Is there a lower cost, long term over-the-counter mouth guard that can be worn at night to prevent teeth grinding? would it prevent future tmj issues?

No: Night guards do not prevent grinding, but balance the bite so that the pressure is more equally distributed. It is impossible for a store bought mouth guard to equilabrate your your bite. The best that you can hope for is a physical barrier between your teeth. As far as preventing tmj, i would ask you to visit a pankey or dawson post graduate bite trained dentist.

mouthguard: There is a drug store guard that is better than nothing- it won't help for TMJ concerns and you will grind through it quickly and then have to spend more for another one.

Yes: Just get one of those mouth guards u buy for athletes. Boil it to soften the mouth guard n without burning yourself place it into your mouth n gently bite into it. Cool it in cold water n you're all set. It's not perfect but will help n save u money.

Complex: As you can see from the other answers, this isn't a simple question. Sometimes the otc guards can be very helpful but often they can make matters worse. I use them in a diagnostic process to try to get people out of pain but very often they aren't a long term solution. Get evaluated by a tmd-aware dentist and ask a lot of questions to get to the bottom of your particular situation.

Immediate relief: Might be attained with using an otc boil and bite device, but long term problems may still present. Diagnosis of the etiology is essential to know how to properly treat and that comes from visiting your dentist who is hopefully proficient at evaluating and treating TMJ / myofacial pain disorders. Also consider an evaluation by your orthodontist to make sure your occlusion is aligned properly.

Night guards: Night guards do not prevent grinding. Basically they protect teeth from being damaged. Over the counter mouthguards are too thick and not bite-balanced, so they can increase grinding, clenching, and TMJ dysfunction. A custom made nightguard can help with TMJ from grinding, but not from clenching. Talk to your dentist, or if possible, seek treatment at a dental school.

Depends: There are many types of mouthguards for grinding and clenching. Over the counter ones actually may be too thick and throw the muscles into more spasms. Dentists can make custom made, well fitting mouthguards, either upper or lower (i like the lower ones.) the guards can be made of soft plastic or hard acrylic...Depends on severity of grinding. For daytime clenching, other types are indicated.

Not great idea: Not likely. Consistent grinders will grind through it quickly. Hard to fit properly. May make you grind worse. Much better - see TMJ expert. Any dentist can be a TMJ expert with the proper training and experience. Most commonly, oral surgeons, prosthodontists, and orofacial pain specialists. Ask your MD, your dentist and your dental society for referrals.