MORPHOLOGY OF DECIDUOUS TEETHMORPHOLOGY OF DECIDUOUS TEETH
Dental Anatomy & OcclusionDental Anatomy & Occlusion
Dent 202Dent 202
Deciduous dentition Set traits
Smaller in size Smaller crown height/tooth length ratio Greater crown width/height ratio
Set traits More bulging B & L cervical ridges
Constricted cervix Buccal cervical ridges on deciduous
molars Occlusal aspect: constricted occlusal table
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
Deciduous incisorsEruption
Mandibular before maxillary incisors Central before lateral incisors
No mamelons, labial grooves or lobes
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
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
Maxillary lateral incisorMuch smaller than centralM & D profiles are more in line
with root profilesDistal incisal angle is more
roundedLabial surface is more convex
MDLingual fossa is deeperMRs more prominentCL is similar to that of centralRounded from incisal aspect
Mandibular central incisor
Bilaterally symmetrical90 degree MI & DI angles Incisal margin is horizontalProminent cingulum with lingual
margin extending incisallyMRs are less marked than those of
max. incisorsLingual fossa is shallower
Mandibular central incisor
Labial surface is flat MDCL is similar to that of Max. incisorsRoot
3 times the height of the crown Narrow & conical with pointed apex
Mandibular lateral incisor
Incisal edge slopes distallyDI angle is roundedD profile is more roundedGreater crown height/MD ratio than mand. centralLL diameter > MD
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
Maxillary canine
MD width > crown heightLabial or lingual views: diamond in
shapeM & D profiles overhang root’sHOCs are much near the cervix than in
permanentLabial & lingual cervical 1/3s are
markedly convexMR prominence is related to race
Minimal in Caucasians Prominent in Mongoloid
No labial ridge or depressions
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
Maxillary 1st molar
Most atypical of all primary or permanent molars Intermediate between a premolar & a molarSmallest molar in all but BL diameter
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
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
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
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
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
Molariform unlike max. 1st
4-cusped toothBuccal 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
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
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
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
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
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
Mandibular 2nd molar
Deciduous teeth - size & eruption
ToothCrown 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
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