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Maxillary Incisors Principal Identifying Features

The maxillary central incisor is the tooth in each maxillary

quadrant of the permanent dentition which is on each side of the

midline.

Normally, the max central incisors are the most prominent teeth in

the oral cavity and so they are most noticeable in the dental arch,

hence they contribute a focal point for the eye of the observer. In

general, the labial outline of the crown conform to the general

outline of the face.

The max central incisor (MCI) is the widest tooth mesio-distally

(MD), the labial surface is less convex than lateral incisor and

canine that give the tooth a rectangular appearance. It is the first

tooth from the midline. It has a slightly straight incisal edge.

Central Incisor Chronology

Appearance of enamel organ 5 m.i.u

First evidence of calcification 3 - 4 months.

Crown completed 4 - 5 years.

Eruption 7-8 y

Root completion 10-11 y

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Labial aspect

Geometric out line

Trapezoid with the smallest side at the cervical line and the larger

side at the incisal ridge, where the central incisor

contacts its neighbors.

The mesial outline

The crown is slightly convex.

The distal outline

The crown is more convex than the mesial outline.

Contact areas

Mesially: approaching the mesio-incisal angle.

Distally: higher towards the cervical line near the

junction between middle and incisal thirds.

Incisal angles

The mesio- incisal angle is nearly a right angle “sharp”

disto-incisal angle is rounded.

The incisal outline

Incisal outline of newly erupted tooth usually reveals mamelons, they

are usually three in number, of which the central mamelon is the

smallest.

A time after eruption the incisal ridge undergoes attrition, the incisal

edge is straight and perpendicular to the longitudinal axis of the tooth.

Cervical line

Semicircle with the curvature root-wise.

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Surface description

The labial surface of this tooth is smoothly convex with the maximum

convexity at the cervical third, referred to as cervical ridge. The labial

surface is marked by 2 faint or shallow vertical grooves which divide

the labial surface into 3 portions or lobes.

The root

Root is cone shaped with blunt apex. A line drawn through the center

of the root and crown of the maxillary central incisor tends to parallel

the mesial outline of the crown and root.

Lingual Aspect

It represent elevations and depressions but the

general outline is the reverse picture of the labial

surface.

The proximal sides of the crown and root converge

lingually, making the lingual surface of the tooth

narrower than the labial surface to accommodate the

horse-shoe shaped alveolar ridge, where the outer

surface of the ridge is wider than the inner surface

that is called lingual convergence.

The root is generally triangular with rounded angles.

Cervical line is similar to that of labial.

Morphologically , lingual surface shows convexities and concavity:

The cingulum: smooth round large convexity present at the

cervical third immediately below the cervical line.

The mesial and distal marginal ridges: they extend from the

cingulum mesial and distally to the incisal ridge.

Incisal ridge (linguincisal edge): elevation (being on a level

with the marginal ridges) making the thickness of incisal edge

from the lingual surface.

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Lingual fossa: lingual depression between the marginal ridges

and extend from the cingulum to the incisal ridge. It has M-

shape and occupying the incisal two third.

Mesial Aspect

The mesial surface of the crown is wedge-shaped or triangular with

the base of the triangular at the cervix and the apex at the incisal

ridge. This allows the tooth to be forced easily through the food

material.

The labial outline of the crown is slightly convex with the

crest of curvature at the cervical ridge.

The lingual outline is convex at the region of the

cingulum. Then it becomes concave as it outlines the

mesial marginal ridge and becomes slightly convex again

as it outlines the linguo-incisal ridge.

The cervical line is concave root-wise.

The incisal ridge is with the line bisecting the tooth.

The root is cone shaped with a blunt apex; the labial outline is

straighter than the lingual outline.

The mesial surface is smooth except for a concavity represents the

contact area.

Distal Aspect

It is similar in oultine to the mesial surface.

But the curvature of the cervical line is less in

curvature then from the mesial surface.

The distal contact area is more cervical than

mesial one.

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Incisal edge distally is broader than mesially so the crown appear

thicker.

Incisal Aspect

The incisal ridge is seen to be centered over the root.

The crown superposes over the root entirely so that nothing of the root

is visible i.e. the crown and the root base on the same long axis.

The crown outline is roughly triangular with somewhat curved labial

outline that form the base of the triangular while the proximal sides

converge toward the cingulum.

Crown is wider MD than LL. Labial

outline is broad, flat compared with the

lingual surface. Cingulum is located off

center toward the distal side. So, MMR is

longer than DMR. Fossa is seen as a

concavity between the two MR and cingulum.

