In order to investigate the characteristics of the facial complex of the Mayo Indian and to make comparisons between the facial complex of the Mayo Indian and the facial complex observed in other ethnic groups, measures of facial angles and linear relationships were obtained from a group of Mayo Indians in the state of Sonora, Mexico.

A simple of thirty subjects, seventeen boys and thirteen girls, with a mean age of 18.3 years was selected for this study. The criteria for selection was based on the integrity of the dental arches, occlusion and tooth morphology. Plaster casts and cephalometric x-rays were made and traced in the standard manner, and the analyses of Downs, Riedel and Wylie applied. Mayo mean values were compared to the mean values for Caucasian, Navajo and Chamula groups. Numerical and graphic comparisons were also made to the American Chinese and American Japanese. The level of significance in difference between means observed for the four primary groups compared was determined by the "t" test.

The results of the study indicate that generally speaking Mayo and Chamula skeletal features equate each other, whereas Navajo and Japanese skeletal features most closely resemble those of the Caucasian, and Chinese exhibited a more retruded chin and the steepest mandibular plane. The dental patterns of the various ethnic groups studied reveal a marked tendency toward dental procumbency when compared to the Caucasian.

On the basis of the data of this study the following conclusions are indicated:

  1. Definite and measurable differences exist in the facial and dental patterns of the six ethnic groups compared.
  2. Statistically significant variation in the relationship of maxillary and mandibular denture bases can occur and still present normal occlusal relationships.
  3. Normal occlusal relationships can be present even with incisors that are heavily angulated toward procumbency.
  4. The prognathism attributed to the Mayo is mainly a dental prognathism, with the maxillary denture playing a primary role.
  5. The dentofacial difference of racial groups are sufficiently unique so that the standards of one should not be applied to another without modification.
  6. When compared to the five other racial groups, the Mayo profile resembles the Chamulas' skeletally, and the Chamula and Navajo dentally.
  7. Skeletal differences between Mayo and Caucasian are limited to the forward position of the Mayo maxillary denture base; dental differences are apparent in all measures due to the procumbent characteristics of Mayo maxillary and mandibular incisors.
  8. When the maxilla is protracted in relation to the cranium and there is a large A-B difference, a concomitant increase in facial convexity is noted along with an increased procumbency of the incisors.

LLU Discipline





Graduate School

First Advisor

Thomas J. Zwemer

Second Advisor

Kenneth R. Lutz

Third Advisor

Howard W. Conley

Fourth Advisor

Gayle H. Nelson

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Head; Indians, Central American; Craniometry



Page Count

vi; 63

Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


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