Comparative dental development and microstructure of ... - UCL

188 A. D. BEYNON ET AL.
Figure 12. Confocal light image of striae of Retzius and enamel cross striations in the cervical region of the
P. nyanzae M 2 . There are six cross striations between adjacent striae. (Fieldwidth 360 μm.)
(S.D.=0·31, range=1·66–2·83). No trend
in values from large to small, or vice versa,
existed through the cuspal dentine of these
teeth.
Measurements of spacings of daily lines in
the more lateral regions of the crowns of
both P. heseloni and P. nyanzae were much
smaller than those made in the axis of the
cuspal dentine (Table 4). At the EDJ they
were typically 1·5 μm or less. Values around
2 μm were more typical at the EDJ in occlusal
areas between cusps and further in
towards the pulp chamber.
The ratio of the amount of dentine
formed to the amount of enamel formed
between the EDJ and accentuated lines
common to both tissues appear in Table 4.
This varied between 1:1·6 and 1:2·8 in P.
heseloni. The most extreme values occur in
the cervical region of the two molars attributed
to P. nyanzae where ratios of 1:3 and
greater can be observed. By way of contrast,
in the dm 2 (Individual IV) and the M 1
(Individual III) attributed to P. heseloni, that
have clear neonatal lines which mark both
the enamel and dentine occlusally, the
ratio of dentine to enamel formation is 1:1
either side of the dentine horn. This occurs
here partly because the high rate of dentine
formation (3·5 μm per day) closely matches
the rate of enamel formation (4·0 μm per
day) in this position. However, some decussation
in the enamel prisms here (but in
none of the dentine tubules) equalizes the
distance over which each tissue forms in this
time.
Crown completion times
The perikymata counts made from the
replicas of all Proconsul tooth surfaces are
presented in detail in Appendix 1 by tooth
type and by each aspect of each tooth