Oral Radiology Unit 2

paralleling technique is also known as?

• right angle technique

• long cone technique

• extension cone paralleling technique

how is the receptor placed when using paralleling technique

placed parallel to long axis of tooth being radiographed

how is the central ray placed when using paralleling technique

perpendicular to the receptor and long axis of tooth

can be used to keep the receptor parallel with the long axis of the tooth

beam alignment device

object-receptor distance description

object = tooth

receptor = film/sensor

O-R distance must be ___ to keep the receptor parallel with the long axis of the tooth

increased

target-receptor distance description

target = tungsten target

receptor = film/sensor

T-R distance must be ___ to ensure that only the most parallel rays will be directed towards the object

increased

what is the XCP beam alignment device used for

• PA (anterior/posterior)

• BW

• endodontics

beam alignment devices

• XCP

• Rinn Snap-A-Ray

• Stabe Bite Block

not digital, film only, styrofoam, disposable

Stabe Bite Block

what size receptor is used for the anterior w/ paralleling

1 and 2

what size receptor is used for the posterior w/ paralleling

2

when taking more than 3 maxillary anterior images what size receptor is used

1

what position should the receptor be when taking an anterior

vertical

what position should the receptor be when taking an posterior

horizontal

rule for paralleling technique receptor placement

must be placed so that it covers entire area you want to capture

rule for paralleling technique receptor position

should be parallel to long axis of tooth (away from tooth, toward middle of oral cavity)

rule for paralleling technique vertical angulation

central ray must be perpendicular to receptor

how should the PID be moving

in up & down motion

PID pointed up = ?

negative vertical angle

PID pointed down = ?

positive vertical angle

rule for paralleling technique horizontal angulation

central ray must be aimed thru contacts of the teeth

rule for paralleling technique receptor exposure

x-ray beam must be centered on the receptor → all areas of receptor are exposed

should anterior or posterior images be taken first?

anterior

if pt has a shallow palate what modifications can be made?

• 2 cotton rolls can be used, one on each side of bite block

• adjust vertical angle by 5-15 degrees

if pt has a maxillary torus what modification can be made?

place receptor on far side of bony growth

if pt has a mandibular tori what modification can be made?

place receptor between tori, NOT on top

if pt has a sensitive mandibular premolar region what modification can be made?

film only - “soften curve of lower edge”

advantages of paralleling technique

• accurate (less distortion than bisecting)

• simplicity - use XCP

• duplicate - the technique

disadvantages of paralleling technique

• receptor placement may be difficult

• beam alignment devices can be large, bulky, uncomfortable

the 2nd method used the take PA radiographs

bisecting technique

divide into 2 equal parts

bisect

divided tooth in 2 equal parts

long axis of tooth

central portion of the primary beam of x-radiation

central ray

the principles of the bisecting technique are based on what?

rule of isometry

when using the bisecting technique how is the receptor placed

along lingual side of tooth

when using what technique is there a point where the receptor contacts the tooth

bisecting technique

what must you visualize when using the bisecting technique

a line that bisects the angle formed by the receptor and the long axis of the tooth

a line that bisects the angle formed by the receptor and the long axis of the tooth

imaginary bisector

how should you direct the central beam when using bisecting technique

perpendicular to the imaginary bisector - two equal triangles are formed

the two triangles formed when using the bisecting technique are ___ and ____

right triangles & congruent (equal)

use of a receptor holder is indicated when using the bisecting technique. Why?

stabilization and patient safety (reducing exposure because pt doesn’t have to hold it)

available receptor holders for bisecting technique

• Rinn BAI

• Stabe

• Snap-A-Ray

• Finger holding (digital method)

not recommended, only if you have to

finger holding

receptor size used for bisecting technique

same as paralleling - size 1 or 2

• book says 2

the term used to describe the alignment of the central ray, both vertically and horizontally

angulation

an aiming ring used with a BAI or XCP instrument will dictate ___?

