Primary researches on the matter were conducted a few years ago:
http://www.overclockers.ru/lab/32457/o-prakticheskoj-polze-zubnoj-pasty-v-sojuze-s-sistemami-ohlazhdeniya.html
http://www.overclockers.ru/lab/41032/poisk-i-testirovanie-alternativ-termopasty.html
use google translate
:banana: