().b). The history of food and nutrition in Iceland can shed light on tooth wear in ancient Icelanders. In FigureThe historyThe 9, history a timeline of foodof food of and andIcelandic nutrition nutrition food in in Iceland Icelandhistory can can shed shedbe seen[42]light light on on tooth . toothBecause wear wear inof ancient inthe ancient lack Icelanders. of Icelanders.salt, drying Inwas FigureIn one Figure9 ,of a timeline the9, a twotimeline ofmost Icelandic of popular Icelandic food ways food history historyfor preserving can can be be seen seen[42] food, [ 42]. mostly Because. Because used ofof thethe on lacklack fish ofof that salt, was drying air-dried was was one of the two most popular ways for preserving food, mostly used on fish that was air-dried oneand of cured the two as moststock popularfish [43]. ways Meat forwas preserving also dried, food, but it mostly was more used commonly on fish that soured was air-dried in lacticand acid. and cured as stock fish [43]. Meat was also dried, but it was more commonly soured in lactic acid. curedDue asto stockthe lack fish of [43 grain,]. Meat there was are also many dried, tales but in it wasthe literature more commonly about the soured dietary in lacticpeculiarities acid. Due of tothe Due to the lack of grain, there are many tales in the literature about the dietary peculiarities of the the lack of grain, there are many tales in the literature about the dietary peculiarities of the Icelanders, Icelanders,Icelanders, which which include include thethe eatingeating ofof dry dry fish fish instead instead of ofbread bread [43]. [43]. It is Itmore is more than likelythan likelythat in that in which include the eating of dry fish instead of bread [43]. It is more than likely that in addition additionaddition to tothe the coarse coarse diet, diet, dried dried foodstuffs contaminated contaminated by bydust, dust, and and in Thjorsardalur, in Thjorsardalur, volcanic volcanic ash ash totoo, thetoo, were coarse were responsible responsible diet, dried for for foodstuffs the the exteextensive contaminated tooth tooth wear wear in by inthe dust,the medieval medieval and inIcelanders. Thjorsardalur,Icelanders. Furthermore, Furthermore, volcanic the lack ash the too, lack wereof grainof responsible grain and and fruits fruits for could could the extensive be be thethe explanation tooth wear fo for inther the the low low medieval caries caries rate rate Icelanders. in the in skullthe skull samples. Furthermore, samples. the lack of grain and fruits could be the explanation for the low caries rate in the skull samples.

