This study examined the relationship between gonial angle and the presence of mandibular tori in 185 individuals. It found a weak correlation between a smaller gonial angle and the presence of mandibular tori, though this correlation was not statistically significant. When edentulous individuals were removed from analysis, no correlation was observed. The gonial angle ranged from 110 to 147 degrees across all subjects, while 34 individuals exhibited mandibular tori ranging from less than 2mm to greater than 4mm in size.

1. Gonial Angle and Mandibular Torus
Adam Martinetti and Karina Coscuna
Humboldt Center for Evolutionary Anthropology, Department of Anthropology, Humboldt State University, Arcata, California
Introduction Results
• The mandibular torus is an exostosis found on the lingual side of the mandible Of the 185 individuals observed, 34 exhibited some amount of mandibular torus
(an extreme example is seen, left). Mandibular tori usually manifest bilaterally (listed by class below). Gonial angle ranged between 110 and 147 degrees in all
(Hassett 2006). subjects. Gonial angle and presence of tori were not quite significantly correlated
within our sample (p=0.0522); when edentulous individuals were excluded from the
• Oral exostoses are benign bony growths, of debated etiology, on the sample, no variance was present (p=0.3664).
maxilla, mandible or palate (Hassett 2006). The presence of all oral exostoses are D is t r ib u t io n o f g o n ia l a n g le
correlated with masticatory stress (Scott et al. 1991). 15
A n g le w it h o u t e x o s t o s is
• Gene variation studies have shown several disorders associated with palatal torus A n g le w it h M T
to be highly correlated with a decreased gonial angle (Van Wesenbeeck et al. 10
F re q u e n cy
2003).
5
• Another phenotypic indicator of the gene responsible for mandibular torus
development, if strongly correlated, could increase the utility of the trait in
bioarchaeological investigations. 0
100 120 140 160
G o n ia l A n g le
Torus Size Age Distribution in Sample
Questions: Does the presence of mandibular tori relate to the gonial angle? Do different exostoses develop at
similar or distinct gonial angles? Torus Class Frequency 80
70
<2mm 6 60 With Mandibular
50
Torus
2-4mm 21 40
With Only Palatal
Torus
>4mm 7
30
With No Exostoses
Materials and Methods 20
Total 34 10
0
10 - 19 20 - 39 40 - 59 60 - 79 80 - 101
• 185 individuals were analyzed from the Maxwell Museum of Anthropology’s Documented Skeletal Collection. Torus by Sex Exostosis Distribution in Sample
Measurements were taken from all individuals within the collection possessing intact mandibles and maxillae.
Sex With MT Total
• Individuals under ten years of age were excluded. Male 25 113
Female 9 72
• Mandibular torus measurements were taken using digital calipers and classified using the method first established by Total 34 185
Eggen (1989), based on the maximal lingual width.
Discussion
• Gonial angle was measured using a mandibulometer (pictured right).
• The lack of a standard method for measuring the mandibular torus can obfuscate
• Palatal tori, buccal exostoses and maxillary exostoses were recorded but not measured. results (Eggen 1989; Hassett 2006). Whether considering all individuals with tori as
part of the same population or separating them by size, as suggested by Eggen
• Dental attrition was scored solely on the molars using the quadrant-system established by (1989), no statistically significant variance was found.
Scott (1979).
• Both mandibular torus and gonial angle tend to be reduced with edentulism (Eggen
• Information on age, sex and cause of death was provided by the museum. and Natvig 1986). The high degree (52%) of individuals we recorded experiencing
some degree of antemortem edentulism is skewed due to the over-representation of
• A Mann Whitney-U test for variance was performed using GraphPad Prism software. Significance was set at p < 0.05. the elderly in our sample.
Acknowledgments
We wish to thank Ariel Gruenthal for her help with this project as well as the faculty at the Humboldt Center for Evolutionary Anthropology for their invaluable input. This project would not have been possible without support • Dental attrition and dental crowding were omitted from our analyses due to the high
from the Department of Anthropology, the College of Arts, Humanities, and Social Sciences, and the Office of Research at Humboldt State University. Skeletal samples were part of the Documented Skeletal Collection from the
Maxwell Museum of Anthropology. We also wish to thank their faculty, in particular, Ms. Carmen Mosley and Dr. Heather Edgar for their help with this study.
degree of edentulism in our sample.
References
Eggen, S. Torus mandibularis: an estimation of the degree of genetic determination. Acta odontologica Scandinavica 47, 409–15 (1989). • If the number of edentulous samples in this study with exostoses (25%) indicates an
Eggen S. & Natvig B. Relationship between torus mandibularis and number of present teeth. Scandinavian Journal of Dentistry 94(3), 233-240 (1986).
Hassett, Brenna. Torus Mandibularis: Etiology and Bioarcheological Utility. Dental Anthropology 19(1) 1-14 (2006).
Igarashi Y., Ohzeki S., Uesu K., Nakabayashi T., and Kanazawa, E. Frequency of mandibular tori in the present-day Japanese. Anthropological Science 116(1), 17-32 (2008).
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Johnson, C. Torus mandibularis: a genetic study. American Journal of Human Genetics 17, 433–442 (1965).
Scott GR, Halffman CM, and Pedersen PO. Dental conditions of Medieval Norsemen in the North Atlantic. Acta Archaeologica 62: 183–207 (1991).
their lifestyle is warranted to determine what could be generating this stress.
Suzuki, M. and Sakai, T. A familial study of torus palatinus and torus mandibularis. American Journal of Physical Anthropology 263–272 (1960).