AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 154:609–614 (2014)
Brief Communication: An Enigmatic Enamel Alteration on the Anterior Maxillary Teeth in a Prehistoric North Italian Population Irene Dori* and Jacopo Moggi-Cecchi Department of Biology, University of Florence, 50122, Firenze, Italy KEY WORDS
lingual groove; upper dentition; incisors
ABSTRACT In this paper we describe a hitherto undocumented modification of the dental enamel surface observed in an Early Bronze Age population from northern Italy. The defect, which can be described as a curvilinear groove, is located on the lingual surface of incisors and canines in the upper jaw. This groove, documented both in the permanent and deciduous dentition, is located at approximately 1 mm from the cervix and extends from the mesiolingual to the distolingual surface. The occur-
rence of the groove is not related to the sex of the affected individuals, but its degree of expression is related to age at death. Because of its morphology, the groove cannot be considered as a result of disruptions in the process of enamel deposition. At the present stage of research we suggest that the groove might have been the result of some kind of dental erosion caused by as yet unidentified chemical factors. Am J Phys Anthropol 154:609–614, 2014. VC 2014 Wiley Periodicals, Inc.
Modifications of the dental enamel surface can be the result of events occurring during dental development (as in the case of hypoplasia and amelogenesis imperfecta), or it can be the result of changes taking place during the life of an individual (such as, for example, tooth wear, noncarious cervical lesions, attrition and oral pathologies like caries). As teeth, unlike bone, do not undergo remodeling throughout life, alterations on their surface are permanent and visible at all times, providing excellent sources of information for anthropological studies, where they can offer useful data for the reconstruction of general conditions of the state of health of past populations. In archaeological material the occurrence of hypoplastic defects is very common, and takes the form of a reduction of the normal enamel thickness because of abnormalities that have occurred during amelogenesis. Thin lines and large grooves, sometimes extending along the entire contour of the crown; isolated pits, large or small areas without enamel, are the various aspects with which these defects can occur on the surface of a tooth (Clarkson, 1989; Hillson and Bond, 1997). Dental enamel hypoplasia is commonly considered to be a nonspecific indicator of stress, as the causes determining its onset may be multiple (nutritional deficiencies, diseases, infections, metabolic disorders, etc.) (El-Najjar et al., 1978; Skinner and Goodman, 1992). Amelogenesis imperfecta (AI) comprises a group of inherited disorders that affect tooth enamel, causing changes in its structure and appearance. In most cases all the teeth (both deciduous and permanent) are affected. The enamel appears to be hypoplastic and / or hypomineralized, and affected teeth show anomalies and irregularities ranging from small pits and thin furrows to vast areas where the enamel is not present (B€ ackman, 1989; Witkop, 1989). This disease can be sporadic or inherited in an autosomal dominant, autosomal recessive, or sexlinked (X chromosome) mode (Crawford et al., 2007). During the individual’s life-span, dental hard tissue is exposed to many physical and chemical factors which
alter the tooth surface. This gradual and irreversible loss of hard tissue is usually defined as “tooth wear” and it can have a chemical or a mechanical origin. In the first case the term “erosion” is used (consisting in a gradual and irreversible loss of hard tissue of the tooth as a result of an acid attack), whereas in the second case the term “friction” or “attrition” (when the loss of hard tissue is because of the contact between teeth) and “abrasion” (when there is a mechanical interaction of the teeth with other materials) are used (Robb et al., 1991). These factors along with “abfraction” (term describing the breakdown of dental hard tissue because of an incorrect nonaxial occlusal load) may be among the main causes of defects known with the term of “noncarious cervical lesions”. These consist in a loss of tooth structure, localized at the cemento enamel junction, and unrelated to dental caries. These defects, whose formation also depends on other factors as saliva, age, gender, diet, and parafuctional habits, have various aspects: shallow or deep lesions with sharp edge, straight or hollow bottom lesions with sharp angled (Osborne-Smith et al., 1999; Walter et al., 2014). Among the major causes of abrasion there is mastication, but also activities that require the use of teeth for purposes other than feeding. Some of these alterations produced by extra-masticatory practices are intentional in nature
Ó 2014 WILEY PERIODICALS, INC.
Additional Supporting Information may be found in the online version of this article. *Correspondence to: Irene Dori; Laboratory of Anthropology, Department of Biology, University of Florence, Via del Proconsolo 12, 50122 Firenze, Italy. E-mail: [email protected] Received 23 December 2013; accepted 30 April 2014 DOI: 10.1002/ajpa.22535 Published online 14 May 2014 in Wiley Online Library (wileyonlinelibrary.com).
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I. DORI AND J.MOGGI-CECCHI TABLE 1. Frequencies of the groove in the Arano skeletal sample, with individuals subdivided by sex and age at death Male
Age 0–6 7–12 13–19 20–45 > 45 Total
N groove
1 16 1 18
N necropolis
2 27 4 33
Female %
50 59.2 25 54.5
N groove
6 1 7
N necropolis
10 2 12
n.d. %
60 50 58.3
total
N groove
N necropolis
%
1 0 4 1
10 7 9 1
10 – 44.5 100
6
27
22.2
N groove
N necropolis
%
1 0 5 23 2 31
10 7 11 38 6 72
10 – 45.4 60.5 33.3 43
N groove: individuals with groove; N necropolis: individuals in the necropolis, per group; n.d.: sex not determined.
and are produced for decorative purposes, or cultural rituals (such as the creation of lines and grooves on the enamel or the filing of the occlusal margins), whereas others are involuntary, the results of repeated gestures (such as the use of toothpicks for therapeutic reasons or oral hygiene, the constant habit of keeping objects inside the mouth, and the use of teeth as a tool for working activities) (Molnar, 1972; Schulz, 1977; Berryman et al., 1979; Larsen, 1985; Ubelaker, 1996). In the process of restoring and studying an Early Bronze Age population from northern Italy we have observed the occurrence, in a large number of individuals, of an unusual alteration of the enamel (a groove) on the lingual surface of maxillary incisors and canines. An extensive bibliographic search has seemed to indicate that nothing like this has been documented in the literature till now. Therefore, the purpose of this note is to describe and analyze the frequency of this unusual morphology in this sample and to discuss its possible etiology.