Note that

The incisal ridge is that portion of the crown which makes up the

complete incisal portion. When an incisor is newly erupted, the incisal

portion is rounded and merges with the mesioincisal and distoincisal

angles and the labial and lingual surfaces. This ridge portion of the crown

is called the incisal ridge. The term edge implies an angle formed by the

merging of two flat surfaces. Therefore, an incisal edge does not exist on

an incisor until occlusal wear has created a flattened surface linguo-

incisally, which surface forms an angle with the labial surface. The

incisal edge is formed by the junction of the linguoincisal surface,

(sometimes called the incisal surface), and the labial surface.

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Variations and anomalies

a) Of all the crown surfaces, the lingual exhibits the greatest variation.

As previously mentioned, a pit may occasionally be present, and the

depth of the fossa has a considerable range.

b) When viewed from the labial or lingual aspects, a wide variation

occurs in the amount of convergence of the mesial and distal

surfaces toward the cervical. When there is little convergence, the

outline of the surface resembles a rectangle, but when great

convergence is present, it is more nearly triangular.

c) Root length may vary considerably, but deflections of the root are

relatively rare. When the root is exceptionally short, in conjunction

with an abnormal contour of the crown, this anomalous condition is

referred to as dwarfed root, and the lack of root support may endanger

the tooth's longevity in the mouth.

d) Hutchinson's incisors: Congenital syphilis sometimes manifests

itself in the central incisor by producing a screwdriver shaped crown,

when it is viewed from the labial aspect.

e) Talon cusp: A large accessory cusp on the lingual surface of

maxillary incisors characterizes this anomaly. Involved teeth often

bear a resemblance to a Phillips screwdriver.

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f) The alveolar bone between the roots of the two central incisors is

occasionally the site of supernumerary teeth or extra teeth, known

as mesiodens. Cysts may also be found in this area.

Lateral Incisor

Principal Identifying Features

The maxillary lateral incisor is the tooth in each maxillary quadrant

of the permanent dentition which is second from the midline.

Contact is shared mesially with the permanent central incisor;

distally with the deciduous canine until its exfoliation at about 12

years, and then with the permanent canine.

General form and function

o The lateral incisor supplements the central incisor in function.

o It resembles the central incisor in all aspects, but on a smaller

scale. In fact, it is smaller in all measurements, except root

length.

o Its relative crown dimensions, differ slightly from the central,

however. It is relatively longer inciso-cervically and narrower

mesio-distally.

o It also is generally a more round tooth than the central incisor.

o The upper lateral incisors display greater variation in form than

any other permanent tooth, except the third molars.

o There are two known forms:

Square form → similar to that of the central.

Rounded form → similar to that of the canine.

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Chronology

Appearance of enamel organ 1 y.

First evidence of calcification 4 - 5 y.

Crown completed y.

Eruption 8 - 9 y.

Root completion 1 1 y.

Labial aspect

Geometric outline

Trapezoid similar to labial aspect of maxillary permanent central

incisor.

Mesial Outline

Similar to maxillary permanent central incisor.

Distal Outline

The distal outline is always more rounded than the mesial outline and

distal outline of maxillary central incisor.

Contact areas

Mesially: at the junction of the middle and incisal thirds.

Distally: more cervical, usually in the center of the middle third.

Incisal angles

The mesio-incisal angle is more rounded.Occasionally, in the

square forms, the mesio-incisal angle is almost as sharp as that

found on most maxillary central incisors. However, a more

rounded mesio-incisal angle is seen more often.

The distoincisal angle is more rounded.

Incisal Outline

It is formed by the incisal ridge.

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Mesial half of incisal outline is relatively straight and distal half

is more rounded curving towards cervical line to join the distal

outline.

The number and prominence of mamelons is variable, but two are

the most common finding.

Cervical Outline

The cervical line curves in a regular arc apically, but less deep

than that of the central incisor.

Surface description

Labial surface is about 2 mm narrower and 2 to 3

mm shorter than the maxillary permanent central

incisor.

It is more convex compared to maxillary

permanent central incisor, both mesiodistally and

incisogingivally.

Labial developmental depressions and imbrication

lines are similar to those of the central incisor.

Root

Usually as long, if not somewhat longer, than that of the central

incisor.

The root is often about 1.5 times the length of the crown.

The root tapers evenly from the cervical line to a point

approximately two thirds of its length apically. In most cases, it

curves sharply from this location in a distal direction and ends

in a pointed apex.

