Signs and symptoms of mandibular dysfunction after introduction of experimental balancing-side interferences

A double-blind study was performed in two groups of young, healthy women without signs or symptoms of mandibular dysfunction. Each group contained 12 individuals. In one of the groups, balancing-side interferences were applied bilaterally, whereas the application was simulated in the other group. The participants were re-examined after 2 weeks. Ten individuals in the experimental group reported one or more subjective symptoms during the 2 weeks, whereas seven exhibited clinical signs of dysfunction. The commonest symptom was headache, and the commonest clinical sign was muscles tender to palpation. In the control group, three individuals reported subjective symptoms, and three had clinical signs of dysfunction. One week after elimination of the interferences, all signs and symptoms had disappeared in all individuals but two. In these two subjects it took 6 weeks before pre-experimental conditions were restored. It is concluded that there is no simple relationship between interferences and signs and symptoms of dysfunction. How the individual reacts to local factors depends on his or her psychic condition. In some individuals addition of balancing-side interferences is sufficient to create dysfunction. The findings thus underline the importance of local factors in the etiology of mandibular dysfunction but show that a relationship is not obligatory.