Lecture 3: Odontochronology &
Introduction to the Projects
What can we do with tooth sections?
• 1. Reconstruct the chronology of dental
development
• 2. Reconstruct the pattern of stress during
dental development
• 3. Estimate life history variables in extinct
species
Measurable Aspects of Dental
Development
Making a tooth
• Daily secretion rate of
enamel and dentine (DSR)
• Periodicity of long period
increments (repeat interval
or RI)
• Extension rate; made up of
angle of striae of Retzius or
Andresen lines and DSR
• Degree of decussation;
curvature of dentine tubules
• Enamel thickness
• Taken together = crown and
root formation time.
Making a dentition
• The ages at initiation and
completion of each tooth
• The age at eruption
(gingival vs alveolar
emergence) of each tooth
• Together create a pattern
of overlap of tooth
formation and eruption
X days
Distance y/x days = extension rate
Distance y
Determination of DSR, RP
& crown formation times
Determination of
crown extension rate
Meniscotherium chamense
Eocene
Striae periodicity determined by measurement
(5 days in langur 845/70)
Striae periodicity determined by count
(7 days in baboon A436)
The age of each ablation pit was determined using growth
increments in dentine and the neonatal line.
8
Neonatal line
in M1
Courtesy R. Ferrell
Birch W & Dean MC (2009). Rates of enamel formation in human deciduous teeth. In Comparative Dental Morphology,
Koppe T, Meyer G & Alt KW, eds. Basel, Karger: pp 116-120.
Matching Accentuated Lines Across Tooth
Types
First Molar
Upper Canine
Courtesy Dr Rebecca Ferrell
M1 Mesial
M1 Distal
Leptadapis magnus
M1
M2
M3
Age in Years
Lower Molar Crown Development in
Leptadapis magnus
?
?
?
Palaeoloxodon
cypriotes: 200 kg
Late Pleistocene
Plate height externally = 60.5 mm, probably M2 or M3,
Internal height along enamel dentine junction (edj) = 53 mm
Estimated plate formation time = 6 yrs
P. falconeri
Matching
Lamellae
in P.
cypriotes
A
500µm
A
B
B
C
C
Estimated offset:
7 days
12 plates; 3 months extra
Estimated total formation
time 6.25 years,
excluding root formation
http://researchnews.osu.edu/archive/neanderpics.htm
Wilson Bands & Linear Enamel Hypoplasias
Variation between individuals from ‘stress’ lines;
accentuated lines in dental tissues
• Mandrills and other primates-