There are in total 8 permanent incisors in the oral cavity. 4 in maxilla, 4 in mandible. Here, we'll study the differences between maxillary incisors and mandibular incisors. The tooth numbers for both central incisors and lateral incisors are different as the arch trait is different in them. The maxillary incisors play a crucial part in the aesthetics of a person as they are most noticeable. This is known as incisal dominance. Compared to them, mandibular incisors are aesthetically less important, being partly hidden by maxillary incisors and lower lip. In the chronology, the mandibular central incisor erupts one year before maxillary central incisor. Similarly, mandibular lateral incisor erupts one year prior to maxillary lateral incisor. Coming to their measurements, maxillary central incisor is clearly larger than mandibular central incisor in all dimensions. However, the maxillary lateral incisor is smaller than mandibular lateral incisor except in the mesodistal dimension. If we compare the incisors within the arches, we see that in maxillary arch, the central incisor is larger than the lateral incisor. However, in mandibular arch, this is opposite. It is the lateral incisor which is larger than the central incisor. If we compare only the mesodistal and labiolingual dimensions, we see that in maxillary incisors, the mesodistal diameter is more than the labiolingual diameter. But, in mandibular incisors, the labiolingual diameter is more than the mesodistal diameter. Now let us study the morphological differences from each aspect starting with the labial aspect. All incisors have a horizontal incisal surface except mandibular lateral incisor in which the incisal surface distally tilts cervically. Coming to the incisal angles, in both maxillary incisors, the mesoincisal angle is sharper than the distoincisal angle. However, in mandibular incisors, both mesoincisal and distoincisal angles are equally sharp. Next, the contact areas. In maxillary incisors, both mesial contact area and distal contact area are at different levels. Like in central incisor, the mesial contact area is in the incisal third and distal contact area is at the junction of incisal and middle third. Similarly, in lateral incisor, the mesial contact area is at the junction of incisal and middle third and distal contact area is in the middle third. However, when we come to mandibular incisors, both contact areas are in the incisal third in both incisors. Next, the lingual aspect. The differences from the labial aspect are seen in the lingual aspect as well. Moreover, all the ridges, incisal ridge, mesial marginal ridge and distal marginal ridge are more prominent in maxillary incisors as compared to mandibular incisors. Similarly, the cingulum is more prominent in maxillary incisors than mandibular incisors. Coming to fossa, lingual fossa in all incisors is V-shaped except in maxillary central incisor in which it is W-shaped. Moreover, in both maxillary incisors, the lingual fossa is more concave and more defined than in the mandibular incisors. Next, the mesial aspect. In both maxillary incisors, the incisal ridge is on the midline axis of the tooth. Whereas in both mandibular incisors, the incisal ridge is lingual to the midline axis. The labial outline in maxillary incisors is more convex than the labial outline in the mandibular incisors. Similarly, in lingual outline, the cingulum appears more convex than in the mandibular incisors. Coming to the root, the root surface in both maxillary incisors is smooth and convex with no concavities. Whereas in mandibular incisors, there is a developmental depression running along the long axis of the tooth. Next, the distal aspect. All the differences seen from the mesial aspect are seen from the distal aspect as well. Finally, the incisal aspect. In maxillary incisors, the mesodistal diameter is more than the labiolingual diameter. However, in mandibular incisors, the labiolingual diameter is more than the mesodistal diameter. In all incisors, the incisal ridge is horizontal and perpendicular to the labiolingual axis. Except in mandibular lateral incisor in which the incisal ridge is not at 90 degree. As the distal side tilts lingually, this is because of a twist present in the crown of mandibular lateral incisor.