PRIMARY TEETH
PRIMARY TEETH
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Primary vs. Permanent Teeth
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Fewer molars (2 vs.
3) and no premolars
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Primary teeth have proportionately larger pulp cavities
than perm teeth
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Distinguished
by long, pointed pulp horns
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Crowns of primary incisors are shorter incisocervically
compared with MD dimension
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Roots:
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Roots of anteriors taper more rapidly
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Are comparatively
longer & slimmer than perm teeth
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Are more
divergent than perm teeth
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Root
trunks are less pronounced than perm teeth
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Enamel ends
abruptly
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Are whiter than perm teeth
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Are smaller than
perm teeth
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Crown : root Ratio is smaller than perm teeth –
meaning they have longer roots
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Crowns are more bulbous & constricted than perm teeth – appear
shorter & fatter than perm teeth
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Cervical ridges are more pronounced than
perm teeth – large facial bulge
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No mamelons on primary teeth
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Primary arch is more circular than the perm arch
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Smoother
occlusally (fewer pit/fissures)
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Narrower occlusal
table
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1mm enamel (uniform
thickness) on occlusal surface vs. 2.5mm of perm teeth
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B and L
surfaces are flatter than perm teeth
(occlusal to the cervical ridge)
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Leeway Space
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The MD widths of the primary molars in any quadrant are
greater than their perm successors (PMs) – (by 2-4mm)
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With respect to their permanent successors, the sum of the
MD diameters of the deciduous M1 & M2 is generally greater
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All Prim Molars
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Differ
the most from the perm teeth that replace them (among molars, canines, lateral
incisors, central incisors)
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Lack an identifiable root trunk
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All Prim 1st Molars
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Cusps:
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In Max Teeth
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Prim à MB > ML
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Perm à ML > MB
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In Mn Teeth
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Prim à ML > MB
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Perm à MB > ML
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Don’t get clowned à They are opposites in Primary vs. Permanent
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Distal
surface is shorter than the mesial, occlusogingivally
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Has a transverse
ridge
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Prominent mesial
marginal ridge
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Prominent MB
cervical ridge
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Present with the greatest morphologic
deviations from permanent teeth
(especially Mn M1)
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All Prim 2nd Molars
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Larger
than M1s & resemble perm M1s
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Show up after
child’s 2nd Birthday (20 months Mn, and 24 n=months Mx)
Individual Primary Teeth
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Prim Mx Central
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Shapes
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M/D view =
§
B/L view =
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Occlusal =
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MD dimension is wider than incisocervical crown height
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Wider MD & shorter
incisocervically than perm
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Straighter incisal edge: SHARPER, more angled incisal
edge
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NO mamelons
(same with laterals)
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Prominent labial AND lingual
cervical ridges!!!!! (This Q gave
teeth A, F, J, L, & T – I got clowned by L – Mn M1)
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Found on lingual
and labial surfaces of all deciduous anterior teeth.
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Most
damaged (with Mx laterals) by baby bottle tooth decay
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Prim Mn Central
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Shapes
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M/D view =
§
B/L view =
§
Occlusal =
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Prominent
cingulum
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Often
has a developmental groove on distal of root
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Has the smallest FL dimension of any crown
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Prim Mx Canine
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Shapes
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M/D view =
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B/L
view = Pentagon
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Occlusal =
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4 lobes
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3 facial, and 1
on the lingual
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Widest primary
anterior tooth
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Appears
wider and shorter than perm
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Crown height is
less than MD diameter
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Diamond-shaped crown from facial aspect (Kaplan –
differs from the pentagonal outline mentioned above)???
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Prominent
cingulum
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Cusp is much
longer & sharper than perm canine
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Cusp points distally (offset distally)
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ODD BALL -- Mesial
cusp ridge is longer than distal cusp ridge (opposite for perm Mx
canines)
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Opposite of what you think for Perm canines and Prim
Mn Canines
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Pulp chamber
looks pointed at incisal tip
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M&D contact
areas located at same level – diff from perm k9.
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K9s in general
are the least commonly missing teeth.
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Prim Mn Canine
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Shapes
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M/D view =
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B/L view = Arrow-shaped from the facial
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Occlusal =
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Smooth labial
surface
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Longer distal
incisal ridge than mesial incisal ridge
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Prim Max 1st Molar
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Shapes
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M/D view =
§
B/L view =
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Occlusal = trapezoidal (peripheral); rectangular
(table)
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*Most
atypical of all Mx molars*
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Crown
does not resemble any other primary or permanent molar crown, but does show
similarities to PM crown.
