dementedness vs dementia

dementedness and dementia both are nouns.

Word	Noun	Adjective	Verb	Adverb
dementedness	Yes	No	No	No
dementia	Yes	No	No	No

As nouns, dementedness and dementia are synonyms defined as:

dementedness and dementia: mental deterioration of organic or functional origin

dementedness (noun)	dementia (noun)
mental deterioration of organic or functional origin	mental deterioration of organic or functional origin