Dr. Holmes practiced general dentistry in Eldridge, Iowa, from 1978-1989. He became an adjunct faculty in the Department of Family Dentistry at Iowa during this time. After completing his specialty training in periodontics in 1991, Dr. Holmes became a group leader in Family Dentistry. In 1997, he joined the faculty at the University of Colorado where he served as chair of the Division of Comprehensive Care. In 2004, he returned to Iowa to accept the DEO position of the Department of Family Dentistry.
Dr. Holmes researches issues about faculty mentoring, curriculum design, and educational outcomes assessment. He has also investigated the oral health characteristics of Sudanese refugees who have resettled in Colorado.
Dr. Holmes ia clinical licensure examiner for the Central Regional Dental Testing Service (CRDTS). He is also a member of Omicron Kappa Upsilon honorary dental society, the Pierre Fauchard Academy, the International College of Dentists, the American Dental Education Association, and the American Dental Association. He is a manuscript reviewer for the Journal of Dental Education.