Generals About Incisors

Generals AboutGenerals About
Incisors AndIncisors And
Particulars AboutParticulars About
Maxillary CentralMaxillary Central
IncisorsIncisors
Howard Chi, D.M.D.Howard Chi, D.M.D.

Learning ObjectivesLearning Objectives
 Generals of incisorsGenerals of incisors
 Traits of incisorsTraits of incisors
 Particulars of maxillary central incisorsParticulars of maxillary central incisors

Generals of IncisorsGenerals of Incisors

General Description Of IncisorsGeneral Description Of Incisors
There are four maxillary incisors:There are four maxillary incisors:
 Two centralsTwo centrals
 Two lateralsTwo laterals
7 8 9 10

There are four mandibular incisors:There are four mandibular incisors:
 Two centralsTwo centrals
 Two lateralsTwo laterals
26 25 24 23

 Central incisors haveCentral incisors have
two mesial surfacestwo mesial surfaces
contacting each othercontacting each other
 If a space exists, it isIf a space exists, it is
known as a diastemaknown as a diastema
(for all teeth)(for all teeth)

Function Of All Incisor TeethFunction Of All Incisor Teeth
1) Cutting food1) Cutting food
2) Enabling articulate speech2) Enabling articulate speech
3) Help support the lips and maintain good3) Help support the lips and maintain good
appearanceappearance
4) Help guide the mandible during its movements4) Help guide the mandible during its movements

MorphologyMorphology
Of TeethOf Teeth
 Generally, any tooth has five surfacesGenerally, any tooth has five surfaces
 Four surfaces and a chewing or cuttingFour surfaces and a chewing or cutting
surfacesurface
 Five aspects are: facial, lingual, mesial, distal,Five aspects are: facial, lingual, mesial, distal,
and incisal or occlusaland incisal or occlusal
I
F
D
L
M

General DescriptionGeneral Description
Of IncisorsOf Incisors
Morphology OfMorphology Of
The Labial SurfaceThe Labial Surface
 Mamelons are usually seen onMamelons are usually seen on
newly emerged incisor teethnewly emerged incisor teeth
 They are three scallops on theThey are three scallops on the
incisal edge - beneath the three facial lobesincisal edge - beneath the three facial lobes
 Usually worn off after tooth in function for awhileUsually worn off after tooth in function for awhile

 When mamelons remainWhen mamelons remain
on an adult,on an adult,
suspect malocclusionsuspect malocclusion

 Developmental depressions are theDevelopmental depressions are the
two shallow vertical depressions ontwo shallow vertical depressions on
the labial surface - dividing thethe labial surface - dividing the
surface into three sectionssurface into three sections
 These sections are called mesial, middle andThese sections are called mesial, middle and
distal lobesdistal lobes
GeneralGeneral
Description OfDescription Of
IncisorsIncisors
D M M

 Perikymata - are fine horizontal lines on thePerikymata - are fine horizontal lines on the
crown surfacecrown surface
GeneralGeneral
Description OfDescription Of
IncisorsIncisors

Traits of IncisorsTraits of Incisors

Class Traits OfClass Traits Of
All IncisorsAll Incisors
Crowns From The FacialCrowns From The Facial
 Are relatively rectangular, longer incisogingivallyAre relatively rectangular, longer incisogingivally
 Are narrowest in the cervical third and broader at theAre narrowest in the cervical third and broader at the
incisal thirdincisal third

 Are more convex on the distal than on the mesial (except 24+25)Are more convex on the distal than on the mesial (except 24+25)
 Mesial contact in the incisal thirdMesial contact in the incisal third
 Distal contact at the junction of incisal and middle thirdsDistal contact at the junction of incisal and middle thirds
Crowns From The FacialCrowns From The Facial

 Distal contact more cervical than the mesial (exceptDistal contact more cervical than the mesial (except
24+25)24+25)
 Cervical lines that are convex (dip) toward the apexCervical lines that are convex (dip) toward the apex
facially and linguallyfacially and lingually
Crowns FromCrowns From
The FacialThe Facial

 Taper from cervical line to the apexTaper from cervical line to the apex
 Wider faciolingually than mesiodistallyWider faciolingually than mesiodistally
(except 8+9, which are roughly equal)(except 8+9, which are roughly equal)
7 7
Roots FromRoots From

 Longer than crownsLonger than crowns
 May bend, usually distally, in the apical one-May bend, usually distally, in the apical one-
third (except 8+9)third (except 8+9)

Crowns FromCrowns From
The LingualThe Lingual
 Mesial and distal sides convergeMesial and distal sides converge
forming narrower surfaceforming narrower surface
 Mesial and distal marginalMesial and distal marginal
ridges that converge towardridges that converge toward
cingulumcingulum

Class Traits Of All IncisorsClass Traits Of All Incisors
Crowns From The ProximalCrowns From The Proximal
 Wedge-shapedWedge-shaped
 Usually have the incisal edgeUsually have the incisal edge
labial to the root axis line forlabial to the root axis line for
the maxillary incisorsthe maxillary incisors
 Usually have the incisal edgeUsually have the incisal edge
lingual to the root axis line forlingual to the root axis line for
the mandibular incisorsthe mandibular incisors

