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Aims: To correlate histologic changes with the stress developed by
various disc interferences via a model of partial anterior disc displacement
in the rabbit temporomandibular joint (TMJ). Methods:
Eighteen male New Zealand rabbits were operated on to expose
the temporomandibular disc without severing its attachments. A
suture was passed around the lateral part of the disc over the
condylar attachments and the 2 strands were fixed in the orbital
cavity. In 9 rabbits, a resorbable suture was used to secure the disc
displacement. In the other 9, a nonresorbable suture was fixed
with a nickel-titanium spring to displace and maintain tension on
the disc. Three non-operated animals served as controls. The animals
were sacrificed at 12 and 24 weeks after surgery, and the
TMJs were prepared for undecalcified histology. Results: In the
first group, the disc remained in a normal position, but its morphology
was modified and small histologic changes were observed
in the cartilage. In the second group, the disc was displaced in various
positions corresponding to the strength delivered by the
spring. Conclusion: Adaptive changes were observed in joints with
a slightly displaced disc, while degenerative changes were associated
with larger disc displacements. In each experimental joint,
histologic changes increased from the medial to lateral parts. This
phenomenon was related to the stress gradient induced by axial
disc rotation over the condyle. Any disc displacement always
resulted in changes in the cartilage.
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