Forensic Dentistry, Second Edition

270 Forensic dentistry

13.3.1 Primary Tooth Formation

Tooth mineralization progresses in an invariant sequence from cusp tips,
through lengthening of the crown’s cervical loop, to formation of the cemento-
enamel junction. Once the crown has formed, root development progresses,
terminating with completion of the root apex or apices.48–50 Dentine forma-
tion precedes and stays ahead of amelogenesis throughout formation.
Most development of the primary teeth occurs in utero. The synthesis
by Lunt and Law^51 continues to be the most comprehensive data available
(also see Kraus and Jordan^52 ). They recorded four development landmarks
for each tooth (Table 13.4): (1) the age at initiation of cusp mineralization,
(2) how much of the tooth crown is mineralized at term, (3) the age after
birth when the crown has finished mineralization, and (4) the age when the
root is complete (root apexification). As shown in Table 13.4, all ten pri-
mary tooth types begin dentin and enamel deposition at their coronal tips
early in the second trimester, and none of the crowns is completely miner-
alized at birth. Consequently, most primary teeth possess a neonatal line
if the infant survives birth.53–55 The maxillary molars are somewhat more
advanced than those in the mandible at term. Mandibular m1 typically
has the crown apices mineralized and united, with the occlusal table com-
plete and evidence of enamel-dentine deposition along the crown’s neck.

Table 13.4 Normative Ages for Key Events in the Development of the
Primary Teeth

Primary
To o t h

Initiation of Cusp

Mineralization

(weeks in utero)

Amount of^ Crown^

Formed at Birth

Postnatal^ Age at

Crown^ Completion^

(months postpartum)

Age at Root

Completion

(years)

Maxilla

i1 14 5/6 1.5 1.5

i2 16 2/3 2.5 2.0

c 17 1/3 9 3.25

m1 15.5 3/4 6 2.5

m2 19 1/5 11 3.0

Mandible

i1 14 3/5 1.5 1.5

i2 16 3/5 2.5 2.0

c 17 1/3 9 3.25

m1 15.5 Occlusal table

complete

5.5 2.25

m2 18 Occlusal table

incomplete

10.0 3.0

Source: Lunt and Law.^51