A permanent tooth emerging behind a still-present primary, or baby, tooth is a phenomenon most common with the lower front teeth. This unusual appearance creates a temporary double row, which can look alarming. While the sight of two teeth occupying the space of one may suggest something is wrong, this is a relatively common occurrence during the transition to adult teeth. This stage of dental development requires monitoring to ensure the permanent tooth moves into its correct position.
Understanding “Shark Teeth”: The Eruption Mechanism
The appearance of a permanent tooth behind a baby tooth is frequently nicknamed “shark teeth” due to the temporary double-row effect, similar to the rows of teeth found in sharks. This occurs due to a variation in the normal process of tooth replacement, which centers on root resorption. The typical process involves the developing permanent tooth moving upward and forward, triggering specialized cells called odontoclasts to dissolve the baby tooth’s root directly above it.
In cases of shark teeth, the permanent tooth erupts slightly off its ideal path, often emerging on the tongue side (lingually). Since the permanent tooth is not directly pushing on the center of the baby tooth’s root, the natural signal for root resorption is missed or delayed. The primary tooth remains anchored, while the permanent tooth bypasses it and pushes through the gums behind it.
What to Expect: Waiting for the Primary Tooth to Fall Out
A “wait and watch” approach is appropriate because the situation often resolves naturally. The permanent tooth, even erupting behind the baby tooth, still exerts pressure against the primary tooth. This natural force is often enough to stimulate the remaining root resorption needed to loosen the baby tooth.
Parents should encourage the child to gently wiggle the baby tooth with their tongue or fingers. This movement helps break down the remaining root fibers and accelerate the exfoliation process. Once the baby tooth is out, the pressure from the child’s tongue during speaking and swallowing naturally guides the permanent tooth forward into its correct alignment. This repositioning typically occurs over a few weeks. Maintaining oral hygiene is important during this period, as the crowded area can trap food debris and plaque.
When to See the Dentist: Signs That Intervention Is Needed
While many cases of shark teeth resolve on their own, professional intervention is necessary if the baby tooth remains in place. The most common criterion for a dental visit is if the baby tooth shows no signs of movement or loosening after the permanent tooth has been visible for six to eight weeks. If the permanent tooth has erupted significantly past the gum line without the baby tooth becoming loose, consult a pediatric dentist.
Other Signs That Intervention Is Needed
Other signs that warrant a dental appointment include the child experiencing pain, swelling, or localized gum infection. A professional assessment is also needed if the permanent tooth is growing at a severe angle or if the double row is present in multiple locations, to prevent long-term alignment issues.
Treatment
The primary treatment in these cases is the extraction of the baby tooth under local anesthesia. This procedure clears the path, allowing the forces of the tongue and cheek muscles to guide the permanent tooth into its proper position over time.