Tooth eruption refers to the emergence of teeth within a person's mouth. The first form of tooth eruption that a human will experience comes in the form of primary teeth. Primary teeth erupt into the mouth around six months to two years of age. At age six, more teeth begin to erupt creating a mixture of primary and permanent teeth. Once the final primary tooth has been lost, permanent teeth erupt into the mouth.
Science has no explanation as to why tooth eruption occurs. Earlier theories based tooth eruption upon the growth of a tooth's root, while other theories determined that the growth of a tooth was caused by bone surrounding a tooth. The present theory includes the impact of the periodontal ligament upon the teeth. Thus far, all theories involving tooth eruption have yet to be proven, though some of the earlier theories have been effectively disproven.
Interestingly, while no concrete evidence exists as to why teeth erupt, all humans go through the same eruption stages. The first stage is the primary stage that includes the eruption of the mandibular central incisors. Primary tooth order includes the eruption of the central incisor, lateral incisor, first molar, canine, and second molar. Following the primary stage, the mixed stage occurs.
During the mixed stage, maxillary teeth erupt beginning with the first molar. Then, the central incisor, lateral incisor, first premolar, canine, second molar, and third molar erupt. Mandibular teeth erupt in an entirely different order beginning with the first molar,central incisor, lateral incisor, canine, first premolar, second premolar, second molar, and third molar.
Crowded or misplaced teeth inside of the mouth tends to occur if primary teeth are lost before permanent teeth can set-in. In this instance, some teeth might move forward causing teeth to become crowded. Crowded teeth can be straightened with the help of an orthodontist, though this attempt at straightening is not always effective.
Following the mixed tooth stage, permanent teeth settle into the mouth. These permanent teeth are accompanied by third molars that are often referred to as wisdom teeth. Most people opt to remove these third molars due to tooth pain and discomfort. While everyone experiences the same tooth eruption stages, eruption can occur at different times depending upon the person. As a general guideline, primary teeth will erupt every six months until a person has reached the age of six. Permanent teeth tend to erupt around twelve years of age.