Cephalometrics in orthodontics

21 January 2015

Introduction

Types

History

Uses

Equipment

Positioning of the Patient

Evaluation of Radiograph

Landmarks and Planes

Analysis

References

Cephalometry

The analysis and interpretation of standardized

radiographs of facial bones

- Using standardized skull radiograph to assess facial,

dental and skeletal relationships as well as airway

analysis

1) Lateral Cephalogram

• Lateral view of skull

• X-ray beam perpendicular to the patient's sagittal plane

2) Frontal Cephalogram

• Anteroposterior view of skull

• X-ray beam perpendicular to the patient’s coronal plane

Cephalometry was modified from anthropological

studies and craniometry(study of cranium)

Introduced in 1931 by Broadbent (USA) and

Hofrath (Germany)

Clinical application of cephalometry was

introduced by Downs

In orthodontic diagnosis and treatment planning.

› Assesment of horizontal/vertical skeletal relationship,

incisor position/inclination, soft tissue profile

› Orthognathic surgery

Helps in classification of skeletal and dental

abnormalities.

Helps in evaluation of treatment results.

› Post-functional to assess skeletal/dental relationship

› Plan retention and monitor post retention phase

Helps in predicting growth related changes.

Research purpose

• Collimated X-ray source - 5 feet from midsagittal plane of

patient

• Cephalostat - head positioner(with 2 ear rods and forehead

clamp)

• Aluminium wedge/ Barium paste - increases soft tissue

definition

• Film - placed 1.5-1.8 foot behind midsagittal plane of

patient with rare earth metal intensifying screen

Cephalostat

Frankfurt Horizontal plane should be parallel to floor.

Ear rods stabilize the patient on the horizontal plane.

Forehead clamp should be fixed for vertical plane

stabilization of patient.

Patient is made to close the mouth in centric occlusion.

Important to examine radiograph for any abnormalities or

pathology Eg. Sella turcica increase in size in pituitary tumor

Digitizing

› Illuminated radiograph viewing screen which is connected to computer.

› Specialized software used to produce tracing

Hand Tracing

› Carried out in a darkened room with light viewing box(X-ray viewer) and all but the areas being traced should be shielded out

› Acetate sheets used as transparency facilitates landmark identification

› Sharp pencil used ( 0.3mm leaded propelling pencil)

› Acetate sheet to be secured using masking tape and tracing oriented in the same position as patient when X-ray taken

› Bilateral landmarks, unless directly super imposed, an average of two should be taken

Cephalometry

Tracing

Sella : Centre of the

pituitary fossa of the

sphenoid bone

Nasion :Junction of

frontonasal suture

Basion :Most anterior point

of foramen magnum

Anterior Nasal

Spine :Most anterior

midpoint of ANS

of maxilla

Posterior Nasal

Spine :Most posterior

midpoint of PNS of

palate

A- Point :Most concave

point of alveolar

process of

maxilla

B- Point :Most concave point of

alveolar process of

mandible

Menton :Most inferior midpoint

of the chin on the

outline of mandibular

symphysis

Pogonion :Most anterior

midsaggital

point along

convexity of

chin

Gonion :Midpoint along curvature of

angle of mandible between

inferior border of body and

posterior border of ramus

Condylion :Most superior

point of

mandibular

condyle

Gnathion :Most anteroinferior

point on mental

symphysis

Orbitale :Most inferior point

of infraorbital rim

Porion :Most superior

point of external

accoustic

Landmarks

Horizontal planes

S.N. Plane – sella to nasion.

F.H. Plane – orbitale to porion.

Occlusal plane – plane bisecting posterior occlusion.

Palatal plane – ANS to PNS of palatine bone.

Mandibular plane – gonion to gnathion.

Vertical planes A-Pog line – point A on

maxilla to pogonion on mandible.

Facial plane – nasion to pogonion,

Facial axis – ptm point to gnathion.

Planes

Examples

Down's

Steiner

Rickett

Harvold

McNamara

Sassouni

Wits by Johnston

Wylie

Tweed

Downs Analysis

First published by Downs in 1948

Most frequently used cephalometric analysis

According to Downs,

“Balance of face is determined by position of

mandible”

Frankfurt Horizontal plane used as reference plan to

degree of retrognathism or prognathism

Skeletal Perimeters

Facial angle

Inferior angle formed by intersection of nasion-

pogonion plane and F.H. plane.

Average value: 87.5o ( 82o - 95o)

Significance: Indication of antero- posterior positioning of

mandible in relation to upper face. - Increased in skeletal class III with prominent chin

- Decreased in skeletal class II

Angle of convexity

Nasion-point A to point A – pogonion.

Average value: 0o ( -8.5o - 10o).

Significance:

- Positive angle suggest a prominent maxillary dental

base in relation to mandible.- Negative angle is indicative of prognathic profile

A-B plane angle

Point A – point B to nasion – pogonion.

Average value: -4.6o ( -9 to 0o)

Significance:

Indicative of maxillo mandibular

relationship in relation to facial plane.

- Negative since point B is positioned

behind point A.

- Positive in class III malocclusion or

class I malocclusion with mandible

prominence

Y-Axis

Sella gnathion to F.H. plane.

Average value: 59.4o ( 53 to 66o)

Significance:

Indicates growth pattern of a individual

- Increased in Class II facial patterns – Vertical growth

pattern of mandible

- Decreased in Class III facial patterns – Horizontal growth

pattern of mandible

Mandibular plane angle

Intersection of mandibular plane with F.H.

Plane.

Average value: 21.9o ( 17 to 28o)

Dental Parameters Cant of occlusal plane

Occlusal plane to F.H. plane

Average value: 9.3o ( 1.5o - 14o)

Gives a measure of slope of occlusal plane relative

to F.H. Plane.

Inter incisal angleAngle between long axes of upper and lower incisors.

Average value: 135.4o ( 130o - 150.5o)

Increased in class I bimaxillary protrusion.

Incisor occlusal plane angle

This is the inside inferior angle formed by the intersection

between the long axis of lower central incisor and the

occlusal plane and is read as a plus or minus deviation from a

right angle

Average value: 14.5o ( 3.5o - 20o)

An increase in this angle is suggestive of increased lower incisor

proclination.

Incisor mandibular plane angle

This angle is formed by intersection of the long axis of the lower incisor and the mandibular plane.

Average value: 1.4o (-8.2o - 7o)

An increase in this angle is suggestive of increased lower incisor proclination.

Upper incisor to A-pog line

This is a linear measurement between the incisal edge of the

maxillary central incisor and the line joining point A to

pogonion.

Average value: 2.7 mm(-1 - 5 mm)

The measurement is more in patients presenting with upper

incisor proclination.

Soft tissue Analysis

Rickett’s E-plane

› Line joining the soft tissue chin and tip of nose. In

balanced face, lower lip lie 2mm (± 2mm) anterior to

this line and upper lip little further posterior

Facial plane› Line between soft tissue nasion and soft tissue chin. In

well balanced face, the Frankfort plane should bisect the facial plane at an angle about 86o and point A should lie on it

The Holdaway line

› Line from the soft tissue chin to upper lip. In a well

proportioned face, if extended, should bisect the

nose

An introduction to orthodontics, Laura Mitchell (3rd

edition)

Radiographic Cephalometrics, Alexander Jacobson

Contemporary Orthodontics, William R. Proffit (4th

edition)

Comparisons of the Consistency and Sensitivity of Five Reference Lines of the Horizontal Position of the Upper and Lower Lip to Lateral Facial Harmony, The Orthodontic Cyberjournal