The apex is relatively sharper than that of the central.

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Lingual aspect:

It is the reverse of the labial aspect. There is lingual convergence of

proximal walls as seen in maxillary permanent central incisor.

Cervical outline: The CEJ curves toward the apical, but is offset to the

distal.

M

Morphologically, lingual surface shows convexities and

concavity: Marginal ridges are more prominent and

stronger than those found on central incisor.

The linguoincisal ridge is well developed.

Lingual fossa (v shape) is deeper and well-

circumscribed.

Cingulum is more prominent.

Palatogingival or palatoradicular groove: a deep

developmental groove originates from the lingual pit, crosses

the distal side of the cingulum and extends on the root for part

or all of its length.

Faults in the enamel of the crown are often found in the deep

portions of these developmental grooves.

Mesial aspect

The mesial surface of the crown is wedge-shaped or

triangular with the base of the triangular at the cervix

and the apex at the incisal ridge. This allows the tooth

to be forced easily through the food material

The mesial aspect is very similar to the central incisor,

with lessened labio-lingual dimensions (1mm), when

compared to the upper central, the crown is shorter,

and the root is relatively longer.

The cervical line: is markedly curved in the direction

of the incisal ridge, but less in depth than that of the

central incisor.

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The incisal ridge is well developed, making the incisal portion and

appears somewhat thicker than that of the central incisor. The mesial

surface is smooth except for a concavity represents the contact area.

The root

Appears as a tapered cone from this aspect, with a bluntly rounded

apical end. This varies in individuals, with the apical end sometimes

being quite blunt, while at other times, it is pointed.

A line drawn through the center of the root tends to bisect the incisal

ridge of the crown.

Distal aspect:

The distal surface is smaller and more convex in all dimensions

than the mesial surface. The width of the crown

distally appears thicker than it does on the mesial

aspect from marginal ridge to labial face, because

of the placement of the crown on the root.

The contact area is shorter and not as incisally

placed, when compared to the mesial contact. It is

normally located at center of the middle third.

The cervical line shows less curvature incisally

than on the mesial surface.

A developmental groove may be found on the

crown extending on the root for part or all of its

length.

Incisal aspect:

All maxillary lateral incisors exhibit more convexity labially and

lingually from the incisal aspect than do the maxillary central incisors.

The incisal aspect shows 2 forms

Resembles the central incisor except

in size (triangular in shape)

Resembles a small canine

(rhomboidal or oval) if :

1-The cingulum is large, as well

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as the incisal ridge.

2-The labiolingual dimension is greater than the

mesiodistal dimension.

Developmental anomalies

The maxillary lateral incisor varies in form more than any other tooth

in the mouth except the third molar.

If the variation is too great, it is considered a developmental anomaly.

For example:

Congenitally missing laterals, i.e.: tooth buds do not form

(agenesis).

Peg shaped laterals: A diminutive peg-shaped crown form, which

is relatively common, and is due to a lack of development of the

mesial and distal portions of the crown.

Talon’s cusp: The incisal portion of the cingulum may

exhibit a tubercle.

Supplemental laterals/supernumerary lateral incisor.

Dens invaginatus: Most common tooth affected. The

lingual pit of the maxillary lateral may be the entrance

site where enamel and dentin have become invaginated

in the tooth pulp cavity.

The palate-gingival fissure may extend all the way

onto the root surface from the adjacent cingulum.

Distorted crowns and unusual root curvatures are more commonly

seen than with any other incisor.

Clinical considerations Congenitally missing lateral incisors may need prosthetic replacement

such as implants.

Peg shaped laterals may require crown veneers for esthetic purpose.

Deep palatogingival developmental groove may cause localized

periodontal disease.

Peg laterals

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Mandibular Incisors

Introduction

Mandibular incisors are four in number, two on each side from the

central line.

These are the first permanent teeth to erupt, replacing deciduous

incisors, and are the smallest teeth in either arch.

The mandibular central incisors are centered in the mandible, with

the mesial surface of each one in contact with the mesial surface of

the other.

The mandibular lateral incisors are distal to the central incisors which

make contact mesially with the central incisor and distally with the

canine.

Mandibular central incisor and lateral are similar in anatomy and

complement each other in function but the central is somewhat

smaller than the lateral incisor.

They have smaller mesiodistal dimensions than any of the other

teeth.

The anatomic form of these teeth differs from that of the maxillary

incisors in that the labial surface is inclined lingually so that the

incisal ridges are lingual to a line bisecting the root.

