Background: The correlation between orthodontics and the development of signs and symptoms of temporomandibular disorders (TMD) is a major concern in the physical rehabilitation field.
Aim: The aim of the study was to observe whether subjects with a history of orthodontics use show differences from subjects who have never used orthodontics in: 1) masseter and temporalis muscle mechanosensitivity; 2) maximal vertical mouth opening (VMO); and 3) the impact of headache on their quality of life.
Design: Cross-sectional study.
Setting: The study was carried out in the Faculty of Nursing, Physiotherapy and Podiatry of the University of Sevilla, Spain.
Population: All participants were pre graduate students from the University of Sevilla, Spain. The final sample comprised 65 subjects (N.=65) with a mean age of 21 ± 2.46 years (18-29) divided into two groups; orthodontics group (N.=31) and non-orthodontics group (N.=34).
Methods: All students followed the same testing protocol. Measurements were taken of the pressure pain threshold (PPT) in two locations of the masseter (M1, M2) and temporalis (T1, T2) muscles, the maximal VMO, and the incidence of headache (Headache Impact Test-6; HIT-6, Spanish version).
Results: The measured values of the masticatory muscle PPTs were lower in the non-orthodontics group. Besides, the maximal VMO and HIT-6 scores were better in the orthodontics group. Nevertheless, none of these intergroup differences were statistically significant (ANOVA test): (M1 P=0.790); (M2 P=0.329); (T1 P=0.249); (T2 P=0.440); (HIT-6 P=0.443); (VMO P=0.626).
Conclusion: A previous history of orthodontics use does not seem to lead to any greater sensitivity of the masticatory muscles, limitations of vertical mouth opening, or greater impact of headache on the subject's quality of life.
Clinical rehabilitation impact: There is no evidence enough to support either a positive or negative correlation between orthodontics and signs and symptoms of TMD. Pain is a subjective perception and it is influenced by several factors. It remains uncertain if the use of orthodontics might be one of them.