Development and Morphology of the Primary Dentition- Pediatric Dentistry

What are the components of the primary dentition?
20 teeth- 5 per quadrant
1. central incisor
2. lateral incisor
3. canine
4. 1st molar
5. 2nd molar

That are the three developmental stages of the primary dentition?
1. prenatal stage
2. birth to complete primary dentition
3. primary dentition until transition

What are the six stages of the Pre-natal stage?
1. initiation (bud stage)
2. proliferation (cap stage)
3. histodifferentiation (bell stage)
4. morphodifferentiation (bell stage)
5. apposition
6. calcification

formation of the dental lamina begins during the ____ week in embryonic life and lasts until ____ years of age.
6th week; 4-5 years

when does primary bud formation occur?
by 2nd month in utero, all 20 deciduous buds are present; all 20 primary tooth buds are initiated simultaneously.

What are the two basic parts which later form the tissues of the tooth in primary bud formation?
epithelial; mesenchymal

During which phase do disturbances in number occur in the primary dentition?
during the initiation of the bud stage of the prenatal stage

What best characterizes the proliferation (cap stage) of the prenatal stage?
increases in size and change in form of the tooth bud.

When does the tooth bud become called the tooth germ?
During the proliferation (cap stage). The epithelial and mesenchymal portions of the tooth are present.

which embryonic tissue portion describes the enamel organ that forms the enamel?
epithelial portion of the tooth germ

Which embryonic tissue portion describes the formation of dentin and pulp from the dental papilla and the cementum, periodontal ligament, and adjacent alveolar bone from the dental follicle.
Mesenchymal portion of the tooth germ

what part of the epithelial portion of the tooth germ forms the enamel?
enamel organ

what part of the mesenchymal portion of the tooth germ forms the dentin and pulp?
dental papilla

What part of the mesenchymal portion of the tooth germ forms the cementum, periodontal ligament, and adjacent alveolar bone?
dental follicle

During which phase of the prenatal stage are the various cells becoming specialized to form the tissues of the tooth?
Histodifferentiation (Bell Stage)

Name two characteristics of the inner enamel epithelium.
1. defines the shape of the tooth
2. elongates and differentiates to become ameloblasts

Which direction does histodifferentiation move in the arch?
in a wave like fashion from the incisal or cusp tip toward the cervical region.

What stage of tooth development determines the size and shape of a tooth?
morphodifferentiation (bell stage)

What marks the start of apposition?
the onset of amelogenesis– Once the odontoblasts produce dentin matrix, the ameloblasts differentiate and produce enamel. The odontoblasts and ameloblasts move away from the DEJ as the matrix forms.

What lays down the matrix that later calcifies into dentin?
odontoblasts

What do the ameloblasts do?
They lay down enamel with hydroxyapatite. There is no uncalcified layer like dentin.

what is the first area of the crown to completely form?
the cusp tip

what is the last area of the crown to develop?
the cervical region

When do maxillary and mandibular primary teeth initiate calcification?
16-18 weeks in utero

when is root development complete in maxillary and mandibular primary teeth?
about 3 years of age

Describe the initiation of permanent tooth bud formation.
initiation of these teeth happens one at a time, starting at the 4th month in utero with the first permanent molar and ends at age 3-4 with the 3rd molars.

describe permanent molar bud formation.
The permanent molar buds develop by distal extension of the dental lamina.

Where do permanent incisor, canines, and premolars develop in relation to the dental organs of the primary teeth they replace?
lingually to the primary teeth they replace; they are not aligned within the jaw before eruption

How many calcifying permanent teeth are developing at birth?
24– calcification of the cusps of the 1st molars begins just before birth.

Where do the premolars develop in relation to their primary teeth predecessors?
lingually in relation to the primary teeth. During development, they move closer to the furcation as the primary teeth move toward occlusion.

The upper gum pad is wider than the lower gum pad and is protruded in front. The relationship of the gum pads is of great significance in predicting occlusion.
The first statement is TRUE. the second statement is FALSE. (the relationship of the gum pads is of little significance in predicting occlusion.

The vertical relationship (overbite) between gum pads varies from…
-4 to +5 mm

What are the three phases of primary tooth eruption?
1. preeruptive phase
2. active eruptive phase (prefunctional phase)
3. eruptive (functional phase)

All movements of the pre-eruptive phase of primary eruption take place in the crypt before the root develops. During the active eruptive phase of primary eruption, the tooth moves occlusally through the bone of the crypt and the connective tissue of the oral mucosa.
Both statements are TRUE.

During which phase do the growing tooth germ move and develop within the alveolar process prior to root formation?
pre-eruptive phase

What are the two types of movement that occur during the pre-eruptive phase of primary teeth?
1. bodily movement- a shift in the entire germ causing apposition and resorption of bone.
2. eccentric growth- movement of the tooth from developmental position to the site of functional occlusion.

Early in the pre-eruptive phase or the primary dentition, the successional teeth develop ___ to their primary predecessors.
lingual to and near the incisal/occlusal level.

When does root formation for primary teeth?
during the active eruptive phase

What marks the onset of clinical eruption? And during which phase?
During the active eruptive phase when the tip of the crown enters the oral cavity. When this occurs, about 1/2 or 2/3 of the roots are formed.

During the ___ phase, adjustments maintain occlusion following attrition.
eruptive (functional phase)

The maxillary teeth are slightly ahead of the mandibular teeth in terms of sequence of eruption. There is a lot of variation in the typical order of eruption.
The first statement is FALSE. The second statement is TRUE.

*The mandibular teeth are slightly ahead of the maxillary teeth in terms of sequence of eruption.

Describe the eruption timing for primary teeth.
1. centrals and laterals- 6 months
2. first molars- 12 months
3. cuspids- 18 months
4. second molars- 24 months

Describe the key characteristics of primary dentition. (comparison to permanent dentition)
1. crowns of the primary anterior teeth are wider mesiodistally.
2. roots are narrower and longer comparatively to the crown size.
3. the pulp chamber is proportionally larger with less tooth structure protection.
4. roots flare out beyond the outline of the crown.
5. the occlusal table is narrower.
6. the cervical ridge buccally on the primary molar is much more pronounced, especially on first molars.
7. the buccal and lingual surfaces of the primary molars are flatter above the cervical curvatures than those of the permanent teeth.
8. they are lighter in color
9. there is a lot of spacing

Describe the two types of spacing in primary dentition.
1. generalized interdental
2. primate spaces- mesial of the maxillary canine; distal of the mandibular canine.

How is the classification of occlusion for primary teeth determined?
by the distal of the second molars.

What kind of relationship will permanent molars assume if the primary molars are arranged in a mesial step arrangement?
Permanent molars will assume a class I molar relationship.

What kind of relationship will permanent molars assume if the primary molars are arranged in a flush terminal plane arrangement?
permanent molars will assume an end-on relationship.

What kind of relationship will permanent molars assume if the primary molars are arranged in a distal step arrangement?
permanent molars will potentially be arranged in a Class II relationship.

What forces cause resorption of primary dentition?
1. pressure from growing and erupting permanent teeth.
2. weakening of the supporting tissues of the primary teeth occurs as a result of root resorption and modifications of the alveolar bone.
3. masticatory forces on the weakened teeth amplify compression of the periodontal ligament and promote resorption of teeth and alveolar bone.

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