Descriptive anatomy of the permanent Maxillary incisors

Question 1

What are diastemas?

Answer 1

In some individuals the 2 maxillary central incisors are separated by a space called diastemas.

Question 2

What are mamelons?

Answer 2

3 small tubercles on incisors that form the incisal edge on newly erupted teeth.

These mamelons are naturally worn away with time and use to produce a more even incisal edge

Question 3

Which incisors are larger; central or lateral?

Answer 3

Maxillary central incisors which are the largest and most prominent teeth in the mouth

Question 4

What is the sequence of time that maxillary central incisors develop through?

Answer 4

Initial calcification (3 - 4 months after birth)

Completion of crowns (4 - 5 years)

Eruption (7 - 8 years)

Completion of root (10 year)

Question 5

What are the features of the maxillary central incisors?

Answer 5

Maxillary and mandibular central incisors are the only neighbouring teeth in the dental arches with mesial surfaces in contact.

Maxillary central incisor is larger than the lateral incisor

Maxillary central incisor is the widest mesio-distally of any anterior teeth

Labial face of maxillary central incisor is less convex than the maxillary lateral incisors or canines. This gives the central incisor a squared or rectangular appearance.

Question 6

How is the maxillary central incisor shaped?

Answer 6

The crown is narrowest in the cervical third and becomes broader towards the incisal third.

Trapezoid shaped as a result.

Distal outline of the crown is more convex than the mesial outline.

The disto-incisal corner is somewhat obtuse and is more rounded than the mesio-incisal angle.

Question 7

What contacts does the maxillary central incisor have with other teeth?

Answer 7

Mesially: In the incisal third near incisal edge

Distally: Near the junction of the incisal and middle third

Labial aspect: Cervical line is smoothly convex.

Question 8

What are the divisions of the maxillary central incisor?

Answer 8

Mesial lobe

Labial lobe

Distal lobe

Lingual lobe/cingulum

Question 9

What does the root of the maxillary central incisor look like?

Answer 9

Single

Cone-shaped

Thick in cervical third and narrows through the middle to a tapered apex.

Question 10

Which is longer; the maxillary central incisor’s crown or root?

Answer 10

Root is slightly longer by about 2 - 3 mm

Question 11

Why is the palatal surface of the maxillary central incisor narrower than the labial side?

Answer 11

Due to convergence of the proximal surfaces lingually.

Cervical line is similar. It has convexities and concavities.

Question 12

What is the cingulum?

Answer 12

The smooth large convexity immediately below the cervical line.

Usually it is well developed and is located off center towards the distal side.

Question 13

Where are the marginal ridges located in the maxillary central incisor?

Answer 13

Mesial and distal ridges vary in prominence from one person to another.

Mesial marginal ridge is longer than the distal.

Both mesial and distal marginal ridges meet at the cingulum and extend into the incisal edge.

Question 14

Where is the maxillary central incisor’s palatal fossa?

Answer 14

It is is a broad concave depression located on the central portion of the palatal surface of the incisor immediately incisal to the cingulum.

Question 15

What are the variations commonly seen in the maxillary central incisor?

Answer 15

Lingual fossa may be deep and smooth

There may be tiny supplemental grooves extending from the fossa

Small pits are often found below the cingulum or at the incisal border where the 2 ridges come together.

Question 16

What shape does the maxillary central incisor have when viewed mesially and distally?

Answer 16

Has a wedge shape or triangular crown with base at the cervix and the apex at the incisal edge. Incisal edge appears chisel shaped.

Question 17

How is the labial outline of the maxillary central incisor shaped?

Answer 17

Convex at the cervical third, slightly convex or nearly flat in the middle and incisal thirds.

Question 18

How is the palatal outline of the maxillary central incisor shaped?

Answer 18

Convex over the cingulum, concave at the mesial margin, and slightly convex at the incisal edge.

The crest of the curvature is on the cingulum.

Question 19

How does the incisal outline angle out?

Answer 19

It is on the line with the root axis.

It is rarely labial to the root axis and occasionally lingual to it

It slants slightly lingually

Question 20

How does the cervical line angle?

Answer 20

It is convex and curves incisally

The cervical curvature on the mesial surface of maxillary central incisor is greater than any surface on any other tooth.

Question 21

How is the root shaped at the cervical line on the mesial side?

Answer 21

It forms a rounded apex which protrudes into the crown.

Question 22

How is the distal side of the maxillary central incisor different to the mesial side?

Answer 22

The distal aspect appears thicker towards the incisal third

The distal curvature of the cervical line is less than on the mesial side

Question 23

When does the initial calcification of the

maxillary lateral incisor take place?

