TMD
In 1980, engineering student Casey Guzay created the 'Quadrant Theorem' and calculated that the centre of mandibular rotation was NOT in the glenoid fossa, as convention dictated, but at the dens between C1 and C2, as shown in the diagram. This indicated that the condyle does not 'rotate' in the fossa, but moves forwards on opening the bite, and retrudes when the bite is closed. This fact can be highly significant when planning treatment for TMD.