Oral Anatomy 2 - The Mandibular First (central) Permanent Incisor
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How can you distinguish between the maxillary and mandibular incisors?
- The mandibular incisors have the smallest mesiodistal dimensions of any teeth in the permanent dentition.
- They can be distinguished from the maxillary incisors not only by their size but also by:
- - The marked lingual inclination of the crowns over the roots
- - The mesiodistal compression of their roots
- - The poor development of the marginal ridges and cingula
How does the mandibular first (central) permanent incisor appear when viewed incisally?
- Viewed incisally, this tooth has a bilaterally symmetrical triangular shape.
- The incisal margin in the specimen may appear flat and worn, although in the newly erupted tooth, three mammelons are usually present.
- The incisal margin is at right angles to a line bisecting the tooth labiolingually.
How does the mandibular first (central) permanent incisor appear when viewed labially?
- Labially, the crown of the incisor is almost twice as long as long as it is wide.
- The unworn incisal margin is straight and approximately at right angles to the long axis of the tooth.
- The mesioincisal and distoincisal angles are sharp and the mesial and distal surfaces are approximately at right angles to the incisal margin.
How do the mesial and distal surfaces appear in the mandibular first (central) permanent incisor?
The profiles of the mesial and distal surfaces appear very similar, being convex in their incisal thirds and relatively flattened in the middle and cervical thirds.
The mesial and distal views show the characteristic wedge shape of the incisor, and the inclination of the crown lingually over the root.
How does the mandibular first (central) permanent incisor appear when viewed lingually?
The lingual surface is smooth and slightly concave, the lingual cingululm and mesial and distal marginal ridges appearing less distinct than those of the maxillary incisors.
What is the root and cervical margin like for the mandibular first (central) permanent incisors?
- The cervical margins on the labial and lingual surfaces show their maximum convexities midway between the mesial and distal boarders of the root.
- The cervical margin on the distal surface is said to be less curved than that on the mesial surface.
- The root is narrow and conical, though flattened mesiodistally.
- It is frequently grooved on the mesial and distal surfaces, the distal groove being more marked and deeper.
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