Mesiodens / Mesiodentes (midline supernumerary teeth)

- What are they? / Pictures. / Why and how often do they form? / What problems can they cause? / Mesiodens diagnosis and treatment.

Before / After

Link to mesiodens treatment makeover.


Link to picture of a mesiodens.

What is a mesiodens?

One developmental problem that a child can experience is the formation of supernumerary (extra) teeth. The most common type of supernumerary tooth is the mesiodens.

By definition this is an extra tooth that lies between a person's central incisors (the center two teeth). If more than one is present, the plural "mesiodentes" is used.

Why do mesiodentes form?

a) Extra tooth buds.

Supernumerary teeth develop from tooth "buds." The question then becomes, why do these extra buds form?

There is no consensus as to their cause but the most widely supported theory suggests that it's simply due to hyperactivity of the dental lamina. (Dental lamina is a type of epithelia tissue that gives rise to tooth buds and therefore teeth. It first appears during the 6th week in utero.)

b) Genetics.

Having a mesiodens tends to correlate with family history. Twins, siblings and multiple generations of a family line frequently share this trait. Females tend to be affected just half as often as males.

c) Medical syndromes.

The presence of a mesiodens is commonly associated with certain medical conditions and syndromes. This includes: cleft lip and palate, craniofacial anomalies, Gardner’s syndrome and cleidocranial dysostosis. But if you do have one, it does not mean you necessarily have one of these concerns.

An erupted mesiodens.

An animation showing expected size of an erupted mesiodens' root.

The white shadow approximates the size and shape of its root.

How often do mesiodentes form?

  • For the general population, the prevalence of hyperdontia (having supernumerary teeth) runs on the order of 0.15 to 3.9%.

    The incidence rate for having a mesiodens (a extra tooth between your center teeth) generally runs between 0.15 and 1.9%. (This may vary with race.)

  • Having an upper mesiodens is much more common than a lower one. (82% of cases.)
  • They may occur individually or as multiples. 1/3rd of people who have one have additional supernumerary teeth.
  • Only about 25% of mesiodentes ultimately erupt (come through the gums, like shown in our picture).

Classifications of mesiodentes.

  • Supplementary - A primary (baby tooth) mesiodens. When compared to neighboring teeth, supplementaries usually look relatively normal.
  • Rudimentary - A permanent (adult) tooth mesiodens. These teeth are usually somewhat abnormal in size and shape.
  • Inverted - This is the situation where the tooth's position is flipped 180 degrees. (The tooth looks as if its headed in the wrong direction.)

What kinds of problems can having a mesiodens cause?

Here are some of the types of complications that can occur when a mesiodens is present.

a) Problems with teeth coming in.

Having a mesiodens is the most common reason for the delay or failure of the eruption of a person's central incisors (their center teeth). Studies suggest that the incidence rate for this complication lies between 26 and 52% of cases.

b) Crooked teeth.

A mesiodens, erupted or not, will frequently cause the adjacent central incisors to become displaced, rotated or have a gap between them (a diastema). Studies suggest that the incident rate for these complications lies on the order of 28 to 63% of cases.

c) Root abnormalities.

The root formation of a person's central incisors may be affected by the presence of the extra tooth (such as having a pronounced curvature). Root damage (resorption) may occur in rare cases.

d) Cysts.

The formation of a cyst in association with a mesiodens has been reported to occur in 4 to 11% of cases.

e) Ectopic eruption.

Rather than coming through the gums in normal fashion, a mesiodens may erupt ectopically (in a strange location or position). This can include the nasal cavity (a possibility with inverted ones) or the patient's palate.

Treatment and management.

a) Supplemental (baby-tooth) mesiodentes.

These supernumeraries are often left alone, as much for the reason that they are overlooked as any other.

It's common for supplemental mesiodentes to erupt, and they typically have a size and shape that is relatively normal when compared to their adjacent teeth. This, combined with the fact that many young children do not see a dentist, means that they frequently have come in and fallen out without ever having been identified.

In cases where an unerupted one is discovered, it is often left alone too for fear that the surgical procedure needed to remove it could result in damage to nearby developing teeth.

b) Rudimentary (permanent tooth) mesiodentes.

Since only about 25% of mesiodens erupt, treatment usually involves managing those still in the jaw bone. The treatment approach chosen will depend upon the person's stage of dental development.


Very young children.

Unerupted rudimentary mesiodentes discovered in very young children are typically left alone for the time being. A part of the concern is that the surgical process that would be needed to remove them could damage nearby developing permanent incisors.

Children with mixed dentition.

Once a child has first entered the mixed dentition stage (a point where their first permanent teeth have started to come in) a dentist may recommend that the extra tooth should be extracted.

Doing so can help to promote the eruption of the permanent incisors (as opposed to the situation where after the supernumerary tooth has been removed the incisors still won't come in). It may also aid the erupting permanent teeth in being able to achieve a more normal alignment.

Older children.

Another approach is to postpone removing the mesiodens until the roots of the adjacent central incisors are almost fully formed (age 10 or so). Even after removing the tooth the incisors may take some months or years to erupt.

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Teens and adults.

The forces that cause tooth eruption diminish with age. That means the later a mesiodens is extracted the more likely that the neighboring incisors won't go ahead and come in on their own.

For this reason, after the removal of the offending tooth the dentist will need to periodically monitor the progress of the incisors via x-rays.

Assisted orthodontic eruption.

In cases where it appears that the incisors have adequate space in which to erupt but haven't shown progress within the last 6 to 12 months, the dentist may determine that they need assistance.

This typically consists of exposing the unerupted teeth (a minor surgical procedure) and then attaching some type of orthodontic appliance (braces) to them so to assist and guide them into place.

An erupted mesiodens.

Animation illustrating before and after mesiodens treatment.

As a solution, the mesiodens is usually extracted and orthodontic treatment performed. [More about this digital makeover case.]

Orthodontic treatment.

Whenever a mesiodens has been present (erupted or unerupted), some degree of generalized full-mouth tooth misalignment is common (tooth crowding, shifted midline). Orthodontic treatment (braces) can be used to correct these issues (like illustrated in our digital makeover picture).

Cases where no treatment is taken.

It's possible that even when a mesiodens is present that a person's permanent teeth have erupted satisfactorily. (If so, possibly the extra tooth has only been discovered unexpectedly later on in life.)

In these types of cases a decision might be made to not remove the tooth but instead monitor it. Periodic observation would include the use of x-rays to evaluate for changes that indicate cyst formation or damage to neighboring teeth.

How are mesiodentes identified?

An x-ray showing a maxillary mesiodens (midline supernumerary tooth).

An x-ray of a mesiodens (supernumerary tooth).

X-ray examination.

Because 75% of mesiodentes don't erupt, the norm is if one is present it isn't seen.

Since they are simply teeth (just extra ones) they can be identified by x-ray examination. One difficulty with early detection however is that the area where they lie isn't always routinely x-rayed.

Other methods.

a) Supplemental (baby tooth) mesiodens.

As mentioned above, baby-tooth supernumeraries frequently do erupt. But due to their normal-looking appearance and the fact that young children often aren't seen by a dental professional, they are frequently overlooked and have come in and ultimately fallen out without ever having been identified.

b) Rudimentary (permanent tooth) mesiodens.

It's fairly common that a search for a mesiodens isn't begun unless the patient's central incisors (one or both) are late in erupting, or else have come in but are displaced.

Additional tip-offs can be that the primary (baby tooth) incisors are overretained (don't fall out). Or else that the permanent incisors have erupted ectopically (in a strange location or position).

[Reference sources for this page.]



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