EXTRAORAL RADIOGRAPHY-CEPHALOMETRY-

PRESENTER:

FAIRUZ BINTI MOHD ZIN

NOOR EVIDIANA BINTI ZOLKOFFELI

NOOR FARAHUDA BINTI MUSTAFAH MAAROF

OVERVIEW

Introduction Indications Principles Equipment Main cephalometric planes and landmarks Procedures References

INTRODUCTION

Cephalometric radiography = standardized and reproducible form of skull radiography used extensively in orthodontic to assess the relationships of the teeth to the jaws and the jaws to the rest of the facial skeleton. (Whaites & Drage, 2013)

Orthodontic = Greek word (orthos means ‘straight, perfect or proper’ ; dontos means ‘teeth’)

a branch of dentistry that specializes in treating patients with improper positioning of teeth when the mouth is closed (malocclusion), which results in an improper bite

Includes treating and controlling various aspects of facial growth (dentofacial orthopaedics) and the shape and development of the jaw.

(Medical News Today, 2014)

Mainly used to study of growth patterns in the craniofacial complex.

Concern on malocclusion and dentofacial deformity (Proffit, Fields & Sarver, 2007)

Malocclusion Abnormal alignment of the teeth and the

way in which the upper and lower teeth fit together.

The upper teeth overlap slightly outside the lower teeth in normal person in which allows the projections (cusps) on each tooth to fit in the depressions of the opposite tooth.

Causes:

Habitual thumb-sucking and/ or tongue thrusting (push the tongue up against the front teeth)

Size mismatch between jaw and teeth

Lost teeth

Certain birth defects of the jaw or fracture

(Murchison, 2014)

(Smile Simplicity, 2015)

Dentofacial deformity

An imbalance of the position, size, shape, or orientation of the bones that comprise upper and lower jaws due to skeletal growth disturbance

Causes:

Childhood fractures of the jaw

Muscle dysfunction

Genetic influences

Other disease (eg. Acromegaly, Rheumatoid Arthritis, Hemimandibular Hypertrophy, Malformed and Supernumerary Teeth)

(Proffit, Fields & Sarver, 2007)

INDICATIONS

Orthodontics

Initial diagnosis to confirm of underlying skeletal and tissue deformities

Treatment planning

Monitoring treatment planning

Appraisal of treatment progress

Research purposes

Orthognathic surgery

Pre-operative evaluation of skeletal and soft tissue patterns

Assist in treatment planning

Post-operative appraisal of the result of surgery and long term follow-up study

Research purposes

(Whaites & Drage, 2013; Mitchell, 2013)

PRINCIPLES

Cephalostat is a machine that holds the head in a set position in relation to x-ray tube and the film

Place at patient’s external auditory meati and the central beam is directed towards the ear rods and to the center of film.

Patient’s head in vertical axis is standardized by ensuring patient’s Frankfort plane is horizontal, manually or placing a mirror at the patient’s head level

Frankfort plane : line joining porion and orbitale

!!!!!Be ensure that the patient’s midsagittal =(1) Vertical and parallel to the

film (lateral cephalometric)(2) Vertical and perpendicular to

the film (PA Cephalometry)

(Gill & Naini, 2011)

EQUIPMENT

Film size : 18 x 24 cm (commonly used)

Intensifying screen (usually 18 x 24 cm)

Extraoral machine with cephalostat

Head stabilizing and ear rods- Ensure standardized patient position- To stabilize patient’s head To attenuate the x-ray

beam selectively in the facial soft tissue region

(Iannucci & Howerton, 2012)

Main Cephalometric Planes

SN plane (sella to nasion)

Mandibular plane

Maxillary plane

Frankfort plane

Main Cephalometric points

1) Sella (S) - The centre of the sella turcica, (determined by inspection).

2) Orbitale (Or) - The lowest point on the infraorbital margin.

3) Nasion (N) - The most anterior point on the frontonasal suture.

4) Anterior nasal spine (ANS) - The tip of the anterior nasal spine.

5) Subspinale or point A - The deepest midline point between the anterior nasal spine and prosthion.

6) Prosthion (Pr) - The most anterior point of the alveolar crest in the premaxilla, usually between the upper central incisors.

7) Infradentale (Id) - The most anterior point of the alveolar crest, situated between the lower central incisors.

8) Supramentale or point B - The deepest point in the bony outline between the infradentale and the pogonion.

9) Pogonion (Pog) - The most anterior point of the bony chin.

10)Gnathion (Gn) - The most anterior and inferior point on the bony outline of the chin, situated equidistant from pogonion and menton.

11)Menton (Me) - The lowest point on the bony outline of the mandibular symphysis.

12)Gonion (Go) - The most lateral external point at the junction of the horizontal and ascending rami of the mandible. Note: The gonion is found by bisecting the angle formed by tangents to the posterior and inferior borders of the mandible.

