maxillary lateral and mandibular incisors

Anatomy Of The Maxillary Lateral

Incisors And Mandibular Central And

Lateral Incisors

Howard Chi D.M.D.

Learning Objectives

• Anatomy of the maxillary lateral incisors

• Anatomy of the mandibular central incisors

• Anatomy of the mandibular lateral incisors

Anatomy of theMaxillary Lateral

Incisors

Morphology Of The Crown From The Labial

• Similar to that of a

central incisor

• More convex, or less

flat mesiodistally

Morphology Of The Crown From The Labial

• Appears more oblong

cervicoincisally

• Mamelons and labial

depression less

prominent than central

Crown Size And Shape From The Labial

• Narrower by about 2mm

from that of a central incisor

• This yields a long,

slender look

• Outline is less symmetrical

than a central incisor + 2 mm

Crown Incisal Proximal Angles From The Labial

• Both the mesio and

distoincisal angle are

more rounded than

central incisor

• Mesioincisal angle is

more acute than

central incisor

Crown Incisal Proximal Angles From The Labial

• Distoincisal is wider and

more obtuse than

maxillary central incisor

• Incisal angle slope more

cervically towards the

distal on a maxillary lateral

Crown Contact Areas From The Labial

• Mesial contact is in the

incisal near the junction of

the incisal and middle thirds

• Distal contact is at the

junction of the incisal

and middle thirds

Tooth Proportions From The Labial

• The root is narrower, but

can be longer than that of a

maxillary central incisor

• This makes the root longer

in proportion to the crown

than a central incisor

Root From The Labial

• The root tapers evenly toward

the rounded apex

• The root commonly curves

distally

Lingual Fossa Of The Crown

• Is smaller in area than

a central incisor

• More pronounced than

a central incisor

• May appear either

shallow or deep

Cingulum Of A Maxillary Lateral Incisor

• Narrower than a

central incisor

• Almost centered on

the long axis of

the root

Marginal Ridges Of A MaxillaryLateral Incisor

• Developed to different

degrees on different teeth

• May be prominent

or inconspicuous

• Can be worn from

attrition

Marginal Ridges Of A Maxillary Lateral Incisor

• Mesial marginal ridge outline is

nearly straight

• Distal marginal ridge is shorter

and curved incisocervically

• Shortness of the distal marginal

ridge is due to slope of the incisal ridge

Lingual Anatomy Of The Crown

• May possess lingual accessory

ridges near cingulum

• Fewer and less common than the

central incisor's

• A lingual pit is frequently present

and often restored to arrest decay

Root From The Lingual

• Narrower on the lingual

side than the labial

• Surface root depression

present on the mesial

Incisal Ridge From The Proximal Aspect

• Usually 1.0 to 1.5 mm thick

and labial to the root axis

• Sloped cervically toward the

lingual from its most labial

portion

Cervical Line From the Proximal Aspect

• Curvature is deep

on the mesial

(2.5mm)

• More curved on

mesial than on

the distal Mesial #7 Distal #7

2.5mm

Root Outline From The Mesial

• Appears blunt from

the proximal

• Root ratio is slightly greater

than the central incisor

Mesial #7

Root Depressions From The Proximal

• Similar to the

central, found

on the mesial

mid-root

Mesial #7 Distal #7

Root Depressions From The Proximal

• Mesial surface

is the least

convex of the

four sides

(another way

of saying its

the flattest)

Mesial #7 Distal #7

Crown Proportion From The Incisal Aspect

The mesiodistal measurement

is greater than the faciolingual

• On some this dimension may be the same

Crown Outline From The Incisal

• Is less symmetrical, but in general, resembles the central

• It is narrower mesiodistally than the central

• Cingulum is nearly centered mesiodistally

Incisal Ridge Contour

• Incisal ridge straighter mesiodistally than a central incisor

Cingulum From An Incisal Aspect

• Centered

mesiodistally

and noticeably

more convex than the central incisor

Labial Contour From The Incisal Aspect

• Noticeably more convex than the maxillary central incisor (type trait)

Anatomy Of The Mandibular Central Incisors

Mandibular Central Incisor From The Labial Aspect

• The surface of the crown

is nearly smooth

• Can have two shallow

depressions in the incisal third

(similar to maxillary, but far less

pronounced)

• Mamelons are usually present

on newly emerged teeth

• Quickly worn off with contact

with maxillary teeth (if not,

suspect malocclusion)


