R' Menachem Mendel Schneerson, z"l would write to people that a Segula for healthy teeth is connected to kiddush Levana
Does anyone know the source of such a concept?
Side point: many times by kiddush Levana he would touch his teeth.
The Taamei Haminhagim says that "saying 'And I shouldn't have a toothache' after 'My enemies shouldn't touch me for evil' is a Segulah against toothache" is from Reb Yisroel Ruzhiner.
Some say that it's in the Siddur Yaavetz.
I found it in the "Siddur Beis Yaakov" (though only in brackets and Rashi script, and is from 1881). but not in Siddur Yaavetz (which was printed in Altuna in 1747 - during R' Yaakov Emden's lifetime and within his city).
So you should probably take the source which links it to Reb Yaakov Emden with a grain of salt.
. Also, to note that the comment linking Reb Yaakov Emden to this Segula also says that the connection seems weak.
There seems to be a Chabad Minhag to do so. See this: