Basic Cephalometrics

Mark H. Taylor, D.D.S., F.A.C.D.

Cephalometrics is a technique employing oriented radiographs for the purpose of making head measurements.

Purpose of Cephalometrics

• Study craniofacial growth• Diagnosis• Planning orthodontic treatment• Evaluation of treated cases

15"60"

Source Plane

X-ray Source

Patient in Head Positioning Device

Mid-saggital Plane

Film Plane

X-ray Film in Cassette

Cephalostat

Cephalostat

Cephalostat

White Black Israeli Chinese Japanese

SNA 82 85 82 82 81

SNB 80 81 78 79 77

ANB 2 4 4 3 4

U1-NA 4 mm, 22 7 mm, 23 5 mm, 24 5 mm, 24 6 mm, 24

L1-NB 4 mm, 25 10 mm, 34 6 mm, 29 6 mm, 27 8 mm, 31

U1-L1 131 119 124 126 120

GoGn-SN 32 32 35 32 34

L1-MnPl 93 100 93 93 96

L1-FH 62 51 57 57 57

Y axis 61 63 61 61 62

from Proffit,Contemporary Orthodontics, 1992

Cephalometric Values for Selected Groups

What Are We Trying to Accomplish?

• Find out skeletal classification– anteroposterior– vertical

• Find out angulation of incisors• Consider soft tissue

– facial profile– airway considerations

What Are We Trying to Accomplish? (In other words)

• Is the patient Class I, II, III skeletal?• Does the patient have a skeletal open bite

growth pattern, or a deep bite growth pattern, or a normal growth pattern?

• Are the maxillary/mandibular incisors proclined, retroclined or normal?

• Is the facial profile protrusive, retrusive, or straight; can the patient breathe normally?

Structures to be Traced

Sella

Porion

Gonion PNS

Menton

Gnathion

Pogonion

B PointA PointANS

Orbitale

Nasion

Articulare

Standard Cephalometric Landmarks

Radiographic Landmarks

SN Plane

Frankfort PlanePalatal Plane

Occlusal Plane

Mandibular Plane

Frequently Used Planes

8822

Antero-posterior maxillary assessment

Skeletal AssessmentSNA

8800

Antero-posterior mandibular assessment

Skeletal AssessmentSNB

22Antero-posterior bimaxillary assessment

Skeletal AssessmentANB

-1 mm-1 mmBO anterior BO anterior to AOto AO

Skeletal AssessmentWits (AO-BO)

6666

Skeletal AssessmentY Axis

5959

Vertical Skeletal Assessment

Skeletal AssessmentY Axis (to Frankfort Horizontal)

3232

Vertical Skeletal Assessment

Skeletal AssessmentNS(SN plane)-GoGn

101044

Incisor Angulation Assessment

Dental AssessmentU1-NS (Max 1 - SN)

2222

Dental AssessmentMax 1 - NA (degrees)

4 4 mmmm

Dental AssessmentMax 1 - NA (mm)

9955

Incisor Angulation Assessment

Dental AssessmentL1-GoGn (Man 1 - GoGn)

2255

Dental AssessmentMan 1 - NB (degrees)

4 4 mmmm

Dental AssessmentMan 1 - NB (mm)

2 mm 2 mm +/- 2+/- 2

Dental AssessmentAPog - Man 1

131300

Inter-Incisor Angulation Assessment

Dental AssessmentU1-L1 (Max 1 - Man 1)

-2 -2 mmmm

CHANGES WITH AGE!

Soft Tissue AssessmentE Plane

>4 >4 mm.mm.

Soft Tissue Assessment

Composite Cephalometric Tracing

Children with airway obstruction, whencompared to normal controls, show:

Nasorespiratory Considerations

• Increased total and lower face heights• More retrognathic mandibles• Steeper (increased) mandibular plane

angles• Spontaneous improvement after

reestablishment of normal respiration

Cases