dementia vs dementedness

dementia and dementedness both are nouns.

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

As nouns, dementia and dementedness are synonyms defined as:

dementia and dementedness: mental deterioration of organic or functional origin

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