leaking toilet?

we have a push button toilet which is leaking from the back. My husband took the cisten off the pan and we sealed all the screw holes with sealent- which are now fine.

Having left it half an hour we found we still had a leak. (bear with me while I try to explain!)
At the back of the toilet pan there is a shallow area where the cisten sits: our cisten doesn't sit snug on the pan, leaving a gap around the bottom- if the toilet hasn't been flushed for a while there seems to be a build up of water in this shallow area which "overflows" trickling down the pan. We used to have a sealent along there but obviously the water found a way out still. Should we attempt to seal this area completely round the bottom of the cisten??