I yawned this morning and my jaw clicked and made a wretching sound. i currently wear a mouth guard because i grind at night. is the noise a concern?

Not if no pain: Clicking sounds in the jaws are common. If you are not having pain, i would not be too worried!

Yes: It is possible you may have some damage in your TMJ (temporomandibular joint which acts like a sliding hinge, connecting your jawbone to your skull) a consult with a dentist who treats TMJ or and oral surgeon is in order. Even if there is no pain i believe a baseline exam is a good idea with the history you have given.

Its OK.: Crepitus refers to joint noises, such as popping and cracking in the joints as tmj. It can be quite disturbing & cause concern, particularly if it shows up suddenly. In most cases, these noises are not indicative of any underlying problem. Most joint crepitus, cracking and popping usually has a 'bark that is worse than its bite.' there is likely no concern. If any pain arises see a prosthodontist.

Could be: Opening wide can pop the lower jaw off the end of the cartilage meniscus that separates the top from the bottom and allows the joint to function. If pain goes away refrain from opening widely.

Probably not: You already wear an Orthotic which is a good first step. Now, report your symptoms to your Dentist to be noted in your chart. If problem repeats Dentist will better be able to follow your progress. The next step is to try to determine why you grind your teeth (which does jaw joint damage). Ask your Dentist if an Orthodontic Consultation is in order.

Depends: Having popping/clicking TMJ noises not necessarily a problem. Many people experience these noises. Without pain or limitation of function the noise itself is not an issue. If you have locking or limited movement, "ear" pain, headaches, morning jaw stiffness/soreness, difficulty chewing, bruxism, previous jaw injuries or other jaw conditions, the problem is more serious. Then see a TMJ specialist.