Morphology of upper lateral incisor tooth.

1. Permanent Maxillary Laterals
Dr. Ridwana Kawsar
BDS (CMC), BCS (Health)
MS (Conservative Dentistry &Endodontics - BSMMU)
Lecturer, Dept. of Conservative Dentistry & Endodontics
Shaheed Suhrawardy Medical College( ShSMC)
Sher-E-Bangla Nagar, Dhaka

2. Class Traits of Incisors
Before discussing the each surface, here we enlist few important class traits of
all permanent incisors those can be used to differentiate other class or groups of
teeth:
• Incisors are rectangular in shape
• They have a longer cervicoincisal dimension than mesiodistal dimension (CI > MD) (Height is more than
width)
• Tapers from the contact area to the cervix in mesiodistal direction (Narrow at the cervical line and broad at
the incisal)
• Mesial outline is less convex than distal outline in all incisors except mandibular central incisors which is
bilaterally symmetrical
• Mesioincisal line angle is less rounded than distoincisal angle except mandibular central incisor
• Mesial contact area is situated in incisal one-third and distal contact is in middle of middle one-third except for
mandibular central incisor, because it is the only bilaterally symmetrical tooth with both contacts at same level
• From labial aspect, the mesiodistal dimension is less than the labiolingual dimension (MD < LaLi)
• All incisors converge lingually, both in crown and root aspect
• Roots are longer than crown, but length of the crown is comparatively longer than the root
• From proximal aspect, both labial and lingual crests of curvature are seen in cervical 1/3
• Teeth are ‘wedge’ shaped from proximal view and have shallow ‘S’ shaped lingual outline
• Incisal edges converge lingually and terminate at mesial and distal ends

3. The maxillary lateral incisor is located distal to maxillary central incisor on both sides of the midline of
the face and mesial to maxillary canine. Like all other incisors, the prime function is cutting of food
during mastication. Both maxillary central and lateral incisors have close resemblance in morphology
and maxillary lateral incisors supplement maxillary centrals in function.
Maxillary lateral incisors are smaller in size from all directions except the root. This tooth is more
rectangular and is less symmetrical than the maxillary central incisor. The crown of the lateral incisor is
shorter by about 1 mm to 1.5 mm in cervicoincisal dimension than any other tooth in both arches. This
feature is not seen in any other tooth.
The maxillary lateral incisor has highest degree of morphologic variation than any other tooth except
third molars. In many individuals, the lateral incisor is found to be missing, resulting maxillary central
incisor directly in contact with maxillary canine. Absence of maxillary incisor may be unilateral and
sometimes, bilateral missing is also noted.

4. Tooth numbering systems used to designate are:
• In the Palmer system, a letter is used in conjunction with a symbol designating
in which quadrant the tooth is found. For the permanent teeth, the left and
right lateral incisor would have the same number ‘2’ but the right one would
have the symbol ‘┘’ underneath it, while the left one would have ‘└’
• In the Universal system, the permanent maxillary lateral incisors are designated
by a number. The right permanent maxillary lateral incisor is known as ‘7’,
and the left is known as ‘10’
• The FDI system is a different system of tooth numbering than the previous
two. For the permanent maxillary lateral incisor, the right one is known as
‘12’, and the left one is known as ‘22’.

5. • First evidence of calcification: 1 year
• Enamel completion: 4–5 years
• Eruption: 8–9 years
• Root completion: 11 years
• Length of the crown: 9.0 mm
• Length of the root: 13 mm
• Mesiodistal width of the crown: 6.5 mm
• Mesiodistal width of crown at cervix: 5.0 mm
• Labiolingual width of the crown: 5.0 mm
• Labiolingual width of the crown at cervix: 6.0 mm
• Depth of curvature at the mesial aspect: 3.0 mm
• Depth of curvature at the distal aspect: 2.0 mm

