Mixed Dentition Analysis & Serial Extraction Flashcards
List the 6 forms of tooth size arch length discrepancy manifestations:
- Lateral incisor eruption forcing premature exfoliation of temporary cuspids
- Patients with severe crowding, the lateral incisor is in contact with the mesial surface of the deciduous first molar (no room for canines)
- After a forced unilateral exfoliation of a deciduous cuspid
- Labial or lingual eruption of permanent incisors
- Premature loss of deciduous molars could lead to arch length deficiencies
- Labial or lingual eruption of cuspids
Prediction of the mesiodistal widths of unerupted cuspids and bicuspids can be done via:
- non radiographic methods
- radiographic methods
Nonradiographic methods to predict the mesiodistal widths of cuspids and bicuspids include:
- Tanaka & Johnston
- Moyers
The prediction of the size of unerupted canines and premolars in a contemporary orthodontic population is correlated to the MD widths of the four permanent lower incisors with the widths of the cuspid, first premolar & second premolar of one side of the maxillary and mandibular arch:
Tanaka & Johnstons (Nonradiographic method)
For Tanaka & Johnstons method, half of the MD widths of the four permanent lower incisors:
+ 11= _______
+ 10.5 _____
maxilla
mandible
Tanaka & Johnston is performed:
Biquadrant
Method of prediction of the MD widths of unerupted canines & premolars
-which can be predicted with minimal error & quickly done
-could be performed by novices or experts
-no need for special equipment or X-rays
-could be done on study models or in mouth
-could be done on both arches
Moyers
List the steps to Moyers prediction of the MD widths of unerupted canines & premolars:
- measure the MD width of the four lower incisors
- determine the REQUIRED SPACE to align the four permanent incisors
- determined the AVAILABLE SPACE
- predict the combined MD widths of the canine & two premolars
- determine the REMAINING SPACE (subtracting the estimated widths of the canine and two premolars from the available space)
Radiographic methods to predict the MD widths of unerupted canines & premolars include: (2)
- Huckaba
- Hixon-Oldfather
Radiographic method to predict the MD widths of unerupted canines & premolars via arch size analysis and tooth size prediction:
Huckaba
The technique for Huckaba is based on the assumption that the magnification degree of a deciduous tooth on an X-ray would be the same as:
The erupting permanent tooth on the same periapical film
List the steps of Huckaba method:
- measure the MD width of the deciduous tooth on the X-ray (Y’)
- measure the MD width of the successor permanent toot on the x-ray (X’)
- measure the MD width of the deciduous tooth on the study model (Y)
- the MD width of the permanent tooth is calculated by a mathematical proportion (X)
List the two equations of huckaba analysis:
Describe variables
X:X’ = Y:Y’
X= X’Y / Y’
X: MD width of permanent tooth (calculated)
X’ MD width of successor permanent tooth on X-ray
Y: MD width of deciduous tooth on study model
Y’: MD width of decidous tooth on X-ray
For Huckaba analysis:
Measuring the MD width of the decidous tooth on the X-ray results in:
Y’
For Huckaba analysis:
Measuring the MD width of the successor permanent tooth on the X-ray results in:
X’
For Huckaba analysis:
Measuring the MD width of the deciduous tooth on the study model results in:
Y
What does the Hixon-Oldfather analysis estimate?
Estimation of the sizes of unerutped canines & premolars radiographically
Developed an equation to predict the MD widths of the unerupted canines & two premolars from children of the iowa facial growth study, by measuring ONLY the teeth from the left side of the each subject:
Hixon-Oldfather analysis
Hixon-Oldfather analysis only measures teeth from the:
left side of each subject
T/F: With the Hixon-Oldfather analysis, the estimated error was significantly reduced reviewing the original equation. Measuring the teeth on BOTH sides of each subject
True
List the steps of the revised Hixon-Oldfather analysis:
- measure the MD widths of lower right central & lateral incisor on the study must molar to mesial odels
- measure the MD widths of the lower first & second right premolars on X-ray
- add both measurements & take that number to the prediction graph to determine the MD widths of the canine & both premolars
- add one standard error to the estimated prediction
- do the same procedure for the left side
- add the predicted widths of the erupted lower incisors to attain the required space from mesial of first molar to mesial of first molar (across arch)
- measure the available space & subtract the required space
If the mixed dentition analysis predicts there is NOT a crowding problem, you should:
continue with periodic patient observation
If the mixed dentition analysis predicts light crowding (1-4mm) you should:
- maintain the arch length with and appliance
- examine patient periodically
(probably will be a need for future ortho treatment)
What is considered light crowding in mixed dentition analysis?
1-4mm
If the mixed dentition analysis predicts crowding of more than 4mm, most probably the patient will:
develop crowding in the permanent dentition which will require ortho treatment after a thorough evaluation
If the mixed dentition analysis predicts crowding in excess of 6mm:
In the mandibular arch the patient will benefit from serial extraction
Pre-requisites for Serial extraction:
- Skeletal class I
- Dental class I
- Bimax dental protrusion
- Dental crowding in excess of 6mm
- light or anterior open bite tendency
- No congenitally missing second premolars
The orderly removal of deciduous & permanent teeth in a determined sequence:
serial extraction
List the main benefits of serial extraction:
- naturally induced movement & alignment of severely crowded anterior teeth
- health improvement of the adjacent tissues
- psychological & cooperation improvement due to the incisor alignment
- decrease on orthodontists workload & stress
- less iatrogenic damages
List the main disadvantages of serial extraction:
- increase of the overbite
- lingual inclination of the incisors
- scarring tissue on the extraction spaces
- diastemas
- alteration on the tongue function
A cephalometric evaluation of the effects of Class I serial extraction procedure found a:
delay on the mandibular growth
Two types of serial extraction:
- conventional serial extraction
- alternative serial extraction
- Premature extraction of deciduous canines provides the space for the incisors to assume normal position over supporting bone
- Extraction of the first deciduous molars permits the desirable early eruption of the first premolars
- Final extraction of the first premolars makes it possible for the canines to erupt in favorable direction
Conventional serial extraction