The permanent dentition and supporting tissue of 140 Yanomama Indians ranging in age from three to more than 40 years was examined for malocclusion, caries, attrition, and periodontal disease. Their oral status is characterized by malocclusion (79%), anterior tooth crowding (55%), a low frequency of caries (l4%), periodontal disease (83%), and a linear progression of occlusal attrition with age. The Yanomama are recognized as having been geographically, genetically, and linguistically isolated for a minimum of 500 years. This situation permits the use of their dental condition to assess the hypotheses that admixture and/or tooth use is chiefly responsible for the widespread malocclusion found in many modern Yanomama populations. Because the Yanomama have seemingly not been affected by foreign admixture, and because they possess marked tooth wear evidencing heavy mastication, neither admixture nor lack of masticatory function can he responsible for a high degree of malocclusion.

INTRODUCTION

The dentition and jaws of many contemporary populations are characterized by high incidence of static and dynamic malocclusion, ranging in frequency from 22.4% to 91.4% (Hrdlicka, 1935; Mills, 1963; Horowitz, 1970). Although malocclusion is rarely found in early hominid and prehominid fossils (Pereira, 1972), it has been observed in the form of tooth crowding in some australopithecine material. (Oppenheimer, 1967). Still, high frequencies of malocclusion are apparently a relatively recent development in some groups of Homo sapiens. Precise causes for changes in the human masticatory system have not been established, but several hypotheses exist for the reduction in jaw and tooth size. Some of the notable hypotheses are: (1) a reduced need for heavy chewing (Benjamin, 1962; Dahlberg, 1963; Mahler, 1967); (2) the advent of tools as substitutes for teeth (Brace, 1964; Brace and Montague, 1965); and (3) possession of some adaptation that reflects selective pressures on a whole functional matrix which involves the teeth and jaws (Bailit and Friedlander, 1966). Another factor that may have contributed to increase in malocclusion, other than the three factors outlined above, is admixture resulting in large teeth in small jaws (Mills, 1963). Therefore, the primary purpose of this paper is to examine the hypotheses concerning dental crowding in a living population which possesses two necessary conditions: (1) low to absent admixture and (2) a huntergatherer type of diet and method of food preparation. The Yanomama Indians living in the Federal Territory of Roraima, South America, were selected, even though they might be classed as tropical forest village farmers in Steward's (l959) sense. The Yanomama have maintained genetic integrity for roughly 500 years.
 

MATERIALS AND METHODS

Three of the Yanomama Indians were the subjects of this study: (1) Surucucu (n=48) who are mountain dwellers and subsist mainly on small birds and bananas, (2) Tototobi (n=48), and (3) Catrimani (n=52). The Tototobi and Catrimani live in river valleys where game animals are plentiful and meat is the staple food. Thus, the tribes can be divided into two nutritionally similar groups: the Surucucu (higher carbohydrate) and Tototobi and Catrimani (lower carbohydrate). The dentition and jaws of the 148 Yanomama Indians (divided into the two generalized nutritional groups) were examine by one us (C.B.P.) for maloccusion, caries, attrition, and periodontal disease. Occlusal attrition was scored with Pedersen's (l955) Index of Attrition. Malocclusion was scored with the Canadian Index (Rubierto, 1958) and caries and periodontal disease assessed with Ramfjord's (l967) Periodontal Disease Index. The groups were divided into four age groups: (1) adolescents: 13-18 years, (2) adults: 19-29 years, (3) mature: 30-49 years, and (4) older to senile adults: 50+ years. However, the data in Table 1 are listed only by sex and with the sexes pooled.

o TOTOTOBI - New Tribes Mission. High Totobi river (affluent of the Demini river), north of the Amazon state near the border with Venezuelan.  o SURUCUCU - Evangelical Mission of the Amazon (Surucucu mountains, source of the Parima river). Federal Territory of Roraima. Near the Venezuelan border.  o CATRIMANI - Catholic mission of "Consolata". Middle of the Catrimani river, Cujubim falls. Federal Territory of Roraima.

Condition ---------------d y d + y d 9 cç + y

Crowding ---------------52.5---- 59.3---- 56.2---- 68.4---- 31.0---- 45.8

Overjet -----------------19.0 ---- 37.0 ----29.1------ 5.2 ----24.1 ---16.6

Overbite ----------------33.3 -----37.0 --- 35.4------ 5.2 ----13.7 ---10.4

Crossbite ---------------33.3 -----33.3 ----33.3 ------21.0 ----6.8 ---12.5.

Edge-Edge ---------------4.7 -----14.8 ----10.4 ------15.8 ----3.4 ----5.3

Mandibular shift ---------0.0 ------0.0 ------0.0 -------5.2 ----3.4 ----4.1

Diastema ------------------0.0 ------7.4 -----4.2 --------0.0 ---27.6 --12.5

Supernumerary teeth ----0.0 ------3.4 -----2.0 --------0.0 -----3.4 ---2.0

Periodontal disease ----- 61.9 ----82.7 ---77.0 -------94.4 ----93.1 -93.6

Caries -----------------------4.7 -----3.4 -----4.2 -------10.5 ----10.3- 10.4

Condition -----------------d g d+ç? d 9 d+9

Crowdling ------------------70.0 ----20.0---- 55.7----- 64.9---- 39.4---- 52.7

Ovejet -----------------------13.5----26.6 ----17.3 -----12.9 ----29.5 ----20.9

Overbite ----------------------5.4 ----13.3 -----7.6 -----22.0 ----22.5 ----17.6

Crossbite --------------------29.7 ----13.3 ----25.0 ----28.5 ----18.3 -----23.6

Edge-Edge ------------------18.9 ---- 20.0 ---19.2 ----14.3 -----11.3 ----12.8

Mandibular sliift -------------5.4 -------0.0 ----3.8 ------3.9 ------1.4 -----2.7