13)Posterior nasal spine (PNS) - The tip of the posterior spine of the palatine bone in the hard palate.

14)Articulare (Ar) - The point of intersection of the dorsal contours of the posterior border of the mandible and temporal bone.

15)Porion (Po) - The uppermost point of the bony external auditory meatus, usually regarded as coincidental with the uppermost point of the ear rods of the cephalostat.

(Whaites, 2003)

PROJECTIONSThe patient is positioned within the cephalostat, with the sagittal

plane of the head vertical and parallel to the film and with the Frankford plane horizontal. The teeth should generally be in

maximum intercuspation.

The head is immobilized carefully with the apparatus with the plastic ear rods being inserted gradually into the external auditory meati.

The Aluminium wedge is positioned to cover the anterior part of the film.

The equipment is designed to ensure that when the patient is positioned correctly, the x-ray beam is horizontal and centred on

the ear rods

- -

The head-stabilizing apparatus of the cephalostat is rotated through 90°

The patient is positioned in the apparatus with the head tipped forwards and with radiographic baseline horizontal

and perpendicular to the film

The head is immobilized within the apparatus by inserting the plastic ear rods into the external auditory meati

The fixed x-ray beam is horizontal with the central ray centred through the cervical spine at the level of the rami

of the mandible

Late

ral

Cephalo

metr

y

Poste

roante

rior

Cephalo

metry

(Whaites & Drage, 2013;Iannucci & Howerton, 2012)

A – Proper patient and film positioning viewed from the front, side and top

B – Lateral Cephalometric radiograph

Resultant image: Structures on the side near the image receptor are magnified less than the structures on the side far from image receptor. Bilateral structures close to the midsagittal plane demonstrate less discrepancy in sized compared with bilateral structures farther away from the midsagittal plane. Structures close to the midsagittal plane (clinoid processes and inferior turbinates should be nearly superimposed. (White & Pharoah, 2009)

Late

ral

Cep

halo

met

ry

(Iannucci & Howerton, 2012)

Cranial collimator shadow

Head support

Ear rod

Aluminium wedge filter

Cervical spine collimator shadow

(Whaites, 2003)

Note the images of the ear rods should appear superimposed on each other. Other shadows of cephalostat equipment and collimator are indicated.

A – Proper patient and film positioning viewed from the side, back and top

B – Posteroanterior Cephalometric radiograph

Resultant image:The midsagittal plane (represented by an imaginary line extending from the interproximal space of the central incisors through the nasal septum and the middle of the bridge of the noise) should divide the skull image into two symmetric halves. The superior border of the petrous ridge should lie in the lower third of the orbit. (White & Pharoah, 2009)

Poste

roan

teri

orC

ep

halo

metr

y

(Iannucci & Howerton, 2012)

ADDITIONAL NOTES ON PROJECTIONS OF EXTRAORAL

RADIOGRAPHY =)

(White & Pharoah, 2009)

References Gill, D. S. & Naini, F. B. (2011). Orthodontics – Principles and Practice (eds). United Kingdom: John Wiley and

Sons - Blackwell

Iannucci, J. M. & Howerton (2012). Dental Radiography – Principles and Technique (4th ed.). United States of America, Elsevier Saunders

Medical News Today (2014). What is Orthodontics? Retrieved Apr 05, 2015 from http://www.medicalnewstoday.com/articles/249482.php

Mitchell, L. (2013). Introduction to Orthodontics (4th ed.). United Kingdom: Oxford University Press

Murchison, D. F. (n.d.). Mulocclusion – misaligned teeth. Retrieved Apr 05, 2015 from http://www.merckmanuals.com/home/mouth-and-dental-disorders/symptoms-of-oral-and-dental-disorders/malocclusion

Proffit, W. R. , Fields, H. W. & Sarver, D. M. (2007). Contemporary Orthodontics (4th ed.). Canada: Mosby Elsevier

SmileSimplicity (2015). What is Mulocclusion? Retrieved Apr 05, 2015 from http://www.smilesimplicity.com/malocclusion/

Whaites, E. & Drage, N. (2013). Essentials of Dental Radiography and Radiology (4th ed.). Retrieved from https://books.google.com.my/books?id=lSSwAAAAQBAJ&pg=PR4&dq=Essentials+of+Dental+Radiography+and+Radiology+4th+ed&hl=en&sa=X&ei=ya9hVafRM5STuASi5YDACg&ved=0CBwQ6AEwAA#v=onepage&q=Essentials%20of%20Dental%20Radiography%20and%20Radiology%204th%20ed&f=false

White, S. C. & Pharoah, M. J. (2009). Oral Radiography – Principles and Techniques (6th ed). United States of America: Mosby Elsevier