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Anatomy of Primary Teeth

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1 Anatomy of Primary Teeth
Steven Chussid D.D.S.

2 Lecture Overview Primary Dentition
General Morphological considerations Implications of Primary tooth morphology

3 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

4 Eruption Patterns of Primary Teeth
Sequence more important than timing Symmetrical pattern Mandibular teeth erupt first

5 Approximate Eruption Schedule
“7+4” Guideline

6 7 Months = First Tooth Erupts

7 11 Months = 4 Erupted Teeth 7 months + 4 = 11 months
0 teeth + 4 = 4 teeth

8 15 Months = 8 Erupted Teeth 11 months + 4 = 15 months
4 teeth + 4 = 8 teeth

9 19 Months = 12 Erupted Teeth 15 months + 4 = 19 months
8 teeth + 4 = 12 teeth

10 23 Months = 16 Erupted Teeth 19 months + 4 = 23 months
12 teeth + 4 = 16 teeth

11 27 Months = 20 Erupted Teeth 23 months + 4 = 27 months
16 teeth + 4 = 20 teeth

12 General Morphologic considerations
Crown Pulp Root

13 Crown of Primary Teeth Shorter Narrower occlusal table
Constricted in the cervical portion Thinner enamel and dentin layers Enamel rods in the cervical area directed occlusally Broad and flat contacts Color is usually lighter

14 Crowns of Primary Teeth
Prominent mesio-buccal cervical bulge seen in primary molars Incisors have no developmental grooves or mammelons

15 Primary Crown Anatomy Mandibular Central Incisors-
Symmetrically flat when viewed from buccal Crown about 1/3 length of root Cingulum present on lingual surface Mandibular Lateral Incisor Similar form to central Usually longer Incisal edge slopes toward distal and DI angle more rounded

16 Primary Crown Anatomy Maxillary Central Incisor
Only tooth that has a greater mesiodistal width than height Prominent cingulum Incisal edge straight Maxillary Lateral Incisor Similar form to cental Smaller and DI angle rounded

17 Primary Crown Anatomy Maxillary Canine Mandibular Canine
Crown constricted at cervical region Well developed, sharp cusp Root is long, more than 2X crown Mandibular Canine Similar form to maxillary Crown shorter and narrower labiolingually

18 Primary Crown Anatomy Maxillary First Molar Mandibular First Molar
Unique appearance Three cusps-MB, DB and Lingual Prominent MB cervical bulge Mandibular First Molar Also unique in appearance Four cusps-MB, DB, ML and DL Transverse ridge

19 Primary Crown Anatomy Maxillary 2nd Molar Mandibular 2nd Molar-
Resembles permanent maxillary first molar but smaller Mandibular 2nd Molar- Resembles permanent mandibular first molar but smaller





24 Pulps of Primary Teeth Relatively larger
Pulp horns are closer to the outer surface Great variation in size and location Mesial pulp horn is higher Pulp chamber shallow Form of the pulp follows the external anatomy Usually a pulp horn under each cusp

25 Pulpal Anatomy

26 Roots of Primary Teeth Roots of anterior teeth are narrower mesio-distally Posterior teeth have longer and more slender roots in relation to crown size Molar roots flare more as they approach the apex Apical foramina may be larger and accessory canals often larger and more numerous

27 Implications of Primary tooth morphology
The progress of caries is much faster in the primary dentition, so incipient lesions should be restored sooner than later! Thinner enamel and dentin Mesial pulp horn higher

28 Procedures in Primary Teeth
Restorative Dentistry Enamel is thinner, therefore modifications are necessary in the cavity prep Broad contacts need to be restored Beware of the mesio-buccal pulp horn May need to do SSC if both proximal surfaces involved Preserve the buccal cervical ridge to obtain mechanical retention for SSC

29 Procedures in Primary Teeth
Surgical Procedures Conical anterior roots facilitate easy removal Flared roots of the molars - use caution as premolar buds are located between the roots Pulp Therapy Pulpotomy- beware of perforations Pulpectomy Difficult on molars due to tortuous and irregular pulp canals Beware of tooth buds

30 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

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