Which cephalometric point represents the centre of ramus of mandible?: (A) Xi-point, (B) Pm-point, (C) Ptm-point, (D) N-point
Answer is A. Xi point:
A point located at the geometric centre of the ramus. The location of the Xi point can be found geometrically by drawing a line through the porion–orbitale (FH) and perpendicularly through the PT vertical (PTV).