orthodontia vs dental orthopaedics

orthodontia and dental orthopaedics both are nouns.

Word	Noun	Adjective	Verb	Adverb
orthodontia	Yes	No	No	No
dental orthopaedics	Yes	No	No	No

As nouns, orthodontia and dental orthopaedics are synonyms defined as:

orthodontia and dental orthopaedics: the branch of dentistry dealing with the prevention or correction of irregularities of the teeth

Other synonyms of orthodontia include dental orthopedics, orthodontics, orthodonture.

orthodontia (noun)	dental orthopaedics (noun)
the branch of dentistry dealing with the prevention or correction of irregularities of the teeth	the branch of dentistry dealing with the prevention or correction of irregularities of the teeth