Chronology

Central incisor Lateral incisor

Appearance of enamel organ 5 m.i.u

First evidence of calcification 3 - 4 months.

Crown completed 4 - 5 years.

Eruption 6 – 7 Ys. 7 – 8 Ys.

Root completion 9 Ys. 10 Ys.

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Central Incisor

It is the narrowest and the smallest tooth mesiodistally of all the

permanent teeth.

These teeth function in biting, and incising, just as do their maxillary

counterparts.

Labial aspect

Labial surface of mandibular central incisor is regular and

very small.

It is bilaterally symmetrical.

Geometric outline.

Trapezoidal with the smallest side cervically.

Mesial and distal outlines.

The mesial and distal outlines of the crown make a straight

drop from the incisal angles to the contact areas. The mesial

and distal sides taper evenly from the contact areas to the

narrow cervix (neck), giving the crown fan shaped

appearance.

Although these two surfaces are nearly parallel at the incisal

edge, they converge toward the cervical margin.

Contact areas: Mesial and distal contacts at equal heights in incisal

third incisal to the junction of the incisal and middle thirds of the

crown near the mesioincisal and distoincisal angles.

Incisal outline.

The incisal edge is straight and is at nearly a right angle to the

long axis of the tooth.

Broadest portion of tooth in incisal third.

Mamelons most always 3 in number occasionally present on newly

erupted teeth.

It is the only incisor where both mesioincisal and distoincisal

angles are sharp and at right angles.

Distoincisal angle is barely more rounded than the mesioincisal

angle.

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Cervical outline.

Is symmetrically and evenly convex toward the root.

Surface description.

The labial surface is smooth and tends to be more convex,

particularly in the cervical third, and flattens out toward the

incisal third.

The developmental grooves may or may not be present. When

present, they appear as very faint furrows in newly erupted

teeth.

The root

The root is single, slender and straight.

The root length is as great, if not greater, than that of the maxillary

central incisor.

The mesial and distal root outlines are straight with the mesial

and distal outlines of the crown down to the apical portion.

The root surface is regular and convex and extremely flattened on

its mesial and distal surfaces.

The apical third of the root terminates in a small pointed taper, in

most cases curving distally. Sometimes the roots are straight.

Lingual aspect

The crown is narrower on the lingual than on the labial

surface (lingual convergence).

The mesial, distal and incisal outlines closely resemble

those of the labial aspect and they are regular and

symmetrical.

The lingual aspect is shallow, with slightly concavity at

the incisal third between the less prominent mesial and

distal marginal ridges then it becomes flat and then

convex as progression from the incisal third to the

cervical third.

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Less prominent smooth, small and centered cingulum and

marginal ridges than maxillary incisors.

The incisal ridge is narrow and rounded or worn flat.

The lingual surface is smooth and devoid of any neither grooves

nor fissures. No other tooth in the mouth, except the mandibular

lateral incisor, shows so few developmental lines and grooves.

Shallow lingual fossa. No lingual pit.

The cervical line is convex toward the root.

The root is slightly narrower on the lingual side than on the labial

side.

Mesial aspect

The geometric outline is triangular. So, the crown is wedge-

shaped but the curvature labially and lingually is less than that

found on maxillary incisors.

The labial outline is almost straight, except near cervical

third where it is convex (cervical ridge). The labial surface is

inclined lingually.

Height of contour (crest of curvature):

o Labial→→ Junction of cervical and middle thirds.

o Lingual→→ Middle of cervical third.

The lingual outline is ‘S’ shaped. It is convex over the

cingulum, in the cervical third. In the middle and incisal thirds

the lingual outline is slightly concave.

The incisal outline. The lingual outline of the narrow incisal ridge is

convex (rounded) or flat because of attrition. Incisal ridge center is

slightly lingual to the root axis.

The cervical line on the mesial and distal surface is marked and

convex incisally about one third the length of the crown.

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The mesial surface is convex and smooth at the incisal third till the

contact point, below the contact area it is flattened and then it

becomes quit flat and even concave till the cervical line.

The contact area is located half way from labial to lingual and in the

incisal third, very close to the incisal edge. It has an ovoid shape.

The root

The labial and lingual outlines of the root are nearly straight

from the cervical line to the middle third; then tapers to the

rounded or pointed apex. The root tapering is rapid in the

apical third. The root apex is on the axis line.

The mesial surface of the root is flat. Usually there is a broad

and deep longitudinal developmental depression on the

mesial surface of the root for most of its length that is deeper

at the junction of the middle and apical thirds.

