How is space maintained when primary teeth are lost prematurely?

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How is space maintained when primary teeth are
lost prematurely?
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PermanentMaxillary Incisors
Beverly York, D.D.S.
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Maxillary Central Lateral Incisors
Class Traits

• The incisal two-thirds of the crowns appear
  flattened or compressed faciolingually, providing
  a long horizontal biting edge or margin
• Distinct and rounded protuberances termed
  mamelons representing developmental lobes
  surmount the incisal margins of all newly erupted
  incisors
• The marginal ridges of all incisors are located
  on the mesial and distal borders of the lingual
  surfaces

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Maxillary Central IncisorCalcification
Eruption Schedule

• Calcification begins 3.5 months
• Crown completed 4.5 years
• Eruption (emergence) .. 7.5 years
• Root completed.. 10 years

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Maxillary Central IncisorFacial Aspect

• Cervico-Incisal length (10.5 mm) is greater than
  the Mesiodistal width (8.5 mm) which is greater
  than the Faciolingual depth (7.0 mm)
• Crown outline is trapezoidal with the shorter
  parallel side at cervix
• Crown width at contact area greater than at cervix

Tooth 9 Facial
D
M
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Maxillary Central IncisorFacial Aspect

• A young tooth may show evidence of mamelons on
  the incisal edge
• Mesioincisal line angle is square (90 degrees)
  Distoincisal angle is rounded
• Incisal edge is relatively straight
• Mesial crown outline straighter than the distal
  outline
• Cervical outline of crown is slightly concave
  incisally and the arc of the curvature is said to
  be part of a SEMICIRCLE

Tooth 9 Facial
M
D
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Maxillary Central IncisorFacial Aspect

• Facial surface may show some evidence of shallow
  vertical developmental depressions delineating
  lobe structure
• Facial surface is relatively flat (only slightly
  convex) in its incisal two thirds
• Mesial contact area is located in the incisal 1/3
  of the crown
• Distal contact area is located at the junction of
  incisal middle 1/3 of the crown
• Root cone shaped with blunt apex slightly distal
  of center with no developmental depressions

Tooth 9Facial
D
M
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Maxillary Central IncisorFacial Aspect

• Facial surface may show horizontal ridges at the
  cervical one-third representing differing rates
  of enamel formation during normal growth patterns
• The raised portions of the ridges (positive
  anatomy) are termed perikymata and the
  horizontal grooves (negative anatomy) are termed
  imbrication lines

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Maxillary Central IncisorFacial Aspect

• Outline of root is cone shaped with a relatively
  blunt apex usually located slightly distal to
  center line of tooth, with no developmental
  depressions
• This tooth is easy to extract in that the
  clinician can rotate the tooth within the
  alveolus, without fear of fracturing the root or
  any osseous tissue

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Maxillary Central IncisorLingual Aspect

• Cervical outline of crown is more concave (toward
  the incisal) than what is seen on facial (it is
  not a semicircle)
• Lingual fossa in incisal ½ of crown surface is
  described as a broad, shallow dish-shaped
  depression
• Lingual fossa is bound by the incisal ridge, the
  mesial and distal marginal ridges and the
  cingulum.
• Lingual fossa is trapezoidal in shape.
• Cingulum Well-developed in cervical ½ of crown.
• The greatest curvature lingually of the cingulum
  and the crest of the cervical line gingivally
  will be slightly distal to the mesiodistal long
  axis bisector of the crown.

Tooth 9Lingual
D
M
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Maxillary Central IncisorMesial Aspect
Tooth 9 Mesial

• Crown outline is triangular with apex at incisal
• Incisal edge is centered faciolingually over the
  root
• The incisal edge is lined up with the height of
  curvature of the cervical line and the apex of
  the root

L
F
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Maxillary Central IncisorMesial Aspect
Tooth 9Mesial

• The cervical line viewed from the mesial aspect
  curves incisally for 1/3 of total crown length.
• This is the greatest height of curvature of the
  cervical line incisally or occlusally found on
  any permanent tooth
• Greatest curvature of the crown outline facially
  and lingually will be in the cervical 1/3 of the
  crown at the crests of the facial and lingual
  cervical ridges
• These facial and lingual crests are opposite one
  another and at the same level

L
F
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Maxillary Central IncisorMesial Aspect