MATERIALS AND METHODS The skeletal sample consists of 72 individuals from the archaeological site of Arano di Cellore di Illasi (about 15 km from the city of Verona, Northern Italy) and dated from the Early Bronze Age (the first two centuries of the second millennium BCE) (Valzolgher et al., 2012). Sample composition, by sex and age, is summarized in Table 1. For the diagnosis of sex and the estimated age at death, standard anthropological methods were used (Ferembach et al., 1980; Smith, 1984; Meindl and Lovejoy, 1985; Ubelaker, 1989; Steckel et al., 2006). All the teeth of the sample, both deciduous and permanent, were carefully scrutinized in order to determine the presence of the groove, which was observed only in some maxillary incisors (central and lateral) and canines. Special attention has been paid in observing teeth still in the alveoli, as the groove, because of its morphology and position (on the lingual surface, very close to the cervix), could easily have been overlooked. High-resolution casts of the affected teeth were produced and examined under a scanning electron microscope (SEM). Frequencies of the groove in the entire skeletal sample were computed, in order to assess a possible relationship with the sex and age of the affected individuals. Other variables considered were the number of affected teeth per individual and the differences in the degree of expression of the alteration, following two broadly defined categories: light (a barely visible groove or a slight indentation in the enamel) and marked (a welldefined groove, in some cases with dentine exposure) (see Results). We also analyzed the presence / absence of calculus deposit in the total sample to establish whether American Journal of Physical Anthropology
there might have been a relationship between calculus occurrence and the groove. In order to describe more accurately the characteristics and the position of these grooves on the tooth surface, the following measurements were taken with a digital caliper: maximum width of the groove; distance between the cervical margin of the defect and the cervix of the tooth; cervico-incisal extension of the groove as the distance between the cervical margin of the defect and its incisal end, along the tooth axis.
RESULTS The groove is usually curvilinear (continuous or interrupted in some cases); it occurs on the lingual surface of the enamel of the maxillary incisors and canines. It has been observed in both the permanent and deciduous dentition, located at approximately one mm from the cervix and extending from the mesio-lingual to the distolingual face. When present, the groove shows no variation in its position or orientation. Figure 1 shows the groove and its different degrees of expression. In some teeth the groove occurs as a faint trace (“light” lesions), with a slight loss of enamel and, in mesial or distal view, with minimal changes in the profile of the crown (Fig. 1A,B); in others it penetrates deep into the enamel, in some cases even exposing the dentine (“marked” lesions), with a deep hollow in the profile (Fig. 1C,D). The analysis of the affected teeth with the SEM allowed us to observe in detail the characteristics of the groove, and to examine, in particular, its internal surface, characterized by a very irregular appearance (Fig. 2 and S1, Supporting Information). The SEM photos (Fig. S1 and 2A -marked-, Fig. 2B -light-) show a corrugated and jagged surface in which there are no traces of striae and furrows usually resulting from mechanical interaction of the tooth surfaces with abrasive contaminants contained in the food and / or with objects or materials held among the teeth (Lalueza Fox, 1992; Repetto, 1994). In four individuals the nonmetric trait “interruption groove” (one of the characters of the Arizona State University Dental Anthropology System and defined as “grooves which cross the cingulum and often continue down the root”) (Turner et al., 1991) is present in close proximity of the enamel alteration (Fig. S2A, Supporting Information), and from the SEM photos it is possible to note that in these cases the curvilinear groove occurs on top of the morphological variant (Fig. S2B, Supporting Information) The number of individuals in the entire sample, divided by sex and age at death, where the groove has been observed, is shown in Table 1. In the analysis an individual was considered affected if at least one tooth showed the groove. The groove is present in 31 out of 72 individuals (43% of the sample) and occurs more
AN ENIGMATIC ENAMEL GROOVE frequently in adults between the ages of 20 and 45 years (n 5 23). No difference was observed in its occurrence (presence / absence) between males and females (X2 test: P 5 0.82, d.f. 5 1), but, on the other hand, males have more teeth affected on average that females (X2 test: P 5 0.002, d.f. 5 1) (Table 2).
Fig. 1. Examples of upper central incisors with the groove with “light” (A, B) and “marked” (C, D) degree of expression. (A) Upper RI1 with “light” groove. Tomb 49, young subject, sex undetermined. (B) Same individual as in (A), view of distal surface of RI1. (C) Upper I1 with “marked” groove. Tomb 52, adult male. (D) Same individual as in (C), view of mesial surface of RI1.
