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Basic Growth and Development of the Face and Dental Arches Development & Morphology of Teeth


 

 

After Logan and Kronfield: JADA 20, 1933 (slightly modified by McCall and Schour). Copyright by the American Dental Association. Reprinted by permission.

Table I-1


Primary teeth generally begin to erupt around six months of age and eruption is completed by 24 to 30 months. Permanent teeth begin eruption between five and six years of age and their eruption is usually completed by 13-14 years of age, except for the third molars (wisdom teeth) which may never erupt.

 

Variations in tooth eruption from normal are not unusual and may be familial. Some infants have erupted teeth at birth (natal) or shortly after (neonatal)1. These teeth are rare and the reported prevalence is 1:21 to 1:30,000. Delayed eruption can also occur because of syndromes (ie: Down’s Syndrome, Ectodermal Dysplasia), developmental defects of teeth, cysts or tumors.

 

Teeth usually erupt earlier for girls than boys and there are also reports of racial differences. Eruption is usually symmetrical and delays of more than 6-12 months from normal should be evaluated.

In the primary dentition, the upper and lower canines will often erupt after the 1st primary molars. The canine teeth are located anterior to the molars and the empty space is often a source of parental concern. 

 

Variations in infant and toddler behavior, sometimes associated with systemic manifestations are common during teething. (See Table I-2) Reported studies are controversial. In spite of the reports parents often will seek assistance. Whether the symptoms are coincidental or associated with infections, they commonly discontinue with the eruption of teeth. Many palliative remedies are available including teething devices and pharmaceuticals, both systemic and topical. Continuation of symptoms beyond 24-48 hours should be evaluated by the physician2 3.

 

Table I-2

Symptoms Attributed to Teething

 
  • Irritability
  • Fever
  • Drooling
  • Diarrhea
  • Mouthing
  • Pain
  • Sleep Disturbance
  • Rash
  • Biting
  • Gum Rubbing
  • Ear Rubbing
  • Decreased Appetite

 

Around five to six years of age preschoolers will begin to notice teeth becoming loose occasionally causing discomfort. This may go on for some time before a tooth is lost – the lower front primary teeth usually are the first lost. This process will continue periodically for the next six to eight years. Again, variability is common with initiation of exfoliation, the rapidity of loss, the associated discomfort, the retention of very loose teeth, and the loss of the final primary tooth around twelve to fourteen years of age. It should be noted, that about the same time the primary teeth begin to exfoliate, the first permanent molars (six year old molars) may begin erupting. This occurs without the loss of any primary teeth, distal to the last primary molar. Here too, there can be some discomfort and irregularities that may require intervention.

 

One of the more common times for a parent to have dental concerns is with the eruption of the permanent lower incisors (front teeth). One or more incisors can erupt lingual or in back of the primary incisors. Often, the lower primary incisors have just become mobile and the parent and/or child is not aware that it is time for these teeth to exfoliate. Parents should be made aware that this is not a dental emergency. They should encourage the child to help exfoliation by wiggling the primary incisors.

Early or delayed loss of primary teeth can be a concern and needs to be evaluated. Premature loss of primary teeth before 5 – 6 years of age can be associated with local factors or systemic problems and requires evaluation and intervention.

 

 

Tooth Eruption/Development


Teething (eruption) and exfoliation of teeth will be described together because one is dependent on the other. (See Table I-1)

 

Table I-1

TABLE CHRONOLOGY OF THE HUMAN DENTITION

 

Tooth Hard Tissue Formation Begins Eruption Root Completed Exfoliation*

 

Primary Dentition


Maxillary

  Central incisor 4 mo in utero 8-12 mo 1 1/2 yr 6-7 yr
  Lateral incisor 4 1/2 mo in utero 9-13 mo 2 yr 7-8 yr
  Cuspid 5 mo in utero 16-22 mo 3 1/4 yr 10-12 yr
  First molar 5 mo in utero 13-19 mo 2 1/2 yr 9-11 yr
  Second molar 6 mo in utero 25-33 mo 3 yr10-12 yr


Mandibular

  Central incisor 4 1/2 mo in utero 6-10 mo 1 1/2 yr 6-7 yr
  Lateral incisor 4 1/2 mo in utero 10-16 mo 1 1/2 yr 7-8 yr
  Cuspid 5 mo in utero 17-23 mo 3 1/4 yr 9-12 yr
  First molar 5 mo in utero 14-18 mo 2 1/4 yr 9-11 yr
  Second molar 6 mo in utero23-31 mo 3 yr 10-12 yr

 

Permanent Dentition


Maxillary

  Central incisor 3-4 mo7-8 yr 10 yr  
  Lateral incisor 10-12 mo8-9 yr 11 yr  
  Cuspid4-5 mo 11-12 yr 13-15 yr  
  First bicuspid 1 1/2 - 1 3/4 yr 10-11 yr 12-13 yr 
  Second bicuspid    2-2 1/4 yr10-12 yr 12-14 yr 
  First molarat birth 6-7 yr 9-10 yr  
  Second molar 2 1/2 - 3 yr 12-13 yr 14-16 yr 
  Third molar 17-21 yr  


Mandibular

  Central incisor 3-4 mo 6-7 yr 9 yr  
  Lateral incisor 3-4 mo 7-8 yr 10 yr  
  Cuspid 4-5 mo 9-10 yr 12-14 yr  
  First bicuspid 1 3/4 - 2 yr 10-12 yr 12-13 yr 
  Second bicuspid 2 1/4 - 2 1/2 yr 11-12 yr 13-14 yr  
  First molar at birth 6-7 yr 9-10 yr 
  Second molar 2 1/2 - 3 yr11-13 yr 14-15 yr  

 

Delayed exfoliation can also be a concern and may be due to local factors or syndromes. Again, with periodic professional oral care and monitoring of development, intervention can be recommended at appropriate times.

As primary teeth erupt the occlusion develops. Here too, alterations from normal are common. They too can be due to environmental factors (habits) and/or congenital/hereditary disorders. The occlusion is assessed by having the child bring their jaws together. This is not always a simple task for some children. When requested they may jut their lower jaw forward or bite to one side or the other. With the primary dentition we are most interested in the anterior posterior relationship of the jaws, the horizontal relationships (from cheek to cheek) and finally the position of the upper and lower teeth. (Figure I-3). Variations from normal should be evaluated depending the child, and if function is compromised, treatment may be indicated.

 

Normal Occlusion in the Primary Dentition

 

Figure 1-3

 

REFERENCES

  1. literature. Cunha RF,  Boer FA, et al. Natal and neonatal and teeth: a review of the Pediatr Dent, 2001; 23:158-162.

  2. Hulland SA, Lucas JO et al. Eruption of the primary dentition in human infants: a prospective descriptive study. Pediatr Dent, 2000; 22:415-421.

  3. Macknin ML, Piedmonte M et al. Symptoms associated with infant teething: a prospective study pediatrics, 2000; 105:747-752

 

ADDITIONAL RESOURCES

  1. Enlow DH, and Hans MG. Essentials of Facial Growth, W.B. Saunders Company, Philadelphia, 1996.

  2. Nowak A. The Handbook-Pediatric Dentistry, 2nd ed. 1999, Chicago, American Academy of Pediatric Dentistry, pp. 7-9.

  3. Oral Health and Learning, NCEMCH, MCHB, DHHS, Arlington, VA 2001.


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