Table 1.
Protocol of the dates of fluorochrome injections and the respective ages in postnatal days (0 = day of birth) of the six individuals at the day of injection.
Figure 1.
Sectioning plane of tooth and fluorescent labels in enamel and dentin.
a. Left M1 exhibiting cuspal wear, buccal view. The red line indicates the location of the sectioning plane running through the highest points of the mesial cusps. b. Micrograph of a bucco-lingual ground section (section plane indicated by red line in Figure 1a) of the worn left M1 showing fluorescent labels (green = calcein; red = oxytetracycline) from the first and second injection periods in enamel and dentin. Age at death 327 days. Crown formation is completed and root formation has commenced. White frames indicate areas where measurements of enamel apposition rate were performed. Buccal to the left. c. Micrograph of a bucco-lingual ground section of an unworn M1 (mesial lobe) that has just erupted beyond the alveolar crest (arrow). Age at death 69 days. Fluorescent labels (green = calcein; red = oxytetracycline) from the first injection period are visible. Crown elongation is still ongoing and fusion of the mineralization fronts in the floor of the infundibulum has not yet occurred. White frames indicate areas where measurements of enamel apposition rate were performed. Buccal to the left. d. Detail of bucco-cervical crown area of the tooth shown in Figure 1b. In the dentin (D), both calcein (green) and oxytetracycline (red) labels are clearly visible. In the enamel (E), only the calcein labels are clearly visible, while the oxytetracycline labels (arrowheads) are only faintly visible. Asterisks mark the EDJ.
Figure 2.
Incremental markings in inner enamel as seen in a ground section.
a. Enamel near the EDJ (asterisks); the depicted enamel portion is located between a calcein band (indicated by the green dashed line) and an oxytetracycline band (indicated by the red dashed line) from injections given 14 days apart. Thirteen (daily) growth increments are located between fourteen laminations (indicated by white lines). In addition, approximately half a growth increment each is located between the calcein label and lamination number 1 and between lamination number 14 and the oxytetracycline label. Arrowheads indicate the position of a Wilson band caused by the oxytetracycline injection. Large arrow indicates overall prism direction; small arrows point to finer incremental markings between successive laminations. Cuspal to top. Section viewed in transmitted light with phase contrast. b. Detail of enamel shown in Figure 2a. Five sub-daily growth increments separated by four sub-daily markings (indicated by white lines) are present between successive laminations (small arrows). Large arrow indicates overall prism direction. White arrowhead indicates Wilson band; black arrowhead indicates a prism showing sub-daily markings. Cuspal to top. Section viewed in transmitted light with phase contrast.
Figure 3.
BSE image of etched section through lingual enamel.
The enamel (E) can be divided into three zones. The inner zone (i), adjacent to the dentin (D), is characterized by prominent interrow sheets of interprismatic enamel. The central zone (c) shows a typical Hunter-Schreger pattern with alternating bands of more or less longitudinally (parazones) and transversely cut (diazones) prisms. The outer enamel zone (o) shows a much less pronounced variation in prism orientation. Arrows mark the position of a Wilson band with a disrupted enamel structure resulting from oxytetracycline injection. Cuspal to top.
Figure 4.
BSE images of hypomature lingual enamel.
a. Overview of the enamel (E) exhibiting a prominent Wilson band (asterisks) that shows a pronounced hypomineralization. Note bright line (arrow) along the EDJ, indicative of a higher mineral content. D = dentin. Cuspal to top. b. Detail of Figure 4a. A disruption of enamel microstructure is visible along the Wilson band (asterisks). Note presence of fine incremental markings in the interprismatic enamel (white arrows) and in the enamel prisms (black arrows). Arrowheads mark fine clefts in the enamel (E); D = dentin.
Figure 5.
BSE images illustrating laminations in outer enamel.
a. Regularly spaced laminations (arrows) are visible in the outer portion of the enamel (E). In contrast, no laminations are discernible in central and inner enamel. D = dentin. Cuspal to top. b. Detail of Figure 5a. Laminations (arrows) in outer enamel. Note that the outcrop of a lamination on the OES is mostly associated with the presence of a small trough (furrow) on the surface. However, single laminations reach the enamel surface without producing a trough (arrowhead). Cuspal to top.
Figure 6.
BSE images showing incremental markings in inner (a) and central (b) lingual enamel.
a. White arrows indicate the course of three laminations visible in interprismatic enamel (IP). Between two successive laminations, five sub-daily increments (asterisks) separated by four darker lines are discernible. Arrowheads mark sub-daily increments in an enamel prism (P). Black arrow indicates overall prism direction. Note occurrence of clefts (crosses) in interprismatic enamel. Cuspal to top. b. Presence of sub-daily incremental markings (arrowheads) in longitudinally sectioned prisms (P) of central enamel. Cuspal to top.
Table 2.
Daily enamel apposition rates (means ± SD) in inner, central and outer third of the enamel layer in different locations of mandibular first molars of four Soay sheep.
Table 3.
Daily enamel extension rates in buccal and lingual enamel of Soay sheep mandibular first molars.
Table 4.
Length of fluorescent band/secretory front in buccal and lingual enamel of Soay sheep mandibular first molars.