Occlusion is a term that is used to refer to the alignment of your teeth. Ideally, your teeth should fit easily within your mouth without any crowding or spacing issues. Also, none of your teeth should be rotated or twisted. The teeth of your upper jaw should slightly overlap the teeth of your lower jaw so that the pointed ridges of your molars fit into the groves of the opposite molar. Deviations from ideal occlusion are known as malocclusion. The type of deviation varies, but any type of misalignment can cause issues. Alignment of upper teeth is needed to prevent the cheeks and lips from being bitten, while alignment of lower teeth is needed to protect the tongue from being bitten.