4. 1.Size
• Smaller in all dimensions
• MD width of primary incisors
and canines is less than their
permanent successors
• The MD width of the primary
molars is wider than their
successors(premolars) but
smaller than their
corresponding permanents.
5. Thickness of E and D in
primary teeth is half the
thickness in permanent
teeth.
Clinical consideration:
The occlusal cavity in
primary teeth must be
shallower.
9. 3.crown
• Wider in MD diameter
than in OG height
• Ant. teeth cup -
shaped
• Post. Teeth square -
shaped
10. 3.Crown (cont.)
• 2. Primary molars are bulbous
due to:
• Markedly constricted necks.
• Pronounced cervical ridges.
• Clinical consideration:
• Difficulty in application of the matrix
band.
• Special care in the placement of the
gingival floor in class II cavity preparation.
11. 3.Crown (cont.)
• The primary molars have:
• 3. Narrow occlusal table:
• (B and L surfaces converge
sharply occlusally)
• Clinical consideration:
• The isthmus portion of a class ǁ
amalgam filling is very narrow
and liable to fracture
12. 3.Crown (cont.) :
• 4. The buccal and lingual
inclines flatter above the
cervical bulge.
• 5. In primary teeth the contact
is large ellipsoid and flattened
area (wider proximal box).
• 6. Cusp heights are less steep
than permanent (more flexible
interdigitating).
13. 3.Crown (cont.) :
• 7. The enamel cap in primary
teeth is thinner and has a
constant depth.
• 8. The enamel cap in primary
molars ends abruptly at the
CEJ (feather-edge in
permanent).
14. 3.Crown (cont.) :
• 9. The enamel rods at the cervix
slope occlusally in primary teeth
instead of gingivally in permanent
teeth.
• Clinical consideration
• There is no need for beveling
of gingival floor in class ǁ cavity
preparation in primary molars.
16. 4. Roots
• The roots of primary teeth are:
• Narrower mesiodistally.
• Longer and more slender in comparison to
the crown (1:2).
• Flare out near the cervix leaving no root
trunk.
17. 4. Root (cont.)
• d. Diverge as they reach the apex
to envelop the permanent
successor (post.)
• Clinical consideration:
• Special care in extraction of
primary molars with un resorbed
root.
• e. Curved roots, thin walls
• (Difficult mech. Prep. of canals).
19. 5. Pulp
• The pulp outline follows the DEJ more
closely in primary than in permanent
teeth.
• The pulp chambers are proportionally
larger than permanent teeth .
• The pulp horns are higher in primary
molars especially the mesial horn.
• Clinical consideration:
• Special attention should be taken when
establishing the depth of cavities in primary
teeth.
20. 5. Pulp (cont.)
• The root canals of the primary molars show:
• D. more lateral branching and apical
ramifications.
• Clinical consideration:
• This makes it impossible to remove all pulp
tissue in the root canals during root canal
therapy.
•
• E. The apical foramina in primary teeth are
relatively wider than in permanent teeth.
22. 6. Histological Variations
• Deciduous
Develop directly from the main
dental lamina
• Permanent
Develop from lingual (for permanent
successors) or distal extension (for
permeant molars) from dental lamina
23. • Deciduous
Enamel and Dentin are less
mineralized
More prone to acidic attack
Easier in cavity preparation
• Permanent
More Mineralized
Less prone
More difficult
Histological Variations
