There are many studies showing a causal connection between mercury fillings and Alzheimer's. I don't have the cites handy but Ill get them . One study on nuns that failed to find a link was invalid becuuse the nuns were divided into groups based on how many fillings they had . This is improper since a nun with three fillings might have have more hg exposure than one with ten depending on whether the fillings are high copper,TMJ, age of fillings gum chewing ,other metals etc. Also, the study included nuns with no teeth and assumed their hg exposure from fillings was therefore zero. Hg s halflife in the brain is 20 years. The nuns with no teeth probably had greater lifetime hg exposure than any others.
Re the Saxe study, it lacked a control group and was conducted by a biased ADA dentist (Saxe),not a pHD toxicologist.