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The groove was observed in a single immature individual (0–6 years), where the affected tooth is a right di2 (Fig. S3A,B, Supporting Information). Unfortunately, its antimere and the central incisors were not preserved. Overall, the groove is present on 74 teeth: 73 permanent and 1 deciduous. When considering only individuals with permanent dentition in which the groove is documented (Table S1, Supporting Information), the analysis shows that it is more common in the upper central incisors (86.5%). A significant difference (X2 test: P 5 0.02, d.f. 5 1) among all of the affected teeth between the left and right jaw is also evident, with the right tooth more frequently affected than the left. In the entire sample, calculus deposit is present in 51 out of 72 individuals (70.8%). An individual was considered affected by calculus if at least one tooth showed some deposit. Table S2 (Supporting Information) shows that occurrence of calculus in the sample showing the groove (30 individuals with permanent dentition) reaches 93.3%. Mandibular teeth were more affected by calculus that the maxillary teeth. Analysis by tooth type showed that lower incisors were the most affected teeth (Table S3, Supporting Information). Concerning the position, calculus deposit occurred most often on the buccal side in the upper teeth and on the interproximal and lingual side in the lower teeth. In no instance calculus deposits occurred at the location of the groove. Table 2 shows the number of affected teeth for each individual together with sex and age at death. Among the 30 individuals with permanent dentition affected, only seven had a complete set of anterior teeth available for observation, and none of them has the groove in all six teeth. In nine individuals (30%) the groove is present only on one tooth, and in most cases it is the RI1. A total of 26.7% (eight individuals) shows the defect on two teeth; five subjects (16.7%) have three affected teeth, and seven (23.3%) have four teeth with the groove. Only one individual (3.3%) shows the furrow on five teeth. In those individuals where more than one tooth is affected, the groove can be present with different
Fig. 2. (A) SEM image of the lingual surface of the LI1 of individual from Tomb 52 with “marked” lesion. (B) SEM image of the lingual surface of the RI1 of individual from Tomb 59 with “light” lesion. In all these images the cervix of the tooth is toward the bottom left.
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I. DORI AND J.MOGGI-CECCHI TABLE 2. Number of affected teeth per individual Right
1 tooth affected tb. 10 tb. 49 tb. 3a tb. 15 tb. 40 tb. 16b tb. 41 tb. 59 tb. 9a 2 teeth affected tb. 4b tb. 55a tb. 60 tb. 4a tb. 16a tb. 58 tb. 64 tb. 68 3 teeth affected tb. 17 tb. 25 tb. 44 tb. 53 tb. 62 4 teeth affected tb. 2 tb. 63 tb. 3b tb. 21 tb. 26 tb. 42 tb. 52 5 teeth affected tb. 35
Left
C
I2
I1
x x x x
x
(X) (X) (X) (X)
(X) x x (x) x x x x x x
I1
I2
C
Age
Sex
x x (X)
x x x x x
x x x x x x x x x
13–19 13–19 20–45 20–45 20–45 20–45 20–45 > 45 > 45
N.D. N.D. F F F F M F M
x x x x
13–19 20–45 20–45 20–45 20–45 20–45 20–45 20–45
N.D. N.D. F M M M M M
x x x x
13–19 20–45 20–45 20–45 20–45
N.D. M M M M
13–19 20–45 20–45 20–45 20–45 20–45 20–45
M F M M M M M
20–45
M
x (X) x x (X) x x x
x (X) x x (X)
(X) (X) (X) (X) (X)
(X) (X) x (X) x x (X)
(X) (X) (X) (X) (X) (X)
(X)
x
(X) x (X) (X) (X) (X) (X) (X) (X) (X) x (X) (X) (X) (X) (X) (X)
x (X) (X) (X) (X) (X) (X) (X) (X) (X)
x x x x (X) x x (X) x (X)
x x
x
(X) (X) (X)
(X) (X) (X) (X) (X) (X)
(X) (X) (X) (X) (X)
(X) x x x x x
(X)
(X)
(X)
(X)
Tomb number is indicated (Tb). Specimens arranged by sex and age at death (blank cell: tooth not present; x: tooth present but not affected; (X): tooth with groove).
degrees of expression on different teeth. In order to analyze the variability in the degree of expression we analyzed all the RI1 involved (the mostly affected tooth); when not available, the LI1 was examined. Individuals whose I1 was unaffected were excluded from this analysis. Similarly, the only di2 affected was not considered. Overall, 27 upper central incisors were examined. The degree of expression of the groove (light or marked) was considered in relation with the age at death of each individual (Table S4, Supporting Information). A “light” groove appears to be more frequent in the (20–45) age group, and no “marked” grooves are present in the (13– 19) age group. Data on the position and the cervico-incisal extension of the grooves are summarized in Table S5 (Supporting Information). In some cases it was not possible to take all the measurements defined, because of the poor condition of the tooth surfaces. The cervico-incisal extension of the groove varied from 1 to 4.6 mm. Its distance from the cervix ranged from 0.2 to 1.7 mm, with average values in the three permanent tooth classes from 0.6 to 0.8 mm. The width of the groove varied from .13 to 1.9 mm, with different mean values in the three permanent tooth classes. American Journal of Physical Anthropology
DISCUSSION The combined analysis of the groove morphology, its position on the crown and distribution in the sample, allowed us to describe different aspects of this enigmatic enamel alteration. This, in turn, has allowed us to provide a framework within which trying to interpret its mode of occurrence. The first issue to address was whether the groove occurred during the development of the tooth or after eruption. The grooves can hardly have been the result of defects occurring during the developmental phase of enamel apposition, as the “parabolic” area of enamel affected does not follow the normal profile of enamel deposition. Also, the groove is extremely localized and it is not present on the labial surfaces of the teeth concerned. The appearance of the groove and its location in a well-delimited area of the tooth surface tend to exclude the result of some form of amelogenesis imperfecta (AI). In these cases, apart from the aspect of the enamel (hypoplastic and / or hypomineralized), the entire surface of the tooth is affected. Further, in most cases the entire dentition is concerned (Pindborg, 1982; Crawford et al., 2007). Finally, the SEM images allowed us to exclude an event which occurred during development, as in a few cases the groove happened to be