• The facial outline of the crown from the crest of
  the facial cervical ridge to the incisal ridge is
  relatively flat (shows very little convexity)
• The lingual outline of the crown from the
  cingulum to the incisal ridge is slightly concave
• The lingual outline of the crown is said to have
  an S shaped contour, denoting the convexities
  over the cingulum and linguo-incisal ridge and a
  concavity over the lingual fossa
• The root surface is relatively smoothly convex
  and has no developmental root depressions
• The root is cone shaped with the blunt apex
  centered faciolingually

Tooth 9Mesial
L
F
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Maxillary Central IncisorDistal Aspect
Tooth 9Distal

• Greatest faciolingual width is in cervical 1/3 of
  the crown
• Incisal ridge and apex of the root are in line
  with each other along the long axis of the tooth
• Note that the convexity of the outline of the
  cingulum begins approximately halfway between the
  incisal ridge and the cervical line on the
  lingual
• The curvature of the cervical line incisally is
  less on the distal than it is on the mesial
  surface by 1.0 mm
• The distal root surface has no developmental root
  depression and is relatively smoothly convex

F
L
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Maxillary Central IncisorIncisal Aspect

• Mesiodistal width (8.5 mm) is greater than the
  faciolingual diameter (7.0 mm)
• Interproximal contact areas (greatest curvature
  mesially and distally) are centered
  faciolingually
• Incisal edge (ridge) is relatively straight and
  perpendicular (at a 90 angle) to the mesiodistal
  bisecting plane
• The incisal edge is positioned parallel to the
  faciolingual bisecting plane
• Note that the mesiofacial line angle is more
  developed than the distofacial line angle

Tooth 9Incisal
M
D
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Maxillary Central IncisorIncisal Aspect

• Crest of the cingulum (greatest curvature on the
  lingual) is slightly distal to the mesiodistal
  bisecting plane of the crown
• Crown outline converges lingually (gets smaller
  from facial to lingual)
• Surface outline between the mesiofacial and
  distofacial outlines is relatively straight
• There is slightly more bulk on the mesial half of
  the crown than on the distal half

Tooth 9 Incisal
M
D
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Maxillary Lateral IncisorCalcification
Eruption Schedule

• Calcification begins 1 year
• Crown completed 4.5 years
• Eruption (emergence) .. 8.5 years
• Root completed.. 11 years

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Maxillary Lateral IncisorFacial Aspect

• Crown length is 1.0 -1.5 mm shorter than the
  maxillary central incisor. Crown width is 2.0 mm
  less than the maxillary central incisor. This
  gives impression that the maxillary lateral
  incisor is relatively long and narrow
• Crown outline is trapezoidal with the shorter
  parallel side at the cervix
• Both mesial and distal incisal line angles are
  rounded and each is more rounded than the
  corresponding incisal line angle of the maxillary
  central incisor. The distoincisal line angle is
  more rounded than the mesioincisal angle
• The mesial proximal contact is at the level of
  the junction of the incisal and middle thirds of
  the crown
• The distal contact is at a level near the middle
  of the middle 1/3 of the crown

Tooth 10Facial
M
D
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Maxillary Lateral IncisorFacial Aspect

• The curvature of the cervical line incisally is
  elliptical and not as broad as that of the
  maxillary central incisor
• The highest point of the curvature of the
  cervical line is likely to be slightly distal to
  mesiodistal bisector of the crown
• Facial crown surface is convex in all directions
• Developmental depressions are evident on the
  crown
• The root converges evenly toward the apex for the
  cervical two thirds of its length
• There is usually a characteristic curve of the
  root toward the distal in the apical third

Tooth 10Facial
D
M
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Maxillary Lateral IncisorLingual Aspect
Tooth 10Lingual

• The lingual fossa is relatively deep, triangular
  in shape and also cup-shaped
• The lingual fossa occupies the incisal two thirds
  of the lingual surface of the crown
• The anatomical features serving as boundaries for
  the fossa include the incisal ridge, the mesial
  and distal marginal ridges and the cingulum
• The cingulum of the maxillary lateral incisor is
  limited to the cervical 1/3 of the crown and the
  mesial and distal marginal ridges form a V as
  they flow into the cingulum

M
D
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Maxillary Lateral IncisorLingual Aspect

• There is a very deep depression or even a pit,
  deep in the fossa behind the cingulum at the
  point of the V
• A developmental groove extending out of the
  lingual fossa between a marginal ridge and the
  cingulum, may be seen on the distal side of the
  cingulum
• This groove may be deep and extend across the
  cementoenamel junction onto the root
• It is termed the linguogingival groove and is
  unique to the maxillary lateral incisor
• Often times, this linguogingival groove is
  decayed or fissured and will need to be restored

