Cephalometrics Flashcards
Define Sella
The midpoint of the sella tursica
Define Nasion
The most anterior part of the frontonasal suture
Define Orbitale
The most inferior, anterior point on the margin of the orbit
Define A point
The deepest concavity in the anterior profile of the maxilla
Define B point
The deepest concavity in the anterior surface of the mandible
Define Anterior Nasal Spine
The tip of the anterior nasal spine of the maxilla
Define Pogonion
The most anterior point on the mandibular symphysis
Define Menton
The lowest point on the mandibular symphysis
Define Gonion
The most inferior, posterior point on the angle of the mandible
Define Porion
The upper midpoint on the external auditory meatus
Define Gnathion
The most anterior, inferior point of the mandibular symphysis
Define Posterior Nasal Spine
The tip of the posterior nasal spine of the maxilla
What are the 3 categories of ANB angles?
- class I = 2-4 degree
- class II = more than 4 degree
- class III = less than 2 degree
Why are cephs used in orthodontics?
- diagnosis and treatment planning
- during active treatment - functional
- towards end of treatment - assess proclination of incisors and if bonded ret needed
- assessing and monitoring growth
How can a ceph be standardised?
- patients head should be in natural head posture with the Frankfort plane horizontal
- cephalostat - head postitioner with ear rods
- X-ray source - 5 feet from patient
- aluminium wedge - soft tissue definition
- film
What is a cephalometric radiograph?
A standardised lateral view of the facial bones and soft tissues
Define Articulare
The point of intersection of the posterior margin of the ascending mandibular ramus and the outer margin of the posterior cranial base
On a cephalometric tracing which plane is considered a stable structure from 7 years of age?
Anterior cranial base (S-N)
Which points connect to make the Frankfort plane?
Porion and orbitale
Which points connect to make the maxillary plane?
Anterior nasal spine and posterior nasal spine
Which points connect to make the mandibular plane?
Gonion and menton
Which points connect to make the SN plane?
Sells and nasion
What errors can occur during cephalometrics?
- errors of projection
* errors of indentification
How can errors be reduced during cephalometrics?
- careful selection of analysis
- understanding point definition
- good quality films
- care when interpreting results
Why is a lateral ceph used in orthodontics?
- aid treatment planning and diagnosis
- assess skeletal pattern - AP and vertical
- during treatment - post functional stage
- monitor growth
- orthographic surgery cases
- assess soft tissues
- assess pathology
- research and audit (with ethical consent)
What is the average angle of SNA?
81 +/- 3
What is the average angle of SNB?
78 +/- 3
What is the average angle of ANB?
3 +/- 2
What is the average MMPA angle?
27 +/- 5
What is the average percentage for lower face height?
55%
What’s the average angle for upper incisors to maxillary plane?
109 +/- 6
What’s the average angle for lower incisors to mandibular plane?
93 +/- 6
What’s the average interincisal angle?
135 +/- 5
What does an aluminium wedge to?
Increases soft tissue definition
How much magnification is seen on a cephalometric radiograph?
7-8%
How far is the X-ray source from the patient for a lateral ceph?
5 foot
How should a patient bite for a lateral ceph?
Patient should bite in intercuspal position
What age the the cranial base considered a stable landmark?
7 years old