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AN ENIGMATIC ENAMEL GROOVE located on top of an “interruption groove”, a nonmetric trait of dentition (Fig. S2B, Supporting Information). Similarly, the defect can hardly be associated with noncarious cervical lesions. These pathologies are mainly documented in first premolars of the all four quadrants, and in general the lesions are more common on the buccal surfaces of teeth (Wood et al., 2008). The next step was to try to establish a possible relationship with extra-masticatory activities. However, wear produced by use of the teeth for work or daily activities (for therapeutic reasons, oral hygiene or from a constant habit of keeping objects inside the mouth), usually leaves typical, subparallel striations, easily detectable with the SEM and totally absent at the bottom of the grooves in the teeth examined. This makes it difficult to postulate the groove as the outcome of a functional activity. The position of the grooves on the lingual surfaces also makes it hard to suggest their possible intentional origin because of decorative, cultural, or ritualistic reasons. The grooves, being in a position not visible during social interactions, would have no decorative functionality, resulting in no expression of a particular status or in identifying membership in a specific group. The highly unusual morphology of the grooves also makes it hard to suggest their origin in friction between teeth from matching jaws; also, in the corresponding mandibular teeth, no traces were found that would suggest a particular type of malocclusion. Table S3 (Supporting Information) suggests that there is no relationship between calculus deposit and presence of the groove. Further, although in the subsample showing the groove the majority of individuals also displayed calculus, the latter occurred mostly on the lower anterior teeth. Thus if we consider all the factors described above, and take into account that the formation of the grooves must have occurred at a later stage after tooth eruption in the mouth, we believe that one working hypothesis is to consider the groove as the result of a chemical erosion because of some acid etching, where the term “erosion” is defined in the literature as “loss of dental hard tissue by a chemical process that does not involve the influence of bacteria” (Pindborg, 1970). Dental erosion is associated with different factors that can have both an extrinsic nature (e.g., food and drink) and an intrinsic one (e.g., gastroesophageal reflux disease or eating disorders) (Ten Cate and Imfeld, 1996). Dental erosion, commonly located on the lingual surface of the maxillary anterior teeth and on the occlusal surface of the lower canine (Johansson et al., 2012), is on the contrary usually absent from the front teeth of the lower jaw which are protected by the presence of the tongue and salivary glands (Robb et al., 1991). In this regard, it is noticeable that in our sample, there is the complete absence of the grooves in the teeth of young individuals (age group 7– 12) (although it remains to be established why a single individual has the groove on his/her di2). It is in this age range that the replacement of milk teeth usually occurs, followed by the eruption of the permanent teeth, in which the groove is documented. The absence of the defect in the dentition of juvenile individuals could be because of the fact that their teeth have not yet been exposed to acid attack for a sufficiently long period of time. Also, an association seems to exist between the groove occurrence and individual age with no grooves present in the dentition of individuals in the (7–12) age group—
2
although one di was affected, whereas frequencies are higher in the young adult and adult groups. More to the point, central incisors (the first anterior permanent tooth to emerge in the mouth) have higher frequencies than lateral incisors and canines, in this order, thus suggesting a relationship between the occurrence and the eruption order of these teeth. No relationship exists between groove occurrence and the sex of the affected individuals; but at the same time a significant difference exists in that males seem to have a higher number of teeth affected. The involvement of some kind of acid etching could also explain why the groove is located at approximately 1 mm from the cervix. Loss of the enamel tissue on the lingual surface of the affected teeth occurs in an area that in the living individual corresponds to the limit of the gingival margin, that is in an area no longer protected by the presence of the gum itself and perhaps more exposed to acid-type attacks. Within the broad interpretative category of acid etching involvement in the appearance of the grooves, a number of other morphological details still remain to be clarified, such as, for example, its shape, as it is not a groove of uniform width and depth but is broader at the apex; or the morphology of its edges, which seem quite sharp; or the exact involvement of the dentine, that will require a histological section of the tooth. In terms of when formation of the grooves occurred, the possibility that the process of erosion has taken place postmortem for some kind of very localized etching agent, although less plausible, remains to be explored in detail. Other possibilities, such as the combination of a mechanical pressure through a metal brace followed by some kind of chemical erosions, should be also taken into account. If the hypothesis of some kind of acid etching is confirmed, it will remain to be established why the attack produced such a localized mark, not diffused over a broader area of the lingual surface and, also, what might have been the factor(s) causing the erosion. It will be also interesting to assess whether this peculiar groove morphology can be observed in other populations from different archaeological contexts.
ACKNOWLEDGMENTS We are grateful to Sovrintendenza Archeologica del Veneto (Luciano Salzani and Paola Salzani) for the opportunity to study the Arano skeletal material. We would like to thank Marta Mariotti, Gilberto Montori, Silvia Bortoluzzi, Silvia Boccone, Giovanna Stefania, Luca Bachechi, Mauro Patalano and Alessandro Riga. Thanks also to Simon Hillson, Chris Dean, Theya Molleson and Alfredo Coppa for their comments.
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El-Najjar MY, DeSanti MV, Ozebek L. 1978. Prevalence and possible etiology of dental enamel hypoplasia. Am J of Phys Anthropol 48:185–192. Ferembach D, Schwidetzky I, Stloukal M. 1980. Recommendations for age and sex diagnoses of skeletons. J Hum Evol 9: 517–549. Hillson SW, Bond S. 1997. Relationship of enamel hypoplasia to the pattern of tooth crown growth: a discussion. Am J Phys Anthropol 104:89–103. Johansson AK, Omar R, Carlsson GE, Johansson A. 2012. Dental erosion and its growing importance in clinical practice: from past to present. Int J Dent 2012, Article ID 632907. Lalueza Fox C. 1992. Information obtained from the microscopic examination of cultural striations in human dentition. Int J Osteoarchaeol 2:155–169. Larsen CS. 1985. Dental modifications and tool use in the western Great Basin. Am J Phys Anthropol 67:393–402. Meindl RS, Lovejoy CO. 1985. Ectocranial suture closure: a revised method for the determination of skeletal age at death based on lateral-anterior suture. Am J Phys Anthropol 68:47– 56. Molnar S. 1972. Tooth wear and culture: a survey of tooth functions among some prehistoric population. Curr Anthropol 13: 511–526. Osborne-Smith KL, Burke FJT, Wilson NHF. 1999. The aetiology of the non-carious cervical lesion. Int Dent J 49:139–143. Pindborg JJ. 1970. Pathology of Dental Hard Tissues. K€openhamn, Denmark: Munksgaard. Pindborg JJ. 1982. Aetiology of developmental dental defects not related to fluorosis. Int Dent J 32:123–134. Repetto E. 1994: Il contributo della microusura dentaria negli studi di paleonutrizione: il sito della media et a del Bronzo di Toppo Daguzzo (Basilicata). Bull Paletn Ital 85:349–365. Robb ND, Cruwys E, Smith BGN. 1991. Is “lingual surface attrition on the maxillary teeth (LSAMAT)” caused by dental erosion? Am J Phys Anthropol 85:345–351.
