Ive never had a filling, or anything done to me at the dentist other than a polish. I hardly ever used to brush when i was a kid, and my sisters did every morning and night, and they have had fillings almost every trip to the dentist. i brush now, but not for the sake of wanting to help my still perfect teeth, its mainly because of icky morning breath.
Im certain that toothpaste manufacturers and dentists work together. The toothpaster makers put something into toothpaste that rots teeth and gums - that makes you go to the dentist - who tells you to brush your teeth. and so the nasty conspiracy of toothpaste and dentists lives on, while they make a fortune out of everyone.

As for the dentist spider - i think if such a thing were around it would have been captured and put through tests by the government and some a story will be released to the media about a water problem causing hillusinations of giant spider men.