Background: Burning mouth syndrome (BMS) is characterized by intense burning sensation of the tongue or other regions of the oral mucosa with no known medical or dental cause. BMS is poorly understood condition which requires multidisciplinary management. Opiorphin is a natural antinociceptor, previously identified from human saliva and demonstrated analgesic properties. It has been reported to involve in pain pathways and could potentially be a biomarker for different types of physiological disorders.
Objective: Because of its abundance in the oral cavity, we aimed to measure the level of opiorphin in unstimulated whole saliva (UWS) of patients with BMS.
Materials and Methods: Demographic data, history taking, oral examination and UWS samples were obtained from 20 BMS patients before starting the drug treatment. Opiorphin levels were measured with a quantitative assay using commercially immunoenzymatic competitive ELISA kit (cat No. E1779h, Wuhan, China) and compared to those of healthy control.
Results: UWS of 20 BMS patients (3 males and 17 females, average age 60.2 years old) were collected. The average concentration of opiorphin in UWS of BMS patients was 1.25+0.79 ng/ml. The result demonstrated that opiorphin in BMS patients’ UWS was significantly lower, compared to 4.16+0.82 ng/ml in the healthy control group (n = 3, 3 females, average age 50.6 years old).
Conclusion: Our results indicate that the decreased levels of opiorphin in UWS of patients with BMS may be associated with the inhibition of analgesic property of encephalin, thereby causing chronic pain. To dates, knowledge on opiorphin’s involvement in pain pathways has been controversial. Further study remains significant to understand the mechanistic role of opiorphin in chronic orofacial pain.

Keywords: Burning mouth syndrome, Salivary opiorphin, Natural nociceptor