Lecture Overview Primary Dentition General Morphological considerations Implications of Primary tooth morphology
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
Eruption Patterns of Primary Teeth
Sequence more important than timing
Symmetrical pattern
Mandibular teeth erupt first
11 Months = 4 Erupted 11 Months = 4 Erupted TeethTeeth
7 months + 4 = 11 7 months + 4 = 11 monthsmonths
0 teeth + 4 = 4 0 teeth + 4 = 4 teeth teeth
15 Months = 8 Erupted 15 Months = 8 Erupted TeethTeeth
11 months + 4 = 15 11 months + 4 = 15 monthsmonths
4 teeth + 4 = 8 teeth 4 teeth + 4 = 8 teeth
19 Months = 12 Erupted 19 Months = 12 Erupted TeethTeeth
15 months + 4 = 19 15 months + 4 = 19 monthsmonths
8 teeth + 4 = 12 8 teeth + 4 = 12 teeth teeth
23 Months = 16 Erupted 23 Months = 16 Erupted TeethTeeth
19 months + 4 = 23 19 months + 4 = 23 monthsmonths
12 teeth + 4 = 16 12 teeth + 4 = 16 teeth teeth
27 Months = 20 Erupted 27 Months = 20 Erupted TeethTeeth
23 months + 4 = 27 23 months + 4 = 27 monthsmonths
16 teeth + 4 = 20 16 teeth + 4 = 20 teeth teeth
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
Crowns of Primary Teeth Prominent mesio-buccal
cervical bulge seen in primary molars
Incisors have no developmental grooves or mammelons
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
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
Primary Crown Anatomy Maxillary 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
Primary Crown Anatomy Maxillary 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 Prominent MB cervical
bulge Transverse ridge
Primary Crown Anatomy Maxillary 2nd Molar
Resembles permanent maxillary first molar but smaller
Mandibular 2nd Molar- Resembles permanent
mandibular first molar but smaller
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
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
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
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
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
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