Dentistry: Mixed Dentition Period Lecture 6
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Questions and Answers

At what age do the first permanent molars typically erupt?

  • 6 years (correct)
  • 8 years
  • 4 years
  • 10 years

What influences the anteroposterior positioning of the permanent molars?

  • Angulation of the premolars
  • Size of the canines
  • Spacing between the incisors
  • Terminal plane relationship of the deciduous molars (correct)

What role do the first permanent molars play in occlusion?

  • They establish and function in occlusion in permanent dentition (correct)
  • They guide the eruption of the incisors
  • They maintain the alignment of the premolars
  • They are responsible for canine guidance

How does a flush terminal plane of the second deciduous molars influence the eruption of the permanent first molars?

<p>It leads to a Class I molar relationship immediately (B)</p> Signup and view all the answers

What is the role of the Leeway space in the development of occlusion?

<p>It allows for mesial shift of the permanent first molar (C)</p> Signup and view all the answers

During which period does the emergence of the first permanent molars and transition of incisors take place?

<p>First transitional period (D)</p> Signup and view all the answers

What is the result of a distal step in the deciduous second molars?

<p>Class II malocclusion (D)</p> Signup and view all the answers

What does a mesial step relationship of primary second molars lead to in the mixed dentition?

<p>Class I molar relation (A)</p> Signup and view all the answers

What is the term for the early shift that occurs during the early mixed dentition period?

<p>Early mesial shift (B)</p> Signup and view all the answers

What causes the closing of any spaces between the primary molars or primate spaces in a spaced arch during early shift?

<p>Eruptive force of the permanent molars (A)</p> Signup and view all the answers

When does the late mesial shift of molars occur?

<p>Late mixed dentition period (A)</p> Signup and view all the answers

What did Nance describe in 1947 related to the combined mesiodistal width of certain teeth?

<p>Leeway Space (D)</p> Signup and view all the answers

What is the expected arch length in the maxilla based on Nance's description?

<p>$1.8$ mm (B)</p> Signup and view all the answers

What is the expected arch length in the mandible based on Nance's description?

<p>$3.4$ mm (B)</p> Signup and view all the answers

What contributes to class II malocclusion despite Leeway space and differential growth?

<p>$\text{Distal step}$ (B)</p> Signup and view all the answers

During which phase does early shift occur?

<p>$\text{Early mixed dentition period}$ (C)</p> Signup and view all the answers

Flashcards

First Permanent Molar Eruption Age

The age at which the first permanent molars begin to erupt.

Anteroposterior Molar Positioning

The alignment of the deciduous molars plays a significant role in how the permanent molars will erupt and align.

Function of First Permanent Molars

These teeth form an important foundation for the permanent bite, helping to establish and maintain the proper alignment.

Flush Terminal Plane

When the deciduous molars are aligned with no spacing, the permanent molars erupt in a proper Class I relationship.

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Leeway Space

The small space between the back of the primary molars and the front of the permanent molars that allows for the permanent molars to shift forward.

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First Transitional Period

The period when the first permanent molars are erupting and the deciduous teeth are being replaced, marks a crucial transition in the development of the bite.

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Distal Step in Deciduous Molars

When the deciduous second molars are misaligned with the front molar being further back, the permanent molars will likely result in a Class II malocclusion.

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Mesial Step in Deciduous Molars

A proper alignment of the deciduous molars with a slight forward tilt of the back tooth can lead to a healthy Class I molar relationship in the permanent dentition.

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Early Mesial Shift

A natural shift of the permanent molars forward, resulting in a more stable occlusion that occurs early in the mixed dentition period.

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Closing of Primate Spaces

The eruptive force of the permanent molars naturally closes any spaces between the primary molars, leading to a more aligned arch.

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Late Mesial Shift

The second significant forward movement of the permanent molars that occurs later in the mixed dentition period.

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Leeway Space Explained

The total mesiodistal width difference between the primary and permanent teeth, providing space for the permanent molars to align correctly.

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Nance's Leeway Space (Maxilla)

The total expected space for the permanent molars in the upper arch.

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Nance's Leeway Space (Mandible)

The total expected space for the permanent molars in the lower arch.

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Distal Step and Class II Malocclusion

Even with Leeway space and growth, a distal step can still result in a faulty Class II malocclusion.

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Early Shift Phase

The period during which the early mesial shift of the permanent molars takes place.

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Study Notes

Molar Eruption and Occlusion

  • First permanent molars typically erupt between 6-7 years old.

Anteroposterior Positioning of Permanent Molars

  • The anteroposterior positioning of permanent molars is influenced by the terminal plane of the second deciduous molars.

Role of First Permanent Molars in Occlusion

  • First permanent molars play a crucial role in occlusion, as they establish the posterior occlusal plane.

Influence of Terminal Plane on Permanent Molars

  • A flush terminal plane of the second deciduous molars allows for a more mesial eruption of the permanent first molars.

Leeway Space and Occlusion

  • The Leeway space contributes to the development of occlusion by providing room for the permanent teeth to erupt.

Emergence and Transition Period

  • The emergence of the first permanent molars and transition of incisors occur during the early mixed dentition period (6-12 years old).

Distal and Mesial Steps

  • A distal step in the deciduous second molars results in a Class II molar relationship.
  • A mesial step relationship of primary second molars leads to a Class III molar relationship in the mixed dentition.

Early and Late Shift

  • Early shift occurs during the early mixed dentition period, where the molars shift mesially to close any spaces between the primary molars.
  • The late mesial shift of molars occurs later in the mixed dentition period.

Nance's Description and Arch Length

  • Nance described in 1947 that the combined mesiodistal width of the primary canines and molars equals the combined mesiodistal width of the permanent canines and premolars.
  • The expected arch length in the maxilla is 38 mm based on Nance's description.
  • The expected arch length in the mandible is 34 mm based on Nance's description.

Class II Malocclusion

  • Class II malocclusion can occur despite Leeway space and differential growth due to other factors such as genetics, habits, or other environmental influences.

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