DESIGNCooperative analysis of participants and controls.DATA SOURCEWiley Online Library, National Institute of Health, ResearchGate, ScienceDirect, Google Scholar.STUDY SELECTIONHuman clinical trials age 18-30 years old, a case-control study included 291 individuals, 192 TMDs and 99 controls. All patients underwent assessment based on a questionnaire and a clinical examination according to Axis I of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Patients who underwent orthodontic treatment were compared to those who did not, regarding their trauma history, bruxism, aggressive teeth brushing, level of oral hygiene, pain scores, muscle tenderness scores and subjective sleep quality.EXCLUSION CRITERIAMedical and/or dental emergencies, subjects with a history of drug, alcohol or medication abuse, fibromyalgia, being pregnant or lactating, having a coexisting mental, psychiatric, or physical disability, cancerous or significant medical problems and the consumption of drugs and/or medications that affect the nervous system including narcotics, TCA (tricyclic antidepressants), anticonvulsant, muscle relaxants and medication overuse headache.DATA EXTRACTION SYNTHESISTo identify differences between groups, categorical independent variables were analysed using the chi-square test or likelihood ratio, while numeric independent variables were analysed using independent t-tests and analysis of variance (ANOVA). A two-tailed level of statistical significance (α) was established at 0.05. Analysis of multicollinearity was performed following the univariate analyses to examine the collinearity among the independent variables and select independent variables with minimal correlation. Among the highly correlated variables, only one was selected for inclusion in the multivariate model, with the specific variable chosen based on contextual considerations.RESULTSThe research comprised a total of 291 individuals, consisting of two distinct groups: the TMD group (192 participants, 66%) and the control group (99 participants, 34%). Within the TMD group, further subcategorization was conducted, including MMP (masticatory muscle pain) with 44 individuals (15%); TMJD with 26 individuals (9%); and TMP (both MMP and TMJ) with 122 individuals (42%).CONCLUSIONSUsing a "holistic" and a "collinearity statistical approach and the utilization of a multivariate model" the conclusion is that TMD is not associated with orthodontics.