From the Division of Periodontics, Columbia University School of Dental and Oral Surgery.

This investigation was supported by United States Public Health Service Research Grant DE 02059-01 to DE 02059-03 from the National Institute of Health, Bethesda, Maryland, and in part by the Joseph E. Levine Foundation.

Read in part at the January 1975 meeting of the. Midwestern Component of the Angle Society.

From the Department of Orthodontics, University of Bergen, Norway.

From the Department of Orthodontics, University of California, School of Dentistry, Los Angeles, California.

Presented before the Midwestern Component of the Edward H. Angle Society, January 1975.

From the Department of Orthodontics and Dental Research unit of the University of the Witwatersrand, Johannesburg, South Africa.

From the Department of Orthodontics, School of Dentistry, Niigata University.

From the Departments of Orthodontics, Loma Linda University and Chemical and Materials Engineering, California State Polytechnic University.