We can say with confidence that malocclusions (misaligned, mismatched, or incorrect relationship between teeth and/or jaws) have practically always existed in human history. In fact there is an estimate that about 30% of the population requires some sort of orthodontic treatment. Factors that create malocclusions include skeletal (jaw) problems, abnormal arch formation due to activities such as thumb sucking / mouth breathing / tongue thrusting, disproportionate size of teeth, misalignment of teeth and/or jaws, and missing or extra teeth.
The proper closing of the mouth in functions such as “biting” requires the coordination of many muscles, joints, teeth, and jaw bones. In a healthy bite, each tooth (with its cusps and grooves) matches nicely with its partner tooth in a relaxed way, simultaneously and with even pressure across the mouth, without additional friction (wear and tear). Problems with occlusions can range from simple jaw and tooth pain, to facial- and head-aches, to neck and back pain, breathing issues, and in extreme cases aesthetics of the face or even speech problems.