The goal of the present proposal is to investigate ANS effects of ULF-TENS stimulation in patients with and without TMD conducting an observational RTC. The enrolled subject (with and without TMD) will be randomly assigned to case and control groups. The case group will receive a total of 40 minutes of TENS stimulation, whereas control group will not. ANS of both groups will be investigated by ANS polygraph and by the use of serum/saliva biomarkers such as: