While they have indeed bred dogs that can handle boar and bears (yep, even bears) I'll let you know that hunting either with only dogs and a pistol is pretty dangerous, and imo, stupid. You're likely to end up with at least one dead dog, and potentially get injured yourself.
If you plan on killing a bear with a handgun, it had better be a damn powerful round...I'd say .44 mag or more. Their skulls are extremely thick so the bone tends to deflect bullets, and they can take multiple shots to the body and still keep rolling. A revolver is typically a MUCH better choice than a powerful single shot pistol.
If you're considering using the dogs to bait the boar or bear, and keep it occupied while you try and get a shot off, I'd advise against it...you're going to end up chased up a tree (if you're lucky) and with a bunch of dead dogs.
I've heard the trick to pistol hunting a dangerous animal like that is to do it from a stand, not just walking around. Gotta get the drop on them, because if they get a chance to fight back you're in trouble. Boar are NASTY...trust me, they're all over Ft. Stewart.