Transcript of "07. The Deciduous Teeth - Dentition"
teeth are that teeth which function
during childhood and then they are shed and
replaced by permanent teeth. The word
deciduous comes from a Latin word meaning to
There are 20 teeth in the deciduous dentition; 10
maxillary and 10 mandibular teeth.
These teeth emerge in children between the ages
of 6 months and 2 years
Beginning at the age of 6 years these teeth are
gradually replaced by the teeth of the permanent
Names: Temporary teeth, milk teeth, baby
teeth. Primary teeth, all are improper terms
because they means that deciduous teeth
are useful for a short period only.
Importance of deciduous teeth
a-They need for many years from 6month to
b-They are importance during growth and
development for proper arrangement of the
permanent teeth and proper development of
the dental arches.
Eruption of the deciduous teeth Start from 6month to
2years and root completed at 3years.
Shedding of the deciduous teeth
is the process of exfoliation of the
Upper and lower central incisors at 7years.
Upper and lower lateral incisors 8y.
Lower canine and first molar 9y.
Upper molar and lower second molar at 10y.
Upper canine 11y.
Roots resorped first at the apex and continues in
the direction of the crown until the entire root is
resorped completely then crown is lost due to
lack of support.
From 6m to 6y deciduous dentition.
From 6y to 12y mixed dentition.
Over 12 years permanent dentition.
Retained deciduous tooth:
Any deciduous tooth remain in the
mouth of the child beyond the age
of 12 years.
in size than the permanent teeth.
The enamel is whiter in color and more
opaque which gives the crown a lighter color
than that of the permanent teeth.
The enamel of the deciduous teeth is less
mineralized, more permeable and more easily
They have shorter crowns with respect to their
The enamel of deciduous teeth ends suddenly
at the cervical line, while in the permanent it
tapers gradually towered the neck of the teeth .
*The crowns are more bulbous, because they are wider
MD compared to their crown length.
*The crown of deciduous teeth are more constricted
cervically as they are narrower at their neck.
*The crown of deciduous teeth have prominent cervical
ridge in anterior teeth (ABC) in posterior teeth cervical
ridge much more pronounced especially upper and
The crown of the deciduous teeth have more
flattened and smooth no depression or perikymata
on the labial surface of anterior teeth.
* Cervical line in deciduous teeth is more or less straight
not curved as in permanent teeth.
*There is no root trunk, root divided immediately at the
neck of the tooth.
of molars are more divergent to
accommodate tooth germ of permanent successors.
Crown to root ratio is greater than permanent 1 to
2 while in permanent 1 to 1.5.
Roots are thin or slender.
The second molar roots are spread widely than the
first deciduous molar.
All deciduous teeth undergo calcification before
birth while only the first permanent molar show
calcification at birth.
There is no mamelones on the incisal edges of
The molar crown have a narrow chewing surface
The cusps of the molars are short, the ridges are not
pronounced and also the occlusal and surfaces groove
and depressions not deep.
The pulp of deciduous teeth
teeth have large
pulp chamber, higher pulp
horn, limited dentine
thickness particularly in
lower second molar.
The enamel of primary molars
is thinner and has more
The enamel rods at the cevical
slope occlusally instead of
gingivally as in the permanent
(a) labial surface is convex ,no developmental lines, MD
width greater than CI length. MI angle is sharp and DI angle
is rounded. IR is straight. Root is cone shape and taper to the
(b) crown smaller than (a) ,CI greater than MD,2 angles are
rounded. Root similar to A but longer.
M slope greater than D slope, MCA and DCA at the same
level about middle of the crown .Well developed long and
sharp cusp .Neck more constricted . M and D outline are
convex .Root is long slender tapering and inclined distally.
(a) geometric outline is trapezoid. Well developed M&DMR,
deep lingual fossa, highly developed cingulum may extend
toward the incisal ridge to the extent that partially divides the
lingual fossa into mesial and distal fossa. Root is very narrow
resembling a ridge extends for its whole length.
(b) smaller than (a).
