Seeing a new tooth emerge behind an existing one can be alarming, creating the visual impression of a “double row” of teeth. This developmental stage is a common occurrence during a child’s transition from primary (baby) teeth to permanent teeth. A permanent tooth erupting on the lingual side (toward the tongue) of the baby tooth signals a slight deviation in the natural replacement process. While the condition looks concerning, it has a straightforward biological explanation and is highly treatable, typically affecting children between the ages of five and eight.
Understanding the “Shark Teeth” Phenomenon
The common nickname for this condition, “Shark Teeth,” accurately describes the two rows of teeth visible at once. In a normal transition, the permanent tooth bud develops directly beneath the primary tooth’s root. As the permanent tooth moves upward, it triggers root resorption, where specialized cells dissolve the primary tooth’s root structure. This resorption causes the baby tooth to loosen and fall out, clearing the path for the permanent successor.
This process fails when the permanent tooth bud develops along an off-track pathway, often positioned too far lingually (behind the primary tooth). Because the permanent tooth is not directly pressing against the primary tooth’s root, it fails to initiate or complete the necessary root resorption. The primary tooth remains firmly anchored, even as the permanent tooth erupts through the gum tissue nearby. This ectopic eruption is most frequently observed with the lower central incisors, though it can occasionally affect the upper teeth or primary second molars.
The lower incisors are particularly prone to this because their permanent successors naturally form on the tongue side of the jaw. If the primary tooth root is strong or its resorption is delayed, the permanent tooth takes the path of least resistance and erupts behind the baby tooth.
When to Intervene: The Urgency of Dental Assessment
The presence of a double row of teeth requires close monitoring to determine if professional intervention is needed. A general guideline is to allow a “watch and wait” period if the primary tooth shows any sign of loosening. Encouraging the child to gently wiggle the baby tooth may help speed up the natural exfoliation process.
If the permanent tooth has been visible for two to three months and the primary tooth remains firm, a dental assessment is warranted. A delay in removing the over-retained primary tooth can have potential long-term consequences for dental alignment. The primary tooth acts as a physical barrier, locking the permanent tooth in its displaced position.
Remaining locked lingually may lead to future crowding and bite issues (malocclusion). Addressing the issue promptly prevents complicated alignment problems that could require extensive orthodontic work later. A dentist will examine the area and likely take an X-ray to confirm that the primary tooth root is intact and preventing the permanent tooth from migrating forward.
Treatment Options and Post-Extraction Care
For a primary tooth that is not loosening naturally, the typical treatment is a simple extraction performed by a dentist or pediatric specialist. This procedure is quick and straightforward, involving the removal of the baby tooth to eliminate the obstruction. This intervention immediately frees the permanent tooth, allowing it the necessary space to move into its proper location.
The most reassuring factor is the phenomenon of self-correction, which occurs once the barrier is removed. The constant pressure exerted by the child’s tongue naturally pushes the lingually displaced permanent tooth forward into the newly created space. This natural force is often sufficient to guide the tooth into its correct arch alignment over weeks or months.
Post-extraction care is minimal, including maintaining a soft diet for a day or two and ensuring good oral hygiene around the extraction site. Parents can encourage the child to use their tongue to gently nudge the new tooth forward, supporting the natural self-correction process. Although the prognosis for self-correction is excellent, follow-up monitoring is necessary to ensure the tooth is successfully moving into alignment.
In rare instances where the permanent tooth does not move forward sufficiently after several months, or if significant crowding exists, an orthodontic evaluation may be recommended. However, for most cases of “Shark Teeth,” removing the primary tooth allows the permanent tooth to assume its intended position successfully.