1unaangleskullxr
A diagnostic X-ray measurement that evaluates the position of the upper jaw relative to the skull base, commonly used for orthodontic treatment planning.
{"Measures the SNA angle to assess upper jaw (maxilla) position","Helps plan orthodontic treatment and jaw surgery","Performed using a standardized skull X-ray (cephalogram)","Normal SNA angle is typically between 78-82 degrees","Results guide diagnosis of jaw alignment problems"}
Key facts at a glance
- LOINC
- 60609-5
- Short code
- UINA-ANG
- Synonyms
- 1U-Na Angle Skull XR
- Category
- chemistry
- Sample
- serum
- Container
- Not applicable - radiographic imaging study
- Units
- N/A
- Ref low
- 1
- Ref high
- 3
- Critical range
- -2 N/A – 6 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- xr-measured
- CPT
- 70350 (Cephalometric radiographic examination)
- SNOMED
- 363400007
- Specimen volume
- Not applicable - X-ray imaging
- Stability
- Not applicable - radiographic image stable indefinitely when properly stored
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
What is this test?
The SNA angle test is a cephalometric analysis performed on a skull X-ray (called a cephalogram). It measures the angle formed by three key points: Sella (the center of the pituitary gland in the skull), Nasion (the bridge of the nose), and A-point (the deepest point of the maxilla or upper jaw). This measurement helps determine the forward position of the upper jaw relative to the skull base.
How is the test performed?
A specialized X-ray machine called a cephalostat is used to take a side-view image of your head. The machine ensures your head is positioned precisely and reproducibly. You will be asked to bite down on a positioning device and hold still for a few seconds while the X-ray is taken. The entire process is quick, painless, and involves minimal radiation exposure.
Why is this test important?
The SNA angle provides crucial information about facial growth and jaw alignment. It helps orthodontists and oral surgeons understand whether your upper jaw is positioned normally, too far forward, or too far backward relative to your skull. This information is essential for creating effective treatment plans.
Reference range
Normal ANB angle range: 1-3 degrees for Class I skeletal relationship. Values <1 degree indicate skeletal Class III relationship; values >3 degrees indicate skeletal Class II relationship. SNA angle normal: 82 degrees (range 78-86). SNB angle normal: 78-80 degrees. Values may vary by ethnicity and age.N/A
Remove all metallic objects including earrings, necklaces, hairpins, and orthodontic appliances if possible. Remove dentures. Inform patient about radiation exposure. Ensure proper head positioning in cephalostat. Patient should remain still during exposure.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings2
Frequently asked questions
Does the test hurt?
How long does it take?
Is the radiation safe?
Do I need to prepare for the test?
When will I get my results?
Sources
- 1
- 2
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy