9:1. Females are more likely to request treatment for TMD, and their symptoms are less likely to resolve. Females with TMD are more likely to be nulliparous than females without TMD. It has also been reported that female caucasians are more likely to be affected by TMD, and at an earlier age, than female African Americans. According to the most recent analyses of epidemiologic data using the RDC/TMD diagnostic criteria, of all TMD cases, group I (muscle disorders) accounts for 45.3%, group II (disc displacements) 41.1%, and group III (joint disorders) 30.1% (individuals may have diagnoses from more than one group). Using the RDC/TMD criteria, TMD has a prevalence in the general population of 9.7% for group I, 11.4% for group IIa, and 2.6% for group IIIa. History Temporomandibular disorders were described as early as ancient Egypt. An older name for the condition is "Costen's syndrome", eponymously referring to James B. Costen. Costen was an otolaryngologist, and although he was not the first physician to describe TMD, he wrote extensively on the topic, starting in 1934, and was the first to approach the disorder in an integrated and systematic way. Costen hypothesized that malocclusion caused TMD, and placed emphasis on ear symptoms, such as tinnitus, otaglia, impaired hearing, and even dizziness. Specifically, Costen believed that the cause of TMD was mandibular over-closure, recommending a treatment revolving around building up the bite. The eponym "Costen syndrome" became commonly used shortly after his initial work, but in modern times it has been dropped, partially because occlusal factors are now thought to play little, if any, role in the development of TMD, and also because ear problems are now thought to be less associated with TMD. Other historically important terms that were used for TMD include "TMJ disease" or "TMJ syndrome", which are now rarely used. References Musculoskeletal disorders Articles containing video clips Pathology of temporomandibular joints, muscles of mastication and associated structures Ailments of unknown cause