* From the Orthodontic Department, University of Manitoba, Winnipeg. Aided in part by the National Research Council Grant DA-131 and by the Winnipeg Children's Hospital Research Fund and by the National Health and Welfare Grant 606-7-222.

From the Forsyth Dental Center-Harvard School of Dental Medicine, Boston, Massachusetts.

*Supported in part by United States Public Health Service Grant DE-02272.

Taken in part from a thesis in partial fulfillment of the requirements for the degree of Master of Science, Loma Linda University, School of Dentistry.

From the Departments of Anatomy and Dental Health, University of Birmingham.

From the Departments of Histology and Orthodontics, University of Illinois at the Medical Center, College of Dentistry.