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Figure 2. Computer-aided 3D reconstructions of the epithelium on the oral surface of the right upper jaw quadrant in humans. (A,B) ED 40–42. The earlier fusion between the medial nasal (mn) and maxillary (mx) processes is clearly apparent (dotted line). A narrow groove (arrowhead) separates the two thickenings of dental epithelium (DE), originating separately from the mn and mx. (C,D) ED 42–44. The DE forms a continuous dental mound. The former fusion between the facial processes (dotted line), including the fusion site on the dental mound (arrowhead), can still be traced. (E) Prenatal week 8. One can see primordia of the deciduous central incisor (i1), lateral incisor (i2), canine (c), and first molar (m1). The mesial part of the i1 has been cut out on 3D to show the shape of the dental and vestibular (VE) epithelia on the section. A shallow furrow on the germ of i2 (arrowhead) suggests the fusion site between the dental epithelia of two origins. The location of the fusion of the mn and mx processes is also detectable in the VE (double arrowhead). An asterisk determines the mouth corner. The midline is shaded. (pc) primitive choana. (F) An insert shows a scheme of the 3D reconstruction of the oral epithelium (OE) and the dental epithelium (DE). It is possible to see the mesenchyme-facing surface of the epithelium (MSE), because the mesenchyme itself was not included in the 3D reconstruction. The shape of tissues on a frontal section is shown in grey. BM, basement membrane.
