WotLK question about dungeon instances reset

[ExSaint123]

i was accompanying my friends who are new to wow and while we were in a dungeon, after a few wipes (more or less 10) which took probably a few hours too (dungeon was big and we were noobs), when we went back into the dungeon after our nth wipe, the mobs suddenly all respawned as if the instance was reset. do instances reset after a certain number of wipes or after a certain time has passed?

[skullatbash]

raid or 5-man dungeon?

Usually raid mobs have 2h respawn timer

Btw instances can be resetted even by right click on your portrait -> reset all instance
By doing this all mobs will be alive again
unless you guys have killed a boss, in that case instanceID is saved for a while, this happens for raid or 5-man heroic dungeons

[Ironbible]

5man dungeons will reset at 4:00am server time unless their is still a player inside the dungeon. If all players leave the instance it will reset to the new day.