A new article in Inside Dentistry (reference below) reveals research that 50% of patients with TMJ disorders (TMDs) the initial onset was a result of Dental Care.
These problems may occur due to direct trauma to the jaw muscles or joints, sustained contractions of jaw muscles, and/or prolonged stretching of the masticatory muscles and joints, ligaments and tendons.
In my experience, this is especially true with procedures like lower molar extractions when bite blocks are not used, root canal therapy on second and third molars and other long appointments.
It is likely that most patients experiencing this were predisposed in some fashion to having jaw issues.

There are many things that can be done to help prevent these problems:
1. The judicious use of Travell Spray and Stretch technique following a long dental appointment can often relax the muscles and allow healing especially if done early. I frequently do this immediately after an appointment and before and/or aftyer on patients with pre-existing issues. Most pain related to TMJ dysfunction is actually Myofascial Pain and Dysfuntion or MPD.

2.Ice and or heat packs over jaw and neck muscles. This is similr to a post exercise muscle pain. Moist heat or heat alternated with ice can be extremely helpful.

3. I am an enormous advocate of the Aqualizer, an oral appliance that utilizes hydraulics to equalize the bite and relax musles. It has been shown to relax not just the jaw muscles but also neck, shoulder and back muscles over a couple of hours.

The use of ULF-TENS is amazing for preventing and allowing rapid healing of this type of problem. the ULF-TENS preconditions the muscles for their “Work Out” and afterward gentle pulsing helps relax muscles by increasing blood flow and pumping out waste products, such as lactic acid.

The Myomonitor is the original ULF-TENS and has an exceptional 50 year safety record. It has been show to be extremely efficient at relaxing muscles physiologically and this has beeen confirmed by surface EMG. The Myomonitor has a second aspect that is also very important, it acts as a SphenoPalatine Ganglion Stimulator and prevents onset of Axis two issues related to stress, anxiety and pain.

Axis two is H-P-A action or Hypothalamus-Pituitary-Adrenal System. This has been known since the work of Hans Selye first opened the medical communities eye to the effect of stress on the human body. SPG Blocks or Sphenopalatine Ganglion Blocks are also amazing at treating many TMJ issues as well as migraines, cluster headaches, anxiety and other pain issues.

It effectively helps turn off sympathetic overload and allow the parasympathetic system to predominate to allow healing.

Most TMJ disorders whether intracapsular or extracapsular are the result of repetitive strain injuries due to bit issues or patient behavior, ie cheerleaders joint or gum chewing. Adding a long dental procedure , trauma of extraction or injection thru muscle can be a significant factor in devloping long term problems.

Reference. Post Operative Jaw and Muscle Pain, a gGuide to Risk Assessment, Prevention and Treatment. Inside Dentistry April 2017 69-76
Brady LA, Fricton J, Eli B

J Am Dent Assoc. 2016 Dec;147(12):979-986. doi: 10.1016/j.adaj.2016.06.017. Epub 2016 Aug 31. Preventing chronic pain after acute jaw sprain or strain.
Fricton J, Eli B, Gupta A, Johnson N.