7. • LABIAL ASPECT
• Shape of the crown: The shape of the crown is roughly ovoid. The mesiodistal width at the cervix is lesser than
the mesiodistal width at the incisal third.
• Outlines of the crown (a) Mesial outline: The mesial outline is straight and the mesioincisal angle is more rounded
when compared with the maxillary central incisor. The height of convexity is at the junction
of middle third and incisal third.
(b) Distal outline: The distal outline is more prominently rounded or convex and the
height of convexity is more cervical.
(c) Incisal outline: The incisal outline is rounded when compared with the straight incisal
outline of the maxillary central incisors.
(d) Cervical outline: The cervical outline curves towards the root.
• Line angles in the
crown from the labial
aspect
(a) Mesioincisal angle: The mesioincisal line angle is rounded.
(b) Distoincisal angle: The distoincisal line angle is more prominently rounded than
mesioincisal angle and is obtuse
• Labial surface: The labial surface is more convex when compared with the central incisors.
• Shape of the root: It is cone shaped with pointed apex. The root is slightly distally inclined or straight
• Outlines of the root (a) Mesial outline: The mesial outline of the root is slightly convex from the cervical third to
the middle third but the convexity decreases from the middle third to the apex.
(b) Distal outline: The distal outline is convex from the cervical third to the middle third; it
gradually tapers and curves distally from the middle third to the apex.

12. Lingual Aspect
• Shape of the crown: The shape of the crown in the lingual aspect is the same as that of the labial side.
• Outlines of the crown: The outlines are similar to those of the labial aspect.
• Lingual surface: The lingual fossa is deeper when compared with the maxillary central incisor. The
increase in depth is the result of increased prominence of the mesial and distal
marginal ridges on the sides.
Cingulum is narrower but more prominent than the maxillary central incisor. It is marked
by developmental grooves at the side of the cingulum called the palatogingival groove or
the palatoradicular groove.
These developmental grooves are usually present on the distal side and might extend
up to varying lengths
on the root.
• Outlines of the root: The outlines are similar to those of the labial aspect and become narrower
towards the lingual side.

15. Shape of the crown: The shape of the crown is triangular mesially. The labiolingual width at cervix is more
than the labiolingual width at the incisal third.
Outlines of the crown (a) Labial outline: The labial outline from the crest of curvature is slightly convex and
curves smoothly from the cervical margin to the incisal ridge. The convexity is more than
in the maxillary central incisor.
(b) Lingual outline: The lingual outline is roughly S shaped as in the maxillary central
incisor, with a slight increase in convexity in the incisal ridge area.
(c) Cervical outline: The cervical curvature is convex towards the incisal edge but the
convexity is less when compared with the maxillary central incisors.
(d) Incisal outline: The incisal ridge is thick and convex and forms the apex of the
triangular shape of the mesial aspect of the crown
Contact Area The contact area in the mesial aspect is present in the junction of the incisal
and middle third.
Outlines of the Root (a) Labial outline: The labial outline of the crown is straight from the cervical third to
the middle third, tapers towards the apex and points towards the labial direction.
(b) Lingual outline: The lingual outline is convex from the cervical third to the middle
third and there is a gradual taper to the apical third.

18. Distal Aspect
Shape of the crown: The shape of the crown is triangular.
Outlines of the crown The outlines of the crown are similar to the mesial aspect except that the depth of curvature
is less prominent.
Contact Area The contact area is located at the middle third.
Outlines of the Root The outlines of the rootare similar to those of the mesial aspect
Incisal Aspect
Shape of the crown: The crown is round or ovoid in the incisal aspect.
Outlines of the crown a. Labial outline: The labial outline is more convex when compared with the maxillary
central incisor. The incisal ridge is seen clearly from this aspect and is straighter
mesiodistally than the central incisors.
b. Lingual outline: The mesial and distal marginal ridges converge towards the cingulum.
The cingulum is centred mesiodistally unlike its position in the maxillary central incisors.

22. Applied Morphology
• The palatogingival groove or the palatoradicular groove may cause periodontal
problems since they pave an easy path for the entry of bacteria.
• The maxillary lateral incisors are the second commonest congenitally missing
tooth next to third molars.
• The palatoaxial inclination of the maxillary lateral incisor is 29°, which makes it
inclined in a palatal direction. Because of such an inclination, abscesses which
form in the periapical region of maxillary lateral incisors usually drain palatally
rather than in the labial aspect.
• Lingual pits are common on maxillary lateral incisors. Lingual pits are present
just above the cingulum.
• An accessary cusp in the lingual surface of incisors is called as Talon’s cusp
which is a developmental anomaly most commonly affecting permanent
maxillary lateral incisor.
• The maxillary lateral incisors show wide variations in morphology, the
commonest being the pointed shape of the crown called the peg laterals.

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