Do tens machines work particularly well for tmj?

No: Tens units "confuse" the brain in the perception of pain signals. Tens may or may not be helpful for many pain conditions but not for any particular painful condition.

Yes, and no: A specific type, ultra low frequency tens is useful in relaxing the chewing muscles that are involved in TMJ conditions. However, without supporting the jaw in that relaxed position with a dental bite appliance (orthosis), the muscles go back to their painful condition quickly. So, as an isolated treatment, even ulf-tens has limited value. As an aid to bite management, it's very helpful.

TENS and TMJ: When used at low frequency a tens unit can be used to provide pain relief and promote the muscles around the TMJ to relax. You may find relief of some of your symptoms but you should select an experienced practitioner to pursue a diagnosis.

One adjunct: Not a first line treatment. But non-invasive. No downside. Most important thing is that your case is managed by a TMJ expert.

Recommended: Most studies reveal that it takes about 30 minutes for low-frequency TENS treatment to begin alleviating pain. Some patients report feeling hours of pain relief from 60-to-90 minute sessions. Best of luck.