Distal aspect

Distal surface is very similar to the mesial surface.

The cervical line is less curved about 1mm less than on the

mesial surface.

The developmental depression on the distal surface of the

root is more marked, with a deeper and more well-

defined developmental groove at its center than the one on

the mesial surface.

Incisal aspect

The geometric outline is roughly four sided, or diamond-shaped.

The incisal ridge (edge) is straight and at right angles to a line

passing labiolingually through the tooth reflecting its bilateral

symmetry (mesial and distal), which is a characteristic feature of

lower central incisor.

The labiolingual diameter is greater than mesiodistal

diameter (the reverse is true for upper incisors).

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The crown tapers lingually, therefore, the labial outline is wider

than the lingual outline.

The labial surface of the crown is slightly convex at incisal third.

The lingual surface of the crown is slightly concave at the incisal

third with centered, smooth, and convex cingulum.

Newly erupted teeth show mamelons which wear off upon

mastication.

Variations and Anomalies:

This tooth is rarely absent. There is great variability in the

lingual inclination of the labial surface of the mandibular

central incisor.

Anomalies are very rare. Occasionally a bifurcated root is

found.

In some Mongoloid peoples, cingulum has a short deep groove

running cervicoincisally. It is a site of dental caries.

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33

Lateral Incisor

Since this tooth supplements the mandibular central incisor so its

design is similar.

It is a little wider mesiodistal than the mandibular central incisor, and

the crown is slightly longer from the incisal edge to the cervical line.

The incisal edge follows the mandibular arch, giving the crown a

slightly twisted appearance on its root

Labial aspect

This tooth resembles the central incisor smooth with

minimal depression, but is somewhat larger and wider

than central mesiodistally in most proportions. The facial

surface is less symmetrical than the facial surface of the

mandibular central incisor.

The crown is tilted distally on the root, giving the

impression that the tooth has been bent at the cervix. This

makes the distal outline of the crown shorter than the

mesial outline.

Mesial and distal contact areas located in incisal third.

The mesial near the incisal edge and the distal just cervical

to the level of the mesial one.

The incisal edge slopes cervical downward (distal sloping) from the

mesioincisal angle, which is slightly less than 90° toward the

distoincisal angle which is rounded.

The mesial border is more nearly straight and longer than the distal

border that can be seen to bulge slightly.

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Lingual aspect

The lingual surface is similar in outline to the labial

surface. The incisal portion of the lingual surface is

concave.

The cervical portion of the lingual aspect is narrower

while the incisal portion is wider. This gives the

crown a more or less a fan shaped appearance.

The cingulum is quite large but blends in smoothly

with the rest of the surface so the cingulum and

marginal ridges more prominent on lateral than

central.

The cingulum is more offset to the distal, and as a

result, the curvature of the cervical line is also offset

distally.

No lingual pit.

The concavity in the lingual aspect is slightly more when

compared to mandibular central incisor.

Proximal aspect (mesial and distal aspects)

Like the central, the crown presents a triangular

outline. When viewed critically, the rotation of the

incisal edge can be seen.

The incisal edge is on or lingual to the mid-root

axis. From the mesial side, the distolingual twist

of the incisal ridge places the distal portion at the

ridge somewhat more lingual than on the mesial.

The distal surface is shorter than the mesial.

The cervical line curvature in both mesially and

distally is slightly less than the central incisors.

The distal contact area is more cervically located

than on the mesial.

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Incisal aspect

As with the mandibular central incisor, but unlike the maxillary

incisors, the crown is broader labiolingually than mesiodistally.

It not bilaterally symmetrical.

The incisal edge is not straight and it curves toward the

lingual in its distal portion (distolingual twist) giving

the crown the appearance of being slightly twisted on

its root. This twist corresponds to the curvature of the

mandibular dental arch.

The distal half of the incisal edge is bent lingually, so that the

distoincisal angle is more lingual in position than the mesioincisal

angle.

The cingulum is slightly off-center to the distal.

The root

Lateral incisor has slightly longer, thicker and wider root in all

dimensions than the central incisor.

The root is single and extremely flattened on its mesial and distal

surfaces.

The root appears very narrow mesiodistally, and tapers gradually

from cervical line toward pointed apex which may slightly to the

distal.

Lateral more likely to have longitudinal developmental grooves that

the distal more pronounced than mesial.

Variations and Anomalies

This tooth is stable, but variations in root length and direction are

occasionally seen also bifurcated root may be found.

Fused mandibular incisors, a missing central, and lateral emerged

distally to the canine may be found.