(c) pronounced cingulum, pronounced M&DMR ,pronounced
DIC&MIC ridges ,lingual ridge well developed its continuation
incisally give tubercle on cusp tip. Root is narrow lingually due
to the lingual convergence.
(a) geometric outline is triangular . C.L is convex toward the
incisal ridge. Labiolingual dimension greater in compared
to the crown length especially at cervical third. Also
crown appear thick labiolingually in the cervical and
middle third. Root is convex and has deep DG or
(b) similar to (a).
(c) show much greater labiolingual dimension at cervical
third. Root is very long. This allows maximum strength to
the canine to resist force applied on it during function.
labiolingual greater than MD. Labial surface
broad & smooth, lingual surface tapers toward
the cingulum, M&D surfaces relatively broad to
allow proper C.A. with adjacent teeth. IR is
straight and centered labiolingually.
(b) similar to (a) but it smaller.
(c) crown appear diamond with pronounced
cervical ridge, MCA&DCA and cingulum. The
cusp tip is distal to the center because M slope
longer than D slope.
labial surface is flat and has no DG. M&D sides
tapers from C.A. to a narrow cervix. Root long and
tapers to pointed apex.
(e) similar to (d) but it is larger in all dimension. IR
sloped toward distal side so the distal contact area
(f) M slope shorter than D slope.
(d) lower central incisor, all elevations are well developed.
Lingual fossa is flattened or slightly concave at the middle third
of the crown. Crown and root is narrower than labial due to the
(e) lower lateral incisor, lingual fossa more concave than lower
central incisor lower central incisor (d). Cingulum more
developed than lower central incisor (d). IR slope downward D.
(f) lower canine similar to upper deciduous canine.
(d) lower central incisor no lingual inclination, IR is centered
over the axis of the root. Well developed cervical ridge and
cingulum. Root is flat and tapers to blunt apex.
(e) lower lateral incisor lingual inclination, C.R. and cingulum
(c) lower canine similar to upper canine but C.R. and cingulum
A lower central incisor, incisal ridge is straight and centered
labiolingually. Labial surface is flat or slightly convex. Also
lingual surface is flat.
B lower lateral incisor, incisal ridge is inclined toward the
C lower canine crown appear diamond . All ridges less
prominent than upper canine. The lingual ridge is raised in the
incisal third & then less distinct .
Maxillary first & second deciduous molars
Maxillary first molar
Maxillary second molar
Buccal aspects of upper deciduous
Well developed cusps
Occ. outline slightly scalloped
Upper D (a): geometric outline of the crown is trapezoid.
Buccal surface is very smooth with little evidence of developmental groove
Occlusal outline has a slightly scalloped appearance with no definite cusp
There is mesio-buccal cervical ridge (MBCR)
3Roots are seen MBR, DBR & LR
Upper E (b):. Geometric outline of the crown is trapezoid.
Crown converge markedly from the contact area to the cervical line.
MBC equal DBC or MBC larger than DBC.
3Roots are seen MBR,DBR& LR. Roots are thicker than D
The roots of both molars are divergent ,long &slender ,no root trunk.
Lingual aspects of upper deciduous molars
Tubercle of carabelli
Crown converge lingually. MLC largest &sharpest
cusps. DLC is very poorly defined small and round.
MMR is prominent. DBC is larger and better
developed than DLC so may be seen. D may be 3cusped type one lingual cusp with no developmental
E MLC is long & well developed. DLC less developed.
Tubercle of carabelli is seen related to MLC.
Mesial aspects of upper deciduous molars
Outline form is trapezoid
with the shortest of uneven
sides is occlusally.
D Crown is constricted at the occlusal 1/3 than cervically.
Crown has pronounced cervical ridge buccally (MBCR). C.L.
shows slight curvature occlusally.
Roots MBR, LR . The DBR hidden by MBR.
E crown is o.5 mm longer than D.
B-L dimension is 1.5-2 mm longer than D .
Roots are 1.5-2 mm longer than D. Cervical line almost straight
MBR is broad & flat.
