The sight of a permanent tooth emerging behind a primary tooth is a frequent dental event, often called “shark teeth” by parents. This temporary double row of teeth is a common developmental stage, typically occurring around age six or seven, most often with the lower front incisors. While the appearance can be surprising, it is usually not a dental emergency and often resolves naturally with observation. Understanding the underlying biology of tooth replacement offers reassurance regarding this process.
Why Permanent Teeth Erupt in the Wrong Position
The normal process of tooth replacement involves the permanent tooth gradually dissolving the root of the baby tooth, a process called root resorption. This root breakdown causes the baby tooth to loosen and fall out, clearing the path for the permanent successor. However, the permanent tooth buds for the lower incisors develop slightly behind the baby teeth, on the side toward the tongue (the lingual side). If the permanent tooth erupts on this altered path and misses the baby tooth’s root structure, root resorption is not properly triggered. The baby tooth remains anchored firmly, and the permanent tooth pushes through the gums behind it, creating the double-row appearance.
The Timing and Normal Resolution
The permanent tooth erupting behind the baby tooth will self-correct once the obstruction is removed. For the lower front teeth, the process should be monitored for two to three months after the permanent tooth first emerges. During this observation period, parents can actively encourage the baby tooth to loosen. Gently wiggling the tooth multiple times a day or encouraging the child to eat crunchy foods helps accelerate the resorption of the remaining root structure. The continuous pressure applied by the tongue and chewing are natural forces that assist in exfoliation. Once the baby tooth is out, the permanent tooth is free to move forward into its correct position.
When Dental Intervention Is Required
A visit to the dentist is necessary if the baby tooth remains firmly in place and shows no significant loosening after the two-to-three-month observation window. Intervention is also warranted if the child experiences persistent discomfort, pain, or difficulty chewing. If the permanent tooth has erupted to a height similar to the baby tooth, it signals that the baby tooth will likely not fall out naturally. The dental intervention is typically a simple extraction of the retained baby tooth. This procedure removes the physical barrier preventing the permanent tooth from migrating into the correct alignment. Removing the baby tooth clears the path, allowing natural forces to begin the alignment process.
Ensuring Proper Tooth Alignment
Once the retained baby tooth is removed, the newly erupted permanent tooth generally moves forward naturally into its proper place in the dental arch. This movement is largely facilitated by the tongue, which exerts constant, gentle pressure on the teeth from the lingual side during speaking and swallowing. The tongue guides the tooth into the space left by the primary tooth. While this type of eruption does not immediately necessitate braces, it can sometimes indicate a potential lack of space in the jaw. If the permanent tooth does not shift into alignment within a few months, or if crowding becomes noticeable, an orthodontic consultation may be recommended. For most children, the natural forces of the mouth are sufficient to correct the alignment.