Will dental crowns make my smile better as I have underbite along with gaps in upper teeth (photos)

You have an orthopedic problem and a cosmetic problem.  Placement of crowns may make future treatment more difficult.I would need to evaluate a case like yours more closely but a combination of orthodontics and orthopedics would be ideal.  It appears that you have a functional protrusive (forward) movement on closure.The DNA Appliance which utilizes Epigenetic Orthodontics/orthopedics would be my first choice of definitive treatment.If you want a quick temporary fix I would suggest a snap on smile.  I would not do crowns without first carefully reviewing all other alternatives.   

You have several problems going on in your mouth. I encourage you to consider the fact that you are only 21 years old. With a long life ahead of you taking the shortcut of doing only crowns may lead to problems down the road. Additionally, your upper teeth aren't evenly spaced so the crowns may not be a uniform and symmetrical as you would like. There might be a compromise between some orthodontics and veneers that would be more ideal and give you a nicer final result. If possible you might try to sit down with your restorative dentist and orthodontist at the same time to discuss your options.