#3 Space Analysis and Cephalometrics Flashcards
Define “Space Available.”
mesial of permanent 1st molar to mesial of contralateral permanent 1st molar
Define “Space Required.”
Mesiodistal width of all teeth
What are the 2 assumptions that are principles of space analysis?
1) The AP position of the incisors is correct (crowding vs. protrusion)
2) The space available will not change because of growth (less valid in children with skeletal problems)
In mixed dentition, how do we estimate crowding/spacing for unerupted teeth?
1) Measurement of teeth on radiographs
2) Estimation from proportionality tables
3) Combination of the above
What 2 tables can be used to estimate the proportionality of mixed dentition?
1 - Moyer’s: Measure total width of permanent mandibular incisors, use table to predict width of permanent canines and premolars
2- Tanaka/Johnston:
– One half the width of permanent mandibular incisors + 10.5 mm = estimated width of mandibular canines and premolars in one quadrant
– One half the width of permanent mandibular incisors + 11.0 mm = estimated width of maxillary canines and premolars in one quadrant
How to you calculate space availability in mixed dentition?
– Measure mesial of permanent 1st molar to mesial of permanent 1st molar
– Divide into 4 segments
– Add together, this is space available

How do you calculate space required in mixed dentition?
1 - Measure the mesiodistal widths of the incisors (Mx/Md)
2 - Width of lower incisors + 21 = estimated size of mandibular canines and premolars
– Width of lower incisors + 22 = estimated size of maxillary canines and premolars
3 - Add incisor width + estimated size of premolars and canines (for either Mx or Md)
– This is space required
– Compare with space available for arch length discrepancy
How to you calculate space availability in permanent dentition?
– Measure mesial of permanent 1st molar to mesial of permanent 1st molar
– Divide into 4 segments
– Add together, this is space available
How to you calculate space required in permanent dentition?
- Measure mesiodistal width of each tooth
– Add together, this is space required
– Compare with space available for arch length discrepancy
What is SNA?
Relative AP position of Maxilla
What is SNB?
Relative AP position of Mandible
What is ANB?
ANB(= SNA-SNB), Relation of Max to Mand
What is a Steiner Analysis?
•relates the A-P position of the maxilla and mandible to the cranial base and to each other
What is the mean SNA?
82° +/- 2
If SNA is > mean, then what?
protrusive maxilla
If SNA is
retrusive maxilla
What is the mean SNB?
80° +/- 2
If SNB is > mean, then what?
protrusive mandible
If SNB is
retrusive mandible
What is the mean ANB?
2° +/- 2
If ANB is > mean, then what?
Class II tendency
If ANB is
Class III tendency
What is the mean MP?
21.9° +/- 3.2 (range 17-28°)
What does high MP mean?
unfavorable hyperdivergent pattern
What does low MP mean?
hypodivergent pattern
What are the 2 vertical proportions?
1 - MP (Mandibular Plane)
2 - % Face Height
What is the growth direction?
Y - Axis
What is Upper Incisor Position relative to?
Face Height
What is Lower Incisor Position relative to?
Mandibular Plane
