Mechanism Research Of Effects Of Temporomandibular Joint Disc Displacement And Various Stresses On Condylar Endochondral Ossification In Growing Rabbit

ObjectivesThis research was aim to study the effects of anterior disc displacement (ADD)of temporomandibular joint (TMJ) and various stresses on condylarendochondral ossification in growing rabbit, and to explore the appropriatestress for endochondral ossification.Methods1. The effects of ADD on condylar endochondral ossification in growing rabbitThe model for ADD of TMJ was established in growing rabbit. Theexpressions of markers of endochondral ossification were detected at1week,2weeks,4weeks and8weeks after surgical ADD.2. The effects of compression on condylar endochondral ossification ingrowing rabbitDifferent compressions (0kPa,15kPa,30kPa,45kPa,60kPa,75kPa)were loaded on the condyles of growing rabbit in vitro. The expressions ofmarkers of endochondral ossification and chondrocyte apoptosis weredetected at7days after loading compression.3. The effects of stresses on endochondral ossification of condylarchondrocyte Different stresses (-50kPa,-30kPa,-10kPa,0kPa,50kPa,100kPa,150kPa,200kPa) were loaded on the condylar chondrocyte. The chondrocyteporliferation and apoptosis, the expressions of markers of generation ofcartilage and endochondral ossification, chondrocyte morphology andultrastructure were detected at3hours after loading stresses.Results1. Endochondral ossification in condyle with ADD was impeded, beasuse ofthe degeneration of cartilage at the1st week and disability of the hypertrophyof chondrocyte after the2nd week.2. Endochondral ossification in condyle in vitro was continued under theloading of appropriate compression (30kPa). Endochondral ossification wasimpeded in the overloading condyles and the condyles without sufficientcompression.3. Endochondral ossification of cultured condylar chondrocyte was boostedunder the stress of150kPa and-50kPa.ConclusionsEndochondral ossification was impeded in the condyle with ADD. TheEndochondral ossification was actived under appropriate stress, and wasimpeded under insufficient and overloading stress.