dog wants to dominate other dogs

When my dog meets another it's calm as they sniff each others nose and tail then my dog will pounce and pin it _to the ground.After my dog has command she'll let the other up & they can be buds.While I understand pack-alpha behavior I'd hate to have vet bills or worse.While I've been hesitante to use a chocker on her,I'm thinking that might clue her in.

The only time I've seen a dog do that to another dog was to attack it. And to make matters worse once a dog is on it's back and scared it will cause other dogs to attack too, even normally docile ones.
   
The dog going on it's back is doing so to be submissive and is frightened. You are right to be concerned about a possible attack, I think it's just a matter of time.
   
I never use choke, pinch or shock collars on a dog. I would use a standard harness that has a ring in the center of the chest area and that is where I'd hook the leash. Having done so I would allow my dog to get close to another dog as long as he is nonthreatening. Watch his body language and listen for growls. I would not allow him to pin another dog down.
   
Hopefully with some carefully supervised socialization, your dog will get over his desire to pounce on another dog.
   
Good Luck!