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.

<p>(Ca = calcein injection; T = oxytetracycline injection).</p

Length of fluorescent band/secretory front in buccal and lingual enamel of Soay sheep mandibular first molars.

<p>N = number of individuals for which data were recorded at the respective postnatal age. Values are averages from measurements on the mesial and distal lobes of individual teeth.</p

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.

<p>The percentages given in brackets in the columns “following oxytetracycline injection” indicate the amount of the respective enamel matrix secretion in relation to that occurring after calcein injection. Values are averages from measurements on the mesial and distal tooth lobes.</p

BSE image of etched section through lingual enamel.

<p>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.</p

BSE images of hypomature lingual enamel.

<p><b>a.</b> 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>b</b>. Detail of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074597#pone-0074597-g004" target="_blank">Figure 4a</a>. 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.</p

Incremental markings in inner enamel as seen in a ground section.

<p><b>a.</b> 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>b.</b> Detail of enamel shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074597#pone-0074597-g002" target="_blank">Figure 2a</a>. 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.</p

BSE images showing incremental markings in inner (a) and central (b) lingual enamel.

<p><b>a</b>. 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>b</b>. Presence of sub-daily incremental markings (arrowheads) in longitudinally sectioned prisms (P) of central enamel. Cuspal to top.</p

Macroscopic aspects of mandibular cheek-tooth rows of <i>Macropus giganteus</i> from low-fluoride areas (a,b) and the high-fluoride area (c,d).

<p>(a) Individual No.4238 (male), buccal view of left tooth row; (b) individual No.2 (female), buccal view of left tooth row; (c) individual No.1000 (female), lingual view of right tooth row; (d) individual No.1109 (female), buccal view of left tooth row. Note the normal whitish appearance of enamel and normal tooth wear in (a) and (b), and the brownish staining of enamel and abnormal wear of M₂ and M₃ in (c) and M_2-4 in (d). Also note the dark brown to black dental calculus partially or entirely (M₁ in (d)) covering the tooth crowns.</p

Light microscopic images of ground sections of mandibular molars of <i>Macropus giganteus</i> from low-fluoride areas, viewed in normal transmitted light (a, b) and in linearly polarized light with λ/1-plate (c).

<p>(a) Left M₃ of individual No.4253 (male), axiobuccolingual section through the posterior tooth half. Note incremental lines (arrows) in the enamel (E) and filling of depressions in the crown surface with cellular cementum (Ce); D: dentine; asterisks: enamel-dentine junction; buccal to right of image. (b) Left M₃ of individual No.2 (female), axiobuccolingual section through the anterior tooth half. Note thin patch of cementum (arrow) locally covering the enamel (E) on the buccal crown flank and more extended covering of the crown with dental calculus (C); D: dentine; asterisks: enamel-dentine junction; buccal to right of image. (c) Higher magnification of buccal enamel of the left M₃ of individual No.2. Note inner tubular enamel (tE) and outer atubular enamel (aE), and distinct layering of the dental calculus (C).</p

BSE images of the polished cut surface of the axiobuccolingually sectioned (anterior tooth half) fluorotic right mandibular third molar of individual No. 1000 (female <i>Macropus giganteus</i>) from the high-fluoride area.

<p>(a) Pronounced hypoplasia of buccal enamel (E). The defects are filled with cellular cementum; Arrowhead: bulbous, multilayered enamel structure exhibiting distinct hypomineralization. Occlusal to top of image. Insert: Light micrograph of buccal crown flank of the sectioned tooth. D: dentine; E: enamel; asterisks: enamel-dentine junction, Occlusal to top of image. (b) Lingual enamel showing tangentially cut multi-layered structures (arrowhead) consisting of aprismatic, hypomineralized enamel. The underlying enamel (E) exhibits a patchy subsurface hypomineralization (asterisk) underneath a thin surface layer of higher mineral content (arrow). Ce: cellular cementum. Occlusal to top of image.</p