well, i think it starts from childhood where until recently "i would say 15-20 years ago" dentist often were the evil characters that cause others to feel the pain & even seems to enjoy it, now it got better & the dentist character n cartoon is more balanced even that u will still find evil ones, also another factor is that as u said some procedures r more painful specially when not done n the proper time- so once a person undergo such procedures & have a bad experience & share that bad experience with others- those others will certainly not view dentist favorably & will think much more than twice before visiting a dentist even f it's really needed. finally i would say "it all starts n kindergarten & school". good post- well done, have a good day