8/11/2019 Dental Equip 03

1/6

1

Intermediate Diagnostic Imaging Studies 1Dental Equipment- Overview

Marc Griffiths

Types of dental equipment

Dental Panoramic

Tomography (DPT)

Lateral Cephalometry

Intra-oral

Dedicated skull

equipment

? CT MPR

Reconstruction

DPT - Design Features

Demonstration of a slice of the patients head

rather than its whole

X-ray tube and cassette are linked simultaneous

movement around a moving pivot.

During exposure, cassette moves around the face

of patient & X-ray tube swings around the head

posteriorly

Only the structures within the focal plane (focal

trough) are projected sharply onto the film

everything else is blurred out

Focal plane

Film moves in front of collimating slit so

exposure of film occurs in a band from one

side to the other

Only a narrow band of film is exposed as

machine rotates.

Dental Panoramic Tomography

Positioning important toensure optimum imagequality

Head should not be rotated(causes asymmetry in

image) Frankfurt plane horizontal

Important to removeearrings and necklaces,braces and dentures

8/11/2019 Dental Equip 03

2/6

2

Panoramic tomographyequipment

Specialised units capableof panoramic views of thewhole jaw or parts of jaw

Some systems canperform localisedcoronal/sagittaltomograms through thedental arch and somecan be converted for usein cephalometry

OPG/Lat Ceph Equipment- Design Features

Power supply/tube design kVp range 60 -90 kVp

Tube Current Low (10-15 mA) preferably a selection should be available

Usually Stationary Anode

Low weight > stress on units drive mechanism

Interlock mechanisms Cassette in position

Tube at start position

Positioning aids Cross Lights

Mirror

Flat cassette utilised in modern units

Dual function or dedicated to either DPT orCeph

Slit beam

emerges from

tube housing

Further slit

collimation

before hitting

film/sensor

Features

Moveable up/down

Handles aid

immobilisation

Cephalometry

Cephalometric lateral - a lateral radiograph of

the whole face to show the relationship of the

upper and lower jaws, the soft tissue profile of

the face, and various bony landmarks

Assessment and follow-up of facial deformity Multiple serial radiographs taken, often over

years as treatment progresses, therefore

reproducibility important

8/11/2019 Dental Equip 03

3/6

3

Lateral Cephalometry Equipment

Head Grip

Immobilisation

Reproducibility

Long FFD for cephs to reduce magnification

Specialised features

Filtration (Duralmin)/Facial Contouring (> dose)

AED

Digital Images

Measurement tools (Radiopaque slide)

Emergency stop switches

Intra-oral Equipment

Dental x-ray sets

Dedicated units with low

power stationary anode tube

Tube is deployed on an

extendable arm for easierpositioning

kVp of 60-70 is normallyused (not less than 60kVp)

Tube current usually fixed -

7.5-10 mA

Exposure is normally varied

by altering the exposure time

Usual range 0.1-0.5 sec but

over 1sec possible

Intra-oral Equipment - Design Features

Power supply/tube design Basic design

Short FFD

minimum focus-skin distance of200mm (NRPB)

Self-Rectified / full waverectification - old equipment

New equipment - constantpotential generator preferable

Rectangular collimation shouldbe an option

Long cable for exposureswitch

Dental x-rayunit

Flexi-arm design

Angle indicationDevice

Patient stability aids

Head rest

Accessory Features

Positioning aids

Self- Rectified (Half-wave) dental unitsFull-wave / Two Pulse dental units

8/11/2019 Dental Equip 03

4/6

4

Constant potential generators

High frequency generators offer effectively constant

potential

Less than 1% voltage ripple

Cross infection control

Essential that equipment easily cleaned

Bite block should have disposable plastic

sheath

Sanitiser should be available to clean ceph

ear pieces

Digital dental equipment

Advantages:

No chemical processing of films

Almost instantaneous image display

Instantaneous positioning errors can be spotted

Digital images may be windowed.

Optimisation of individual patient dose

DICOM 3.0 compliant

Digital images can be sent anywhere in the world!

Example of digital intra-oral unit

Digital sensor may reduce patient exposure by up to 95 percent(Ref: http://www.planmeca.com/pdf/DXIflyen_0203.pdf)

Charged Coupled Devices (CCD)

Various sizes

Planmeca Dixi2 Digital Intraoralsystem

Resolution

Normal

13 lp/mm,

Pixel size 38 m

Enhanced

26 lp/mm

Pixel size 19 m

Dynamic range

14bit (16384 grey tones)

File sizes

26x37mm

1.3MB/5.3MB

8/11/2019 Dental Equip 03

5/6

5

Example of software used/ images obtained Digital OPG units

Planmeca Dimax2Digital DPT andCephalometricsystem

Direct digital CCD

(charge coupled

device)

Resolution 6 lp/mm

Pixel size 33 m

File size 4.5-7.7 MB

for DPT

Lateral Cephalostat

Digital manipulation of data

CT Equipment

Multi-Slice CT scanners

Fast image acquisition

Exquisite isotropic resolution

Multi Planar Reconstruction

Excellent planning for Facial Injury /

cancer patients (prosthesis)

Examples of CTreconstruction

8/11/2019 Dental Equip 03

6/6

6

References & furtherinformation

http://www.xograph.com

http://www.planmeca.com http://www.ctscan.co.uk/dent_frames_images.html

Carter p., (1994) Chesneys Equipment for Student Radiographers, 4TH

Edition, London, Blackwell Scientific Publications

Stockley S., (1992) A Manual of Radiographic Equipment, London,

Churchill Livingstone

Essentials of Dental Radiography and Radiology Eric Whaites

Churchill Livingstone

A Guide to Dental Radiography (Fourth Edition) Mason andBourne Oxford University Press

Guidance Notes for Dental Practitioners on the Safe Use of X-ray Equipment NRPB 2001