• Crown is five-eighths the width

of a maxillary central

• Crown is proportionally narrow in comparison to its length


• The tooth is so symmetrical it is

difficult to tell left from right

• Only difference is the mesial

cervical line curve more incisally

than the distal


• The mesial and distal outlines is

straight in the incisal third

• The crown tapers to the cervical

third

• Contacts are well within the

incisal one third


• Labial surface is convex

mesiodistally in the cervical third

• Mesio and distoincisal angle is

nearly 90 degrees


• Distoincisal angle may be more

rounded (slightly) than the

mesioincisal angle


• Mesial and distal contact areas are

within the incisal third at roughly

the same height (type trait)

• Root longer than crown

proportionally compared to the

maxillary incisors


• The root is narrow mesiodistally,

but wide faciolingually

• The root is tapered evenly on both

sides from the cervical line to the

apex, root tip may curve to the

distal


Mandibular Central Incisor From The Lingual Aspect

• The outline is much more

symmetrical than all other incisors

• The lingual crown surface is

smooth and shallow with a slight

concavity in the middle and

incisal thirds

• The cingulum is convex, small and centered

• The marginal ridges and lingual fossa are scarcely discernible, if at

all

• No grooves, pits or accessory ridges are present

Mandibular Central Incisor From The Lingual Aspect

Mandibular Central Incisor From The Proximal Aspect

• The incisal edge is on or lingual

to the long axis of the root

• Mesial cervical line (CEJ) extends

2mm incisally

• Distal cervical line extends .4 mm

less than the mesial

• The facial height of contour is

located in the cervical third

• The lingual height of contour is

located on the cingulum, within

the cervical third


• The labial contour is so slightly

curved that it often appears flat

• The lingual contour is convex on

the cingulum, concave in the

fossa and flat towards the incisal


• The facial and lingual sides of the

root are nearly straight from the

cervical line to the middle third

• The root then tapers to its apex


• Roots are flat mesiodistally

compared to their maxillary

counterparts

• Roots are wider faciolingually

than mesiodistally by

approximately 2mm


Root depressions can be

found on both the

mesial and distal

aspects in the

middle third

of the roots


#25 Mesial #25 Distal

Mandibular Central Incisor From The Incisal Aspect

• The labiolingual measurement of the crown is greater than the mesiodistal measurement (this is quite different from the maxillary counterparts)

• The labial and lingual height of contour is centrally located

• The incisal edge runs in a straight line mesiodistally and is roughly 2mm thick


• The cingulum is centered, smooth and has a convex outline

• The labial surface is slighly convex in the incisal one third and noticeably convex in the cervical third


Anatomy Of The Mandibular Lateral Incisors

Mandibular Lateral Incisor From The Facial View

• Similar to the central, smooth

and minimal depressions

• Labial surface is convex

mesiodistally, more in the

cervical third and less in the

incisal third

• Crown is tilted distally on the

root, giving a bent appearance

• This makes the distal outline

of the crown shorter than the

mesial aspect


• The distoincisal angle is

noticeably more rounded than

the mesioincisal angle

• This aids in telling left

from right


• The mesial contact is in the

incisal third, near the incisal edge

• The distal contact is in the

incisal third, but cervical to the

level of the mesial contact


• Crown is narrower with respect

to its length

• Root is narrow mesiodistally,

tapering gradually from the

cervical line to the apex. It may

have a distal curvature


Mandibular Lateral Incisor From The Lingual View

• Similar to the central, but not

bilaterally symmetrical

• Crown is tilted distally, and tapers

lingually in the middle and cervical

thirds

• The cingulum is slightly distal

to the long axis of the root, similar

to the maxillary central

• This makes the mesial marginal

ridge longer than the distal


• Marginal ridges and lingual fossa

are not conspicuous and

generally smooth

• The root is narrower lingually

than facially


Mandibular Lateral Incisor From The Proximal View

• The incisal edge is on or

lingual to the long axis

of the root

• From the mesial a distolingual

twist of the incisal edge places

the distal portion more lingual

Central Lateral

• The C.E.J. curves 2 mm

incisally on the mesial aspect

• The C.E.J. curve 1.4 mm

incisally on the distal aspect


• The facial and lingual heights

of contour are in the cervical

third

• The labial outline is nearly

flat in the middle and incisal

thirds


• The root is straight from

cervical to middle third

• The distal portion of the

root contains a depression

that is more distinct than

the mesial


Mandibular Lateral Incisor From The Incisal View

• The crown is broader faciolingually than

mesiodistally

• Not bilaterally symmetrical, distal is twisted

• The cingulum is off center to the distal with a barely dicernible lingual fossa

• The labial outline is slightly convex in the incisal one third

Mandibular Lateral Incisor From The Incisal View

maxillary lateral and mandibular incisors

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