Evaluation of IL-1β and CRP mRNA expression levels by RT-PCR in postorthodontic treatment patients with temporomandibular joint disorders: a cross-sectional Study.

Aim: Temporomandibular joint disorder (TMD), which affects the masticatory muscles, temporomandibular joint, and surrounding tissues, can manifest as inflammation. This study aims to explore the expression levels of the inflammatory biomarkers, interleukin (IL)-1β and C-reactive protein (CRP), in TMD patients who have undergone orthodontic treatment.

Materials and methods: Buccal swabs from 105 postorthodontic treatment patients were analyzed using real-time polymerase chain reaction to assess the expression levels of IL-1β and CRP in each group after messenger ribonucleic acid extraction. Patients were also examined using the Diagnostic Criteria for TMD (DC/TMD) to determine if they met the criteria for a TMD diagnosis. The TMD group was subdivided into three categories based on the DC/TMD.

Results: The study included 37 patients who did not develop TMD (group 0) and 68 participants who developed TMD after orthodontic treatment, including 17 with pain-related TMDs (group 1), 29 with intra-articular TMDs (Group 2), and 22 with combined pain-related and intra-articular TMDs (group 3). CRP expression was higher than IL-1β in groups 1 and 2, and IL-1β expression was higher than CRP in group 3. The Kruskal-Wallis test showed that IL-1β and CRP expression levels in groups 1, 2, and 3 were not statistically different. Sex and adult age had considerable effects on the occurrence of TMD in patients after orthodontic treatment.

Conclusions: Higher IL-1β expression was found in postorthodontic treatment patients with more complex TMD. This study strengthens the evidence of inflammation through IL-1β and CRP expression in individuals with TMD, especially after orthodontic treatment.