Figure 1

3D-models and μCT-scans of equine incisors. a: 3D model of an upper left first incisor (Triadan 201). Numbers indicate reference points (rp). 1 = Most occlusal point of the distal part of the occlusal table; 2 = Most occlusal point of the labial part of the occlusal table; 3 = Most occlusal point of the mesial part of the occlusal table; 4 = Most occlusal point of the palatal part of the occlusal table; 5 = Most apical point of the palatal enamel cover; 6 = Most apical point of the labial enamel cover. b: 3D model of an upper left first incisor (Triadan 201). Characters indicate reference planes. OP = Occlusal plane, calculated from rp1-rp4; SP = Sagittal plane, calculated from rp2, rp4, rp5, rp6. c: Sagittal μCT - cross section (according to the described sagittal plane SP) of an upper left first incisor (Triadan 201). Characters indicate reference planes. OP = Occlusal plane; SP = Sagittal plane; Numbers indicate reference points (rp). 2 = Most occlusal point of the labial part of the occlusal table; 4 = Most occlusal point of the palatal part of the occlusal table; 5 = Most apical point of the palatal enamel cover; 6 = Most apical point of the labial enamel cover.; 7 = Most apical point of the tooth, labial side; 9 = Most apical point of the infundibular enamel, labial side; 8 = Most apical point of the infundibular enamel, palatal side; 10 = Most apical point of the tooth, palatal side. d: Sagittal μCT - cross section of an upper left first incisor (Triadan 201). Lower-case characters and solid orange lines indicate measure-lines; Lower-case characters and turquoise dotted lines indicate calculated lines. a = Labial length of the tooth, a’ = Palatal length of the tooth; b = Labial length of the enamel cover; b’ = Palatal length of the enamel cover; c = Labial length of the infundibular enamel; c’ = Palatal length of the infundibular enamel; w = Labial length of the root; w’ = Palatal length of the root; x = Distance between the apical infundibular limit and the most apical point of the labial enamel cover; y = Distance between the infundibular limit and the most apical point of the palatal enamel cover; z = Mean length of the infundibulum. e: 3D model of an upper right first incisor (Triadan 101), view on the palatal side of the tooth. Red points and numbers indicate reference points (rp). 7 = Most apical point of the tooth, labial side; 10 = Most apical point of the tooth, palatal side. Characters indicate reference planes, SP = Sagittal plane. Lower-case character and orange line indicates measure-line. a’ = Palatal length of the tooth. Distances between rps, which are not aligned on the sagittal plane (rp 7 and 10) were measured on the 3D surface, following a virtual plane, bisecting the apex sagittally.