endodontics vs endodontia

endodontics and endodontia both are nouns.

Word	Noun	Adjective	Verb	Adverb
endodontics	Yes	No	No	No
endodontia	Yes	No	No	No

As nouns, endodontics and endodontia are synonyms defined as:

endodontics and endodontia: the branch of dentistry dealing with diseases of the dental pulp

endodontics (noun)	endodontia (noun)
the branch of dentistry dealing with diseases of the dental pulp	the branch of dentistry dealing with diseases of the dental pulp