Crowns From The ProximalCrowns From The Proximal
1) Labial and lingual crest of1) Labial and lingual crest of
curvature (greatest bulge) that iscurvature (greatest bulge) that is
in the cervical thirdin the cervical third
2) Lingual is convex-concave2) Lingual is convex-concave
(s-shaped)(s-shaped)
3) Cervical line proximally is convex3) Cervical line proximally is convex
and curves incisallyand curves incisally
Concave
Convex
1
2 3

The ProximalThe Proximal
Widest at the cervical and taper to aWidest at the cervical and taper to a
rounded apexrounded apex
Depression in middle third of mesialDepression in middle third of mesial
root surface (mandibular also have distalroot surface (mandibular also have distal
depression)depression)
Mesial ViewDistal View

Crowns From The IncisalCrowns From The Incisal
 A shallow concavity just incisal to the cingulumA shallow concavity just incisal to the cingulum
called the lingual fossacalled the lingual fossa
 An incisal ridgeAn incisal ridge
 A labial contour that is broader and less curvedA labial contour that is broader and less curved
than the lingualthan the lingual
lingual fossa
incisal ridge

Arch Traits Of IncisorsArch Traits Of Incisors
Mandibular IncisorsMandibular Incisors
1) are smaller than maxillary1) are smaller than maxillary
2) look more alike2) look more alike
3) are nearly the same size3) are nearly the same size
4) have smaller roots than maxillary4) have smaller roots than maxillary
5) are flatter on mesial and distal sides5) are flatter on mesial and distal sides
6) have crowns and roots relatively wider6) have crowns and roots relatively wider
faciolingually than mesiodistallyfaciolingually than mesiodistally

Arch Traits Of IncisorsArch Traits Of Incisors
7) have contact areas located near the incisal7) have contact areas located near the incisal
ridgeridge
8) have smoother lingual surfaces than maxillary8) have smoother lingual surfaces than maxillary
9) have incisal ridges on or lingual to the root9) have incisal ridges on or lingual to the root
axisaxis
10) have wear or attrition only on the incisal10) have wear or attrition only on the incisal
edge (not on lingual surface)edge (not on lingual surface)
11) have root that are longer in proportion to11) have root that are longer in proportion to
the crownsthe crowns

Particulars ofParticulars of
Maxillary CentralMaxillary Central
IncisorsIncisors

The Maxillary Central IncisorThe Maxillary Central Incisor
Incisal View
Distal ViewMesial View
Lingual View Facial View

Maxillary Central IncisorMaxillary Central Incisor
Labial SurfaceLabial Surface
Crown - Shape and SizeCrown - Shape and Size
 Crown is the longest of all humanCrown is the longest of all human
crown and widest of all incisorscrown and widest of all incisors
 Usually longer (incisogingivally)Usually longer (incisogingivally)
than wide (mesiodistally)than wide (mesiodistally)
 Crown is narrowest in theCrown is narrowest in the
cervical thirdcervical third
Facial View

Crown - Incisal Proximal AnglesCrown - Incisal Proximal Angles
 MesioincisalMesioincisal angle is slightlyangle is slightly
rounded and nearly a 90 degreerounded and nearly a 90 degree
angleangle
 DistoincisalDistoincisal angle is moreangle is more
rounded and somewhat obtuserounded and somewhat obtuse
 IncisalIncisal edge slopes cervicallyedge slopes cervically
towards the distaltowards the distal

MaxillaryMaxillary
Central IncisorCentral Incisor
Crown - Contact AreasCrown - Contact Areas
 Mesial is in the incisal third - near incisal edgeMesial is in the incisal third - near incisal edge
 Distal near junction of incisal and middle thirdsDistal near junction of incisal and middle thirds
D M

Crown - ProportionsCrown - Proportions
 The root is just slightlyThe root is just slightly
longer than the crownlonger than the crown

Root - ShapeRoot - Shape
From The LabialFrom The Labial
 Root is thick in the cervical third, narrowsRoot is thick in the cervical third, narrows
through the middle to a blunt apexthrough the middle to a blunt apex
 Central incisor root is the only root that is as thickCentral incisor root is the only root that is as thick
mesiodistally as faciolingually at its cervixmesiodistally as faciolingually at its cervix

MaxillaryMaxillary
Central IncisorCentral Incisor
Root - Shape From The LabialRoot - Shape From The Labial
 Because it is short and conical,Because it is short and conical,
this tooth is a poor risk tothis tooth is a poor risk to
support prostheticssupport prosthetics

Lingual SurfaceLingual Surface
Crown - Lingual FossaCrown - Lingual Fossa
 Lingual fossa is developed toLingual fossa is developed to
different degrees (from shallowdifferent degrees (from shallow
to deep)to deep)
 Centrals with a deep fossa and prominentCentrals with a deep fossa and prominent
marginal ridges are termedmarginal ridges are termed
"shovel-shaped incisors""shovel-shaped incisors"

