Cephalometric analysis practical Flashcards
How do you clically assess skeletal pattern
use all 3 planes
1) anterior posterior
2) vertical
3) transverse
ideal relationship of skeletal pattern anterior posterioe (class 1)
mandible set just back from maxilla and forhead
classes of anterior posterior skeletal patterns
1 mandible just set back from mx and forehead
2 mandible set back with, maxilla alinged
3 top jaw set forwards from forehead, mandible too far forwards
Idel vertical plane
frankfort mandibular planes angl
- lines coverage at back of head
- face is roughly in equal 3rs (see pic )
non ideal FMPAs(vertical skeltal patthen)
lines converge further abck from head - reduced FMPA - lower anterior face height - deep overvite lines converge forwards from the head - increased FMPA - lower face height icreased - generally have anterior open bite
uses of cephalomenry
diagnosis
treatment planning
measure growth
assess treatment
limits of cepthalmetry
slightly magnified (2d image of 3D object)
not a science
sources of error
types of errors that can occur
systematic bias
random
errors affecting validiy
1) positioning of head in cephalostat
2) magnification and distortion
3) 3D object projected to 2D image – projection errors
4) landmarks defined for convenience rather than anatomical validity
- eg if you change the teeth position will change anatomical points that you measure against
5) remodelling (upper incisors)
errors affecting reproducability
1) blurring of image due to movement during exposure
2) variation in film contrast
3) thickness of pencil
4) perceptive limits of human eye
5) inconsistency of the human eye
Growth predication problems
adding of average amounts (averge is very variable)
- not accurate
- skeletal pattern remians the same in 60%
reference point may chanege
measurements that are taken in cephalometry
sella nasion A point B point anteriot nasal spine posterior nasal spine menton gonion
sella
midpoint of the pituitary fossa
naison
most anterior point on the frontonasal suture
what does the line between N and S equal
roughly anterior cranial base
stable landmark
A point
deepest point on anterior surface of maxilla
B point
deepest concavity on the antierior surface of the mandible
line between Aand B points
used to measure the top jaw to the lower jaw
anterior nasal spine
tip of bony anterior nasal spine
posterior nasal spine
tip of posteiro nasal spine
usually near last molar tooth
menton
lower most point on the mandibular symphysis
gonion
constructed point
at the intersection of the lines tangent to the postieor margin of the ascending ramus and the md symphysis
teeth markings for cephlometrics
upper incisor (apex and tip) lower incisor (apex and tip_
final measurements for cephalometrics
SNA
SNB
AMB
MMPA
SNA
averge 81 degrees
indicates position of mx relative to cranial base
SNB
indicate position of mandible relative to cranial base
AMB
relationship of the 2 jaws to each other less then 2 indicates class 3
upper incisors degree of proclination
ANS to PNS
over 115 incisors are proclined
less than 104 incisors are retro clined
lower incisors degree of inclination
M and Go plane, long axis of lower incisors
greater tha 94 proclined
less than 90 retero clined
