Maxillary Incisors Anatomy and Features

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Questions and Answers

What is the first evidence of calcification for maxillary central incisors?

1 month

3-4 months (correct)

6 months

4-5 years

Which of the following is a primary function of permanent incisors?

Chewing fibrous materials

Cutting food (correct)

Grinding food

Stabilizing jaw

Which feature is characteristic of the labial aspect of maxillary central incisors?

Rounded mesioincisal line angle

The widest MD of all incisors (correct)

1 mamelon present

Narrowest MD of all incisors

How does the CEJ curve on maxillary central incisors when viewed from the mesial aspect?

Curved incisal (most pronounced) Signup and view all the answers

What is the primary difference between the mesial and distal aspects of the maxillary central incisors?

The CEJ is less curved on the distal aspect Signup and view all the answers

How does the incisal ridge appear in comparison to that of the central incisor?

Slightly thicker due to heavy development Signup and view all the answers

What is the typical appearance of the cingulum from the mesial aspect?

Significantly pronounced and convex Signup and view all the answers

In the distal aspect, how does the width of the crown compare to that of the mesial aspect?

Thicker than the mesial aspect Signup and view all the answers

What is a common finding at the distal side of the cingulum?

A deep developmental groove Signup and view all the answers

Which feature is less pronounced when comparing the crown's curvature at the cervical line to that of the central incisor?

The curvature is less marked in an incisal direction Signup and view all the answers

What characteristic differentiates the mesial and distal outlines of a maxillary lateral incisor?

The mesial outline is longer than the distal. Signup and view all the answers

Which anomaly is commonly observed in maxillary lateral incisors?

Missing teeth. Signup and view all the answers

What is the typical outline shape when viewed from the incisal aspect of a maxillary lateral incisor?

Triangular outline. Signup and view all the answers

What is the relative size of the root of a maxillary lateral incisor compared to its crown?

Is about 1.5 times the length of the crown. Signup and view all the answers

Which of the following correctly describes the labial aspect of the maxillary lateral incisor?

Narrower mesiodistally and shorter cervico-incisally. Signup and view all the answers

Study Notes

Morphology of Permanent Incisors

Human dentition is diphyodont, meaning it develops in two stages: primary (deciduous) and secondary (permanent).
Primary dentition formula: I 2/2 C 1/1 M 2/2. Erupts between 6 months and 28-4 months. Sheds between 6 and 12 years.
Secondary (permanent) dentition formula: I 2/2 C 1/1 P 2/2 M 3/3. Erupts between 6 and 18-25 years.

Stages of Human Dentition

Edentulous stage: 0-6 months
Eruption of primary dentition: 6 months - 2.5 years
Functioning primary dentition: 2.5 - 6 years
Mixed dentition: 6-12 years
Permanent dentition: 12+ years
Full permanent dentition: (18-25)+ years

Dental Terms

Dental arch: maxillary and mandibular
Tooth class:
- Incisor: incisal edge
- Canine: one pointed cusp
- Premolar (bicuspid): 2 cusps
- Molar: 3 or more flattened cusps
Identification traits: set, arch, class, and type traits

Terms of Orientation

Various anatomical terms are used to describe tooth positions and surfaces (e.g., angle, apex, buccal, distal, facial, labial, lingual, mesial, occlusal, point, etc.).

Includes terms for surfaces, angles, edges, cusps, cingulum, fossa, ridge, and cervical lines, lobes, mamelons, lingual pits and developmental groove.

The permanent incisors

Eruption sequence: 41/31, 1/2, 42/32, 12/22
Functions: cutting, esthetics, and speech
Class traits: incisal 2/3 flattened MD & compressed LL, long horizontal MD biting edge, 2 or more mamelons, marginal ridges parallel to long axis

Chronology

Maxillary central incisor: first evidence of calcification (3-4 months), enamel completed (4-5 years), eruption (7-8 years), root completed (10 years)
Maxillary lateral incisor: first evidence of calcification (1 year), enamel completed (4-5 years), eruption (8-9 years), root completed (11 years)

The permanent maxillary incisors

Arch traits: wider MD, smaller height/width proportion, greater MD/LL proportion, conical root in central incisors
Type traits: size, height/width proportion in crown, MD/LL proportion in crown and root

