Traumatic occlusion is a morbid condition that is caused by repeated occlusal stresses exerted on the periodontium that exceed the physiologic limits of tissue tolerance and contribute to the breakdown of the supporting tissue of the teeth. In reviewing these cases, the authors obtained the following results. 1. Roentgenographic examination revealed the typical signs of traumatic occlusion: severe resorption of roots, destruction of alveolar bone. 2. The major factor of traumatic occlusion is abnormal occlusal force. 3. The rsorptions of roots and periodontal changes which are caused by traumatic occlusion depend on the individual variation of the physical potential. 4. The pathologic features of traumatism are basically different from those of inflammation.