Cephs Flashcards
What is the definition of Sella and what does it house? (Clue: Tursica)
The midpoint of the Sella Tursica. It houses the Pituitary gland.
What is the Nasion?
The Nasion is the most anterior of the frontonasal suture.
What is the Orbitale?
The Orbitale is the most inferior anterior point on the margin of the orbit
What is the A point?
The A point is the deepest concavity of the anterior profile of the maxilla.
Why is it hard to identify the A point.
Because as the roots move during treatment, it can be difficult to find the A point.
What is the B point (clue:symphysis)
The B point is the deepest concavity of the mandibular symphysis
What is ANS and what does it stand for? (clue:process)
Anterior Nasal Spine. This is the tip of the anterior process of maxilla.
What is PNS and what does it stand for?
Posterior Nasal Spine. It is the tip of the posterior nasal spine of maxilla.
What is the Porion? (PO)
The porion is the midpoint of the external auditory meatus.
What is the Pogonion? (Pog)
The pogonion is the most anterior part of the mandibular symphysis.
What is the Menton? (Me)
The Menton is the lowest point of the mandibular symphysis.
What is the Gonion? (Go)
The Gonion is the most inferior posterior point on the angle of the mandible.
What is the Gnathion?
The Gnathion is the lowest part of the midline of the chin or mandible.
What are the 4 plane is cephalometric and what point make up each plane.
SN - Sella to Nasion. Represent cranial base from 7 yrs old
Frankfort plane - porion orbitale
Maxillary plane - ANS to PNS
Mandibular plan - Gonion to Menton
What is SNA and what does it indicate?
SNA - Sella Nasion and A point. Indicates AP relationship of maxilla to cranial base.
What is SNB and what does it indicate?
SNB - Sella Nasion and B point. Indicates AP relationship of Mandible to cranial base.
What is ANB and what does it indicate?
ANB - A point, Nasion and B point. Indicates AP relationship of mandible and maxilla.
Class 1 - 2-4
Class 2 - less than 4
Class 3 - more than 2
How do you assess the vertical skeletal relationship using cephs?
MMPA or Facial proportions (formula?)
What happens to the lower incisor mandibular plan angle IF the MMPA angle is increased?
The lower incisors are usually retroclined and the LIMnP angle is decreased.
ANGLES IN EASTMAN:
SNA
SNB
ANB
MMPA
Ui MxP
Li MxP
INTERINCISAL ANGLE
SNA 81
SNB 78
ANB 3
MMPA 27
Ui MxP 109
Li MxP 93 (-120=MMPA)
Interincisal angle 133
Soft tissue relationship - what is E line and harmony plane?
E line: Soft tissue line from chin to nose. Upper lip - 4mm from line or posterior Lower line - 2mm from line
Harmony plane: soft tissue chin to lip. Bisect nose
Name types of cephalometric analysis
1) Wits (where the nasion is difficult to locate. Instead of using cranial base, assess ap jaw discrepancies)
2) Opal
3) Eastman
Definition of Cephalometrics
It is the measurement of the head from sagittal plane.
Measurement of soft tissues, bones and teeth.
Why must ceph be standardised and how?
Ceph should be reproducible to accurately compare same patient at different time frames.
- natural head posture with frankfort plane parallel to ground and horizontal.
What equipment do you use for ceph?
- cephalostats - earrods sit in external auditory meatus
- film - with intensifying screen.
- aluminium wedge - soft tissue definition
- collimated xray source - 5 foot from pt
Why is there magnification of cephs and how to prevent mistakes?
7-8% magnification bcos of divergent of beam.. Scale included.
What is the radiation dose?
6 MicroSv
Why do we take cephs?
1) treatment planning and diagnosis - skeletal, dentoalveolar and soft tissues
2) during treatment
3) end of treatment
4) research
5) assess or monitor growth
Methods to analyse (clue:trace?)
1) Light box and tracing paper
2) electronic automatic system
What are the points to consider when tracing cephalometrics?
1) validity
2) stability of points
3) reproducibility
What are the types of errors when tracing cephalometrics?
1) systematic - over/underestimation
2) random - no pattern
Specific errors of cephalometrics
1) error in projection - 2 dimensions in radiograph of a 3 dimensional objection
2) error in identification - landmarks, operator or ceph analysis used
How can you reduce errors in cephalometrics?
1) the careful selection of analysis
2) good understanding of the points you are plotting
3) good film quality
4) care when interpreting points
