The Role Of Lateral Pterygoid Muscle In The Fracture Area Of Traumatic Ankylosis Of Temporomandibular Joint

Temporomandibular joint (TMJ) ankylosis is a common disease that leading tolimitation of mouth opening, masticatory difficulty and affects patient’s physical andmental health. It is different and laborious to treat TMJ ankylosis in clinical. Re-ankylosisis one of the most frequently seen complications. The trauma, especially the sagittalfracture of the mandibular condyle is the main cause of TMJ ankylosis and it is calledtraumatic TMJ ankylosis. The mechanisms of how traumatic TMJ ankylosis develops aftertrauma are still unclear. We consider the distraction osteogenesis caused by the traction ofthe lateral pterygoid muscle leads to new bone overgrow and then plays an important rolein the genesis of traumatic TMJ ankylosis. As is known, the lateral pterygoid muscleattaches the condyle, and when it contract, the fractured is pulled to the forward, down and the inside. If accompanied the articular disc damaged and mandibular movementlimited at the same time, it tend to occur the TMJ ankylosis. Due to the samples in vitrofor a long time, it may affect the results of the experiment two. So we selected36sheepsin the two experiments. Then randomized24from them were used for experiment one,and the other for experiment two. Morphology observation and Micro CT scanning wereused to observed the changes of condyle morphology and bone structure parameters inexperiment one. Then the RT-qPCR and immunohistochemistry were used to observechanges of osteogenesis molecular to discuss the role and the mechanism of the lateralpterygoid muscle in the traumatic TMJ ankylosis.Experiment oneThe role of lateral pterygoid muscle at the fracture area of traumaticankylosis of temporomandibular jointObjective: To investigate the role of the lateral peterygoid muscle in the new boneformation during healing of sagittal fracture of the mandibular condyle and to discuss therelationship with the ankylosis of temporomandibular joint. Methods: Oblique sagittalfracture with the disc removed to the inside on the right side condyle of24adult sheepswas made by osteotomy. In the control group (n=12) the lateral pterygoid muscle cut, andin the experimental group (n=12) was not. Four sheeps were killed at4,12and24weeksafter operation respectively. The trabecula number (Tb.N), trabecula thickness (Tb.Th),trabecula space (Tb.Sp) and bone volume fraction (BV/TV) of the fractured condyles weremeasured, and the data were analyzed by SPSS13.0. Results: All of the TMJ did not accurankylosis. All of the condyle of the left side was not changed. The shape of condyle waschange more in the experimental group than in the control. In the experimental groupTb.N, Tb.Th and BV/TV increased (P<0.05), and Tb.Sp decreased (P<0.05). Theparameters in the2groups were statistically defferent (P<0.05). In the control group theparameters were not significantly changed (P>0.05). Conclusion: The lateral peterygoidmuscle can promote the new bone formation in the reconstruction of the mandibular condyle during healing of sagittal fracture.Experiment twoThe mechanism of lateral pterygoid muscle promate the morphology ofthe condyle and the changes of osteogenesis at the fracture areaObjective: To investigate the mechanism of the lateral peterygoid muscle in the newbone formation during healing of sagittal fracture of the mandibular condyle, and to revealthe relationship with the traumatic ankylosis of temporomandibular joint. Methods:Another12adult sheeps were randomized into two groups. Preparation of animal model isseem to the experiment one. Detecting the expression of collagen I (COL I), osteocalcin(OCN) and transforming growth factor-β1(TGF-β1) by RT-qPCR andimmunohistochemistry. Results: The expression of COL I, OCN and TGF-β1mRNAchanged more in the experimental group than in the control. In the experimental group(P<0.05), it has a rising trend of COL I, TGF-β1and OCN mRNA in the experimentalgroup by the time (P<0.05); and in the control group, it was rising at4week, then itreduced gradually. The results of immunohistochemistry show that the expression of COLI and TGF-β1expressed by osteoblast changed more in the experimental group than in thecontrol, and rising gradually by the time in the experimental group (P<0.05) and it isreduce gradually in the control group (P<0.05). Conclusion: The lateral peterygoidmuscle has the trend to promote the progress of TMJ ankylosis. It is one of the importantpathogenic factors of TMJ ankylosis and the mechanism is seemed to the distractionosteogenesis.