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Copy of Copy of The Decade of Data - Sandy Pentland - MIT

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Deema Altwerqi

on 2 October 2013

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Transcript of Copy of Copy of The Decade of Data - Sandy Pentland - MIT

Primary spacing
* A primary dentition without spacing is followed by crowding in approximately 40% of cases.
* Baume found that the primary dentition can be either spaced or closed.
Primary spacing occurs in the maxilla in 70% of children & in the mandible in 63%.
Primary Dentiton
absence of skeletal discrepancies
large (greater than 10 mm) arch-length deficiency
normal overbite
(usually) Class I malocclusion
a commitment on the practitioner’s part to finishing the case.
U.S. Public Health

Mild Crowding:
Mild Crowding:
-NY Times
“Serial extraction” or “guidance of eruption”

Should coincide with its phase of active eruption
Serial Extractions are as Follows:
The Ideal Guidelines for
In Primary & Mixed Dentition
Surveys conducted by the U.S. Public Health Service in the 1960s found in a sample of 8,000 that 40 percent of children (aged 6 to 11 years) and 85 percent of youths (aged 12 to 17 years) have crowding problems.

Disharmony between the size of the teeth & available space in the alveolus with NO skeletal, muscular or occlussal functional features.
Commonly associated with Class I & dental ClassII malocclusion.
Crowding not only caused by dysfunction
as well as disharmony between the sizes of the teeth & the available space, but also skeletal imbalance, abnormal lip & tongue functioning
The exact cause of crowding or malocclusion in general is unknown. Several researchers have suggested that the problem is hereditary. Another author believed there are true signs of hereditary & environmentally induced tooth-size/jaw-size discrepancy.
In the case of space shortages of 10 mm or more
To resolve tooth- size/arch-length problems.
begun in the early mixed dentition eventually culminates in the
extraction of the permanent first premolars
serial extraction for both Class I and Class II occlusions
should coincide with its phase of active eruption.
The rate of formation of the permanent premolar did not change after the extraction of its primary precursor.
Crowding & irregularity are the most prevalent components of a malocclusion in dental patients.

Diagnosing and treating space problems requires an understanding of the etiology of crowding and the development of the dentition

Proper management of space in the primary and mixed dentition can prevent unnecessary loss in arch length.

However, an immediate eruption spurt occurred following extraction of the primary molar regardless of its stage of development and the age of the child.
The goal of the distal movement
of the canine and general alleviation of tooth-size/arch-length discrepancy.
Removal of the primary canines as
the permanent lateral incisors erupt.
Primary first molars are extracted to speed the eruption of the first premolars.
permanent first premolars are removed to allow the permanent canines to erupt in the first premolar space
Development of the Dentition

Mixed Dentition
reduced after the premature
loss of the primary incisor.
This is particularly true if:
The incisor is lost very early.
There is no primary spacing in the dentition
There is a tendency toward a Class II molar relationship. or if
The incisors have a deep overbite relationship.
Arch length
84 percent would have adequate space if a lip bumper was used to move the mandibular first molars 1 mm distally.
Mesial Shift
77 percent of the patients would have adequate space to accommodate an aligned dentition, if leeway space was preserved
Early Mesial shift
In patients with a spaced primary dentition & a flush or straight terminal plane
Closes the space distal to the primary canines (primate space)
Transforms the molar relationship into a Class I relationship

Late Mesial Shift
A)Conventional Space Analysis:
In patients with a closed primary dentition (no primate space)
The transformation into a Class I molar relationship may not occur until the exfoliation of the primary molars.
The permanent first molars migrate forward to close up the excess Leeway Space

Space maintenance
in the developing dentition can prevent unnecessary
loss in arch length.
Was first proposed by Nance in 1947
Consists of comparing the amount of space available for the alignment of the teeth to the amount of space required for proper alignment.
The size of the unerupted permanent teeth can be estimated using one of the following methods:

1)Measuring the teeth on a radiograph & adjusting for the magnification by a simple proportional relationship 2)Estimating the size of the unerupted teeth from a prediction table. 3)Combination of both methods.

The difference in size between the primary molars and the succedaneous premolars

The average leeway space :
2.2 mm (1.1 mm per side) in the maxilla
4.8 mm (2.4 mm per side) in the mandible
Leeway Space
Incisor liability
It is the size differential between the primary and permanent incisors

on average the permanent Maxillary incisor are, 7.6 mm larger than the primary incisors
Mandibular permanent incisors, are 6.0 mm larger than the corresponding primary teeth

B)Tanaka & Johnston Analysis:
one-half of the mesiodistal widths of 4 lower incisors + 10.5 mm = Width of the Mandibular canines & premolars in one quadrant
one-half of the mesiodistal width of the four lower incisors + 11.0 mm = Width of the Maxillary canine & premolar in one quadrant
Adv: Reasonable accuracy, does not require radiographs nor prediction tables
Dis: Do not takes into account the axial inclination of the mandibular anterior teeth, the effects of the curve of Spee, ethnic group biases or facial profile
Developed by Merrifield.
Took into account the tooth measurement, cephalometric correction & soft-tissue modification.
This method also indicated the exact area (anterior, middle or posterior) where the crowding occurred.
C)Total Space Analysis:
Space Problems Categorizes
1.1 mm
< 2 mm
2-4 mm
5-9 mm
Extremely Sever
10 mm or more
Moderate Crowding:
Moderate Crowding:
*Cause Inherent lack of space.
*Maxilla Mesial tipping or mesial-lingual rotation of the permanent 1st molars.
*Mandible Mesial tipping of the permanent 1st molars
Eruption Sequence
The most favorable sequence of eruption is as follows:
first molar
central incisor
lateral incisor
first premolar
second molar
second premolar
first molar
central incisor
lateral incisor
first premolar
second molar
second premolar
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