The permanent maxillary central incisors

Labial aspect: widest MD of all incisors, 3 mamelons (middle smallest), mesial raised shoulder, distal low shoulder, 2 labial lobe grooves, rounded mesioincisal line angle, somewhat rounded mesial contour, distal contour converges cervically, mesial HOC (contact point) within incisal third, distal HOC at junction between incisal & middle thirds, CEJ (cementoenamel junction) convex cervically, root conical & inclined distally
Lingual aspect: scopop-like surface, lingual fossa (more prominent in maxillary), mesial & distal marginal ridges, cingulum, CEJ more convex than labial, root is narrower from lingual view, chisel shaped, labial HOC in the cervical third , CEJ curved incisally (pronounced), incisal edge coincides with the long axis, root is conical.
Distal aspect: CEJ less curved than mesial, triangular outline, labial outline slightly convex, mesial outline longer than distal, labial lobe grooves

The permanent maxillary lateral incisor

Crown closely resembles that of the central incisor, smaller than central incisor except for root length, varying in form more than any other tooth except the third molar, peg shaped lateral is a developmental anomaly.
In some individuals: missing tooth, presence of palato-gingival groove (may predispose to periodontal disease), presence of large pointed tubercle (part of cingulum), deep developmental groove, twisted or distorted root, or crown.

The permanent maxillary lateral incisors

Labial aspect: narrower MD & shorter IC, more rounded, MI angle, DI angle more rounded, M & D outlines, HOCs farther from incisal edge, mesial HOC between middle & incisal thirds, distal HOC at center of middle third, root conical and slightly inclined distally.

Labial aspect / Continued

Relatively narrow mesiodistally (2mm narrower than central incisor)
Cervico-incisal measurement is 2-3mm shorter than the central incisor.
Root is about 1.5 times the length of the crown, tapers evenly from cervical line to two thirds its length apically, curves sharply distally, and ends in a pointed apex.
Root sometimes straight, sometimes curves mesially.

Lingual aspect

Marginal ridges and cingulum are more pronounced, lingual fossa is deeper
Developmental groove/pit prominent (especially in the distal side of cingulum)
Mesial and distal marginal ridges are marked.
Cingulum prominent with deep developmental grooves.
Incisal ridge more developed.
Lingual fossa more concave.
Tapers towards the lingual.

Mesial aspect

Mesial aspect more convex, cingulum more convex, CEJ less curved.
Similar to a small central incisor, except root appears longer, crown shorter, and labio-lingual measurement less.
Curvature of cervical line marked incisal direction.
Incisal ridge thicker than the central.
Root tapered, cone shaped, with blunt apex (sometimes) and pointed (other times).
Line drawn through center of root bisects incisal ridge of the crown.

Distal aspect

Crown appears thicker distally than mesially.
Curvature of cervical line usually less than the mesial surface.
Developmental groove found extending towards the root.

Incisal aspect

Ovoid outline, smaller MD than central, labial outline rounded, ML & DL line angles rounded.
Sometimes resembles central incisor or a small canine.
Cingulum may be larger, incisal ridge wider, mesio-distal width greater than usual. - More convexity labially and lingually.

Maxillary and Mandibular Incisors

Size and Eruption: tables with measurements and eruption times (for maxillary central, lateral, and mandibular incisors)

Comparative Anatomy: Incisors of Interest in other Species

Various animal incisor adaptations: fur combing, tree chopping, meat stripping, continuously growing incisors
Lemurs, Aye-Aye, Sheep, Ruminants, Narwhals, Elephants and their relatives (mammoth), Horses (central pit),

Incisal Relationship

Classes I, II, III, Overjet, Reverse overjet. Overbite
Diagrams showing different relationships between the upper and lower teeth.

Human Dentition Stages

Diagram showing the stages of human dentition showing deciduous teeth.

Chronology of tooth development and eruption

Tables showing details of tooth development and eruption time, including evidence of calcification, crown completion, eruption, and root completion for deciduous and permanent teeth.

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Description

This quiz tests your knowledge on the anatomy and characteristics of maxillary central and lateral incisors. Explore questions covering their calcification, primary functions, and distinguishing features when viewed from different aspects. Perfect for dental students and professionals looking to refresh their expertise.