It sounds semi-plausible until you skim the paper and notice that they seem to be conceding that if the linkage exists, it's happening prenatally because of the mother's fillings. That seems like it would greatly attenuate the effect suggested, and also makes it reminiscent of the vaccine claims.
Also, much of the writing tone and rhetoric is floridly crank-style.
It can't be because of the child's fillings. Most autistic children are diagnosed well before age 6, which is about when baby teeth start to fall out. How many kids get cavities filled in baby teeth? Some probably, but I expect most diagnosed children have never had a cavity filled.
Also, much of the writing tone and rhetoric is floridly crank-style.