What are some instances when dental braces are the only option, as opposed to bonding or veneers?

Degree: The greater the degree of malalignment, the more of a chance you will need traditional orthodontics. Make sure your advice is coming from a board certified orthodontist. Most aren't.

Severe Crowding: If your teeth are severely crowded and malpositioned, then laminate placement would be difficult and esthetics would be questionable. Since your occlusion is a mystery, consult with a local dentist.

Straight Teeth: Use of braces may provide the most conservative and predictable final results with straight and healthy teeth.

Many: Moderate to severe crowding or spacing, excessive vertical overbite or horizontal overjet, skeletal imbalance, and many other situations. See a fully qualified Orthodontist for initial examination (usually free) to discuss what Orthodontics can do for you. Often Orthodontist and Restorative Dentist work hand in hand to provide you with best possible care. Seek quality, not shortcuts.

There are some: Lots of crowding or conversely lots of spacing. A bit over or under bite or skeletal imbalances. I would see an orthodontist for a free consult to determine your best course of action

When you need braces: Bonding and veneers can make crooked teeth look straight. Braces move the teeth, so they actually are straight. If you have jaw pain, difficulty chewing, misalignment of the jaw, or other functional concerns, you need braces. If your only concern is cosmetic, then bonding or veneers may be an option. However, if the gaps, crowding, or rotation is severe, braces may still be needed