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Brief Communication: An Enigmatic Enamel Alteration on the Anterior Maxillary Teeth in a Prehistoric North Italian Population Irene Dori* and Jacopo Moggi-Cecchi Department of Biology, University of Florence, 50122, Firenze, Italy KEY WORDS
lingual groove; upper dentition; incisors
ABSTRACT In this paper we describe a hitherto undocumented modification of the dental enamel surface observed in an Early Bronze Age population from northern Italy. The defect, which can be described as a curvilinear groove, is located on the lingual surface of incisors and canines in the upper jaw. This groove, documented both in the permanent and deciduous dentition, is located at approximately 1 mm from the cervix and extends from the mesiolingual to the distolingual surface. The occur-
rence of the groove is not related to the sex of the affected individuals, but its degree of expression is related to age at death. Because of its morphology, the groove cannot be considered as a result of disruptions in the process of enamel deposition. At the present stage of research we suggest that the groove might have been the result of some kind of dental erosion caused by as yet unidentified chemical factors. Am J Phys Anthropol 154:609–614, 2014. VC 2014 Wiley Periodicals, Inc.
Modifications of the dental enamel surface can be the result of events occurring during dental development (as in the case of hypoplasia and amelogenesis imperfecta), or it can be the result of changes taking place during the life of an individual (such as, for example, tooth wear, noncarious cervical lesions, attrition and oral pathologies like caries). As teeth, unlike bone, do not undergo remodeling throughout life, alterations on their surface are permanent and visible at all times, providing excellent sources of information for anthropological studies, where they can offer useful data for the reconstruction of general conditions of the state of health of past populations. In archaeological material the occurrence of hypoplastic defects is very common, and takes the form of a reduction of the normal enamel thickness because of abnormalities that have occurred during amelogenesis. Thin lines and large grooves, sometimes extending along the entire contour of the crown; isolated pits, large or small areas without enamel, are the various aspects with which these defects can occur on the surface of a tooth (Clarkson, 1989; Hillson and Bond, 1997). Dental enamel hypoplasia is commonly considered to be a nonspecific indicator of stress, as the causes determining its onset may be multiple (nutritional deficiencies, diseases, infections, metabolic disorders, etc.) (El-Najjar et al., 1978; Skinner and Goodman, 1992). Amelogenesis imperfecta (AI) comprises a group of inherited disorders that affect tooth enamel, causing changes in its structure and appearance. In most cases all the teeth (both deciduous and permanent) are affected. The enamel appears to be hypoplastic and / or hypomineralized, and affected teeth show anomalies and irregularities ranging from small pits and thin furrows to vast areas where the enamel is not present (B€ ackman, 1989; Witkop, 1989). This disease can be sporadic or inherited in an autosomal dominant, autosomal recessive, or sexlinked (X chromosome) mode (Crawford et al., 2007). During the individual’s life-span, dental hard tissue is exposed to many physical and chemical factors which
alter the tooth surface. This gradual and irreversible loss of hard tissue is usually defined as “tooth wear” and it can have a chemical or a mechanical origin. In the first case the term “erosion” is used (consisting in a gradual and irreversible loss of hard tissue of the tooth as a result of an acid attack), whereas in the second case the term “friction” or “attrition” (when the loss of hard tissue is because of the contact between teeth) and “abrasion” (when there is a mechanical interaction of the teeth with other materials) are used (Robb et al., 1991). These factors along with “abfraction” (term describing the breakdown of dental hard tissue because of an incorrect nonaxial occlusal load) may be among the main causes of defects known with the term of “noncarious cervical lesions”. These consist in a loss of tooth structure, localized at the cemento enamel junction, and unrelated to dental caries. These defects, whose formation also depends on other factors as saliva, age, gender, diet, and parafuctional habits, have various aspects: shallow or deep lesions with sharp edge, straight or hollow bottom lesions with sharp angled (Osborne-Smith et al., 1999; Walter et al., 2014). Among the major causes of abrasion there is mastication, but also activities that require the use of teeth for purposes other than feeding. Some of these alterations produced by extra-masticatory practices are intentional in nature
Ó 2014 WILEY PERIODICALS, INC.
Additional Supporting Information may be found in the online version of this article. *Correspondence to: Irene Dori; Laboratory of Anthropology, Department of Biology, University of Florence, Via del Proconsolo 12, 50122 Firenze, Italy. E-mail: [email protected] Received 23 December 2013; accepted 30 April 2014 DOI: 10.1002/ajpa.22535 Published online 14 May 2014 in Wiley Online Library (wileyonlinelibrary.com).
