MRI-confirmed Disc Displacement in the Clinically Normal Temporomandibular Joint

The prevalence of temporomandibular joint (TMJ) disc displacement (DD) in temporomandibular joint and muscle (TMJD) symptom free subjects is unclear. Objectives: In normal subjects, estimate the prevalence of DD in those who report a lifetime absence of TMJD symptoms, and in those with a past history of symptoms but symptom free in the preceding 6 months. Methods: In an ongoing study, "Research Diagnostic Criteria: Reliability and Validation," 684 subjects (82% female, 18% male) received independent clinical examinations by two gold-standard examiners and interpreted TMJ imaging. These examiners then reached a consensus on the subjects' diagnostic status. Among those subjects who were both clinically normal and without symptoms for at least 6 months, data were collected for four groups: a) lifetime history negative and MRI findings negative for DD; b) lifetime history negative and MRI findings positive for DD; c) lifetime history positive for symptoms and MRI findings negative for DD; and d) lifetime history positive and MRI findings positive for DD. The analysis was performed using Fisher's Exact Test, Proc Freq (SAS Institute). Results: Among 111 clinically normal subjects, 73 reported no lifetime history of symptoms and their MRI was negative. Twenty-eight had a negative lifetime history with an MRI positive for DD. Nine had a positive history but the MRI was negative. One had a positive history with the MRI positive for DD. The proportion of positive MRI among history-negative subjects (28/101=0.28) was greater than, but not statistically different (p=0.16) from, the proportion of positive MRI among history-positive subjects (1/10=0.10). Conclusion: In this symptom-free study sample, a previous history of TMJD symptoms did not predict presence or absence of TMJ DD. In addition, more than one-fourth of clinically normal subjects had a DD. This study was supported by NIDCR Grant U01-DE013331.