The primary dentition is the first set of teeth, also known as deciduous teeth because they are shed and replaced by permanent teeth.
There are 20 primary teeth in total, with 10 per dental arch, compared to 32 permanent teeth with 16 per arch.
Primary teeth include incisors, canines, and molars (no premolars).
In the Universal Numbering System, primary teeth are designated by capital letters A through T.
In the International Numbering System, digits 5-8 are used for quadrants, and 1-5 indicate tooth position from the midline.
Mineralization of primary teeth begins in utero at 13-16 weeks, and by 18-20 weeks, all primary teeth have started to mineralize.
The first primary tooth (mandibular central incisor) erupts around 6-10 months of age.
The primary dentition takes 2-3 years to complete, with root formation finishing in the primary maxillary second molar.
A 6-month delay or acceleration in eruption is considered normal.
The sequence of eruption is more important than the actual dates.
Specific tooth types tend to erupt in pairs; asymmetry may require dental imaging.
Young females tend to shed primary teeth and have permanent teeth earlier than young males.
Interproximal spaces are usually present between primary teeth to allow for the alignment of larger permanent teeth.
Developmental primate spaces are located between the primary maxillary lateral incisor and canine, and between the primary mandibular canine and first molar.
Primary molars are replaced by permanent premolars.
Permanent molars erupt distal to the primary second molars.
Primary teeth are smaller overall than permanent teeth but are not simply "mini-me" versions.
Differences Between Primary and Permanent Teeth
Crowns of primary teeth are shorter relative to their total length.
Crowns are more constricted at the cementoenamel junction (CEJ), making them appear bulbous.
The occlusal table on primary posteriors is narrower than on permanent counterparts.
A distinct bulging cervical ridge is present on the facial and lingual cervical third surfaces of primary teeth.
Contacts are broad and flat within the primary dentition.
Roots of primary teeth are narrower and longer than the crown length.
Molar roots flare more as they approach the apex.
Apical foramina may be larger with more numerous accessory canals.
Roots may show partial resorption as teeth are shed.
Pulp chambers and pulp horns are relatively larger in primary teeth, especially the mesial pulp horns of the molars.
Pulp horns are closer to the outer surface, and pulp chambers are shallow.
The dentin of primary teeth is thinner than that of permanent teeth.
Enamel is also relatively thin but has consistent thickness over the dentin of the crown.
Primary teeth have a whiter tone of enamel due to increased opacity.
Enamel rods in the cervical area of primary teeth are directed occlusally.
Clinical Considerations for Primary Dentition
Primary teeth function in esthetics, mastication, and speech for 5-12 years.
They hold open the eruption arch space for succedaneous permanent teeth.
Extracted primary teeth can result in crowding and occlusal complications in the permanent dentition.
Ignoring carious primary teeth can lead to serious oral infections and discomfort.
Supervising adults must perform early homecare and allow for regular professional dental care to prevent early loss of primary dentition.
The risk of endodontic complications is greater in primary teeth due to thinner enamel and dentin.
Larger pulp chambers and pulp horns increase the risk of pulpal exposure during tooth preparation.
Pulpotomies may lead to endodontic root perforations.
The distinct bulging cervical ridge of primary teeth must be considered with homecare and restorative procedures.
Prolonged nighttime use of a baby bottle with caries-causing beverages can cause early childhood caries (ECC), also known as baby bottle tooth decay.
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.
Early dental care can keep the primary dentition healthy and assess the need for interceptive orthodontic therapy.
Extraction and other surgical procedures during the primary dentition period must be done with extreme caution due to the nearby developing tooth germs of the permanent dentition.
Dental imaging before primary molar extraction is done to confirm a permanent replacement.
If the permanent replacement is missing due to partial anodontia, extraction of the primary molar should be avoided.
A space maintainer may be placed after extraction to save the arch space for the permanent tooth to erupt into.
Primary Incisors
Each dental arch has four primary incisors: central and lateral.
Primary incisors resemble their permanent successors with a distinct bulging cervical ridge on labial and lingual surfaces.
They have the same arch position, function, and general shape as their permanent counterparts.
Dental professionals sometimes note wear or attrition of the incisal ridges from bruxism, possibly forming an end-to-end bite.
Primary Maxillary Central Incisor, E and F (#51 and #61)
The crown appears wider mesiodistally than incisocervically, opposite of its permanent successor.
It is the only anterior tooth of either dentition with this crown dimension.
Mesial and distal outlines are more rounded due to cervical constriction.
The incisal outline is relatively straight but slopes toward the distal with attrition.
Primary maxillary central incisors have no mamelons, leaving the labial surface smooth.
Rarely have developmental depressions, imbrication lines, or perikymata.
No pits are evident on the lingual surface.
The cingulum and marginal ridges on the lingual surface are more pronounced, and the lingual fossa is deeper than in the permanent successor.
The CEJ curves distinctly toward the incisal but less than on its permanent successor.
From the incisal surface, the crown appears wider mesiodistally than labiolingually, and the incisal ridge appears almost straight.
The single root is generally round in shape and tapers evenly to the apex but is longer relative to crown length than the permanent central incisor.
Primary Maxillary Lateral Incisor, D and G (#52 and #62)
The crown is similar to the central incisor but much smaller in all dimensions.
It is longer incisocervically than mesiodistally, opposite of the central incisor.
The incisal angles are more rounded than the central incisor.
The root is similar to the central incisor, but is longer in proportion to its crown and its apex is sharper.
Primary Mandibular Central Incisor, O and P (#71 and #81)
The crown looks more like the primary mandibular lateral incisor than its permanent successor or any primary maxillary incisor.
It is quite symmetrical, similar to its permanent successor.
It is not as constricted at the CEJ as the primary maxillary central incisor.
From the labial aspect, the crown appears wide compared with its permanent successor.
Mesial and distal outlines taper evenly from the contact areas.
The lingual surface appears smooth and tapers toward the pronounced cingulum.
Marginal ridges are less pronounced than those of the primary maxillary incisor; the lingual fossa is shallower.
The CEJ curvature on the mesial surface is greater than on the distal.
It is much wider labiolingually than its permanent successor.
The incisal ridge is centered over the root and divides the labial and lingual into equal halves.