Crown - CingulumCrown - Cingulum
 Usually well developed andUsually well developed and
toward the distaltoward the distal
(X marks the spot)(X marks the spot)
 Distal to the root axis line bisectingDistal to the root axis line bisecting
the root longitudinallythe root longitudinally
X

Crown - Marginal RidgesCrown - Marginal Ridges
 Marginal ridges areMarginal ridges are
prominentprominent
 Mesial marginal ridge is longerMesial marginal ridge is longer
than distal due to the distalthan distal due to the distal
placement of the cingulumplacement of the cingulum

Crown - Lingual Anatomy VariationsCrown - Lingual Anatomy Variations
1) the fossa may be deep but smooth (no lingual1) the fossa may be deep but smooth (no lingual
ridges)ridges)
2) may possess accessory lingual ridges (1 to 4)2) may possess accessory lingual ridges (1 to 4)
3) may possess a lingual pit near incisal border3) may possess a lingual pit near incisal border
of cingulum where m + d marginal ridgesof cingulum where m + d marginal ridges
meetmeet

Root - ShapeFrom TheLingualRoot - ShapeFrom TheLingual
 Likeall anterior teeth thissurfaceisLikeall anterior teeth thissurfaceis
convex and narrower mesiodistallyconvex and narrower mesiodistally
than thelabial surfacethan thelabial surface
 Somewhat flat on mesial sideSomewhat flat on mesial side
approaching thelingualapproaching thelingual
 A mesial depression running longitudinalA mesial depression running longitudinal
isoften presentisoften present
M

Proximal SurfacesProximal Surfaces
Crown - Incisal EdgeCrown - Incisal Edge
 Slightly labial to long axis of the rootSlightly labial to long axis of the root
(can be mid-root)(can be mid-root)
 From distal, the distoincisal edge may beFrom distal, the distoincisal edge may be
just lingual to the axis line due to slightjust lingual to the axis line due to slight
twisting of incisal edgetwisting of incisal edge
 Labial outline is convex in cervical, flatLabial outline is convex in cervical, flat
to broadly curved in the middle andto broadly curved in the middle and
incisal thirdsincisal thirds
Distal View
Mesial View

Crown - Cervical Line (CEJ)Crown - Cervical Line (CEJ)
 Like all anterior teeth the cervical line curvesLike all anterior teeth the cervical line curves
incisally on mesial and distal surfacesincisally on mesial and distal surfaces
 Curvature is greater on the mesial than the distalCurvature is greater on the mesial than the distal
Distal ViewMesial View

Crown - Crest Of CurvatureCrown - Crest Of Curvature
 The labial crest (height of contour)The labial crest (height of contour)
is in the cervical third just incisalis in the cervical third just incisal
to the cervical lineto the cervical line
 On the lingual in the cervical thirdOn the lingual in the cervical third
Mesial View
L

Root - OutlineRoot - Outline
 Root trunk thick or wide at cervix andRoot trunk thick or wide at cervix and
tapers evenly to a rounded apextapers evenly to a rounded apex
 Lingual outline nearly straight in cervicalLingual outline nearly straight in cervical
third, curving labially in middle andthird, curving labially in middle and
apical thirdsapical thirds
 Labial outline slightly convexLabial outline slightly convex
Distal View
Mesial View

Root DepressionRoot Depression
 Mesial surface is somewhat flattened with aMesial surface is somewhat flattened with a
longitudinal depression in the middle thirdlongitudinal depression in the middle third
 Mesial depression is located at junction ofMesial depression is located at junction of
middle and lingual thirds of the rootmiddle and lingual thirds of the root

Root DepressionRoot Depression
 Distal similar to mesial, exceptDistal similar to mesial, except
distal is convex not flatteneddistal is convex not flattened
 Distal lacks a depressionDistal lacks a depression

Incisal AspectIncisal Aspect
Crown WidthCrown Width
 Crown outline noticeably wider mesiodistally thatCrown outline noticeably wider mesiodistally that
faciolinguallyfaciolingually

Crown OutlineCrown Outline
 Crown is roughly triangular, somewhatCrown is roughly triangular, somewhat
curved labial outlinecurved labial outline

Incisal Ridge ContourIncisal Ridge Contour
 Ridge 1.5 to 2 mm thick and slightly curvedRidge 1.5 to 2 mm thick and slightly curved
from mesial to distalfrom mesial to distal
 Distoincisal angle is slightly lingual to theDistoincisal angle is slightly lingual to the
mesioincisal anglemesioincisal angle
1.5 - 2mm

CingulumCingulum
 Cingulum is off-center to the distal, with aCingulum is off-center to the distal, with a
longer mesial marginal ridgelonger mesial marginal ridge

Labial ContourLabial Contour
 Labial contour is broadly convexLabial contour is broadly convex
 On some teeth a portion may be nearly flatOn some teeth a portion may be nearly flat
 Possess two slight depressions (mesial andPossess two slight depressions (mesial and
distal) on the labial surface in middle anddistal) on the labial surface in middle and
incisal thirdsincisal thirds

Generals About Incisors

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