Descriptive anatomy of the permanent Maxillary incisors Flashcards
What are diastemas?
In some individuals the 2 maxillary central incisors are separated by a space called diastemas.
What are mamelons?
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
Which incisors are larger; central or lateral?
Maxillary central incisors which are the largest and most prominent teeth in the mouth
What is the sequence of time that maxillary central incisors develop through?
Initial calcification (3 - 4 months after birth)
Completion of crowns (4 - 5 years)
Eruption (7 - 8 years)
Completion of root (10 year)
What are the features of the maxillary central incisors?
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.
How is the maxillary central incisor shaped?
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.
What contacts does the maxillary central incisor have with other teeth?
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.
What are the divisions of the maxillary central incisor?
Mesial lobe
Labial lobe
Distal lobe
Lingual lobe/cingulum
What does the root of the maxillary central incisor look like?
Single
Cone-shaped
Thick in cervical third and narrows through the middle to a tapered apex.
Which is longer; the maxillary central incisor’s crown or root?
Root is slightly longer by about 2 - 3 mm
Why is the palatal surface of the maxillary central incisor narrower than the labial side?
Due to convergence of the proximal surfaces lingually.
Cervical line is similar. It has convexities and concavities.
What is the cingulum?
The smooth large convexity immediately below the cervical line.
Usually it is well developed and is located off center towards the distal side.
Where are the marginal ridges located in the maxillary central incisor?
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.
Where is the maxillary central incisor’s palatal fossa?
It is is a broad concave depression located on the central portion of the palatal surface of the incisor immediately incisal to the cingulum.
What are the variations commonly seen in the maxillary central incisor?
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.
What shape does the maxillary central incisor have when viewed mesially and distally?
Has a wedge shape or triangular crown with base at the cervix and the apex at the incisal edge. Incisal edge appears chisel shaped.
How is the labial outline of the maxillary central incisor shaped?
Convex at the cervical third, slightly convex or nearly flat in the middle and incisal thirds.
How is the palatal outline of the maxillary central incisor shaped?
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.
How does the incisal outline angle out?
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
How does the cervical line angle?
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.
How is the root shaped at the cervical line on the mesial side?
It forms a rounded apex which protrudes into the crown.
How is the distal side of the maxillary central incisor different to the mesial side?
The distal aspect appears thicker towards the incisal third
The distal curvature of the cervical line is less than on the mesial side
When does the initial calcification of the
maxillary lateral incisor take place?
Initial calcification at 10 - 12 months after
When is the crown completed for the maxillary lateral incisor?
4 - 5 years
When does eruption of the maxillary lateral incisor take place?
At 8 - 9 years of age
When is the root of the maxillary lateral incisor completed?
At 11 years of age
What is different about the maxillary lateral incisor compared with the maxillary central incisor?
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
Where does the crown of the maxillary lateral incisor come into contact with mesial and distal teeth?
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
What is the incisal outline of the maxillary lateral incisor shaped like?
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
How is the maxillary lateral incisor angled?
It tapers towards the pointed apex. The point is curved in the distal direction.
Which root is longer; the maxillary central incisor or the maxillary lateral incisor?
The maxillary lateral incisor (usually 1.5x the length of the crown)
Which face if the incisor is larger and which is smaller?
It is narrower on the palatal surface than on the labial surface due to the convergence of the proximal surfaces lingually.
How does the cingulum differ between the central and the lateral maxillary incisors?
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.
How are the marginal ridges oriented in the maxillary lateral incisor?
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
How is the palatal fossa different in lateral incisors compared with central incisors?
Although smaller in area they are more pronounced than central incisor.
It may be shallow or deep and more concave
What is the deep palatal pit and what is its significance?
Deep palatal pit can form enclosed by the cingulum and this is prone to decay
How is the apex angled in the lateral maxillary incisor?
Curved distally
What are the features of the crown of the maxillary lateral incisor?
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.
How is the crown shaped differently in the lateral maxillary incisor distally?
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.
How is the crown shaped differently in the lateral maxillary incisor mesially?
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.
What are the common anomalies that affect the maxillary lateral incisors?
Malformed maxillary lateral incisor
Missing lateral incisor
What are the identifying features of the maxillary central incisor?
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
What are the identifying features of the maxillary lateral incisor?
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.
