The goal of this observational study is to determinate temeporomandibular disorders (TMDs) and levels of biomarkers in 30 rheumatoid arthritis patients and 30 healthy controls.

Aims are:

• to determine TMDs symptoms in both groups using a validated Reasearch Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) protocol
• to determine levels of interleukin-4 (IL-4), interleukin-18 (IL-18) and interferon-gamma (IFN-γ) in saliva and serum in RA patients and control group
• to determine levels of biomarkers (Ca, Mg, P, AST,ALT,ALP,GGT,urate) in serum of RA patients and control group
• investigate the correlation between cytokines level in saliva and serum
• to determine the effect of TMDs on cytokine and biomarker levels Participants will be clinicaly examined by DMD in accordance with the RDC/TMD guidelines to receive both Axis I and Axis II diagnoses. After examination participants would be asked for saliva and blood sample.

Rheumatoid arthritis (RA) is chronic inflammatory autoimmune disease characterized by symmetrical peripheral polyarthritis with consequent joint destruction. Predominantly affecting wrist and foot joints, RA can also affect temporomandibular joint (TMJ) causing temporomandibular disorders (TMDs). 4-80% of RA patients suffer from TMDs.

It remains unclear why some RA patients do not have TMDs and don't suffer from orofacial pain, depression and somatization. The present study was therefore designed to explore the level of cytokines and biochemical parameters from saliva and serum in RA patients and control participants to examine their correlation with TMDs. Study results could provide valuable insights for the understanding of the orofacial pain and depression onset in RA patients Participants would be examined by a non-blinded examiner with knowledge to which group the patient was in. After intraoral examination Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) will be used as an international diagnostic protocol for TMDs. Assessment included clinical examination of TMJs and masticatory muscles with measurement of mandibular dynamics. The participants will be requested to spit 2 mL of unstimulated saliva into a sterile tube with their head slightly bended forward. Saliva samples were stored at -20℃ until analysis. Blood samples will be collected in Vacutaners. Serum calcium (Ca), magnesium (Mg), phosphate (P), uric acid, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT) were measured up to 6 hours after collection. Serum aliquots were stored at -20℃ until cytokine analysis. An Invitrogen assays were used to analyze salivary and serum concentration of IL-4,IL-18 and IFN-γ.

Inclusion Criteria:

• Signed informed consent, demonstrating that the patient understands the procedures required for the study and the purpose of the study
• Patients diagnosed with RA according to 2010 ACR-EULAR RA criteria.

Exclusion Criteria:

• Refusal to sign informed consent form
• Diagnosed chronic systemic disease
• Any infection including TB, HIV, Hepatitis B or C
• Malignancy
• Pregnancy
• Smokers

Patients with RA were recruited during their routine monitoring by rheumatologists.

The control group were recruited from among regular patients visiting hospital for annual systematic examination.