A/aleykum warax wbk...
 well with the little dental knowledge that i have learnt in the past 5 years..TEETHING DOES NOT CAUSE DIARRHOEA...it is always a complaint of mothers to say that the child is having diarrhea coz of teething.....Teething which is the process through which the teeth push through the gums concidentally takes place at a time when maternal defense that the child was born with has been exhausted and their own immune system is not strongly built as yet....irritation of the gums could be caused by teething..but severe systemic upsets.irritability,crying,loss of appatite etc.are unrelated to teething and a physician should be consulted...

first of all i thanks to allah that allow me to participate the discussion ofdoes teething cause diarrhea , after that iam greeting all the participaters in the greeting of islam (a salaamu calaykum wa raxmatulaahi wa barakaatu).

if i start for my point of view, teething occur normally after the child is 6 months and latter , that is not that teething cause the diarrhea but its the child recieved immunity from his mother , when the child delivered, and we know that the immunity wear off or go off at the time of 6 months and surrounding that areas , so the child get in a new phase , and his immunity is still underdeveloped . so any normal flora that stayed in the gasrtointestinal tract  get a chance to approach a new infection causing the diarrhea. so that it is "achange of one state into another"
so i concluded my idea and my little knowledge that the cause is normal flora esp eschericoli(E.coli ) one of the enterobacteriae that also causes the baby acute bacterial meningitis , are the cause behind this problem , and so many other microorganisms e.g fungi ( candidiasis) and etc

 thanks