Effect of occlusal splint on oxidative stress markers and psychological aspects of chronic temporomandibular pain: a randomized controlled trial

Temporomandibular disorders (TMD), when progress to a chronic state, might contribute to psychosocial or psychological distress. This study aimed to evaluate the effect of stabilization splint (SS) therapy on pain, pain-related disability and psychological traits of chronic TMD patients, as well as to assess selected oxidative stress (OS) biomarkers during 6-month treatment and associate them with the symptoms of anxiety and depression. Thirty-four participants were randomly assigned into two treatment groups [SS and placebo splint (PS)]. Primary outcomes were pain intensity and pain-related disability while secondary outcomes included depressive and anxiety symptoms. The influence of the treatment type was analyzed with regards to the levels of OS biomarkers in saliva. Participants treated with SS demonstrated significantly greater improvement in pain-related disability (Pain-free mouth opening: p = 0.018, η(2) = 0.166; Number of disability days: p = 0.023, η(2) = 0.155) and greater reduction of depressive symptoms scores (p = 0.007, η(2) = 0.207). When compared to the PS group, participants in the SS group showed a significant reduction of oxidant/antioxidant ratio (p = 0.018, η(2) = 0.167) at a 3-month follow-up. A stabilization splint provides advantages over PS in the treatment of depressive symptoms and pain-related disability. Furthermore, clinical success in terms of reduction of depressive symptoms, which correlates with the reduction of oxidative stress markers in the SS group, indicates that oxidative stress is related to psychological factors in chronic TMD patients.