The effect of removal of the disc on the friction in the temporomandibular joint.
OBJECTIVE
The amount of friction in the temporomandibular joint (TMJ) is dependent on the joint components, including the synovial fluid, disc, and articular surface cartilage. As friction in the TMJ is less than in other (discless) joints, we hypothesized that this is caused by the presence of the disc.


METHODS
The frictional coefficient of the TMJ was first measured in the intact porcine joint (n = 10). After the disc was removed the measurement of frictional coefficient was conducted again. Furthermore, the subsequent effects of loading duration and the application of hyaluronic acid (HA) were examined.


RESULTS
The mean frictional coefficient in the intact joint was 0.0177 (SD 0.0021). After disc resection it became 0.0361 (SD 0.0063). The frictional coefficient increased with the length of the preceding loading duration and exceeded 0.0635 (SD 0.0085) after 30 minutes. Subsequent application of HA resulted in a slight decrease of the frictional coefficient.


CONCLUSIONS
The presence of the disc reduces the amount of friction in the TMJ. This reduction is likely due to the role of the disc in reducing the amount of incongruity between the articular surfaces and in increasing synovial fluid lubrication.
Tanaka
Eiji
E
Department of Orthodontics and Craniofacial Developmental Biology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan. etanaka@hiroshima-u.ac.jp
Dalla-Bona
Diego A
DA
Iwabe
Tatsunori
T
Kawai
Nobuhiko
N
Yamano
Eizo
E
van Eijden
Theo
T
Tanaka
Masao
M
Miyauchi
Mutsumi
M
Takata
Takashi
T
Tanne
Kazuo
K
D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects / Q000502:physiology; D017276:Friction; D006820:Hyaluronic Acid / Q000494:pharmacology; D008153:Lubrication; D013314:Stress, Mechanical; D013552:Swine; D013582:Synovial Fluid / Q000502:physiology; D013704:Temporomandibular Joint / Q000502:physiology*; D019224:Temporomandibular Joint Disc / Q000502:physiology / Q000601:surgery*
D006820:Hyaluronic Acid