text: how long does it take to fill 7 cavities in one sitting (dentists!)? ok it u have like 7 cavitys in ur mouth how long would u have to sit there and have the cavitys filled...aproximatly that would depend on how large filling is going to be.  if they were all simple class v fillings then it could be done in 30 minutes or so.  if they were all more complex fillings involving 4 sufaces... it could take 2 1/2 hours or so.  generally the dentist will prep all the teeth and then fill all of the teeth.