Answer 23

Initial calcification at 10 - 12 months after

Question 24

When is the crown completed for the maxillary lateral incisor?

Answer 24

4 - 5 years

Question 25

When does eruption of the maxillary lateral incisor take place?

Answer 25

At 8 - 9 years of age

Question 26

When is the root of the maxillary lateral incisor completed?

Answer 26

At 11 years of age

Question 27

What is different about the maxillary lateral incisor compared with the maxillary central incisor?

Answer 27

The maxillary lateral incisor is smaller in all dimensions.

Lateral incisor is more convex shaped

Lateral incisor is more oblong cervicoincisally than the central incisor.

The lateral incisor has a similar mesial outline but at the mesioincisal angle the lateral incisor is more rounded than that of the maxillary central incisor

Lateral incisor’s convexities are much more well-developed than central incisors

Question 28

Where does the crown of the maxillary lateral incisor come into contact with mesial and distal teeth?

Answer 28

Mesial: In the incisal third near or at the junction of incisal and middle third

Distal: More cervical than the mesial contact area; at the junction of incisal and the middle third or in the middle third

Question 29

What is the incisal outline of the maxillary lateral incisor shaped like?

Answer 29

Both mesioincisal and distoincisal angles are more rounded than those on the central incisors.

Mamelons and labial depressions are less common and less prominent.

Cervical outline is similar to that of the central incisor

Question 30

How is the maxillary lateral incisor angled?

Answer 30

It tapers towards the pointed apex. The point is curved in the distal direction.

Question 31

Which root is longer; the maxillary central incisor or the maxillary lateral incisor?

Answer 31

The maxillary lateral incisor (usually 1.5x the length of the crown)

Question 32

Which face if the incisor is larger and which is smaller?

Answer 32

It is narrower on the palatal surface than on the labial surface due to the convergence of the proximal surfaces lingually.

Question 33

How does the cingulum differ between the central and the lateral maxillary incisors?

Answer 33

Cingulum is well developed in both but narrower in lateral incisor than on the central incisor.

It is almost centered on the root axis, not distally located as for incisors.

Question 34

How are the marginal ridges oriented in the maxillary lateral incisor?

Answer 34

They are developed to different degrees on different teeth. Sometimes they are noticeable other times they not.

The mesial marginal ridge outline is nearly straight

The shorter distal marginal ridge is curved cervi-incisally as on central incisor

Question 35

How is the palatal fossa different in lateral incisors compared with central incisors?

Answer 35

Although smaller in area they are more pronounced than central incisor.

It may be shallow or deep and more concave

Question 36

What is the deep palatal pit and what is its significance?

Answer 36

Deep palatal pit can form enclosed by the cingulum and this is prone to decay

Question 37

How is the apex angled in the lateral maxillary incisor?

Answer 37

Curved distally

Question 38

What are the features of the crown of the maxillary lateral incisor?

Answer 38

Geometric shape is triangular.

The mesial aspect is similar to the central

The incisal ridge appears somewhat thicker than that of the central incisor faciolingually and on a line with the root axis.

Question 39

How is the crown shaped differently in the lateral maxillary incisor distally?

Answer 39

Contact area is more cervical and the width of the crown is thicker distally due to distolingual twist of crown as well as shortness of the crown distal outline.

Question 40

How is the crown shaped differently in the lateral maxillary incisor mesially?

Answer 40

Mesial contact area is at junction of incisal and middle thirds

Cervical line is deep, well marked, averaging 2.5mm and more curved than the distal.

Question 41

What are the common anomalies that affect the maxillary lateral incisors?

Answer 41

Malformed maxillary lateral incisor

Missing lateral incisor

Question 42

What are the identifying features of the maxillary central incisor?

Answer 42

Maxillary surface straight and at right-angles to incisive edge

Disto-incisal angle more rounded

Crown large in proportion to root

Widest anterior tooth

Well-marked marginal ridges on concave palatal surface

Large convex cingulum

Crown inclined palatally

Smooth, convex labial surface

Single tapering root with rounded triangular cross-section

Question 43

What are the identifying features of the maxillary lateral incisor?

Answer 43

Mesio-incisal angle acute; disto-incisal angle more rounded

Incisive edge has marked downward slope to the shorter distal surface

Crown more rounded and narrower mesiodistally than central incisor

Cingulum on palatal surface encloses the pit

Palatal surface more concave than upper central incisor

Single root with elegant taper to pointed, distally-curving apex.