Premolars, often called bicuspids, are eight permanent teeth located in the adult mouth. They are positioned between the canine teeth and the larger molars, serving as a transitional chewing surface. As part of the permanent dentition, they are not designed to be shed naturally. Premolars should remain in the mouth for a lifetime unless removed due to disease or intentional procedures. The confusion about premolars stems from the complex transition from primary to permanent teeth.
Understanding the Primary-Permanent Tooth Transition
The belief that premolars fall out stems from a misunderstanding of which primary teeth they replace. A child’s mouth does not contain primary premolars, as this class of tooth is unique to the permanent adult dentition. The teeth that occupy this space are the primary, or deciduous, molars. Children have eight primary molars overall.
Natural tooth loss, known as exfoliation, occurs when the root of the primary tooth is dissolved by the pressure of the developing permanent tooth beneath it. Once the root is weakened, the primary molar loosens and falls out, typically between the ages of 10 and 12. This shedding creates the necessary space for the permanent premolar to erupt and take its place. Primary molars are the predecessors of permanent premolars.
The permanent molars (first, second, and wisdom teeth) do not replace any primary teeth. Instead, they erupt behind the primary teeth to expand the dental arch. This means permanent premolars are a new addition to the dental structure, taking over the grinding function previously performed by the primary molars.
When Premolars Emerge
The appearance of permanent premolars occurs during the mixed dentition phase. They begin to erupt after the first permanent molars and many permanent incisors have already emerged. The first permanent premolar typically emerges around ages 10 to 11, replacing the primary first molar.
The second permanent premolar follows shortly after, erupting between the ages of 11 and 12. Premolars are among the last teeth to fully emerge before the permanent canines and second molars complete the dental arch. Their arrival marks a significant developmental stage, transitioning the child’s bite toward a mature adult occlusion.
Causes of Premolar Loss in Adulthood
Since premolars are permanent teeth, their loss in adulthood is due to disease, trauma, or intentional removal. The primary cause of permanent tooth loss is advanced periodontal disease, often called gum disease. This chronic bacterial infection destroys the soft tissue and supporting alveolar bone surrounding the tooth root. As bone is lost, the premolar becomes mobile, eventually requiring extraction.
Decay and Trauma
Extensive dental caries, or decay, is another major reason for loss that leads to structural failure. If decay progresses deep into the tooth, it compromises the structural integrity of the crown and root, potentially leading to fracture or infection of the dental pulp. When damage is too severe to be restored, the tooth must be extracted to prevent infection spread. Physical trauma, such as an accident, can also cause fractures that necessitate immediate removal.
Orthodontic Extraction
In some cases, premolars are intentionally removed for therapeutic reasons, most commonly in orthodontics. Orthodontists may extract one or more first premolars to create necessary space within a crowded dental arch. This allows the remaining teeth to be properly aligned and corrects severe bite issues. This planned removal is a strategic decision to achieve a stable and functional bite.