Deciduous Teeth: Primary Dentition

• Deciduous teeth function during childhood, shed, and are replaced by permanent teeth.
• The word "deciduous" originates from a Latin term meaning "to fall off', comparable to how deciduous trees shed leaves.
• Deciduous teeth emerge in children between 6 months and 2 years of age.
• There are 20 deciduous teeth, with 10 in the maxillary arch and 10 in the mandibular arch.

Deciduous Dentition

• Central incisor

• Lateral incisor

• Canine

• First molar

• Second molar

• There are no premolars in the deciduous dentition

• The gradual replacement of deciduous teeth with permanent teeth begins at around age 6.

• Common nicknames include "primary teeth", "milk teeth", "baby teeth", and "temporary teeth"

• Deciduous teeth are present in the mouth typically from 6 months to 10-12 years.

• Deciduous teeth are crucial for proper alignment, spacing, and occlusion of the permanent dentition.

• Premature loss of deciduous teeth can lead to destructive outcomes.

Functions of Sound Deciduous Teeth

• Enables efficient chewing of food
• Maintains normal facial appearance
• Facilitates clear speech
• Preserves space for the eruption of permanent teeth

Characteristics of Deciduous Teeth

• Smaller
• Whiter
• More consistent in shape
• The enamel is less mineralized, more permeable and more easily worn down than permanent teeth
• Shorter crowns with respect to their roots
• Thinner layers of enamel and dentin
• Pulp cavities are proportionally larger
• Pulp horns are high
• Crowns have a marked constriction at the neck.
• Enamel bulges close to the cervical lines rather than gradually tapering
• Crowns appear bulbous

Anterior Teeth Characteristics

• No depressions or perikymata on the labial surface of incisor crowns
• No mamelones on the incisal edges
• Prominent cervical ridge on the facial surface
• Prominent cingulum

Posterior Teeth Characteristics

• Molar crowns are narrow buccolingually and wide mesiodistally
• Molar crowns are short cervico occlusally
• Occlusal surfaces are shallow
• Cusps are short
• Ridges are not pronounced
• Grooves are not deep
• Buccal cusps are not pointed; cusp slopes meet at a very wide obtuse angle
• Few if any grooves or depressions
• Root furcation is near the crown
• Little if any root trunk
• Roots are thin and widely spread to allow for the development of permanent successors

Maxillary Incisors Characteristics

• Crowns are short and wide (Length = Width)
• The cervix appears more constricted compared to permanent teeth
• The MI angle is sharp and acute, while the DI angle is obtuse
• Lingual surface exhibits a prominent cingulum
• Marginal ridges and the lingual fossa are shallow

Mandibular Incisors Characteristics

• Crowns are small, narrow, and long
• Cingulum, lingual ridges, and fossa are poorly developed
• Incisal edge lies on the long axis
• Incisal angles are sharp
• Roots of mandibular incisors are long, thin, and straight
• Can be confused with the permanent canine because of its large crown and thick labiolingual proportions

Maxillary Canine Characteristics

• Crowns may be as wide as they are long
• Crowns are constricted at the cervix more than the incisors
• Mesial cusp slope is longer than the distal one (opposite of the permanent canine)
• Labial surface is strongly convex, particularly at the cervical one third
• Longitudinal ridge (labial ridge) connects the cervical ridge with the cusp tip
• Shallow grooves lie on either side
• Root is longest of the deciduous teeth (may be more than twice the crown length)
• Well-developed cingulum, mesial and distal marginal ridges, and cusp ridges
• Ridges are less prominent in comparison to permanent canines
• Cervical third of the crown is much thicker than in the deciduous incisors
• There is a prominent labial cervical ridge
• The root is bulky in its cervical and middle thirds, tapering most in the apical third
• Incisal aspect resembles a diamond shape
• Cusp tip is distal to the center of the crown
• Crown is broader labiolingually than the incisors, but is still wider mesiodistally than labiolingually

Mandibular Canine Characteristics

• Crown is shorter than the maxillary canine
• Crown is much longer than it is wide
• Cusp tip may be pointed like an arrow
• Ridges are less pronounced compared to those found on the maxillary canine
• Mesial cusp slope is shorter than the distal cusp slope (opposite to the maxillary deciduous canine)
• Root is at least 2 mm shorter than the maxillary canine