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Intermediate form
between PM and Molar
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Crown somewhat resembles a perm PM, but the root form is typical of a perm Molar
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Of primary molars, prim Mx M1 bears the greatest resemblance to a perm PM
·
One Q gives ‘resemblance to Mx PM2’ as the correct
answer
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Smallest prim molar
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Bicuspid (2 main
cusps = MB & ML, 2 indistinct distals)
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MB
cusp > ML cusp
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Cervical ridge in the MB area – most
prominent cervical ridge among primary Mx teeth!!!!!
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The mesial surface is larger than the distal surface
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From a facial view, BOTH Primary Mx M1 and
M2 have a short root trunk
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The cervical line on the mesial curves slightly toward
the occlusal – it does not
have a straight cervical line
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H-shaped
occlusal pit-groove area
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3 Roots
(root structure corresponds to that of perm Mx M1)
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Number and form of the roots corresponds to Mx M1
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Short root trunk
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Does the Prim
Mx M1 has a lingual groove??? à NO!!!
Right
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Prim Max 2nd molar
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Shapes
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M/D view =
§
B/L view =
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Occlusal =
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Same
characteristics as perm Mx M1 (The tooth it most closely resembles)except:
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MB cusp
is almost same size as ML
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MB pulp horn is
longest and largest
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Normally has
a Cusp of Carabelli, just like Perm Mx M1
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Most likely primary tooth to have an oblique ridge – (looks like
perm Mx M1)
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Has the greatest FL dimension of all
primary teeth!!!!!
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The
difference between Primary Mx M2 and Permanent Mx M1 is that the primary tooth
has a much narrower
measurement at the CEJ compared to its contact area
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They are similar in that both crowns converge to the distal
and lingual
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NOT that they both have well developed 4 cusps, oblique
ridges, well developed marginal ridges, or rectangular outline
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From a facial view, BOTH Primary Mx M1 and M2 have a short
root trunk
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Last Primary tooth to erupt
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This is the primary molar that typically has a transverse
ridge, oblique ridge, & a DL groove
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3 Roots
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Short root trunk
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Primary Mx M2, roots are less curved than Permanent Mx M1
Right 
v
Prim Mand 1st Molar
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Shapes
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M/D view =
§
B/L view =
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Occlusal = Rhomboidal peripheral
outline; Rectangular table (if you
disregard the large MB ridge)
Ø Unlike any other tooth
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Both Prim Mn M1 and
M2 have central and lingual grooves
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Most normally
exhibits a Distal Triangular Fossa
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Based on morphology, a Class II MO prep would be the most
difficult on a primary Mn M1 (of any teeth)
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Because of HUGE MB pulp horn!!
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4 cusps = 4
pulp horns (don’t be thinking that it has 5 just because a perm Mn M1 has 5)
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ML cusp is highest & sharpest!!!!!
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MB and ML make up transverse ridge
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Oval with MB
expansion
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Cervical ridge/Bulge in the MB area
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Which primary tooth has a facial cervical ridge which is
so distinctly prominent that it is uniquely different from ALL other teeth?
Primary Mn M1!!!!!
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The CEJ is most apically positioned on the mesial 1/3 of
the crown of a primary Mn M1
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S
Shaped cervical ridge
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The Distal portion is shortest occlusogingivally
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A prominent transverse ridge distinctly separates
the mesial portion from the remainder of the occlusal table!!!!!
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Roots
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2
Left
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Prim Mand 2nd molar
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Shapes
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M/D view =
§
B/L view =
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Occlusal =
Ø Closely resembles a
perm Mn M1 occlusally
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Same characteristics as perm Mn M1 except:
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Has a more
prominent facial cervical ridge
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MB, DB, and D cusps of prim Mn M2 are about same size
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The easiest way to distinguish between primary Mn M2
& perm Mn M1 is comparative size
of D cusps
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Not the widest in the cervical like the perm Mn M1 (primary teeth are constricted)
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Has 3 occlusal fossae, like a perm Mn M1
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5 cusps – does not have 4 cusps (don’t get clowned)
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All 3 buccal cusps are the same size
(unlike perm M1)
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