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1usenaangleskullxr

Published: August 9, 2026Updated: August 16, 2026

This test measures the angle between the upper front tooth and a line connecting the skull base landmarks on a skull X-ray, used to evaluate jaw relationship and facial growth.

Quick summary

{"Measures the angle between upper incisor and sella-nasion line on skull X-ray","Helps assess jaw alignment and facial growth pattern","Used in orthodontics and oral surgery treatment planning","Normal angle ranges from 82-84 degrees in adults","Abnormal angles may indicate jaw protrusion or retrusion"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
60611-1
Short code
UCI-SN Angle
Synonyms
1U-SeNa Angle Skull XR
Category
chemistry
Sample
serum
Container
Not applicable (imaging study)
Units
N/A
Ref low
102
Ref high
110
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
xr-measured
CPT
70350
SNOMED
3631008
Specimen volume
Not applicable (radiographic imaging)
Stability
Not applicable (imaging study)
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
1–24 hours
Order
routine

What is this test?

The Sella-Nasion to Upper Incisor (SNA) angle test is a cephalometric analysis performed on a skull X-ray (cephalogram). It measures the angle formed between the line connecting the sella (center of the pituitary gland) to the nasion (bridge of the nose) and a line drawn through the upper central incisor tooth. This measurement helps dentists and oral surgeons understand the positional relationship of the upper jaw to the skull base.

During the test, a specialized X-ray machine takes a side-view image of your head. The dentist or orthodontist then uses specific landmarks on the X-ray to draw lines and measure the angle. This is a routine diagnostic procedure in orthodontic treatment and jaw surgery planning.

Reference range

Normal angle typically ranges from 102° to 110° in Caucasian adults; may vary by ethnicity and population normsN/A

Specimen: serum

Patient should remove all metallic objects, jewelry, and dental appliances before X-ray exposure. Inform patient about radiation exposure precautions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings2

Frequently asked questions

Does this test require blood draw?
No. Despite the test being categorized under chemistry, this is actually an imaging test (skull X-ray/cephalogram). No blood sample is needed. The sample type 'serum' in the test information may be a data entry error.
Is the X-ray safe?
Yes, modern dental X-rays use very low doses of radiation. The exposure is minimal and considered safe. Lead aprons are typically used to protect other body parts. The benefits of getting accurate diagnostic information usually outweigh the small radiation risk.
How long does the test take?
The actual X-ray exposure takes only a few seconds. The entire appointment for positioning and taking the image usually takes about 10-15 minutes. The analysis and measurement may be completed after your appointment.
Do I need to prepare anything before the test?
No special preparation is needed. You should remove any jewelry, glasses, or metal objects that might interfere with the X-ray. Inform your dentist if you are pregnant.
  1. 1
    American Association of Orthodontists - Cephalometric X-raysSource
  2. 2
    Mayo Clinic - Dental X-raysSource

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.

Medical Disclaimer

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