Baby Teeth (deciduous teeth)

- Tooth types.  /  Eruption and tooth-loss timetables.  /  Complications and abnormalities.

During their lifetime, a person will have two sets of teeth. An initial set that serves them during childhood, and then another that will hopefully last them for the remainder of their life.

  • This first set is usually just referred to as the baby or milk teeth.
  • More formally, they are termed the primary or deciduous dentition.

Baby teeth usually begin to come in (erupt) at around age 6 months. And in most cases, by age 12 years all of them have fallen out (exfoliated) and been replaced by the second ("permanent") set of teeth. (See the tables below for more precise ages.)

 

Types of baby teeth: Incisors, cuspids and molars.

Types of baby (deciduous) teeth.

A set of baby teeth includes:

  • All totaled, there are 20 individual primary teeth.
  • They are equally divided (10 each) between the upper and lower arches (jaws).

[Test yourself on the subject of baby tooth identification by taking one of our quizzes.

 
A child has 20 baby (primary) teeth.

A child has 20 baby teeth.

Types and numbers.

As a set, the primary teeth are composed of:

  • 8 Incisors - The center two front teeth are their central incisors. The teeth positioned just to their sides are their lateral incisors.
  • 4 Cuspids - These teeth, also termed canines or eyeteeth, lie next in line behind the incisors.
  • 8 Molars - The first and then second molars are positioned furthest toward the rear of the mouth.


When do the baby teeth come in? (Tooth eruption.)

  • Although a child's deciduous teeth begin to calcify in utero (before the child is born), they typically don't become visible in the mouth until about age 6 months.
  • Usually by age 2 to 2 1/2 years all have erupted and are in place.
Primary tooth eruption time frames.
Tooth type Lower arch Upper arch
Central incisors 6 1/2 months 7 1/2 months
Lateral incisors 7 months 8 months
Cuspids 16 to 20 months 16 to 20 months
First molars 12 to 16 months 12 to 16 months
Second molars 20 to 30 months 20 to 20 months

Variations.

The precise age at which teeth come in can vary. Some children get their teeth relatively early, others later.

  • These variances often correlate with family histories, in the sense that what a child experiences is similar to that which took place with one of their siblings or parents.
  • A 6-month variation in the time of eruption of a tooth is considered normal.
  • Usually the corresponding teeth on each side of the jaw come in during a similar time frame.


When does a child loose their primary teeth? (Tooth exfoliation.)

Baby teeth exfoliate (fall out on their own) as their permanent replacements come in. The table below gives the typical age range for this event for each type of tooth, as well as the kind of permanent tooth that replaces it.

Primary tooth exfoliation (shedding) time frames.
Tooth type Lower arch Upper arch Permanent replacement tooth.
Central incisors 6 - 7 years 6 - 7 years Central incisor
Lateral incisors 7 - 8 years 7 - 8 years Lateral incisor
Cuspids 9 to 12 years 10 to 12 years Canine
First molars 9 to 11 years 9 to 11 years First premolar
Second molars 10 to 12 years 10 to 12 years Second premolar

Exfoliation ages can vary.

Just as with tooth eruption, the precise age at which a deciduous tooth is lost can vary, often by months or years (see the table above). When one does, it can be expected that the corresponding tooth on the other side will be shed during a similar time frame.

The permanent tooth erupting underneath a baby tooth.

An early stage of tooth exfoliation/eruption.

The timing depends on the permanent tooth underneath.

A permanent tooth must reach a certain point in its development before it can erupt.

Eruption initiates once the tooth's crown portion (the non-root part) has completed calcification. But typically 2/3rds of its root must form before it will emerge from the jawbone and into the mouth. (A tooth's root may not finish completely forming until some years after its eruption.)

That means if the natural progress of a child's dental development is comparatively slow, it will delay the age (by months, and possibly years) at which their primary teeth are lost.


Baby teeth (deciduous teeth) are replaced by permanent teeth.

Baby teeth just fall out because their root gets too short to anchor them.

Why do baby teeth come out so easily?

It may seem strange that a child's deciduous teeth are anchored so firmly for so long and then, right on schedule, just seem to fall out.

There's an easy explanation for this. Despite the way that exfoliated baby teeth look, for most of their lifespan they do have a substantial root complex. But as the permanent tooth underneath continues to gradually erupt, its presence causes their root to resorb (dissolve away).

As our graphic illustrates:

  1. As the permanent tooth moves through the jawbone ever closer to the surface, the root of the baby tooth above becomes shorter and shorter.
  2. Finally a point is reached where it's no longer substantial enough to keep it anchored and it is easily dislodged.


What should you do if your child's baby teeth don't come in or fall out on schedule?

If your child's primary teeth don't come in or aren't lost as expected, it will take an evaluation by your dentist to determine what type of attention, if any, is required. This exam will likely require taking one or more x-rays.

A retained baby tooth due to no permanent replacement.

There was no replacement for this baby tooth.

Possible problems or issues -

A) Missing teeth.

Teeth that never form, of course, won't erupt. This deficiency may involve only one, just a few, or possibly several teeth.

In the case of missing permanent ones, the primary tooth they were intended to replace will not fall out as expected. A retained deciduous tooth can't be expected to last a lifetime and a plan for its eventual replacement should to be made.

[Here's a digital smile makeover case that illustrates this point.]

A retained baby tooth due to the impaction of its replacement tooth.

This baby tooth's replacement is impacted and can't come in.

B) Tooth crowding / misalignment.

Abnormalities with baby tooth exfoliation may be due to issues involving poor tooth orientation or alignment.

After an evaluation, the child's dentist can explain what treatment can be used (either immediately or in stages as the child develops) to help to make room for and/or guide the permanent teeth into place.

Examples

  • Crowded baby teeth may call for the use of "serial extractions." This is a process where selected baby teeth are removed a little bit early so to facilitate the eruption of the permanent teeth underneath.
  • Some severely misoriented permanent teeth may be impacted (unable to erupt). If so, their corresponding baby tooth will be retained.
  • It may need to be extracted and the impacted tooth surgically exposed so some type of orthodontic appliance can be used to guide it into its proper place.

A maxillary supernumerary tooth that interuputing with permanent tooth eruption.

This supernumerary tooth is interfering with normal tooth eruption.

C) Extra teeth.

Supernumerary (extra) permanent teeth may block or otherwise interfere with nearby teeth from coming into place. This can result in retained baby teeth.

The solution is typically to remove the supernumerary and then, if needed, orthodontically guide the neighboring teeth into place.

D) Normal abnormalities.

Sometimes what a parent interprets as being a problem, while not exactly ordinary, is something that can be expected to either resolve on its own or require only minor dental treatment (such as the dentist removing the offending baby tooth).

These types of situations might include:

  • Permanent teeth that erupt slightly off target, resulting in baby teeth that aren't loose enough to fall out on their own.
  • Permanent incisors that come in on the backside of the baby teeth, resulting in a "double row."
  • Eruption complications associated with fused baby teeth.

E) Medical syndromes.

A number of medical conditions are known to be associated with the premature or delayed loss of baby teeth.

  • Premature loss - Fibrous dysplasia, Juvenile diabetes, Histiocytosis, Cyclic neutropenia, Hypophosphatasia, Chediak-higashi syndrome, Vitamin D resistant Rickets.
  • Delayed loss - Cleidocranial dysplasia, Sclerosteosis, Gardner's syndrome, Vitamin D resistant Rickets, Downs syndrome, Hypopituitarism, Hypothyroidism.

Immediate action may not be required but a general plan for managing the child's dental situation should be made.

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