Figure 9. Timeline of Icelandic food history (adapted from Mehler 2011 [42]). Figure 9. Timeline of Icelandic food history (adapted from Mehler 2011 [42]). Figure 9. Timeline of Icelandic food history (adapted from Mehler 2011 [42]). Two dairy products are most characteristic of Icelandic foodstuffs. The first, namely whey (Icel. Twomysa), dairy is a watery products part of are milk most that characteristicseparates from the of curd Icelandic in the process foodstuffs. of making The the ﬁrst, second namely major whey Two dairy products are most characteristic of Icelandic foodstuffs. The first, namely whey (Icel. (Icel.diary mysa), product, is a watery skyr. Most part ofof milkthe whey that was separates processe fromd by thepouring curd it in into the a process wooden of barrel making with the open second majormysa),holes diary is in a waterythe product, lid for part fermentation. skyr. of milk Most that ofWhen separates the this whey process from was the was processed curd finished, in the by mysa process pouring had ofturned it making into into a thewoodenlactic second acid, barrel major withdiarysýra, open product, which holes was skyr. in thethen Most lid mixed for of fermentation. thewith whey water was in the Whenprocesse ratio thisof done processby part pouring acid was with it ﬁnished, into 11 partsa wooden mysa water. had barrel This turned drink with intoopen lacticholeswas acid, in the the s everydayý ra,lid whichfor fermentation.thirst-quencher was then mixed Whenin Iceland with this until waterprocess the inmid-20th was the ratiofinished, century of one mysa[42]. part Lactose had acid turned is with a disaccharide 11into parts lactic water. acid, Thissýra,sugar drink which found was was thein milkthen everyday andmixed makes thirst-quencherwith up wateraround in 2%–8% the in ratio Iceland (by weight)of one until ofpart themilk. acid mid-20th As with the whey 11 century parts fermented, water. [42]. about Lactose This drink is awas disaccharidehalf the of everyday the lactose sugar thirst-quencher was found converted in milk to in andlactic Iceland makes acid until along up th aroundwithe mid-20th other 2–8% by-products century (by weight) [42]. [44]. Lactose Lactic of milk. acid is Asa was disaccharide the the whey most important food conservation medium in Iceland. Leathery meat was cooked and put into lactic fermented,sugar found about in milk half and of the makes lactose up around was converted 2%–8% (by to lactic weight) acid of alongmilk. As with the other whey by-products fermented, about [44]. acid afterwards to make it softer [42]. According to Saga literature, skyr was used in all Nordic Lactichalf of acid the was lactose the mostwas converted important to food lactic conservation acid along mediumwith other in Iceland.by-products Leathery [44]. Lactic meat was acid cooked was the countries during the middle Ages. In Iceland, skyr was eaten two or three times a day up until the most important food conservation medium in Iceland. Leathery meat was cooked and put into lactic and put20th into century lactic [43]. acid afterwards to make it softer [42]. According to Saga literature, skyr was used in acid afterwards to make it softer [42]. According to Saga literature, skyr was used in all Nordic all NordicExtensive countries studies during have the been middle made Ages. on tooth In Iceland,erosion in skyr young was people eaten in two Iceland or three in recent times years. a day up untilcountriesDr. the Thorbjorg 20th during century Jensdottir the [ 43middle]. has Ages.been at In the Iceland, forefront skyr of thosewas eaten who havetwo studiedor three the times erosive a day effects up untilof the 20thExtensiveacidic century beverages [43]. studies in the have country. been madeThe capability on tooth of erosion acidic beverages in young to people erode dental in Iceland enamel in depends recent years. Dr. ThorbjorgExtensive Jensdottir studies hashave been been at themade forefront on tooth of thoseerosion who in haveyoung studied people the in erosiveIceland effects in recent of acidic years. beveragesDr. Thorbjorg in the Jensdottir country. The has capability been at the of acidicforefront beverages of those to who erode have dental studied enamel the depends erosive noteffects only of onacidic the pH beverages of the drink, in the but country. also on The its buffering capability capacity. of acidic Her beverages study showed to erode that dental the erosive enamel potential depends of whey, mysa, was very high [45]. Mysa and Sýra in the medieval period is believed to have contained

Dent. J. 2017, 5, 24 10 of 12

Dent. J. 2017, 5, 24 10 of 12 not only on the pH of the drink, but also on its buffering capacity. Her study showed that the erosive potential of whey, mysa, was very high [45]. Mysa and Sýra in the medieval period is believed to havemuch contained higher concentrations much higher of concentr lactic acidations than of that lactic which acid canthan be that found which in the can same be found modern in the products, same modernmanufactured products, under manufactured much different under and much more di controlledfferent and conditions more controlled [44]. conditions [44]. InIn the VikingViking period,period, the the storage storage of of food food or or the the production production of dairy of dairy products products commonly commonly took placetook placein small in outhousessmall outhouses next to next the longhouse.to the longhouse. Up until Up the until 20th century,the 20th Icelandiccentury, farmsIcelandic always farms included always a includedroom for a the room production for the production of whey and of skyr, whey and and large skyr, wooden and large barrels wooden or storage barrels trunks or storage were typicaltrunks werefeatures typical of storage features rooms, of storage as seen rooms, in Figure as seen 10 in, taken Figure during 10, taken the during excavation the excavation of the Viking of the Age Viking farm AgeStong farm in Thorsardalur, Stong in Thorsardalur, not far from not the far archaeological from the archaeological site, Skeljastadir site, Skeljastadir [46]. [46].

FigureFigure 10. 10. WheyWhey barrel barrel imprints imprints in in the the storage storage room room of of the the farm Ston Stongg (from Agustsson 1989 [46]). [46]).

