descriptive anatomy of maxillary permanent incisors

DESCRIPTIVE DESCRIPTIVE ANATOMY OF ANATOMY OF MAXILLARY MAXILLARY PERMANENT PERMANENT

INCISORSINCISORS

Prof. A. ElsahnProf. A. Elsahn

GENERAL GENERAL CHARACTERISTICSCHARACTERISTICS


1.1. There are There are four maxillary incisorsfour maxillary incisors, , two on each side of the midline.two on each side of the midline.

2.2. The first incisors occupy the central The first incisors occupy the central space on either side of the midline space on either side of the midline of maxillae with their mesial of maxillae with their mesial surfaces in contact, so they are surfaces in contact, so they are often referred to as often referred to as “maxillary “maxillary centrals.”centrals.”

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Prof. A. Prof. A. ElsahnElsahn

4.4. In some individuals the two upper In some individuals the two upper central incisors are separated by a central incisors are separated by a space called a space called a “diastema.”“diastema.”

3. 3. The second incisors are farther to The second incisors are farther to the midline or lateral “distal” to the the midline or lateral “distal” to the centrals, so they are called centrals, so they are called lateral lateral incisorsincisors. .

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5.5. Unworn, newly erupted incisors Unworn, newly erupted incisors have three small tubercles have three small tubercles “mamelons”“mamelons” forming the incisal forming the incisal edge. These mamelons soon worn edge. These mamelons soon worn away, with use, to a flat edge.away, with use, to a flat edge.


UPPER FIRST UPPER FIRST PERMANENT INCISORPERMANENT INCISOR

““Maxillary Central Maxillary Central Incisor”Incisor”


Initial calcificationInitial calcification 3-4 months after 3-4 months after birthbirth

Completion of crownCompletion of crown 4-5 years4-5 years

EruptionEruption 7-8 years7-8 years

Completion of rootCompletion of root 10 years10 years


CHRONOLOGYCHRONOLOGY

They are the largest of all incisors and They are the largest of all incisors and are the most prominent in the month.are the most prominent in the month.

GENERALGENERAL


LABIAL ASPECTLABIAL ASPECTTHE CROWNTHE CROWNa. Shape and sizea. Shape and size

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10.510.5

Is the longestIs the longest inciso-inciso-gingivallygingivally of all human of all human

tooth crowns “average = 10.5 tooth crowns “average = 10.5 mm”, although sometimes a mm”, although sometimes a mandibular canine (cuspid) mandibular canine (cuspid) may appear to be a slightly may appear to be a slightly

longer overall, “average = 11 longer overall, “average = 11 mm”mm”

Is by far the widest Is by far the widest mesio-mesio-distallydistally of all the four types of of all the four types of incisors “average = 8.5 mm”incisors “average = 8.5 mm”

8.58.5



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

The geometric outline of the crown is trapezoid with the smallest uneven arm cervically.

So …

The distal outline of the crown is The distal outline of the crown is more convex than the mesial outline. more convex than the mesial outline.

DDMM


The mesial and incisal sides of the The mesial and incisal sides of the tooth join at a nearly right angle.tooth join at a nearly right angle.

The distoincisal corner is somewhat The distoincisal corner is somewhat obtuse and is more rounded than the obtuse and is more rounded than the mesioincisal angle. mesioincisal angle.

b. Incisal Proximal Anglesb. Incisal Proximal Angles

DDMM


MesialMesial

In the incisal third, In the incisal third, i.e.i.e. very near the incisal very near the incisal edge.edge.

DistalDistal

Near the junction of the incisal and the middle Near the junction of the incisal and the middle third, third, i.e.i.e. more cervical than the mesial one. more cervical than the mesial one.

c. Contact Areasc. Contact Areas


The incisal margin of the newly erupted, The incisal margin of the newly erupted, unworn tooth reveals three minor elevations unworn tooth reveals three minor elevations “tubercle”, so-called “tubercle”, so-called MamelonsMamelons, the central , the central is the smallest while the two laterals are is the smallest while the two laterals are approximately equal.approximately equal.

These mamelons soon worn giving a regular These mamelons soon worn giving a regular straight incisal edgestraight incisal edge..

d. Incisal Outlined. Incisal Outline


The cervical line “cemento-enamel The cervical line “cemento-enamel junction” is markedly convex root-junction” is markedly convex root-words labially.words labially.

e. Cervical Outlinee. Cervical Outline


The labial surface of the crown The labial surface of the crown is:is: Smoothly convex, though frequently Smoothly convex, though frequently

flattened incisallyflattened incisally

Marked by two faint vertical developmental Marked by two faint vertical developmental grooves dividing the surface into three grooves dividing the surface into three lobes and incisally three mamelonslobes and incisally three mamelons

f. Morphology of the Labial Surfacef. Morphology of the Labial Surface


Also,Also, Perikymata “imbrication lines,”Perikymata “imbrication lines,” are fine are fine

horizontal line on the labial surface of horizontal line on the labial surface of the newly erupted teeth may be revealed the newly erupted teeth may be revealed and become lost owing to abrasion by and become lost owing to abrasion by tooth brushing.tooth brushing.


SingleSingle

Cone-shapedCone-shaped

Thick in the cervical thirdThick in the cervical third

Narrows through the middle to a blunt apexNarrows through the middle to a blunt apex

Slightly longer than the crown by about 2-3 Slightly longer than the crown by about 2-3 mmmm

THE ROOTTHE ROOT


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

The cervical line is similar.The cervical line is similar.

It has It has convexitiesconvexities and and concavities.concavities.

