Figure 3. Apoptosis in 3D reconstructions of the dental epithelium in the cheek region of the mandible at ED 15.5, 16.5, and 17.5. Apoptosis presented by apoptotic cells and bodies (black dots) is increased in Ta mice. It is distributed mesio-distally to a similar extent in all Ta morphotypes, but it affects different structures according to the specific tooth pattern (compare with Fig. 1). The mesenchymal face of the dental and adjacent oral epithelium is shown from an aerial view in subtypes Ic, IIa, and IIb of Ta dentition. The pictures have been unified to present the right-side dentition. Various stages of tooth development are shown in subtype Ic: the cap of T₁ and the early cap of T₂ at ED 15.5, the cap-bell transition stage of T₁ and the cap of T₂ at ED 16.5, and the bell of both T₁ and T₂ at ED 17.5. In morphotypes IIa and IIb, the T₁ showed from early cap to well-formed cap stage at ED 15.5–16.5 and the bell stage at ED 17.5. The bud of T₃ in morphotype Ic and T₂ in morphotypes IIa and IIb were distinct at ED 17.5. The abortive cap (double arrowhead) and abortive bud (single arrowhead) represent the most mesial primodium in morphotype II. "mer" = mesial epithelial ridge (the epithelial ridge extending mesially from the primordium of the most mesial cheek tooth). Arrow = apoptosis in the pEK.