Deciduous, or baby teeth, generally begin to loosen and shed around the age of six or seven, continuing until approximately age twelve. This transition allows the permanent teeth to emerge. When a baby tooth lingers past this expected timeline, it warrants investigation by a dental professional. A retained baby tooth indicates an underlying issue is preventing the natural shedding mechanism.
How Baby Teeth Normally Fall Out
The natural shedding of a baby tooth is a coordinated biological process driven by the permanent tooth developing beneath it. This mechanism is called root resorption, where specialized cells called odontoclasts dissolve the root structure of the baby tooth. As the permanent tooth begins its eruption, it applies pressure and releases chemical signals that initiate the breakdown of the baby tooth’s root. This progressive dissolution removes the tooth’s support, causing the tooth to become loose and eventually fall out.
The permanent tooth is the primary catalyst for this shedding, clearing its path into the dental arch. If the permanent tooth is not positioned correctly or is congenitally absent, the baby tooth may remain firmly in place.
Specific Reasons for Tooth Retention
One major reason a baby tooth fails to loosen is ankylosis, where the tooth root fuses directly to the jawbone. This fusion eliminates the periodontal ligament, preventing the root from dissolving and the tooth from moving. An ankylosed tooth often appears shorter than its neighbors because it fails to keep pace with jawbone growth, sometimes leading to a submerged appearance. Dental trauma or infection are thought to be contributing factors to this condition.
A second common cause is ectopic eruption, where the permanent tooth grows along an abnormal path and misses the root of the baby tooth entirely. Since the permanent tooth is not positioned directly beneath the baby tooth, it cannot trigger the necessary root resorption process. This incorrect positioning most frequently affects the upper canine teeth or the first permanent molars. The permanent tooth may emerge in an unusual location, such as on the roof of the mouth, while the baby tooth remains solid.
Dental agenesis is the congenital absence of the permanent tooth that is supposed to replace the baby tooth. If the successor tooth never forms, there is no biological signal or physical force to initiate root resorption. The baby tooth, lacking a replacement, can remain functional for many years, sometimes into adulthood. This condition, also known as hypodontia, is often hereditary.
Severe physical crowding in the jaw can impede the eruption of the permanent tooth, forcing it into an abnormal angle or position. This lack of space prevents the permanent tooth from making the proper contact necessary to resorb the baby tooth’s root. The permanent tooth may become impacted or erupt outside the normal line of the arch.
Potential Problems Caused by Delayed Shedding
When a baby tooth is retained too long, it can lead to complications with the developing adult dentition. One serious outcome is the impaction of the permanent tooth, which becomes trapped in the jawbone because the baby tooth is blocking its path. This blockage can cause the adult tooth to become submerged or to erupt at an incorrect angle.
Delayed shedding commonly causes misalignment and crowding issues. If the permanent tooth emerges behind the retained baby tooth, often called “shark teeth,” it erupts into an occupied space. This forces the permanent tooth into an incorrect position, potentially leading to bite problems.
An un-shed baby tooth can exert pressure on its neighbors, possibly damaging the roots of adjacent permanent teeth. In cases of ankylosis, the retained tooth can cause adjacent teeth to tip inward, collapsing the space needed for the adult tooth. It can also prevent the opposing tooth in the opposite jaw from aligning correctly, causing it to over-erupt.
When to Consult a Dentist
A dental consultation is warranted when a baby tooth remains solid and shows no signs of loosening past the typical age range of seven or eight years. Parents should look for specific warning signs, such as the permanent tooth visibly erupted behind the baby tooth. Any reports of pain, swelling, or discomfort around the retained tooth should also prompt a visit.
A dentist will use a clinical exam and dental X-rays to determine the cause of the retention. X-rays confirm the presence or absence of the successor permanent tooth and check its position. Depending on the diagnosis, management may involve monitoring, or if the permanent tooth is blocked, the retained baby tooth may need extraction. In cases of dental agenesis, the retained baby tooth may be maintained as long as it is healthy and structurally sound.