5.5. Conclusions Conclusions InIn addition addition to to the the coarse coarse diet diet of of dried dried meat meat and and fish, ﬁsh, probably probably contaminated contaminated by by abrasive abrasive material, material, itit is is postulated that that acidic acidic beverages beverages and and acidic acidic food, food, were were also also responsible for for the the extensive tooth tooth wear in medieval Icelanders.

Acknowledgments: TheThe present present study study is is a a part part of of the research project Odontological investigation on archaeologicalarchaeological human remains fromfrom SkeljastadirSkeljastadir inin Thjorsardalur,Thjorsardalur, which which was was supported supported by by the the Research Research Fund Fund of ofthe the University University of of Iceland Iceland and and the the Research Research Fund Fund of of the the Icelandic Icelandic Dental Dental Association. Association.

Author Contributions: Both authors havehave substantiallysubstantiallycontributed contributed to to the the reading reading of of this this article article and and approved approved its final version. its final version. Conflicts of Interest: The authors declare no conflict of interest. Conflicts of Interest: The authors declare no conflict of interest. References References 1. D’Incau, E.; Couture, C.; Maureille, B. Human tooth wear in the past and the present: Tribological 1. D’Incau, E.; Couture, C.; Maureille, B. Human tooth wear in the past and the present: Tribological mechanisms, scoring systems, dental and skeletal compensations. Arch. Oral Biol. 2012, 57, 214–229. mechanisms, scoring systems, dental and skeletal compensations. Arch. Oral Biol. 2012, 57, 214–229. [CrossRef][PubMed] 2. Johansson, A. A cross-cultural study of occlusal tooth wear. Swed. Dent. J. Suppl. 1992, 86, 1–59. 2. Johansson, A. A cross-cultural study of occlusal tooth wear. Swed. Dent. J. Suppl. 1992, 86, 1–59. [PubMed] 3. Steffensen, J. Knoglene fra Skeljastaðir i Þjórsárdalur. In Forntida Gårder i Island: Meddelanden Från Den 3. Steffensen, J. Knoglene fra Skeljastaðir i Þjórsárdalur. In Forntida Gårder i Island: Meddelanden Från Den Nordiska Arkeologiska Undersökningen i Island Sommaren 1939; København: Munksgaard, 1943; pp. 227–260. Nordiska Arkeologiska Undersökningen i Island Sommaren 1939; Munksgaard: København, Denmark, 1943; 4. Gestsdóttir, H. The Palaeopathological Diagnosis of Nutritional Disease: A Study of the Skeletal Material pp. 227–260. from Skeljastaðir, Iceland. Master’s Thesis, University of Bradford: Bradford, UK, 1998. 4. Gestsdóttir, H. The Palaeopathological Diagnosis of Nutritional Disease: A Study of the Skeletal Material 5. Richter, S. Odontological Investigation on Archaeological Human Remains from Skeljastadir in from Skeljastaðir, Iceland. Master’s Thesis, University of Bradford, Bradford, UK, 1998. Thjorsardalur. Master’s Thesis, University of Iceland, Reykjavík, Iceland, 2005. 5. Richter, S. Odontological Investigation on Archaeological Human Remains from Skeljastadir in Thjorsardalur. 6. Caufield, P.W.; Li, Y.; Bromage, T.G. Hypoplasia-associated severe early childhood caries—A proposed Master’s Thesis, University of Iceland, Reykjavík, Iceland, 2005. definition. J. Dent. Res. 2012, 91, 544–550. 6. Caufield, P.W.; Li, Y.; Bromage, T.G. Hypoplasia-associated severe early childhood caries—A proposed 7. Millard, A.R.; Gowland, R.L. A bayesian approach to the estimation of the age of humans from tooth definition. J. Dent. Res. 2012, 91, 544–550. [CrossRef][PubMed] development and wear. Archeol. Calcolatori 2002, 13, 197–210. 7. Millard, A.R.; Gowland, R.L. A bayesian approach to the estimation of the age of humans from tooth development and wear. Archeol. Calcolatori 2002, 13, 197–210.

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