What to Tell Your Patients About Tooth Eruption

Marvin H. Berman, DDS


As we approach the beginning of a new year, I’m reminded of the questions that dentists, parents, and children have about when their teeth are coming in and when they’re falling out.

Why do some infants experience the eruption of their baby (primary) teeth as young as 3 or 4 months old whereas others may be 10 months old with no evidence of tooth eruption? In some instances, newborns may come into the world with two or three teeth already visible, usually supernumerary or extra teeth. 

For generations, children have been singing “All I Want for Christmas Is My Two Front Teeth” after losing their baby central incisors and anxiously awaiting their permanent central incisors. How early is early? How late is late? And when should we be concerned? We certainly don’t want to create alarm. But on the other hand, we don’t want to overlook a potential problem.

So, let’s review some common facts.

The 20 primary teeth are calcifying in utero during the late first trimester and second trimester of pregnancy. The primary central incisors usually begin to erupt at 6 months in infancy, the lateral incisors at 8 months, the first primary molars at 12 months, the canines at 18 months, and the second primary molars at 24 months.

The permanent teeth begin to erupt at 6 years old with the arrival of the 6-year molar, which  erupts behind all the existing primary teeth. Most commonly, the central incisors erupt at 7 years, and the lateral incisors erupt at 8 years. The first bicuspids appear at 10 years, and the canines erupt at 11 years. The second bicuspids and second molars both show up at 12 years. The third molars or wisdom teeth, if not congenitally absent, erupt somewhere in the early to late teens.  

Now, there are some general rules of thumb when there are significant departures from these normal patterns. For example: 

  • If an infant is 8 months old and no teeth have erupted, but you see little bulges in the gums corresponding to the outline of teeth, do nothing. But if an infant is 10 months old with no outlines of teeth visible, take a radiograph to assess the possibility of congenitally absent teeth. At the same time, you might speak to the child’s pediatrician about the possibility of hormonal imbalances, such as thyroid issues.
  • If an infant is 2 years old with the primary central incisors and primary canines erupted, the first primary molar is erupting, and the second primary molars are peeking through, but no maxillary primary lateral incisors are visible, you can be reasonably sure that those teeth are congenitally missing. Take a radiograph to verify.
  • As a general rule, a panoramic radiograph should be taken at the age of 6 or 7 years when the primary teeth are beginning to exfoliate and the permanent teeth are beginning to erupt to look for any indication of supernumerary or congenitally missing teeth
  • A child is approaching the age of 12 years and the anterior primary teeth have all been replaced with their permanent successors, but the primary molars don’t seem to be exfoliating. A radiograph of the roots of the primary molars reveals very little resorption, while the roots of the unerupted succeeding permanent teeth are almost fully formed and would like to make their move. This is usually an indication for extraction of the primary teeth to allow the permanent ones to erupt. On the other hand, if the roots of the permanent teeth are only half formed, that would be an indication that the exfoliation and eruption processes although late are in synch, so no extractions are indicated at this time.

Note, however, in the above example that a thorough medical history may reveal details that would warrant a change of direction. 

With most children, baby teeth falling out and permanent teeth coming in is an amazingly orderly phenomenon. But there are many situations where there are discrepancies between the size of the permanent teeth and the ability of the mouth to accommodate them, resulting in crowded or “crooked” teeth, necessitating orthodontic treatment.

This subject warrants further discussion. But general dentists, pediatric dentists, and  orthodontists should be able to recognize aberrant clinical situations related to tooth eruption and be able to provide competent counsel and/or treatment.

Dr. Berman is an internationally recognized pediatric dentist with a career as a successful practitioner and as a popular world-class lecturer spanning more than 5 decades. He has been an ambassador for dentistry as a health reporter on CBS (News Radio 78) and via media appearances as a consumer advisor for the ADA, the Chicago Dental Society, and the Academy of Pediatric Dentistry and as co-author of Essentials of Modern Dental Practice. He has published numerous articles and is a member of many professional and service organizations including honorary membership in the Hinman Dental Society. He can be reached at marvy18@me.com.

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