Is wearing a mouth guard at night a bad alternative to the "night guard"?

It can be: A night guard is generally made of a hard materal so when gringing your teeth slide easily over the acrylic. Mouth guards are made of soft materal and when you grind on it while sleeping it may create strain or pressure on the jaw muscles and cause pain. It may be ok for a short tem fix but not as a perminant solution.

Well...: It's not a good alternative to wearing a night guard. A night guard will be much smaller and more comfortable, as it will be molded to your teeth much better. It may provide a similar benefit but be careful not to gag or choke on the mouth guard as it is not meant to be worn while sleeping.

Not really: You may try another alternative : grindcare it is an external biofeedback device I have been using with great success. No bulky appliances in your mouth!

Not if you are: Both night guard and moth guard separate the teeth if both are custom fit and you are comfortable , you can wear either.

Custom guard: Custom guards are the best, especially if they are designed to help with airway issues, bruxism/ clench/ grind issues, tmj/tmd issues, or muscle pain issues in head/neck. For mouth guards and sports guards, they are best used to protect teeth during sports.

Not really but...: 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.