There is a delicate balance between the development of a foetus, growth of the various body parts and functions before and after birth, including the development and eruption of primary (baby) and permanent teeth throughout the developmental period. Any, even slight, disturbance of this balanced rate and timing of growth and development will cause imperfections in the development of the dentition of an individual. In fact, there are very few people with absolutely perfectly developed and aligned teeth.
Some more severe congenital conditions may lead to missing teeth altogether, while various other congenital or environmental factors may cause one tooth or group of teeth such as third molars to be missing (a common condition). Some minor imperfections in the developmental process can cause a tooth (or teeth) to become impacted – the regular eruption is obstructed in some way and the affected tooth may not erupt at all, or only partially. Any tooth may become impacted but lower third molars (wisdom teeth) are most commonly affected. The common cause for impaction of a tooth is a minor mismatch in the timing and / or rate of the development of the tooth and the growth of the jaw or parts of the jaw at that stage, probably combined with a lack or natural loss of enamel at the contact points between the teeth around the arch of erupted teeth. This is particularly so for the last teeth to erupt (third molars or wisdom teeth).
Teeth that are in some way obstructed, rather than erupting partially or not erupting at all, may erupt in abnormal locations and / or in some misaligned fashion (ectopic teeth). Another disturbance may originate from supernumerary teeth if in the developmental process more teeth than the regular number are formed (hyperdontia). Supernumerary teeth may hinder the development and eruption of regular teeth but can simply lie causing no problems somewhere in the jaws.
Ectopic or impacted, partially erupted teeth are at risk of developing complications such as advanced caries (tooth decay) or periodontal disease (gum disease).
The theme of striking the right balance features prominently with the topic of impacted or ectopic teeth in general. There are many cases where untreated impacted or ectopic teeth do not cause any harm, and where orthodontic treatment (straightening of teeth) is not necessary. There are cases where a watch & wait policy is best, and at the other end of the scale are those cases where interventions are necessary.