morphology

1. MORPHOLOGY OF DECIDUOUS TEETH
Dental Anatomy
Dent 201
Summer semester
2005/2006

2. Deciduous dentition
Set traits
 Smaller in size
 Smaller crown height/tooth length ratio
 Greater crown width/height ratio

3. Set traits
 More bulging B & L cervical ridges
 Constricted cervix
 Buccal cervical ridges on deciduous
molars
 Occlusal aspect: constricted occlusal table

4. Deciduous dentition
 Set traits
 Molar roots
• More slender & relatively longer
• More bowed & flared outward
• Shorter root trunk
 Milk-white in color
 Enamel is thinner & pulp chamber is large
Some class, arch & type traits in permanent
dentition are applied to deciduous dentition
Only new traits will be discussed

5. Deciduous incisors
 Eruption
 Mandibular before maxillary incisors
 Central before lateral incisors
 No mamelons, labial grooves or lobes

6. Maxillary Central incisor
 The only incisor with MD breadth >
crown height
 M & esp. D profiles overhang root
profiles
 No labial grooves, depressions or
lobes
 Cingulum
 Bulging & more incisally located
 May extend further toward the incisal
edge – lingual ridge
 Unmarked by pits or grooves
 MRs are clearly evident

7. Maxillary Central incisor
 Constricted cervix from
all aspects
 In proximal surfaces
CL is more convex
incisally
 Conical root with
rounded apex
 Diamond-shaped from
incisal aspect

8. Maxillary lateral incisor
 Much smaller than central
 M & D profiles are more in line
with root profiles
 Distal incisal angle is more
rounded
 Labial surface is more convex
MD
 Lingual fossa is deeper
 MRs more prominent
 CL is similar to that of central
 Rounded from incisal aspect

9. Mandibular central incisor
 Bilaterally symmetrical
 90 degree MI & DI angles
 Incisal margin is horizontal
 Prominent cingulum with lingual
margin extending incisally
 MRs are less marked than those of
max. incisors
 Lingual fossa is shallower

10. Mandibular central incisor
 Labial surface is flat MD
 CL is similar to that of Max. incisors
 Root
 3 times the height of the crown
 Narrow & conical with pointed apex

11. Mandibular lateral incisor
 Incisal edge slopes distally
 DI angle is rounded
 D profile is more rounded
 Greater crown height/MD ratio than mand. central
 LL diameter > MD

12. Mandibular lateral incisor
 Cingulum, fossa & MRs
are similar to those of
mand. Central
 Root
 Narrow & conical
 Apex has D inclination
 D surface has narrow
vertical depression

13. Maxillary canine
 MD width > crown height
 Labial or lingual views: diamond in
shape
 M & D profiles overhang root’s
 HOCs are much near the cervix than in
permanent
 Labial & lingual cervical 1/3s are
markedly convex
 MR prominence is related to race
 Minimal in Caucasians
 Prominent in Mongoloid
 No labial ridge or depressions

14. Mandibular canine
 Crown height > MD width
 Less cervically converging M & D
profiles
 Labial or lingual aspects: arrow in
shape
 No labial ridge or grooves
 HOCs are much near the cervix than
in permanent
 LL diameter < that of deciduous
max. canine
 Less prominent cingulum or MRs &
shallower fossae than in deciduous
max. canine

15. Maxillary 1st molar
 Most atypical of all primary or permanent molars
 Intermediate between a premolar & a molar
 Smallest molar in all but BL diameter

16.  Cusps
 Bicusped (only MB & ML cusp
are present)
 A small DB cusp is frequently
present on the D cusp ridge of
the MB cusp
 Parastyle on the M ridge of MB
cusp
 DL cusp rarely occurs
 In some cases, a nodular
tubercle on the L portion of the
D MR resembles a DL cusp
Maxillary 1st molar

17.  Buccal aspect
 MD diameter >> crown height
 M part is higher OC than D
because it is more projected
cervically onto the root area
 Marked cervical constriction
 Root
• Very little root trunk
• 3 roots strongly divergent
• L root is midway between the 2 B
roots
Maxillary 1st molar