Tooth 10Lingual
M
D
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Maxillary Lateral IncisorMesial Aspect
Tooth 10Mesial

• Greatest curvature of both the facial and lingual
  crown outlines is in the cervical 1/3 and each is
  identified as a cervical ridge
• Incisal ridge is in line with mid-point of the
  faciolingual diameter
• Facial crown outline is convex from facial
  cervical ridge crest to incisal ridge
• Lingual crown outline is slightly concave from
  lingual cervical ridge to the incisal ridge
• Curvature of the cervical line toward the incisal
  is greater on the mesial surface than on the
  distal surface
• The curvature of the cervical line extends for
  1/3 of the crown length but not as great of a
  distance as on the maxillary central incisor
  since the lateral incisor has a shorter crown
  length
• Apex of the root is facial to the faciolingual
  long axis bisector
• If there is any evidence of a root depression, it
  will be slight

F
L
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Maxillary Lateral IncisorDistal Aspect
Tooth 10Distal

• The incisal ridge and root apex will not be in
  line with each another, but the incisal ridge is
  centered faciolingually
• The facial outline of root is straighter and less
  length than the lingual outline when measured
  from cervical line to apex of root
• The cervical line curves for a shorter distance
  incisally on the distal surface than on the
  mesial surface

L
F
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Maxillary Lateral IncisorIncisal Aspect

• Crown wider mesiodistally (6.5 mm) than it is
  faciolingually (6.0 mm)
• Incisal ridge is centered F-L
• Incisal ridge crosses approximately midway
  between the facial and lingual outline however,
  it usually shows some curvature with the
  convexity toward the facial
• The facial outline is more continuously convex
  than that of the maxillary central incisor and
  the mesiofacial and distofacial line angles are
  more rounded (less prominent)
• Lingual crown outline converges sharply toward
  the lingual.
• The crest of the lingual outline of the cingulum
  will be slightly to the distal of the mesiodistal
  bisector (all cinguli on anterior teeth incline
  or point slightly toward the distal)

Tooth 10 Incisal
M
D
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Maxillary Lateral Incisor
Except for 3rd molars, maxillary lateral incisors
are associated with the most developmental
anomalies.

• Often congenitally missing (aplasia)

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Maxillary Lateral Incisor
Except for 3rd molars, maxillary lateral incisors
are associated with the most developmental
anomalies.

• Microdontia (abnormally small teeth)

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Maxillary Lateral Incisor
Except for 3rd molars, maxillary lateral incisors
are associated with the most developmental
anomalies.

• Peg lateral (only middle facial lobe develops)

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Maxillary Lateral Incisor
Except for 3rd molars, maxillary lateral incisors
are associated with the most developmental
anomalies.

• Dens in dente (tooth within a tooth)

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Maxillary Lateral Incisor
Except for 3rd molars, maxillary lateral incisors
are associated with the most developmental
anomalies.

• Supernumerary teeth (teeth in addition to normal
  construct)

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Hutchinsons Incisor

• An anomaly associated with the development of
  the incisors associated with congenital
  syphilis.
• Crown of incisors resemble the shape of
  screwdrivers.
• Also associated with Mulberry Molars as the
  permanent 1st molars begin calcification at
  birth (to 3 years) and are in progress when the
  incisors development is affected (3 months to 5
  years)

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Hutchinsons Incisor
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Maxillary Central Lateral Incisors
Type Traits
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Maxillary Central Lateral Incisors
Summary of Comparisons Contrasts
gtCentral is larger than the Lateral gtCentral is
more angular than the Lateral gtCentral has a
straighter root, while the Lateral has a root
that is often curved or pointed to the
distal gtIncisal third of the facial surface of
the Central is fairly flat, while the incisal
third of the lateral exhibits more
convexity gtCentral exhibits minimal variation,
while the Lateral is one of the most variable
permanent teeth gtCrests of the cingulum on both
incisors are offset to the distal gtCentral has a
trapezoidal shaped lingual fossa, while the
Lateral has a triangular shape fossa gtFrom an
incisal view, both incisors display contact areas
that are centered faciolingually gtBoth incisors,
from a proximal view, display an incisal edge
that is centered over the crest of curvature of
the CEJ and their respective root apices gtFrom a
lingual view, the Lateral frequently displays a
fissured or carious lingual pit, while the
Central does not
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The End
Permanent Maxillary Incisors