Malocclusion is abnormal alignment of the teeth and the way in which the upper and lower teeth fit together.
Normally, the upper teeth overlap slightly outside the lower teeth. This overlap allows the projections (cusps) on each tooth to fit in the corresponding depressions of the opposite tooth. Proper alignment makes for the most effective chewing and also distributes chewing forces equally. Chewing produces over 150 pounds (1,000 kilopascals) of force on the molars and clenching during sleep produces 250 pounds (1,700 kilopascals). If malocclusion causes the forces to be unequally distributed, teeth can wear abnormally, portions of the crown may fracture, and teeth may eventually loosen.
