$r(1,4) is the same as $ran(1,4), try using elseif it come in handy for big scripts.

Example:

on *:text:!dentist*:#: {
  /set %dentist $r(1,4)
  if (%dentist == 1) { msg $chan WAAAAAAAAA I DON WANNA GO TO DE DENTIST WAAAAAAAAA :'O }
  elseif (%dentist == 2) { msg $chan I gotta get a tooth pulled YOUR NOT GETTING MY TOOTH!!! :-X }
  elseif (%dentist == 3) { msg $chan I Juft Gwot Mye Toof Puwwed }
  elseif (%dentist == 4) { msg $chan I LIKE DENTISTS }
}

Then again if you get the $gettok statement up there then use that.