Diagnostic group differences in temporomandibular joint energy densities

Structured Abstract ObjectivesCartilage fatigue, due to mechanical work, may account for precocious development of degenerative joint disease in the temporomandibular joint (TMJ). This study compared energy densities (mJ/mm(3)) in TMJs of three diagnostic groups. Setting and Sample PopulationSixty-eight subjects (44 women, 24 men) gave informed consent. Diagnostic criteria for temporomandibular disorders (DC/TMD) and imaging were used to group subjects according to presence of jaw muscle or joint pain (+P) and bilateral disk displacement (+DD). Material and MethodsSubjects (+P+DD, n=16; -P+DD, n=16; and -P-DD, n=36) provided cone-beam computed tomography and magnetic resonance images, and jaw-tracking data. Numerical modeling was used to determine TMJ loads (F-normal). Dynamic stereometry was used to characterize individual-specific data of stress-field dynamics during 10 symmetrical jaw-closing cycles. These data were used to estimate tractional forces (F-traction). Energy densities were then calculated as W/Q (W=work done or mechanical energy input=tractional forcexdistance of stress-field translation, Q=volume of cartilage). anova and Tukey-Kramer post hoc analyses tested for intergroup differences. ResultsMeanstandard error energy density for the +P+DD group was 12.7 +/- 1.5mJ/mm(3) and significantly greater (all adjusted p<0.04) when compared to -P+DD (7.4 +/- 1.4mJ/mm(3)) and -P-DD (5.8 +/- 0.9mJ/mm(3)) groups. Energy densities in -P+DD and -P-DD groups were not significantly different. ConclusionDiagnostic group differences in energy densities suggest that mechanical work may be a unique mechanism, which contributes to cartilage fatigue in subjects with pain and disk displacement.