Summary
Highlights
This video introduces the mandibular central incisor, the third tooth covered in a dental anatomy marathon. Dr. Clara, a practicing dentist, aims to simplify complex dental information for students. She also offers a five-step tooth identification cheat sheet.
There are two mandibular central incisors (numbers 25 and 24). They are located at the jaw's midline, with their mesial surfaces touching. This tooth is the smallest incisor, the smallest anterior tooth, and the smallest tooth overall. It's also the most symmetrical, making it a common test question. Its function is to cut, bite, shear food, support lips, aid aesthetics, and assist speech. It erupts at ages 6-7, with root completion by age 9, and calcification begins at 3-4 months.
The crown of the mandibular central incisor is trapezoidal, taller incisocervically than mesiodistally, and is the narrowest mesiodistally of all teeth. It has a straight incisal ridge, potentially with three mammelons upon eruption. Both mesial and distal outlines are straight, with sharp incisal angles and contact points (heights of contour) in the incisal one-third. Notably, unlike most other teeth, its distal contact is not more cervical than its mesial contact; they are equal, which is an important test exception. The labial surface is smooth and flat, and the root is narrow mesiodistally, bending distally at the apical one-third.
The lingual surface shares the same outline as the facial but is less smooth. It features a weak lingual fossa bordered by faint mesial and distal marginal ridges, a lingual incisal edge, and a weak, centered cingulum. There are no developmental lines or grooves. The crown and root taper lingually, narrowing in mesiodistal dimension from facial to lingual.
From the proximal view, the crown is triangular or wedge-shaped with its base at the cervix. The facial outline is convex at the cervical one-third and then straight. The lingual outline is S-shaped, convex over the cingulum, then concave. The cervical line curves significantly towards the incisal, with the mesial curve being more pronounced. The incisal ridge is positioned lingual to the tooth's long axis. The root is wider faciolingually than mesiodistally, having a ribbon-like shape, and features broad developmental depressions, more pronounced distally.
The incisal surface has a diamond shape, tapering from the incisal ridge to the cingulum, and is wider faciolingually. The incisal ridge is lingual to the center of the tooth. It exhibits bilateral symmetry, meaning the mesial and distal aspects are nearly identical. The facial height of contour, cingulum, and incisal ridge are all centered. The mandibular central incisor typically has one root and one canal, though two canals (one facial, one lingual) are a common variation, found in 40% of cases. A cross-section of the root shows a narrower mesiodistal dimension compared to the faciolingual dimension.
The mandibular central incisor is a relatively uniform tooth with little variation. The video concludes this part of the dental anatomy series, with the next video focusing on the mandibular lateral incisor.