I have fixed on braces and need a mouthguard for sparring. Now I've found mouthguards for braces however most of them are only for my upper teeth, do I'm not sure whether I need a double mouthguard or not? Any thoughts.
The standard for mouth guards is to only be for the upper teeth. This is pretty consistent from what I've seen in several contact sports (hockey, American football, rugger, boxing), both for the boil-and-bite type and for custom guards prepared for you by your dentist. I have never seen or used a mouth guard that also covers the lower teeth.
Orthodontists can properly fit a mouthguard for braces. Many of them consider it cheap insurance. I would say that your orthodontist is the best resource to answer this question, but obviously he is also unaware.
If you point him to this link (https://www.shockdoctor.com/double-braces-mouthguard) , he should be able to start asking the right questions in the right places.