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I. DORI AND J.MOGGI-CECCHI TABLE 1. Frequencies of the groove in the Arano skeletal sample, with individuals subdivided by sex and age at death Male
Age 0–6 7–12 13–19 20–45 > 45 Total
N groove
1 16 1 18
N necropolis
2 27 4 33
Female %
50 59.2 25 54.5
N groove
6 1 7
N necropolis
10 2 12
n.d. %
60 50 58.3
total
N groove
N necropolis
%
1 0 4 1
10 7 9 1
10 – 44.5 100
6
27
22.2
N groove
N necropolis
%
1 0 5 23 2 31
10 7 11 38 6 72
10 – 45.4 60.5 33.3 43
N groove: individuals with groove; N necropolis: individuals in the necropolis, per group; n.d.: sex not determined.
and are produced for decorative purposes, or cultural rituals (such as the creation of lines and grooves on the enamel or the filing of the occlusal margins), whereas others are involuntary, the results of repeated gestures (such as the use of toothpicks for therapeutic reasons or oral hygiene, the constant habit of keeping objects inside the mouth, and the use of teeth as a tool for working activities) (Molnar, 1972; Schulz, 1977; Berryman et al., 1979; Larsen, 1985; Ubelaker, 1996). In the process of restoring and studying an Early Bronze Age population from northern Italy we have observed the occurrence, in a large number of individuals, of an unusual alteration of the enamel (a groove) on the lingual surface of maxillary incisors and canines. An extensive bibliographic search has seemed to indicate that nothing like this has been documented in the literature till now. Therefore, the purpose of this note is to describe and analyze the frequency of this unusual morphology in this sample and to discuss its possible etiology.
MATERIALS AND METHODS The skeletal sample consists of 72 individuals from the archaeological site of Arano di Cellore di Illasi (about 15 km from the city of Verona, Northern Italy) and dated from the Early Bronze Age (the first two centuries of the second millennium BCE) (Valzolgher et al., 2012). Sample composition, by sex and age, is summarized in Table 1. For the diagnosis of sex and the estimated age at death, standard anthropological methods were used (Ferembach et al., 1980; Smith, 1984; Meindl and Lovejoy, 1985; Ubelaker, 1989; Steckel et al., 2006). All the teeth of the sample, both deciduous and permanent, were carefully scrutinized in order to determine the presence of the groove, which was observed only in some maxillary incisors (central and lateral) and canines. Special attention has been paid in observing teeth still in the alveoli, as the groove, because of its morphology and position (on the lingual surface, very close to the cervix), could easily have been overlooked. High-resolution casts of the affected teeth were produced and examined under a scanning electron microscope (SEM). Frequencies of the groove in the entire skeletal sample were computed, in order to assess a possible relationship with the sex and age of the affected individuals. Other variables considered were the number of affected teeth per individual and the differences in the degree of expression of the alteration, following two broadly defined categories: light (a barely visible groove or a slight indentation in the enamel) and marked (a welldefined groove, in some cases with dentine exposure) (see Results). We also analyzed the presence / absence of calculus deposit in the total sample to establish whether American Journal of Physical Anthropology
there might have been a relationship between calculus occurrence and the groove. In order to describe more accurately the characteristics and the position of these grooves on the tooth surface, the following measurements were taken with a digital caliper: maximum width of the groove; distance between the cervical margin of the defect and the cervix of the tooth; cervico-incisal extension of the groove as the distance between the cervical margin of the defect and its incisal end, along the tooth axis.
RESULTS The groove is usually curvilinear (continuous or interrupted in some cases); it occurs on the lingual surface of the enamel of the maxillary incisors and canines. It has been observed in both the permanent and deciduous dentition, located at approximately one mm from the cervix and extending from the mesio-lingual to the distolingual face. When present, the groove shows no variation in its position or orientation. Figure 1 shows the groove and its different degrees of expression. In some teeth the groove occurs as a faint trace (“light” lesions), with a slight loss of enamel and, in mesial or distal view, with minimal changes in the profile of the crown (Fig. 1A,B); in others it penetrates deep into the enamel, in some cases even exposing the dentine (“marked” lesions), with a deep hollow in the profile (Fig. 1C,D). The analysis of the affected teeth with the SEM allowed us to observe in detail the characteristics of the groove, and to examine, in particular, its internal surface, characterized by a very irregular appearance (Fig. 2 and S1, Supporting Information). The SEM photos (Fig. S1 and 2A -marked-, Fig. 2B -light-) show a corrugated and jagged surface in which there are no traces of striae and furrows usually resulting from mechanical interaction of the tooth surfaces with abrasive contaminants contained in the food and / or with objects or materials held among the teeth (Lalueza Fox, 1992; Repetto, 1994). In four individuals the nonmetric trait “interruption groove” (one of the characters of the Arizona State University Dental Anthropology System and defined as “grooves which cross the cingulum and often continue down the root”) (Turner et al., 1991) is present in close proximity of the enamel alteration (Fig. S2A, Supporting Information), and from the SEM photos it is possible to note that in these cases the curvilinear groove occurs on top of the morphological variant (Fig. S2B, Supporting Information) The number of individuals in the entire sample, divided by sex and age at death, where the groove has been observed, is shown in Table 1. In the analysis an individual was considered affected if at least one tooth showed the groove. The groove is present in 31 out of 72 individuals (43% of the sample) and occurs more
AN ENIGMATIC ENAMEL GROOVE frequently in adults between the ages of 20 and 45 years (n 5 23). No difference was observed in its occurrence (presence / absence) between males and females (X2 test: P 5 0.82, d.f. 5 1), but, on the other hand, males have more teeth affected on average that females (X2 test: P 5 0.002, d.f. 5 1) (Table 2).
