-odontiasuff. The form of, manner of treating, or condition of the teeth: orthodontia.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.-odontia a combining form occurring in compound words that denote a condition of or treatment applied to the teeth (orthodontia). [see -odont, -ia] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.