07. The Deciduous Teeth - Dentition
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Transcript of 07. The Deciduous Teeth - Dentition
Deciduous 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 fall off.
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 dentition.
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 12 years. b-They are importance during growth and development for proper arrangement of the permanent teeth and proper development of the dental arches.Avoid premature loss of deciduous teeth.
Eruption of the deciduous teeth Start from 6month to
2years and root completed at 3years.
6m
7m
16m
12m
20m
24m
14m
18m
8m
7m
Shedding of the deciduous teeth Shedding is the process of exfoliation of the
deciduous teeth. Shedding dates: 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.
Smaller 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 worn down.
They have shorter crowns with respect to their roots.
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 lower D. 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.
Roots 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 anterior teeth.
The molar crown have a narrow chewing surface buccolingually.
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
Deciduous 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 consistent depth.
The enamel rods at the cevical slope occlusally instead of gingivally as in the permanent teeth.
(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 apex.
(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.
Constricted neck
Sharp cusp
(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.
MMR
DMR
LF
LR
2L fossae
(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 concavity.
(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.
Root convex with DG
CL convex toward IR
Greater Labiolingual
(a) 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.
(d) 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 more cervically.
(f) M slope shorter than D slope.
MD
(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 lingual convergence.
(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 less developed.
(c) lower canine similar to upper canine but C.R. and cingulum less developed.
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 distal side.
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 .
AB C
Mandibular lower central deciduous incisor
Labial aspect Lingual aspect Mesial aspect Distal aspect
Mandibular lower lateral deciduous incisor
labial lingual Mesial Distal
Mandibular lower deciduous canine
Labial
Lingual
Mesial
Distal
Maxillary first & second deciduous molars
Maxillary second molar
Maxillary first molar
Buccal aspects of upper deciduous molars
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
form. 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.
Upper (D)Upper (E)
Occ. outline slightly scalloped
MBCR
Well developed cusps
Lingual aspects of upper deciduous molars
D 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 3- cusped type one lingual cusp with no developmental groove.
E MLC is long & well developed. DLC less developed. Tubercle of carabelli is seen related to MLC.
Upper (D) Upper (E)
MLC DLC
MMRMLC DLC
Tubercle of carabelli
Lingual narrower than buccal
Trapezoid outline
Mesial aspects of upper deciduous molars
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
line. MBR is broad & flat. LR is extend lingually beyond crown outline, It is long&
slender& it is above middle 1/3 curves buccally.
Upper (D)Upper (E)
MBCR
MBR
LRM
BR
LR
Board& flatOutline form is trapezoid with the shortest of uneven sides is occlusally.
Distal aspects of upper deciduous molars
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.
LR
LR
DBR
MBR
Bifurcation at lower level
C L straight
DLC
DBC
DBR
MBR
DBC
DLC
Poorly developed
Long& sharp
MLC Lingual outline is semicircular
Buccal outline is straight
Occlusal aspects of upper D
Rectangular
Rectangular with oblique ridge
Heart shape
HexagonalBC
LC
MBC
MLC
DBC
DLC
B
D
L
MD
B
L
MD
B
L
LC
MBCDBC
MBC
OR
DBC
MLCDLC3Supplemental groove
Distal occlusal groove
MBCR
MBCR
M
Occlusal aspects of deciduous upper molars
D the occlusal surface is rectangular. The crown converge lingually & distally. 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 mesial. 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
This teeth does not resemble any of the other teeth either deciduous or permanent .It appears strange and primitive.
The second deciduous molar
It resembles the first permanent molar (lower 6) but it is smaller in size.
Buccal aspects of lower deciduous molar
D : geometric outline is trapezoid Mesiobuccal cusp is longer than
distobuccal cusp. 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
MBC=BC=DBC. Two roots MR&DR, they are long,
slender & diverge M-D at middle and apical 1/3. No root trunk.
E D
M. outline is straight
Distal outline is converge markedly to the C.L.
MBCDBC
MBCR
DD
MBCBCDBC
Long, slender& diverge roots
Lingual aspects of lower deciduous lower molars D crown and root converge
lingually. MLC is long and sharp. DLC is well developed and
rounded. MMR is well developed
(regarded as third lingual cusp).
E crown and root converge lingually.
MLC=DLC Parts of 3 B cusps may be
seen. Mesial part of the crown is
longer than distal part.
DE
MLC long& sharp DLC rounded
MMR
MLC DLC
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. Root apex is flat and almost square. E: MLC is longer than MBC. Compared to lower 6 the cervical ridge
is prominent in lower E & it more constricted occlusally( due to the flatting of the buccal outline above the cervical line to buccal cusp tip).
M root is broad ,flat & blunt apex sometimes serrated apex.
D E
M root
Flat
MBCR
MBCMLC
Root apex is flat & almost square
Deep DG
MLC longer
MBC
Broad& flat
Serrated
Distal aspects of lower first deciduous molar D: distal aspect differs from
mesial aspect: 1-crown has an equal length
B&L. 2-DBC&DLC are not so long
and sharp as MBC&MLC. 3-DMR is less developed than
MMR. 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 apical third.
D root
DBCDLC
MBCMLCDMR
M root
Distal aspects of lower second deciduous molar
E: distal aspect differs from distal aspect:
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.
DBCBC
MBCMLC
DLC
DMR
D root
M root
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.
Rhomboidal outline Rectangular
outline
Buccal
Lingual
Mesial Distal
Buccal Lingual
Mesial
Distal