18.  Mesial aspect
 Mesial marginal groove
 B HOC is more cervically
located than L
 Buccal cervical ridge is more
prominent in 1st molars than
in 2nd
 Roots
• B roots are straight & buccally
directed
• L root is banana shaped with
strong B curved apical 1/3
Maxillary 1st molar

19.  Occlusal aspect
 Trapezoidal
 M & D profiles are straight & slightly L convergent
 B cusp > L
 B triangular ridge more prominent than L
 B groove separates DB cusp from MB
 Central pit
 Central groove
 Transverse ridge (oblique ridge?) between B groove & D MR
 H-shaped pit/groove pattern
• Central groove
• Triangular supplemental grooves
 M & D marginal grooves
Maxillary 1st molar

20.  Morphologically considered
a model for the permanent
1st maxillary molar
 Allows prediction of what
the 1st maxillary molar will
look like
 This concordance is called
isomorphy
 Set traits
 Cervical constriction
 Cervical 1/3 bulging
 Little root trunk
 Roots thinner & divergent
Maxillary 2nd molar

21.  Molariform unlike max. 1st
 4-cusped tooth
 Buccal aspect
 2 cusp: MB & DB
 M half > D half
 M half projects more occlusally &
occupies 2/3s of crown area
 M profile is straight
 D profile is curved and overhanging
 CL inclines downward from D to M
 Roots
• 2 divergent roots; M & D
• M is longer
Mandibular 1st molar

22.  Lingual aspect
 2 cusps: ML & DL
 ML cusp is conical & larger
than DL
 Outlines of B cusps are
visible
 CL is more straight &
horizontal than that of the B
aspect
Mandibular 1st molar

23.  Mesial aspect
 Buccal cervical ridge (BCR)
 From MB cusp tip a straight incline to
BCR
 Transverse ridge connecting MB & ML
 M MR is high & prominent
 Mesial marginal groove separates M MR
from ML cusp ridge
 CL is convex occlusally & lower on the
B end
 Root
• Extremely broad BL (sometimes as
broad as the crown)
• Frequently bifid apex
Mandibular 1st molar

24.  Distal aspect
 All 4 cusps & M root profiles
are visible
 B profile is less bulging than
from mesial aspect
 D MR is lower and less
prominent than M MR
 CL is more straight &
horizontal than that of M
aspect
Mandibular 1st molar

25.  Occlusal aspect
 Without the BCR, it is rectangular
 BL width is grater from M than D
 MB cusp is the largest, followed by
ML, DB & DL
 M Transverse groove, interrupted by
 Central groove; extends from M pit to
central pit
 M pit
• 2 supplemental grooves; of which ML
crosses M MR
 Central pit
 B& L grooves
 Often a D pit
Mandibular 1st molar

26.  Morphologically considered
a model for the permanent
1st mandibular molar
 Allows prediction of what
the 1st mandibular molar
will look like
 This concordance is called
isomorphy
 Set traits
 Cervical constriction
 Cervical 1/3 bulging
 Little root trunk
 Roots thinner & divergent
Maxillary 2nd molar

27. Deciduous teeth - size & eruption
Tooth
Crown
height
MD crown
diameter
BL crown
diameter
Tooth
length
Age at
eruption
51 or 61 6.0 mm 6.5 mm 5.0 mm 16.0 mm 7.5 mths
52 or 62 5.6 mm 5.1 mm 4.0 mm 15.8 mm 8 mths
81 or 71 5.0 mm 4.2 mm 4.0 mm 14.0 mm 6.5 mths
82 or 72 5.2 mm 4.1 mm 4.0 mm 15.0 mm 7 mths
53 or 63 6.5 mm 7.0 mm 7.0 mm 19.0 mm 16-20 mths
83 or 73 6.0 mm 5.0 mm 4.8 mm 17.0 mm 16-20 mths
54 or 64 5.1 mm 7.3 mm 8.5 mm 15.2 mm 12-16 mths
55 or 65 5.7 mm 8.2 mm 10.0 mm 17.5 mm 20-30 mm
84 or 74 6.0 mm 7.7 mm 7.0 mm 15.8 mm 12-16 mm
85 or 75 5.5 mm 9.9 mm 8.7 mm 18.8 mm 20-30 mm