Players get HM #04 Strength in the Safari Zone after retrieving the lost teeth. Once players have the HM, they can teach the move Strength to any number of eligible Pokémon. The move allows players to move heavy boulders out of the path.
To start the quest for the missing teeth, players need to talk to the Warden of the Zone. He will tell the player that he is missing his golden teeth. Afterwards, the player will need to walk to Zone 3 of the Safari Zone. Zone 3 is to the southwest of Zone 2 where the Warden's house is.
In order to get to the area faster, players can use Surf to cut across lakes. This makes it easier for players who do not know the precise location of the golden teeth, as the Safari Zone measures time as the number of steps taken.
Players can use the Strength HM as soon as they obtain it. There are a few extra items, such as a rare candy, that can be obtained in the Safari Zone once the player has a Pokémon that can use strength. The player will mostly use Strength in future dungeons, so the move should be taught to a Pokémon the player typically keeps in their party.