The appearance of a larger, permanent tooth erupting directly behind a smaller baby tooth can be startling for any parent. This situation is a frequently seen developmental stage in early childhood dentition, most often occurring around the age of six or seven. While it may look concerning, seeing a new tooth emerge before the old one has fallen out is generally a common and temporary experience. This process is a normal variation in the exchange of primary teeth for permanent teeth and rarely indicates a serious problem requiring immediate intervention.
Identifying the Appearance of “Shark Teeth”
This dental phenomenon is often informally referred to as “shark teeth” because the child temporarily appears to have two rows of teeth, much like some species of sharks. The visual effect of a new, sometimes jagged, tooth peeking out on the tongue side of a baby tooth often causes initial alarm. This double-row presentation is most commonly observed with the lower front teeth (mandibular central incisors), which are typically the first baby teeth to be replaced.
The eruption can also occur with the upper molars later in childhood, around age eleven. In most cases, the permanent tooth emerges slightly off-center on the lingual side (the side toward the tongue) of the jaw. Although the sight of a permanent tooth fully or partially erupted behind a firmly held baby tooth seems alarming, it is a common occurrence during the transition years.
The Mechanism of Permanent Tooth Eruption
The development of permanent teeth normally involves a biological process that ensures the baby tooth is shed before the adult tooth takes its place. As the permanent tooth grows and pushes upward, it stimulates specialized cells to dissolve the root of the baby tooth, a process called root resorption. This gradual dissolution causes the baby tooth to become loose and eventually fall out, clearing the path for the permanent tooth.
In the case of “shark teeth,” the permanent tooth develops on the tongue side of the jaw and follows a slightly different trajectory. If the permanent tooth does not align perfectly to push directly against the center of the baby tooth’s root, the root resorption process may fail to fully trigger or complete. The permanent tooth then erupts lingually (behind the primary tooth) because the baby tooth’s root remains intact and holds the tooth firmly in place. This slight misalignment is the explanation for the double-row appearance.
When to Consult a Dentist
If the permanent tooth has emerged and the baby tooth is noticeably loose, the situation will often resolve on its own. Parents should encourage children to gently wiggle the loose baby tooth with their tongue or clean fingers to help accelerate the natural exfoliation process. Once the baby tooth is gone, the constant pressure from the tongue will often guide the permanent tooth forward into the correct position over a few months.
Intervention from a dental professional becomes necessary if the baby tooth remains firmly in place two to three months after the permanent tooth has begun to erupt. If the permanent tooth is more than half-erupted and the baby tooth shows no signs of loosening, a dentist may need to assess the situation with an X-ray. The typical treatment is extraction of the baby tooth to ensure the permanent tooth has adequate space to move into its proper alignment.