Thanks for asking your question. From the picture your provided it appears that you may be missing some teeth on the upper arch (or they haven't come in yet). Your front teeth look big because your teeth behind them are extra small. My recommendation would be braces to move your front teeth together, and then doing something about the missing or unerupted teeth. I suggest you visit an orthodontist who will be able to give you a definitive treatment plan. If you are missing teeth, your dentist or a prosthodontist will need to get involved for final restorations after orthodontic treatment is completed. Good luck to you in getting your gap closed and improving your smile!