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What is According to SAWHNEY'S classification of TMJ ankylosis, complete joint architecture is destroyed by osseous union and no sigmoid notch is identifiable, this is: and explain in detail?
SAWHNEY'S GRADING OF ANKYLOSIS 

TYPE 1: Flattening or deformity of the condyle with little joint space seen on the radiograph. Extensive fibrous adhesions seen during operations. 
TYPE 2: Bony fusion of the outer edges of the articular surfaces with no fusion in the deeper areas of the joint. 
TYPE 3: A bridge of bone is seen between ramus of the mandible and zygomatic arch. 
TYPE 4: Entire joint is replaced by a mass of bone.