Morphology of Primary Teeth

Dr Heba Mohd El khodary

Objectives:

Identify and distinguish morphologic differences in primary teeth.

Apply the knowledge of morphology in clinical procedures for children

Primary Dentition

20 primary teeth as compared to 32 permanent teeth

No premolars in the primary dentition The primary molars are replaced by the

premolars The permanent molars erupt distal to

the primary second molars

General Morphologic considerations CrownCrown RootRoot PulpPulp

I- Size & Color

Smaller

MD width of ant. Primary < ant. Permanent teeth

MD width of Primary molars > Permanent premolars

Bluish-white (Primary) vs grayish-white or yellowish-white (Permanent) This has to be kept in mind during shade

selection for composite restoration or crown restoration.

II- Crown Crown form ( MD > OG ) anterior = cup posterior = square This is important during the selection of the stainless steel crown.

Bulbous crown: Steep Bulbous crown: Steep Cervical constriction /Prominent cervical bulge

[ G. floor – Matrix type ].

Care must be taken while preparing the proximal box, as there is risk of pulp exposure at the

site of constriction. Class II cavity should be restored with proper placement of wedges at the

constricted area so that the matrix band is adapted well to the tooth surface.

Narrow occlusal table: Narrow occlusal table: Convergence of buccal & lingual walls.

The width of he cavity should also be less in a deciduous tooth.

Contact area Contact area in primary broader, flatter and more gingival:

[B&L wall of proximal box extend towards embrasure / gingival seat below contact area]

Primary

Cup

Cervical

constriction

Square

II- CrownII- Crown Thin EnamelClinical significance:1. Early diagnosis of caries2. Bur size (recommended bur is no 330 pear

shaped )

3. Sufficient bulk of restoration Care must be taken during cavity preparation, not to extend

very deep as there is increased chance of pulp exposure.

Enamel rods incline occlusally vs horizontal or apical in gingival 1/3

No beveling at the gingivo-cavo surface line angle is not required, as no enamel remain unsupported.

III- RootRoots are longer & more

slender.Crown root ratio bigger

in primary teeth.Roots are narrower MD

than those of permanent.No root trunk in primary

molarsRoots of primary molars

are widely divergent to accommodate buds of permanent premolars : Extraction ?

Roots are more Slender & longerCrown/Root ratio

No

Root

trunk

Widely

Divergent

roots

IV- Pulp• Follows the morphology of crown• Higher pulp horns / mesial• Pulp chamber is larger in relation to

crown size compared to permanent teeth / cavity depth

• Canals of primary molars have many lateral branches and apical ramifications

• Wide apical foramina• Increased blood supply : typical

inflammatory response• Less nerve fibers : less sensitivity to

pain

Summary

Primary teeth have Thinner enamel and dentin layers Pulp horns closer to the outer surface Mesial pulp horn much higher Relatively larger pulps Enamel rods direct slightly occlusally in the cervical

area Cervical area is constricted significantly Roots flare as they approach the apex More tortuous and irregular pulp canals

During Cavity Preparation: The depth of the cavity should be less. The width of the cavity should also be less in a deciduous

tooth. Care must be taken while preparing the proximal box,

as there is risk of pulp exposure at the site of constriction. Care must be taken during cavity preparation, not to

extend very deep as there is increased chance of pulp exposure.

Enamel beveling at the gingivocavo surface line angle is not required, as no enamel remain unsupported.

The proximal box preparation may have to be extended widely to break the contact free.

Thank you