A Brief Comment on Functional Use of Intentionally Filed Teeth     Dental mutilation, also known as intentional dental modification, is an interesting cultural practice that has enjoyed a long and diverse history in many populations around the globe. There are many explanations for groups to artificially alter the morphology of their teeth. For instance, some researchers believe dental modifications are indicative of beautification (Fastlicht 1976; Romero 1958; Rubín de la Borbolla 1940), ethnic markers or tribal identification (Handler 1994; van Reenen 1978a, 1978b, 1986), and social status (Fastlicht 1948, 1976). For those interested, Milner and Larsen (1991) offer a detailed discussion of this practice. Aside from these reasons for engaging in this interesting behavior, a fundamental question exists when considering intentional dental modification: What is the longevity of filing signature marks on modified teeth under masticatory function? Several authors have examined various methods for filing teeth (Havill et al., 1997; van Rippen 1917). In a gross macroscopic example, van Rippen (1917) states that blades manufactured from obsidian were used to file or cut the incisal and mesial and/or distal margins of teeth in some prehistoric Mesoamerican populations. Havill and co-workers (1997) utilize scanning electron microscopy (SEM) to examine the signature marks left on intentionally modified teeth. Their study suggests that striations on the incisal borders of teeth are indicative of intentional filing.

    In this study, we examined a modified mandibular incisor found in the vestibule of Cueva de las Arañas (Cave of the Spiders), an ossuary cave located in the Olancho Valley of northeastern Honduras near Catacamas. The cave is situated a few hundred meters from Cueva del Rio Talgua (Cave of the Glowing Skulls), an important ossuary cave discovered and investigated in 1994 by Dr. James E. Brady of California State University-Los Angeles. Extensive investigations in the cave included survey and mapping, excavation of the cave entrance, documentation of the black and red cave paintings, and in situ analysis of the calcite veneered human remains. A radiocarbon date derived from charcoal recovered near the passage entrance to the ossuary chamber in the back of the cave was calculated at 915 B.C., a date similar to those from Cueva del Rio Talgua. There are no radiocarbon dates available from the entrance of the cave where the modified tooth was recovered. Besides the modified tooth, excavations in the vestibule recovered additional human remains, numerous Classic period (300-900 AD) pottery sherds, worked shell, stone beads, hematite objects, obsidian blades, faunal remains, and a fragment of a corncob.

    We documented the filed (modified) tooth from a gross morphological perspective as well as using microscopic methods. The tooth is a mandibular left lateral incisor that exhibits characteristics consistent with intentional filing of the incisal, mesial, and distal margins (see Figure 1). The type of modification corresponds to Romero's (1958) C-6 category. As a result of the modification, a band of dentine is exposed across the incisal margin of the tooth. In addition, a small area of fractured enamel is evident at the labial apex of the crown. This defect suggests the tooth functioned normally after modification.

    Several photomicrographs of the tooth surface and the incisal margin were produced with a Cambridge Stereoscan 360 Scanning Electron Microscope. The enamel surface was examined in an attempt to identify evidence of intentional modification (such as striations) or signatures of functional wear (such as pitting and linear scratches). Dr. Charles Brooks and Mr. Gregory Jones of the Department of Material Science and Engineering of the University of Tennessee provided access to the SEM as well as several hours of technical assistance in sample preparation and image production. All specimens examined were sputter coated with gold by a Hummer I Technics sputter coater within a nitrogen plasma field. Specimen surfaces were scanned at 20Kv with varying probe currents in an effort to maximize image quality. Finally, black and white Polaroid images were taken of select features and surfaces.

    Along the labial and incisal surfaces of the tooth, filing marks similar to the type reported by Havill and co-workers (1997) were not present (see Figures 2, 3 and 4) . However, most surface features evident were consistent with normal attritional processes (see Teaford 1991; Teaford and Lytle 1996). Scratches and pits were observed on the mesial and distal plateaus. Several scratches were also present along the incisal margin. It appears that attritional processes have obliterated filing marks. The tooth does show evidence of trauma at the labial incisal margin where a small area of enamel has fractured (Figure 2). Although not visible in these figures, a distally oriented wear facet is present on the lingual aspect of the incisal margin, possibly suggesting that the upper incisors were also modified.

    In order to examine the potential microscopic modifications within the architecture of the tooth, three 1.2mm sections were cut from the embedded crown fragment using the techniques outlined by Marks and co-workers (1996). Dr. Murray Marks of the Department of Anthropology at the University of Tennessee Knoxville provided access to the Mineralized Tissue Laboratory where the tooth was imbedded and thin sections were cut. The labial portion of the crown separated from the root as the tooth dried during decompression in the SEM chamber. Therefore, it was possible to examine the entire enamel and dentine structure without embedding the complete tooth or the lingual half of the modified crown. The thin sections were examined by transmitted light microscopy (TLM) and closely scrutinized for the presence of dead tracts. We specifically focused on the mesial plateau section because it was adjacent to most heavily modified portion of the crown and would have been directly impacted by filing.

    Using gross macroscopic and SEM methods of investigation we did not find evidence of filing as defined by Havil and co-workers (1997). Based on this, we assume that the tooth was modified and normal masticatory processes resumed post filing. Attritional wear is evident on all surfaces of this tooth. No dead tracts were observed in any section of the crown including the heavily modified mesial plateau (Marks, Personal Communication 1998). The lack of dead tracts within the dentine below the modified areas suggests that attrition quickly erased the signatures of artificial alteration. However, we found no reference specifically outlining the time required for the development of dead tracts. Therefore, we are unable to provide an estimate of time since modification. Had this individual lived longer, the modified crown would have gradually reduced. There may be a bias in the archaeological record because natural tooth wear in older individuals might destroy evidence of intentional modification on teeth (Milner and Larsen 1991). That is, through the natural process of tooth wear consistent with a gritty diet (see Teaford and Lytle 1997), individuals who possess dental modifications as young adults may actually wear the modification away. Thus as time passes the teeth may not reveal intentional modification even though those teeth may have been modified.

    In this study, we examined a filed lateral mandibular incisor from Honduras to see if evidence of filing on the distal and mesial borders of the incisal surface is present. Based on our investigation, the pits and striations evident under SEM are consistent with marks made by normal masticatory function. Any signature filing ?marks? have either worn away or were not present initially after the filing episode. The longevity of filing signature marks is potentially short due to high attrition in most maize-dependent Mesoamerican populations.
 
 

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