Fig. 1. Examples of upper central incisors with the groove with “light” (A, B) and “marked” (C, D) degree of expression. (A) Upper RI1 with “light” groove. Tomb 49, young subject, sex undetermined. (B) Same individual as in (A), view of distal surface of RI1. (C) Upper I1 with “marked” groove. Tomb 52, adult male. (D) Same individual as in (C), view of mesial surface of RI1.
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The groove was observed in a single immature individual (0–6 years), where the affected tooth is a right di2 (Fig. S3A,B, Supporting Information). Unfortunately, its antimere and the central incisors were not preserved. Overall, the groove is present on 74 teeth: 73 permanent and 1 deciduous. When considering only individuals with permanent dentition in which the groove is documented (Table S1, Supporting Information), the analysis shows that it is more common in the upper central incisors (86.5%). A significant difference (X2 test: P 5 0.02, d.f. 5 1) among all of the affected teeth between the left and right jaw is also evident, with the right tooth more frequently affected than the left. In the entire sample, calculus deposit is present in 51 out of 72 individuals (70.8%). An individual was considered affected by calculus if at least one tooth showed some deposit. Table S2 (Supporting Information) shows that occurrence of calculus in the sample showing the groove (30 individuals with permanent dentition) reaches 93.3%. Mandibular teeth were more affected by calculus that the maxillary teeth. Analysis by tooth type showed that lower incisors were the most affected teeth (Table S3, Supporting Information). Concerning the position, calculus deposit occurred most often on the buccal side in the upper teeth and on the interproximal and lingual side in the lower teeth. In no instance calculus deposits occurred at the location of the groove. Table 2 shows the number of affected teeth for each individual together with sex and age at death. Among the 30 individuals with permanent dentition affected, only seven had a complete set of anterior teeth available for observation, and none of them has the groove in all six teeth. In nine individuals (30%) the groove is present only on one tooth, and in most cases it is the RI1. A total of 26.7% (eight individuals) shows the defect on two teeth; five subjects (16.7%) have three affected teeth, and seven (23.3%) have four teeth with the groove. Only one individual (3.3%) shows the furrow on five teeth. In those individuals where more than one tooth is affected, the groove can be present with different
Fig. 2. (A) SEM image of the lingual surface of the LI1 of individual from Tomb 52 with “marked” lesion. (B) SEM image of the lingual surface of the RI1 of individual from Tomb 59 with “light” lesion. In all these images the cervix of the tooth is toward the bottom left.
American Journal of Physical Anthropology
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I. DORI AND J.MOGGI-CECCHI TABLE 2. Number of affected teeth per individual Right
1 tooth affected tb. 10 tb. 49 tb. 3a tb. 15 tb. 40 tb. 16b tb. 41 tb. 59 tb. 9a 2 teeth affected tb. 4b tb. 55a tb. 60 tb. 4a tb. 16a tb. 58 tb. 64 tb. 68 3 teeth affected tb. 17 tb. 25 tb. 44 tb. 53 tb. 62 4 teeth affected tb. 2 tb. 63 tb. 3b tb. 21 tb. 26 tb. 42 tb. 52 5 teeth affected tb. 35
Left
C
I2
I1
x x x x
x
(X) (X) (X) (X)
(X) x x (x) x x x x x x
I1
I2
C
Age
Sex
x x (X)
x x x x x
x x x x x x x x x
13–19 13–19 20–45 20–45 20–45 20–45 20–45 > 45 > 45
N.D. N.D. F F F F M F M
x x x x
13–19 20–45 20–45 20–45 20–45 20–45 20–45 20–45
N.D. N.D. F M M M M M
x x x x
13–19 20–45 20–45 20–45 20–45
N.D. M M M M
13–19 20–45 20–45 20–45 20–45 20–45 20–45
M F M M M M M
20–45
M
x (X) x x (X) x x x
x (X) x x (X)
(X) (X) (X) (X) (X)
(X) (X) x (X) x x (X)
(X) (X) (X) (X) (X) (X)
(X)
x
(X) x (X) (X) (X) (X) (X) (X) (X) (X) x (X) (X) (X) (X) (X) (X)
x (X) (X) (X) (X) (X) (X) (X) (X) (X)
x x x x (X) x x (X) x (X)
x x
x
(X) (X) (X)
(X) (X) (X) (X) (X) (X)
(X) (X) (X) (X) (X)
(X) x x x x x
(X)
(X)
(X)
(X)
Tomb number is indicated (Tb). Specimens arranged by sex and age at death (blank cell: tooth not present; x: tooth present but not affected; (X): tooth with groove).