LINGUAL ASPECTLINGUAL ASPECTa-shape and size:a-shape and size:


Smooth large convexity Smooth large convexity immediately below the immediately below the cervical line.cervical line.

Usually well developed and is Usually well developed and is located off-center toward the located off-center toward the distal side. Therefore, it lies distal side. Therefore, it lies distal to the root axis line. distal to the root axis line.

b. The Cingulumb. The Cingulum

MM DD

DD MM


It is a broad concave depression It is a broad concave depression in the central portion of the in the central portion of the lingual surface, immediately lingual surface, immediately incisal to the cingulum.incisal to the cingulum.

It is bounded by the mesial and It is bounded by the mesial and distal marginal ridges and the distal marginal ridges and the incisal ridge. incisal ridge.

It varies in depth, in some teeth It varies in depth, in some teeth it is shallow; in others, deep.it is shallow; in others, deep.

c. Lingual Fossac. Lingual FossaM

MR

MM

RDM

RD

MR

IRIR


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

The mesial marginal The mesial marginal ridge is longer than the ridge is longer than the distal.distal.

They converge at the They converge at the cingulum and extended cingulum and extended to the incisal ridge. to the incisal ridge.

d. Marginal Ridgesd. Marginal RidgesDD

DD

MM

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Lingual fossa may be deep but Lingual fossa may be deep but smooth.smooth.

There may be tiny supplemental There may be tiny supplemental grooves extending from the cingulum grooves extending from the cingulum to the lingual fossa.to the lingual fossa.

Small pit is often found just below the Small pit is often found just below the central portion of the cingulum or at central portion of the cingulum or at its incisal border where the two its incisal border where the two ridges come together in this location.ridges come together in this location.

e. Variations in Lingual Anatomye. Variations in Lingual Anatomy


The lingual surfaces of the root The lingual surfaces of the root is convex and is narrower is convex and is narrower mesio-distally than the labial mesio-distally than the labial surface due to the lingual surface due to the lingual convergence of the proximal convergence of the proximal sides.sides.

It is flattened on the mesial side It is flattened on the mesial side with a longitudinal depression with a longitudinal depression and convex on the distal like and convex on the distal like the labial side. the labial side.

THE ROOTTHE ROOT

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PROXIMAL ASPECTSPROXIMAL ASPECTS

Mesial and Distal

Mesial and Distal

MESIAL ASPECTMESIAL ASPECT


The geometric outline is a wedge-The geometric outline is a wedge-shaped or triangular crown with its shaped or triangular crown with its base at the base at the cervixcervix and the and the apexapex at the at the incisal ridge.incisal ridge.

Sometimes appears chisel-shaped.Sometimes appears chisel-shaped.

a. General Shapea. General Shape


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

The crest of curvature “greatest The crest of curvature “greatest bulge” is in the cervical third just bulge” is in the cervical third just incisal to the cervical line. incisal to the cervical line.

b. The Labial Outlineb. The Labial Outline

La.La.

La.La.Prof. A. ElsahnProf. A. Elsahn

Convex over the cingulum, concave at the Convex over the cingulum, concave at the mesial marginal ridge, and slightly mesial marginal ridge, and slightly convex at the incisal ridge.convex at the incisal ridge.

The crest of curvature is on the cingulum.The crest of curvature is on the cingulum.

c. The Lingual Outlinec. The Lingual Outline


Is on a line with the root axis.Is on a line with the root axis.

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

It slant slightly labio-lingually. It slant slightly labio-lingually.

d. Incisal Edge “Ridge”d. Incisal Edge “Ridge”

La.La.


Convex and curves incisallyConvex and curves incisally

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

e. Cervical Linee. Cervical Line


THE ROOTTHE ROOT

Thick or wide at the cervix Thick or wide at the cervix and tapers evenly to a and tapers evenly to a rounded apexrounded apex

It is somewhat flattened with It is somewhat flattened with a longitudinal depression in a longitudinal depression in the middle third.the middle third.

Prof. A. Prof. A. ElsahnElsahn

Similar to the mesial Similar to the mesial outline but with little outline but with little differencesdifferences

It appear somewhat It appear somewhat thicker toward the incisal thicker toward the incisal thirdthird

The distal curvature of the The distal curvature of the cervical line is less in cervical line is less in extent than on the mesialextent than on the mesial

DISTAL ASPECTDISTAL ASPECT

DDMM


THE ROOTTHE ROOT

Similar to the shape from the Similar to the shape from the mesial aspect except:mesial aspect except:

1.1. Its surface is convex rather Its surface is convex rather than flattened. than flattened.

2.2. It does not have a It does not have a depression.depression.

DDMM


The crown is roughly triangular with somewhat The crown is roughly triangular with somewhat curved labial outline forming the base and the curved labial outline forming the base and the proximal sides converge toward the cingulum.proximal sides converge toward the cingulum.

The crown is wider mesiodistally than The crown is wider mesiodistally than faciolingually.faciolingually.

INCISAL ASPECTINCISAL ASPECT


The cingulum is located off-center to The cingulum is located off-center to distal. distal.

The labial contour usually appear The labial contour usually appear broad convex but sometimes may be broad convex but sometimes may be nearly flat.nearly flat.


DDDD MM MM

The incisal edge is The incisal edge is 1.5 – 2 mm 1.5 – 2 mm thick.thick.

The lingual fossa is seen as broad The lingual fossa is seen as broad concavity between the two marginal concavity between the two marginal ridges. ridges.

1.5-2mm1.5-2mm


descriptive anatomy of maxillary permanent incisors

Documents

elsahn d

elsahn upper

elsahn b

elsahn proximal aspects

incisal outline

elsahn general characteristics

elsahn lingual aspectashape

incisal ridge