If you have a strong gag reflex, you’ll find a lower mouth guard to be most comfortable. However, if you have dental work or missing teeth down below, you should opt for a top guard. As far as specific night guards, there are many that give a comfortable fit. The Oral-B Nighttime Dental Guard is thinner than most, making it less bulky and intrusive. You want to look for a guard that’s flexible, not too stiff or thick, and a good fit for your chompers.