I have suffered from TMJ, dental grinding, periodically over the last 20 years. The result is aching in my 2 remaining wisdom teeth and neck pain.
When my now retired dentist diagnosed this initially he made a dental guard/plate which along with aspirin solved the problem. Since then I occasionally get flare-ups due to stress. As my bite changed a bit over the years I started using over the counter guards which I find effective and less costly though they take a bit of patience getting the initial fit correct.
Recently, I bought the ProDental Thin and Trim Guard hoping for a better fit and I have not been disappointed. I did waste one guard trying a bit too hard to get the fit right but the second attempt went well. My dental pain has just about completely gone after 2 weeks of wearing and last night I slept without it. I did develop a cheek irritation after 1 week so I e mailed MKC Products and Dr Closson promptly responded with a suggestion of some careful trimming. This solved the problem and my cheek is fine now.
The product is not particularly different from others on the market but this version is a bit thinner and fits well and I don't drool which happens with a thicker guard.
I give the ProDental Guard a "B+" and Customer Support an "A+". The customer support is what really sets this product from the others.

This is a pretty good mouth guard and well priced for three. I like the three pack because it's a bit of an art to getting a good fit. I messed up on the first one leaving it in the hot water for two seconds too long. I noticed on that one that it gave me a gag response putting it in my mouth so I trimmed the ends of the second one. I also took it out of the water almost as soon as I put it in. I sucked and pushed in place with my tongue which made a good fit. I grind my teeth and I think I could sleep in this. I couldn't in the drug store brand and my dentist keeps reminding me of how my teeth are being worn down. I plan to wear this in the day sometimes when I'm stressed and automatically clench my teeth. I think it will help with jaw pain over time. Its not thin but comfortable when you get a tight fit.

This product works great. It took 2 tries on the same guard to get a good fit and a little trimming. After sleeping the first night I wanted a little tighter fit so I just boiled water and repeated the fitting process. I found the trick was putting the warm guard in my mouth and sucking in on the guard to pull it close to my teeth while rubbing with my fingers to push inward on my teeth. Now it fits snug and I love it. I sleep so much better and wake rested. It has made a big difference for me. And much less expensive than the guard the dentist wanted to sell me.

I liked these so much, I got a second set. These are such a help for my grinding. It took awhile to figure out exactly how to mold them, but now I feel pretty competent. I cut them down alot before dipping in the hot water, and stretch them out to make them thinner. I also go back and redip several times to get a good fit. I've even cut off the ends, melted just the end piece, flattened it out, and used just that for an extra set. I don't put them very far back, so it works great.

I'd rather make my own mouth guard than shell out hundreds of dollars for one that is uncomfortable and doesn't work. My bite is pretty bad, and, as a result, it wasn't until my third try that I successfully made a ProDental guard. But my second attempt should be a reasonable back up. I definitely recommend this product.