degrees of expression on different teeth. In order to analyze the variability in the degree of expression we analyzed all the RI1 involved (the mostly affected tooth); when not available, the LI1 was examined. Individuals whose I1 was unaffected were excluded from this analysis. Similarly, the only di2 affected was not considered. Overall, 27 upper central incisors were examined. The degree of expression of the groove (light or marked) was considered in relation with the age at death of each individual (Table S4, Supporting Information). A “light” groove appears to be more frequent in the (20–45) age group, and no “marked” grooves are present in the (13– 19) age group. Data on the position and the cervico-incisal extension of the grooves are summarized in Table S5 (Supporting Information). In some cases it was not possible to take all the measurements defined, because of the poor condition of the tooth surfaces. The cervico-incisal extension of the groove varied from 1 to 4.6 mm. Its distance from the cervix ranged from 0.2 to 1.7 mm, with average values in the three permanent tooth classes from 0.6 to 0.8 mm. The width of the groove varied from .13 to 1.9 mm, with different mean values in the three permanent tooth classes. American Journal of Physical Anthropology
DISCUSSION The combined analysis of the groove morphology, its position on the crown and distribution in the sample, allowed us to describe different aspects of this enigmatic enamel alteration. This, in turn, has allowed us to provide a framework within which trying to interpret its mode of occurrence. The first issue to address was whether the groove occurred during the development of the tooth or after eruption. The grooves can hardly have been the result of defects occurring during the developmental phase of enamel apposition, as the “parabolic” area of enamel affected does not follow the normal profile of enamel deposition. Also, the groove is extremely localized and it is not present on the labial surfaces of the teeth concerned. The appearance of the groove and its location in a well-delimited area of the tooth surface tend to exclude the result of some form of amelogenesis imperfecta (AI). In these cases, apart from the aspect of the enamel (hypoplastic and / or hypomineralized), the entire surface of the tooth is affected. Further, in most cases the entire dentition is concerned (Pindborg, 1982; Crawford et al., 2007). Finally, the SEM images allowed us to exclude an event which occurred during development, as in a few cases the groove happened to be
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AN ENIGMATIC ENAMEL GROOVE located on top of an “interruption groove”, a nonmetric trait of dentition (Fig. S2B, Supporting Information). Similarly, the defect can hardly be associated with noncarious cervical lesions. These pathologies are mainly documented in first premolars of the all four quadrants, and in general the lesions are more common on the buccal surfaces of teeth (Wood et al., 2008). The next step was to try to establish a possible relationship with extra-masticatory activities. However, wear produced by use of the teeth for work or daily activities (for therapeutic reasons, oral hygiene or from a constant habit of keeping objects inside the mouth), usually leaves typical, subparallel striations, easily detectable with the SEM and totally absent at the bottom of the grooves in the teeth examined. This makes it difficult to postulate the groove as the outcome of a functional activity. The position of the grooves on the lingual surfaces also makes it hard to suggest their possible intentional origin because of decorative, cultural, or ritualistic reasons. The grooves, being in a position not visible during social interactions, would have no decorative functionality, resulting in no expression of a particular status or in identifying membership in a specific group. The highly unusual morphology of the grooves also makes it hard to suggest their origin in friction between teeth from matching jaws; also, in the corresponding mandibular teeth, no traces were found that would suggest a particular type of malocclusion. Table S3 (Supporting Information) suggests that there is no relationship between calculus deposit and presence of the groove. Further, although in the subsample showing the groove the majority of individuals also displayed calculus, the latter occurred mostly on the lower anterior teeth. Thus if we consider all the factors described above, and take into account that the formation of the grooves must have occurred at a later stage after tooth eruption in the mouth, we believe that one working hypothesis is to consider the groove as the result of a chemical erosion because of some acid etching, where the term “erosion” is defined in the literature as “loss of dental hard tissue by a chemical process that does not involve the influence of bacteria” (Pindborg, 1970). Dental erosion is associated with different factors that can have both an extrinsic nature (e.g., food and drink) and an intrinsic one (e.g., gastroesophageal reflux disease or eating disorders) (Ten Cate and Imfeld, 1996). Dental erosion, commonly located on the lingual surface of the maxillary anterior teeth and on the occlusal surface of the lower canine (Johansson et al., 2012), is on the contrary usually absent from the front teeth of the lower jaw which are protected by the presence of the tongue and salivary glands (Robb et al., 1991). In this regard, it is noticeable that in our sample, there is the complete absence of the grooves in the teeth of young individuals (age group 7– 12) (although it remains to be established why a single individual has the groove on his/her di2). It is in this age range that the replacement of milk teeth usually occurs, followed by the eruption of the permanent teeth, in which the groove is documented. The absence of the defect in the dentition of juvenile individuals could be because of the fact that their teeth have not yet been exposed to acid attack for a sufficiently long period of time. Also, an association seems to exist between the groove occurrence and individual age with no grooves present in the dentition of individuals in the (7–12) age group—
2
although one di was affected, whereas frequencies are higher in the young adult and adult groups. More to the point, central incisors (the first anterior permanent tooth to emerge in the mouth) have higher frequencies than lateral incisors and canines, in this order, thus suggesting a relationship between the occurrence and the eruption order of these teeth. No relationship exists between groove occurrence and the sex of the affected individuals; but at the same time a significant difference exists in that males seem to have a higher number of teeth affected. The involvement of some kind of acid etching could also explain why the groove is located at approximately 1 mm from the cervix. Loss of the enamel tissue on the lingual surface of the affected teeth occurs in an area that in the living individual corresponds to the limit of the gingival margin, that is in an area no longer protected by the presence of the gum itself and perhaps more exposed to acid-type attacks. Within the broad interpretative category of acid etching involvement in the appearance of the grooves, a number of other morphological details still remain to be clarified, such as, for example, its shape, as it is not a groove of uniform width and depth but is broader at the apex; or the morphology of its edges, which seem quite sharp; or the exact involvement of the dentine, that will require a histological section of the tooth. In terms of when formation of the grooves occurred, the possibility that the process of erosion has taken place postmortem for some kind of very localized etching agent, although less plausible, remains to be explored in detail. Other possibilities, such as the combination of a mechanical pressure through a metal brace followed by some kind of chemical erosions, should be also taken into account. If the hypothesis of some kind of acid etching is confirmed, it will remain to be established why the attack produced such a localized mark, not diffused over a broader area of the lingual surface and, also, what might have been the factor(s) causing the erosion. It will be also interesting to assess whether this peculiar groove morphology can be observed in other populations from different archaeological contexts.
ACKNOWLEDGMENTS We are grateful to Sovrintendenza Archeologica del Veneto (Luciano Salzani and Paola Salzani) for the opportunity to study the Arano skeletal material. We would like to thank Marta Mariotti, Gilberto Montori, Silvia Bortoluzzi, Silvia Boccone, Giovanna Stefania, Luca Bachechi, Mauro Patalano and Alessandro Riga. Thanks also to Simon Hillson, Chris Dean, Theya Molleson and Alfredo Coppa for their comments.
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