Primary teeth, also known as deciduous or “baby” teeth, are typically replaced by permanent successors through a process called exfoliation, which usually concludes around age 12 or 13. Retaining a primary tooth into the mid-teen years, such as at age 15, is atypical and requires professional dental attention. A tooth remaining past the expected timeline is called a retained primary tooth.
Primary Causes of Retained Teeth at Age 15
The most frequent reason for retention is the complete absence of the underlying permanent tooth, a condition called hypodontia. Without the adult tooth present to push and guide it, the primary tooth’s root does not undergo natural resorption. This lack of a successor allows the primary tooth to remain firmly anchored in the jawbone.
Even when the permanent tooth exists, its failure to erupt can prevent shedding. This occurs if the adult tooth is physically blocked or positioned incorrectly, known as impaction or ectopic eruption. The permanent tooth may be angled away from the primary tooth’s root or trapped beneath bone, preventing the necessary pressure for exfoliation.
Another cause is ankylosis, where the primary tooth fuses directly to the alveolar bone of the jaw. This fusion eliminates the periodontal ligament space necessary for normal movement and exfoliation, locking the tooth in place. Ankylosed teeth often appear submerged compared to adjacent permanent teeth as the jaw grows around them. These three conditions—hypodontia, impaction, and ankylosis—account for most instances of retained primary teeth.
Potential Consequences of Delayed Shedding
Allowing a retained primary tooth to remain untreated can lead to significant issues with bite alignment, or malocclusion. The primary tooth occupies space needed for the permanent tooth, forcing the adult tooth into an incorrect position or causing it to remain impacted. This displacement often results in crowding and shifting among adjacent permanent teeth.
Retained primary teeth often sit awkwardly next to permanent teeth, creating areas difficult to clean effectively. This misalignment increases the risk of plaque accumulation, making the retained tooth and its neighbors susceptible to decay and periodontal disease. Additionally, primary tooth roots are less robust than permanent roots, potentially leading to faster deterioration.
If the permanent tooth is present but impacted, its continuous efforts to erupt can damage surrounding structures. The pressure from the trapped permanent tooth may inadvertently cause resorption damage to the roots of the retained primary tooth or adjacent permanent teeth. Addressing the retained tooth prevents this ongoing damage.
Dental Assessment and Management Strategies
The first step in assessment is diagnostic imaging, typically using a panoramic radiograph or a localized X-ray. These images confirm whether the permanent successor tooth exists, its exact location, and its orientation within the jawbone. The X-ray also reveals if the primary tooth is ankylosed or if there is damage to the roots of neighboring teeth.
If imaging confirms an impacted permanent tooth, standard treatment involves removing the retained primary tooth. This extraction clears the path, often allowing the permanent tooth to begin natural eruption. In some cases, eruption requires orthodontic intervention, using braces or specialized appliances to guide the impacted tooth into its correct position.
When the cause is hypodontia, the treatment focuses on long-term space management. If the retained primary tooth is healthy, stable, and aesthetically acceptable, one strategy is to maintain it for as long as possible. Careful monitoring ensures the tooth remains free of decay and that the surrounding bone structure stays intact.
Eventually, most retained primary teeth require replacement, especially if they become ankylosed or wear down significantly. Planned extraction in late teens or early adulthood allows for prosthetic replacement options. Common solutions include a fixed dental bridge, which uses adjacent teeth for support, or a dental implant, a surgical fixture placed directly into the jawbone to support a crown.
In specialized cases, autotransplantation may be considered, involving surgically moving a non-essential tooth, like a wisdom tooth, to replace the extracted primary tooth. The choice between maintenance, a bridge, or an implant is highly individualized. This decision depends on the patient’s age, bone health, and the overall orthodontic plan.