Is dry gangrene treatable ?

No: Dry gangrene means that tissue is dead but not infected. If left alone, it will auto-amputate, or it can be surgically removed. Either way, the tissue will not heal or grow back.

No treatment: Dry gangrene by definition is dead tissue. If it is dry you can allow it to seperate and fall off depending on where it is. The most important issue is why it happened and how to prevent it from recurring. The body will heal the living tissue and the gangrene will fall off like a scab.