Fifth stage‐Orthodontic

Assist. lec. Rawaa saadoon HashimPOP department

College of DentistryUniversity of Basrah

Cephalometric

Lecture 4

Objectives:# Definition of cephalostat as machine.

#Indication of cephalometric analysis.

#Identification of cephalometric land marks.

# soft tissue analysis.

# Assessing growth and treatment changes.

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Introduction

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Cephalometry is the analysis andinterpretation of standardized radiographsof the facial bones. In practice,cephalometrics has come to be associatedwith a true lateral view.

For definition of the soft tissue outline of theface, either thin layer of barium paste canplaced down the central axis of the face or analuminum wedge positioned so as to attenuatethe beam in that area.

The Cephalostat

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The cephalostat consists of an X-raymachine which is at a fixed distancefrom a set of ear posts designed to fitinto the patient’s external auditorymeatus.

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Indication for cephalometric evaluation: 

Monitoring the progress of treatment

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An aid to diagnosis

A pre-treatment record

Research purposes

Evaluating cephalometric radiographs:

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Hand tracing: Proprietary acetate sheets are the best medium as their

transparency facilitates landmark identification.

A sharp pencil should be used.

The acetate sheet should be secured onto the film with masking tape, which does not leave a sticky residue when removed.

The tracing should be oriented in the same position as the patient was when the radiograph was taken, i.e. with the Frankfort plane horizontal.

For landmarks which are bilateral (unless they are directly superimposed) an average of the two should be taken.

Digitizing• digitizer which comprises an illuminated radiographic

viewing screen which is connected to the computer

• Information from a lateral cephalometric film is entered into computer by mean of cursorused to record the horizontal and vertical (x, y) co-ordinates of cephalometricpoints and bony and soft tissue outlines.

• Specialized software can then be employed to utilize the information entered to produce a tracing and/or the analysis of choice

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• Cephalometric analysis is also of value in identifying the component partsof a mal-occlusion and probable etiology factors, it is useful when a tracingis finished to reflect why that individual has that particular mal-occlusion

• It should always be remembered that cephalometric is an adjunctive tool toclinical diagnosis, and differences of cephalometric values from the averageare not in themselves an indication for treatment.

• Cephalometric errors can occur owing to incorrect positioning of thepatient and incorrect identification of landmarks.

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Measurements Mean value

SNA 81˚SNB 78˚

ANB 3˚

Upper incisor to maxillary

plane

109˚

Lower incisor to mandibularplane

93˚

Inter incisal angle 135˚

MMPA 27˚

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Cephalometric analysis: general points 

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Point A

Anterior nasal spine (ANS)

Anatomical Porion (Pr)Posterior Nasal Spine (PNS)

Sella (S)

SN line

Frankfort plane

Mandibular plane

Maxillary plane

Point B

Nasion (N)

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•Angle ANB

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Antero-posterior skeletal pattern

ANB < 2˚ Class III

2˚ < ANB <4˚Class I

ANB >4˚ Class II

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Vertical skeletal pattern: 

• The Maxillary–Mandibular PlanesAngle. The average angle between themaxillary plane and the mandibularplane (MMPA) is 27 ±4°.

• Frankfort Mandibular Planes Angle(FMPA). The average angle is 28 ±4°.

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Incisor positionIncisor position

The average value for the angle form between the upper incisor & the maxillary plane is 109˚. The average value for lower incisor angle is 93˚ for an individual with an average MMPA 27˚.

NOTE: there is a relationship between the MMPA & the lower incisor angle.

Soft tissue analysis

• Rickett’s E-plane

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Assessing growth and treatment changes

• compare radiographs either of groups of patient for research purposesor of the same patient over time to evaluate growth & treatmentchanges

• During treatment it can be helpful to determine the contributions thattooth movements & /or growth have made to the correction & to helpensure that, where possible, a stable result is achieved example cl IIdiv I.

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The advantage of standardizing lateral cephalometric radiograph

Cranial base

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The maxilla

•Growth of the maxilla occurs on all surfaces by periostealremodeling

• for the purpose of interpretation of growth & /ortreatment changes the least affected surface is the anteriorsurface of the palatal vault, although the maxilla iscommonly superimposed on the maxillary plane at PNS.

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The mandible

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Mandibular landmarks which change least with growth(in order of usefulness): The innermost surface of cortical bone of the symphysis. The tip of the chin. The outline of the inferior dental canal. The crypt of the developing third permanent molars from the time

of commencement of mineralization until root formation begins.

Recap:• Cephalometry as machine, indications and analysis.

• Evaluating cephalometric radiographs by hand tracing and

digitizing.

• soft tissue analysis.

• Assessing growth and treatment changes.

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