4. Development Of Dental Arches And Occlusion In The Mixed And Permanent Dentition. Stage Sequencing

Question 1

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Mixed dentition beginning and end

Answer 1

6 years of age and lasts until approximately 12 years of age

Question 2

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Mixed dentition is divided into

Answer 2

• The first transitional period
• Intertransitional period
• Second transitional period

Question 3

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Eruption time and guiding mechanism of first permanent molar during first transitional period

Answer 3

• First permanent molar erupts at age 6=>
• Guided into dental arch by distal surface of deciduous second molar

Question 4

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Different scenarios of eruption patterns for the first permanent molar

Answer 4

• Flush terminal plane
• Mesial step
• Distal step

Question 5

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Eruption scenarios of Flush terminal plane and how it can be overcome

Answer 5

• Transition to a Class I molar relationship can occur by early or late shift
• Early shift driven by eruptive force of first permanent molar
• Late shift occurs when lack of primate space
• To overcome flush terminal plane, physiological spaces, Leeway Space, and forward growth of mandible can be utilized

Question 6

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Result of mesial step

Answer 6

Class I molar relationship

Question 7

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Result of distal step

Answer 7

Class II molar relationship

Question 8

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Exchange of incisors during first transitional period, and concept of “incisal liability

Answer 8

• Deciduous incisors replaced by permanent incisors=>larger
• Difference between space needed for accommodating permanent incisors and available space is called “incisal liability

Question 9

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Mechanisms involved in overcoming incisal liability

Answer 9

• Utilizing interdental spaces from primary dentition
• Increase in inter-canine width
• Changes in incisal inclination, where permanent incisors erupt more labially than primary incisors=>
• Increases dental arch in sagittal direction

Question 10

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Composition of maxillary and mandibular arches during intertransitional period

Answer 10

Deciduous and permanent teeth

Question 11

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Stability of intertransitional period, and changes typically occurring during this stage

Answer 11

Relatively stable, w/ only minor changes occurring

Question 12

Development Of Dental Arches And Occlusion In The Mixed And Permanent

What continues to happen with root formation during the intertransitional period

Answer 12

• Root formation of emerged incisors and first molars continues=>
  *Accompanied by increase in alveolar process height

Question 13

Development Of Dental Arches And Occlusion In The Mixed And Permanent

What characterizes second transitional period

Answer 13

Replacement of deciduous molars and canines by premolars and permanent canines

Question 14

Development Of Dental Arches And Occlusion In The Mixed And Permanent

How combined mesiodistal width of primary teeth compare to that of permanent teeth during second transitional period

Answer 14

*Usually greater than mesiodistal width of the permanent canine and premolars

Question 15

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Name of surplus space between primary and permanent teeth

Answer 15

“Leeway space of Nance.”

Question 16

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Leeway space measurements for the maxilla and mandible

Answer 16

• Maxilla=>1.8mm
• Mandible=>3.4mm

Question 17

Development Of Dental Arches And Occlusion In The Mixed And Permanent

How excess leeway space utilized in mandible

Answer 17

• For mesial shift of mandibular molars=>
• Establish class I relationship

Question 18

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Three periods of physiological raising of the bite

Answer 18

a. With eruption of first primary molar at age 2.5
b. With eruption of first permanent molar at 6
c. With eruption of second permanent molar and permanent canine at 12

Question 19

Development Of Dental Arches And Occlusion In The Mixed And Permanent

What happens when diastema is less than 2mm

Answer 19

Spontaneous closure occurs

Question 20

Development Of Dental Arches And Occlusion In The Mixed And Permanent

What happens when diastema is more than 2mm

Answer 20

Spontaneous closure is unlikely, and treatment is indicated

Question 21

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Treatment for a diastema typically involves

Answer 21

*Closure of the gap, followed by frenectomy if necessary

Question 22

Development Of Dental Arches And Occlusion In The Mixed And Permanent

Ugly duckling stage

Answer 22

• Normal developmental stage
• 7-12 years, preceding eruption of permanent canines
• Upper central and lateral incisors tipped laterally due to crowding created by unerupted canines=>
• Push on roots of incisors producing tipping and midline space (median diastema) between anteriors
• Should not be mistaken for malocclusion

Question 23

Development Of Dental Arches And Occlusion In The Mixed And Permanent

What causes shift in position of upper permanent lateral incisors

Answer 23

• Crowns of upper permanent canines push roots of upper permanent lateral incisors mesially=>
• Crowns of laterals shift distally
• Same happens to central incisors

Question 24

Development Of Dental Arches And Occlusion In The Mixed And Permanent

How the “ugly duckling” condition self-corrects

Answer 24

• Self-corrects as soon as canines erupt
• Crowns of canines push crowns of laterals and centrals back mesially

Question 25

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Factors that contribute to lingual eruption of lower permanent lateral incisors

Answer 25

* Tooth buds of permanent lateral incisors placed more lingually than those of primary laterals=> * Erupt more lingually

Question 26

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Circumstances under which lateral incisors can position properly despite their lingual eruption

Answer 26

* **If enough space in mandibular arch=>** * Lateral incisors position properly=> * Forces applied by **tongue and lip**

Question 27

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Cause of late mesial shift in mandibular first permanent molar

Answer 27

* **Mandibular first permanent molar moves mesially into class I molar relationship=>** * Exfoliation of primary teeth

Question 28

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Disadvantage of late mesial shift

Answer 28

* **Arch length decreases**=> * Mesial movement of mandibular first permanent molar

Question 29

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Age at which permanent dentition typically established

Answer 29

12 years of age

Question 30

# Development Of Dental Arches And Occlusion In The Mixed And Permanent When permanent dentition starts to form in the jaws

Answer 30

* **After birth** * Except for **cusps of first permanent molars=>** * Form before birth

Question 31

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Where premolars develop in relation to roots of deciduous molars

Answer 31

* Premolars develop below diverging roots of deciduous molars

Question 32

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Purpose of curve of Spee and curve of Wilson

Answer 32

**Complement paths of condyles during movement of mandible**

Question 33

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Inclination of crowns of mandibular and maxillary posterior teeth

Answer 33

* Crowns of mandibular posterior teeth incline lingually * Crowns of maxillary posterior teeth incline buccally

Question 34

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Significance of curve of Wilson becoming deeper posteriorly

Answer 34

So inclination of molars is greater than premolars

Question 35

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Why buccal cusps of mandibular molars and palatal cusps of maxillary molars usually appear longer

Answer 35

Due to curve of Wilson and associated tooth inclinations

Question 36

# Development Of Dental Arches And Occlusion In The Mixed And Permanent How space created for second and third permanent molars in maxilla and mandible

Answer 36

* In maxilla=>**bone apposition of tuber maxillae** * In mandible=>**absorption of ramus mandibulae**

Question 37

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Characteristics of an ideal occlusion in permanent dentition

Answer 37

* Class I relationship in canine and molar region * Vestibular cusps of mandible occluding with central fossae of maxillary teeth * Multipoint contact in the posterior segment * Coinciding midlines * Upper incisors overlapping lower incisors by 1/3 of the clinical crown * Overjet of around 2-3mm

Question 38

# Development Of Dental Arches And Occlusion In The Mixed And Permanent Variations observed in eruption sequence of permanent teeth in maxilla and mandible

Answer 38

* 6-1-2-4-3-5-7 or 6-1-2-3-4-5-7 in the maxilla * 6-1-2-3-4-5-7 or 6-1-2-4-3-5-7 in the mandible