Could braces fix my huge overbite for sure? how do docs guanrantee this?

Overbite: No, and there are never any guarantees regarding treatment outcome. Some orthodontic problems require surgery. Get two or even three orthodontic consults in your area and after a careful evaluation, they can explain what they feel can and cannot be done and how best to accomplish that.

Carefully: Overbite, either horizontal or vertical, is usually just the tip of the iceberg. A qualified orthodontic specialist will fully evaluate your malocclusion and then discuss treatment options with you. There are no guarantees, but know that with full cooperation on your part, and the team of specialist required for your care, the result will be remarkable.

There is no warranty: Whether the overbite is dental or skeletal can have a big impact on treatment. If your jaw structure is incorrect with huge overbite, the treatment may involve braces along with surgical procedures. Medical treatment always "AS IS" and without any warranties of any kind. Only reasonable medical probability.