proper angulation

without an aiming ring the ____ must determine both the horizontal and vertical angulation

radiographer

moving the tube head side to side

horizontal angulation

same principle for paralleling, bisecting, and bitewing techniques

horizontal angulation

if incorrect horizontal angulation occurs, the teeth will be __?

overlapped

moving the PID up and down

vertical angulation

measured in degrees ( 0-90 + or - ) and is marked on the side of tube head

vertical angulation

central ray is directed to it is perpendicular to the receptor and long axis of the tooth

paralleling technique

central ray is directed perpendicular to the imaginary bisector

bisecting technique

when taking a bitewing what should the vertical angulation be

+10 degrees

(teach says 5-10 degrees)

correct vertical angulation will give you an image that is __?

the same length as the tooth

incorrect vertical angulation will produce an image that is either shorter than the subject

foreshortened

incorrect vertical angulation will produce an image that is longer than the subject

elongated

due to too much vertical angulation or from a central ray that is directed perpendicular to the receptor and not the imaginary bisector

foreshortened images

PID is too steep (close to 90 degrees)

foreshortened images

due to too little vertical angulation or if the central ray is perpendicular to the long axis of the tooth and not the imaginary bisector

elongated images

PID is too flat (close to 0 degrees)

elongated images

rule for bisecting technique receptor placement

receptor must cover the area to be examined

rule for bisecting technique receptor poistion

receptor placed against lingual surface of tooth

when using bisecting technique the occlusal edge of the film should be about how far beyond the incisal or occlusal edge

1/8 “

when using bisecting technique the apical edge of the receptor must rest on the ___ for maxillary projections

palate

when using bisecting technique the apical edge of the receptor must rest on the ___ for mandibular projections

alveolar tissue

central ray is perpendicular to imaginary bisector

vertical angulation

central ray directed thru the contact areas of the teeth

horizontal angulation

if you do not center the beam on the receptor to make sure all areas of the receptor are exposed you will have ___?

cone cut

patient preparation

• explain procedure

• chair to comfortable working height

• adjust pt headrest to comfort

• max. arch parallel to floor

• midsagittal plan perpendicular to floor

equipment preparation

• correct exposure factors (time, mA, kVp)

• open sterile packages

exposure sequence

anterior 1st, posterior, bitewings last

if you do not follow an exposure sequence what could happen

omit an area or double expose an area

when doing anterior first, start with ___ and end with ___

UR canine & LR canine

when doing posterior what side do you start with

right side : UR - PM then M LR - PM then M.

the go to left side: UL - PM then M LL - PM then M

(when not using XCP)

advantages of bisecting technique

• can be used without receptor holding device

• decreased exposure time because of short cone

disadvantages of bisecting technique

• image distortion - short cone = more magnification

• angulation problems - hard to visualize imaginary bisector

• unnecessary exposure - when using finger holding method

used to examine interproximal surfaces and crestal bone

bitewing technique

BW radiographs include ___?

crowns of max and mand teeth on same film

beam alignment devices used for BW technique

XCP and Bitewing tab

what size BW receptor is used for pediatric dentition under age 6

0

what size BW receptor is used when 6 yr molars erupt (1st molar)

1

what size BW receptor is used when 12 yr molars erupt (2nd molar)

2

not really used, longer than size 2 but not wider

size 3

considered the “bitewing receptor”

size 3

premolar BW placement

front edge should capture distal of canine

Molar BW placement

front edge should capture distal of 2nd premolar

rules for BW tech

• correct receptor placement

• occlusal plan is in middle of receptor

• correct horizontal angulation

• correct vertical angulation (+10)

• PID is centered over receptor to avoid cone cut

exposure sequence for BW with PAs

take bitewings at end of FMX

exposure sequence for BWs alone

premolar then molar

used to check crestal bone in pts with moderate to severe periodontal disease

vertical BWs

if a pt had all right side premolars extracted what modification should be made for BW

just one BW on one side

if a pt. has an edentulous space what modification should be made for a BW

place cotton roll in that space so receptor doesn’t fall

if pt. has a boney growth what modification should be made for a BW

do NOT put on top of boney growth, put past/beyond/between