LR is extend lingually beyond crown outline, It is long&
slender& it is above middle 1/3 curves buccally.
Distal aspects of upper deciduous molars
Lingual outline is
Buccal outline is
D Crown converge distally (narrow than mesially). Cervical
ridge is not so marked as mesially. Cervical line is straight or
slightly curved occlusally.
E also it is narrower distally than mesially.
The lingual outline appears semicircular, while the buccal outline is straight.
DB&DL cusps are about the same length. Cervical outline is straight. All
three roots seen from this aspect. The point of bifurcation between DB& L
roots is higher towered the crown than any other aspects.
Occlusal aspects of upper D
Occlusal aspects of deciduous upper molars
D the occlusal surface is rectangular. The crown converge lingually &
The occlusal surface presented , CF&MTF the two fossae are connected by
central developmental groove.
Central pit in the central of the center fossa from it extended B groove.
Mesial pit in the MTF give three grooves one buccally, one lingually & one
Oblique ridge found between ML&DB cusps. If there is no oblique ridge
central developmental groove extend from mesial pit & give disto-occlusal
groove . Disto-occlusal groove give lingual groove between ML&DL cusps.
E The occlusal surface is rhomboidal, has 4 well
developed cusps & small fifth cusp.
Oblique ridge between ML&DB cusps. Central fossa,
MTF,DTF, BG,LG,CG. The occlusal surface resemble the
occlusal surface of upper 6
Mandibular first deciduous molar
teeth does not
resemble any of the
other teeth either
permanent .It appears
strange and primitive.
The second deciduous molar
resembles the first
(lower 6) but it is
smaller in size.
Buccal aspects of lower
D : geometric outline is trapezoid
Mesiobuccal cusp is longer than
As in upper D mesiobuccal cervical ridge
is prominent (MBCR) makes the cervical
line dips downward to outline this shape.
There are two roots MR&DR.
E: geometric outline is trapezoid, the
small of uneven side cervically.
3 buccal cusps are equal in size
Two roots MR&DR, they are long,
slender & diverge M-D at middle and
apical 1/3. No root trunk.
Distal outline is
to the C.L.
Lingual aspects of
molarsroot converge MLC long&
D crown and
MLC is long and sharp.
DLC is well developed and
MMR is well developed
(regarded as third lingual
E crown and root converge
Parts of 3 B cusps may be
Mesial part of the crown is
longer than distal part.
Mesial aspects of deciduous lower molars
Geometric outline is rhomboidal.
D buccal outline is flat above the
convex of the MBCR. It is longer than
lingual outline (cervical line extends
upward in B-L direction)
The lingual outline extends out lingually
beyond the confines of root base.
MBC is placed over the root base. Deep
Root apex is flat and almost square. DG
E: MLC is longer than MBC.
Compared to lower 6 the cervical ridge
is prominent in lower E & it more
Root apex is
constricted occlusally( due to the flatting flat & almost
of the buccal outline above the cervical square
line to buccal cusp tip).
M root is broad ,flat & blunt apex
sometimes serrated apex.
Distal aspects of lower first deciduous
D: distal aspect differs from
1-crown has an equal length
2-DBC&DLC are not so long
and sharp as MBC&MLC.
3-DMR is less developed than
4-B outline less curved at the
cervical 1/3 .
5-C.L. is straight.
6-Distal root is shorter, more
rounded, taper more in its
Distal aspects of lower second
distal aspect differs from
1- Distal surface is narrower
than mesial surface
MBC&MLC are seen ,also
the DLC well developed.
2- DMR is shorter &at lower
level than MMR.
3- Distal root tapers more at
the apical third.
Occlusal aspects of lower deciduous molars
D : occlusal aspect is rhomboidal in shape.
E: occlusal aspect is rectangular in shape.
MD dimension at the buccal side larger than MD dimension
at the lingual side so the crown converge lingually.
Also the crown converge distally .
DTF not so well defined as mesial fossa.
DMR is not as highly developed as mesial marginal ridge.