Anatomy – Primary Dentition

Anatomy – The Primary Dentition

Human teeth are divided largely into two groups of teeth which a genetically regulated.  From 6 months old to 12 years old primary teeth are present in the mouth.  Developmentally the dentition commences mineralization (calcification) at about 16 weeks in utero and continues through foetal life, birth and completes growth at approximately 3 years of age.
The first primary teeth erupt into the mouth at about 6 months post natal. The final primary teeth to erupt teeth to the mouth are the second primary molars.  These are the only teeth in the mouth until approximately 6 years old when the first permanent molar erupts.
From 6 years old to 12 years old there are both primary teeth and permanent teeth present in the mouth
From 12 years only permanent teeth are present.

[See Clark DH  Practical Forensic Odontology. 1992, Wright. Oxford. ISBN 0-7236-1511-X] Chapter 3.
For Dental Age Estimation purposes, only the teeth on the Left side are used.  This is because there is almost perfect Right – Left Symmetry in Tooth Development. Statistically there is no advantage in using contralateral teeth as the data from each side would need to be combined and averaged.
This bilateral symmetry has the advantage that if a tooth is lost due to trauma or developmental absence, the contralateral tooth can be substituted.

Skull of a child approximately 3 years old.  This shows the complete primary dentition of 20 teeth which highlights the 10 teeth discernible on the Left side.

PrimDent01

 

Occlusal view of the Maxillary (Upper Arch) of the complete Primary Dentition.
The teeth on the left side are labelled using the British Dental Journal Notation
[ see Tooth Nomenclature ]

PrimDent03

 

Occlusal view of the Mandibular (Lower Arch) of the complete Primary Dentition.
The teeth on the Left side  are labelled using the British Dental Journal Notation.

PrimDent04
[ see Tooth Nomenclature ]

It is unusual for primary teeth only to be used for Dental Age Estimation.  Investigators who wish to obtain reliable data should see [ Liversidge HM, Molleson T. Variation in crown and root formation and eruption of human deciduous teeth.  American Journal of Physical Anthropology 2004; 123: 172-180 ].

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