Describe the similarities and differences among the teeth in relationship to location and function.
List the range of eruption dates of each tooth in the human dentition and the exfoliation dates of the primary dentition.
Discuss variations in the eruption patterns.
Discuss the causes of exfoliation and retention of primary teeth.
Name and classify each tooth according to the Universal Numbering System, the Palmer Notation system, and the FDI system.
Compare the primary and permanent dentition with respect to size, shape, color, location, number, and function.
Compare the primary and permanent dentitions with respect to susceptibility to disease.
Primary Dentition
Total primary teeth: 20
Teeth per arch: 10
Incisors: 8
Canines: 4
Molars: 8
Also called: Temporary, Baby, Deciduous, Milk teeth.
Universal Tooth Numbering System
Primary teeth are designated by capital letters A through T.
Eruption
Eruption dates vary, give or take 6 months.
Eruption sequence does not usually vary much.
Tooth types tend to erupt in pairs - look for asymmetry.
Approximate Eruption and Exfoliation
6 months - 2 years: All primary teeth are erupting.
2-6 years: All 20 primary teeth are present.
6 years: First permanent molars appear, primary mandibular centrals are shed.
6-9 years: All 8 incisors are exfoliated and replaced by permanent counterparts.
9-12 years: All canines and molars are shed and replaced by canines and premolars.
12 years: Second molars erupt.
Primate Spaces
Interproximal spaces mainly between the primary maxillary lateral incisor and canine, and also between the primary mandibular canine and first molar.
Considered normal and desirable because space is necessary for the proper alignment of the future permanent dentition.
Functions of Primary Dentition
Efficient chewing.
Support for lips, cheeks, overall facial appearance.
Speech.
Maintaining space for eruption of permanent teeth.
Ensures proper alignment, spacing, occlusion, jaw growth, and development.
Decay in primary dentition can lead to discoloration of permanent teeth.
Clinical Considerations
Care for primary teeth/oral cavity starts with parent education.
Supervised homecare must begin early, even before the first primary teeth erupt into the oral cavity, to prevent premature loss of the primary teeth.
Prolonged Bottle Use
Prolonged nighttime use of a baby bottle with cavity-causing beverage or sugar on pacifier may be a factor for extensive acute caries of the primary teeth.
AKA- early childhood caries or baby bottle decay.
Early Childhood Caries (ECC)
Commonly called baby bottle tooth decay.
It is a type of acute caries.
First Dental Appointment
A child’s first dental appointment should occur within 6 months of the eruption of the first primary tooth and no later than 12 months of age.
The intent of this recommendation is to provide information to the child’s supervising adults, which will help to establish positive preventive behaviors, prevent serious dental problems, and check for proper development/growth.
Primary Incisors
Each arch has 4 primary incisors - 2 centrals and 2 laterals.
Same arch position, function and general shape as permanent incisors.
Often edge to edge relationship.
Primary Maxillary Incisors
Resemble their permanent successors
Except: more prominent cervical ridge on both labial and lingual.
Extensive wear is often noted (attrition).
Primary Maxillary Central Incisors
The only anterior teeth that are wider mesiodistally than incisocervically.
Rounder M and D outlines due to cervical constriction.
No mamelons.
Usually no developmental depressions, imbrication lines, or pits on the lingual.
Prominent cingulum, marginal ridges, and lingual fossa.
Less CEJ curvature on D than on M (similar to permanent).
Single, round root, longer relative to crown length than permanent.
Primary Maxillary Lateral Incisors
Overall smaller than the central.
Longer incisocervically than mesiodistally (opposite of the central).
Root longer in proportion to the crown than centrals.
Not as constricted at CEJ as primary maxillary central.
L surface is smooth with prominent cingulum.
Marginal ridges and L fossae less pronounced than maxillary.
Greater CEJ curvature on M.
Single, long, slender root.
Slightly flattened proximal root surfaces.
Primary Mandibular Lateral Incisors
Crown is wider and longer than central.
More prominent cingulum and deeper lingual fossa.
Incisal edge slopes distally.
Cingulum offset toward the distal (similar to permanent).
Root may have distal curvature in apical third.
Primary Canines
4 primary canines, 2 in each arch
Mainly resemble the outline of their permanent successors, but with more prominent cervical ridge on both labial and lingual
Primary Maxillary Canines
When first erupted, cusp is longer and sharper than permanent
Mesial cusp slope is longer than the distal
Well developed cingulum and marginal ridges
Often tubercle is present on the cingulum
Root is 2x length of the crown, slender
Root inclined distally
Primary Mandibular Canines
Smaller labiolingually than maxillary
Distal cusp slope is longer (similar to permanent)
Lingual surface is smoother
Root is almost 2x length of the crown, slightly shorter than maxillary
Primary Molars
Function for about 9 years until replaced by permanent premolars
Primary second molars resemble permanent firsts
Crowns are shorter occlusocervically than mesiodistally
Roots are thin and wide spread beyond crown outlines creating space for premolar crowns
Primary Maxillary First Molars
Does not resemble any other tooth
Prominent buccal cervical ridge
Height of contour:
Buccal: cervical third
Lingual: middle third
Occlusal table:
4 cusps
2 mesial cusps largest
DL may be absent
Prominent transverse ridge
Oblique ridge present
Occlusal table:
H-shaped groove pattern
Central, M triangular, D triangular fossae present
Buccal groove
Central groove
C, M and D pits
3 root branches
Lingual root is longest (similar to permanent)
Primary Maxillary Second Molars
Larger than first
Resembles permanent first molar, and usually has a cusp of Carabelli
The root formation marks the completion of primary dentition.
Primary Mandibular First Molars
Does not resemble any other tooth
Prominent buccal cervical ridge
Height of contour:
B cervical 1/3
L middle 1/3
4 cusps, M are larger
Transverse ridge
2 roots
Primary Mandibular Second Molars
Larger than the first
Resembles permanent mandibular first molar
Five cusps
3 buccal cusps nearly equal size
Comparison of Primary to Permanent Dentition
Primary teeth are smaller overall and have whiter enamel than the permanent teeth because of the increased opacity of the enamel, which covers the underlying yellow dentin.
The crown of any primary tooth is short in relation to its total length.
The crowns are also more constricted or narrower, at the CEJ, making them appear bulbous in comparison to the thinness of tooth neck.
A cervical ridge on both labial and lingual surfaces of anterior teeth and on B surfaces of the molars in primary teeth
Root(s) of primary teeth narrower, but more divergent
Crown-to-root ratios of primary teeth smaller than the ratios of their permanent dentition counterparts
Pulp chambers and pulp horns are relatively large in proportion to those of the permanent teeth, especially the mesial pulp horns of the molars.
Compared to permanent teeth, primary teeth have:
Thinner dentin.
Thinner enamel.
Risk of endodontic complications is greater for the primary dentition because the enamel and dentin are thinner.
In addition, because the pulp chamber and pulp horns are also larger, there is increased risk of pulpal exposure during cavity preparation.
Primary vs. Permanent: Differences
Primary teeth are whiter, more opaque enamel
Overall smaller
Roots longer in proportion to crowns
Posterior more divergent roots
Narrower CEJ, making teeth appear more bulbous
Cervical ridge on anterior teeth
Larger pulp horns and chambers
Overall thinner dentin
Primary and Permanent: Similarities
Incisors and Canines have same arch position and function
Anteriors have similar marginal ridges and cingulum on lingual
Incisors have more CEJ curvature on Mesial
Mandibular laterals cingulum offset toward the distal