Diastema ---------------------2.7 -------0.0 ----1.9 ------1.3 -----11.8 -----7.4

Supernumerary teeth -------2.7 -------0.0 ----1.9 ------1.3 ------2.8 ------2.0

Periodontal disease ------- 81.0 -----50.0 ---50.7 ----78.9 -----88.7 -----83.7

Caries -----------------------24.3 -----26.6 ----25.0 ----15.6 ----11.3 -----13.5

Conditions accounting for the 77.6 % malocclusion in Yanomama. Frequencies are for individuals with one or more caries.

RESULTS

Malocclusion shows no significant sexual dimorphism in either the Surucucu (X2 = 1.77, p>0.05), or the Tototobi and Catrimani (X2=2.60, p>0.05). The two groups (mountain, valley) also have no significant difference in their frequencies of malocclusion (X2 = 0. 164, p>O.O5). Frequencies of traits denoting malocclusion (overjet, overbite, crossbite, edge-to-edge bite, and mandibular shift) are shown in Table 1. The incidence of caries for all of the 148 Yanomama Indians is 13.5 %, which is considerably lower than had been expected (Table 1). The lowest frequency of caries in the two nutritional groups was 4.2 % in the Surucucu (higher carbohydrate diet). The Catrimani and Tototohi had 25.0 % and 10.4 % caries, respectively. The frequency of periodontal disease is relatively uniform in the Yanomama. The Surucucu have the lowest frequency of all (77.0 %). The Catrimani have 80.7 %, and the Tototobi have 93.6% respectively (Table 1). The degree of attrition in the Yanomama shows an almost direct relation to age.

DISCUSSION AND CONCLUSIONS

Neither malocclusion nor severe occlusal attrition seems to seriously impair the masticatory efficiency in the Yanomama Indians. Physiological occlusal abrasion over time eliminates the tooth cusps without impairing the masticatory efficiency in any obvious way. Attrition increases with age, considerably reducing the total crown height. Physiological occlusal abrasion and vigorous mastication are seemingly beneficial to periodontal health. In addition, the amount and degree of malocclusion are not sexually dimorphic.

YANOMAMA ORAL CONDITION

Admixture cannot be the primary factor in the high frequency of malocclusion, since the Yanomama have been geographically isolated for at least 500 years. Thus, neither reduced chewing not admixture explain the high frequency of malocclusion. Since tooth crowding seem,, to account for so much of the malocclusion, future studies are needed. These studies should concentrate on understanding the processes that determine positioning, tooth and jaw size, and the adaptive value of ideal occlusion, if any.

LITERATURE CITED

Bailit NN, and Friedlander JS (1966) Tooth size reduction: a hominid trend. Am. Anthropol. 68:665-672. Benjamin FB (1962) Personal communication.
Brace CL (1964) The fate of the 'Classic' Neanderthals: a consideration of hominid catastrophism. Curr. Anthropol. 5:3-43.
Brace CL, and Ashley Montague MF (1965) Man's Evolution: an Introduction to Physical Anthropology. New York: Mactnillan Co. Dahlherg AA (1963) Analysis of American Indian dentition. In DR Brothwell (ed.): Dental Anthropology. New York: Pergamon Press, pp. 149-177.
Hrdlicka A (1935) Normal variation of the teeth and jaws and orthodonty. Int J Orthodont 21:1009. Mahler PE (1971) Further evidence for the reduction of post-Pleistocene hominid dentition. Am J Phys Anthropol 35(2):268.
Mills JRE (1963) Occlusion and malocclusion of the teeth of primates. In DR rothwell (ed.): Dental Anthropology. New York: Pergamon Press, pp. 29-51.
Oppenheimer AM (1967) Tooth size reduction: a hominid trend. Am Anthropol 69 (5):514-515.
Pedersen PO (1955) The degree of attrition of the deciduous teeth and first permanent molars of primitive and urbanized Greenland natives. Brit Dent J 99:35-43.
Pereira CB (1972) Periodontal Disease, Occlusion, Attrition and Other Dental Characteristics in Primitive Brazilian Men. Campus Avançado Boa Vista / Roraima. Universidade Federal de Santa Maria.
Rafjord SP ( 1967) The periodontal disease index. J Periodont 38:602-610.
Rubierto D (1958) The evaluation of community dental health. A systein for recording statistical analysis. Dental Statistics and Dental Research Section, Division of Medical Statistics. Department of Health for Ontario, Canada.
Steward JH, and Faron LC (1959) Native Peoples of South America. New York: McGraw-Hiil

(**) Department of Anthropology Arizona State University, Box 872402, Tempe, AZ 85-287-2402 USA (CGT)

	Christy G. Turner II e Cléber em Temple, Arizona,  ocasião em que Cléber ditou aulas no curso de pós  gradução em antropologia da Universidade de Arixona,   a convite do Prof. Turner II
	Christy G. Turner II e Cléber no Rio de Janeiro, em 1982,   ocasião em que o Prof. Turner veio ao Brasil, pesquisar  crânios de Sambaquis e solicitou o auxílio de Cléber.

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