Mandibular Incisors: Anatomy and Function

• Four mandibular incisors exist: two central and two lateral incisors.
• Mandibular incisors function to cut food during chewing.
• They facilitate speech, support lip structure, and contribute to esthetics.
• As the mouth's smallest teeth, mandibular incisors have a blade-shaped crown and single root.
• These teeth sit between the mandibular canines, with centrals at the midline and laterals distal to the centrals.

Mandibular Central Incisors

• The mandibular central incisor is the smallest tooth in the lower arch and the narrowest mesiodistally in the permanent dentition.
• Eruption typically occurs between ages 6 and 8.
• Crown dimensions are smallest mesiodistally.
• Root length usually exceeds crown length.
• The labial crown surface is smooth and convex.
• A shallow lingual fossa marks the relatively smooth lingual surface.
• The incisal edge runs straight and perpendicular to the labiolingual axis.
• Mesial and distal surfaces are relatively flat, contacting the adjacent central incisor on the mesial and the lateral incisor on the distal.
• The crown appears symmetrical from the incisal aspect.
• Its single root is narrow and cone-shaped.
• A blunt root apex typically features longitudinal grooves on the mesial and distal aspects.
• The pulp cavity is narrow, following the tooth's external shape.
• The pulp cavity features three pulp horns, with the middle one being the largest.
• Extraction is difficult due to the small root size and the root's propensity to fracture.
• These incisors show the greatest symmetry of all incisors.

Mandibular Lateral Incisors

• Mandibular lateral incisors are slightly larger than their central counterparts.
• Eruption occurs between 7 and 9 years of age.
• The crown is both wider and longer than that of the central incisor.
• The incisal edge shows slight rounding, with the distoincisal angle more rounded than the mesioincisal angle.
• While the crown is wider, root length approximates that of the central incisor.
• Labial appearance resembles the central incisor.
• The single root, slightly wider and longer than the central incisor's, typically curves distally, displaying longitudinal grooves on the mesial and distal sides.
• The pulp cavity mirrors the central incisor but is slightly larger.
• The distoincisal angle is generally more rounded than the central incisor's angle.
• Compared to centrals, these incisors are wider and longer.
• The tooth is also fan-shaped, with a distally twisted incisal ridge.

Similarities Between Mandibular Central and Lateral Incisors

• The central and lateral incisors are the smallest teeth in the mouth.
• Both are single-rooted.
• Both have a relatively simple morphology.
• Both function to cut food.
• A cingulum is present on the lingual surface near the cervical line.
• The incisal ridge is located labial to the root's long axis.
• The pulp cavity is narrow and mirrors the tooth's external shape.
• The pulp cavity contains three pulp horns.

Differences Between Mandibular Central and Lateral Incisors

• Mandibular central incisors are smaller than the lateral incisors.
• Central incisors are more symmetrical compared to the lateral incisors.
• While central incisors have a straight incisal edge, lateral incisors have a slightly rounded one.
• The lateral incisor root is slightly wider and longer.

Clinical Considerations

• Mandibular incisors are prone to periodontal disease due to their small size and close spacing.
• Their small mesiodistal width makes them susceptible to crowding, increasing plaque accumulation, risks of caries, and periodontal disease.
• Extraction is complicated by the small root size, which is prone to fracture.
• Their small size and unique shape can make restoration challenging.
• They are critical for anterior guidance during mandibular movements; altered position or morphology can impact the temporomandibular joint.
• Peg-shaped lateral incisors represent a common developmental anomaly.
• Diastemas can occur between central incisors.
• Lingual version is a common malocclusion.
• Incisal edges may show wear from attrition or abrasion.
• Root resorption can occur due to trauma or orthodontic treatments.

Mandibular incisors are the most anterior teeth in the lower arch, playing a crucial role in incising food, speech, and esthetics. These teeth, including central and lateral incisors, are the smallest in the permanent dentition with a simple morphology. The mandibular central incisor is the smallest tooth of the arch.