Dental imaging

Question 1

What is the enamel?

Answer 1

Hard white outer part of the tooth

Question 2

What is the dentin?

Answer 2

Hard tissue containing microscopic tubes

Question 3

What is the pulp cavity?

Answer 3

Soft ‘living’ inner structure – contains blood vessels and nerves

Question 4

What is gingiva?

Answer 4

Word for gums

Question 5

What are the periodontal ligament? and periodontal membrane

Answer 5

Tissue that helps hold the teeth tightly to the jaw

Question 6

What is the cementum?

Answer 6

Connective tissue layer that binds the roots of the teeth firmly to the gums and jaw (maxilla or mandible)

Question 7

Development of teeth stages

Answer 7

A initiation (bud stage) Growth
B Proliferation (cap stage) Growth
C morpho differentiation, histodifferentiation (bel stage) Growth
D Apposition Calcification
E (before emergence) Eruption
F (after emergence) Eruption
G Attrition
H Attrition

Question 8

Teeth, how many does an adult have?

Answer 8

An adult typically has 32 teeth;
Incisors (x 8)
Canines (x 4)
Premolars (x 8)
Molars (x 8)
Wisdom Teeth (x 4)

Question 9

How many teeth do children have?

Answer 9

A child typically has 20 primary (milk/baby) teeth;
Incisors (x 8)
Canines (x 4)
Molars (x 8)

Question 10

Tooth Eruption, when do most erupt?

Answer 10

Most have erupted by the age of 13, with the exception of wisdom teeth which generally erupt at 18

Question 11

What are the Muscles of Mastication?

Answer 11

The primary muscles include:
Masseter
Temporalis
Lateral pterygoid
Medial pterygoid

Question 12

What examinations do we do for Intra-Orals

Answer 12

Periapical
Show all of a tooth, including the surrounding bone

Bitewings
Show only the crowns of the teeth and the adjacent alveolar crests

Occlusal
An area of teeth and bone

Question 13

Periapical – Paralleling Technique

Answer 13

Image receptor placed in packet, then in a holder & positioned in the mouth parallel to the long axis of the tooth under investigation.

X-ray beam directed towards the middle of the film at right angles (both vertically & horizontally).

Receptor holder means patient does not have to hold the IR.

Question 14

Tube Head of the Intra-Oral Machine (note flashcard)
Small, compact and lightweight

Stationary anode x-ray tube
Suitable for short, lower dose studies
Space saving

Answer 14

Tube Head of the Intra-Oral Machine (note flashcard)
Small, compact and lightweight

Stationary anode x-ray tube
Suitable for short, lower dose studies
Space saving

Question 15

Periapical – Bisecting-Angle Technique

Answer 15

Used when unable to use paralleling technique – often due to large receptor size or patient anatomy – PATIENT COMFORT

Receptor is positioned as close to the lingual surface of the teeth, resting in the palate or in the floor of the mouth.

The plane of the IR and long axis of the tooth form an angle at the point where the IR is in contact with the tooth – an imaginary line bisects this angle, and CR is directed perpendicular to this

The need for these projections can occur if patient anatomically has a shallow palate, shallow or tender floor of the mouth, tongue tie

Question 16

Paralleling vs Bisecting-Angle

Answer 16

Paralleling Technique
Minimises geometric distortion
Presents teeth and supporting bone in true anatomical relationships
Increased image sharpness
Minimal magnification

More distortion because the IR and teeth are not parallel to each other
Harder to position central ray – more difficult to visualise bisecting line
IR is often less stable as finger may be used to hold it in place

Question 17

Upper Standard Occlusal technique

Lower 90° Occlusal technique

Answer 17

Upper Standard Occlusal
Bean pointed at nasal angle and IR is flat in patients mouth, there is about a 65 degree angle for the IR to tube.

Lower 90° Occlusal
Patients head is tilted back, and IR is flat in patient`s mouth. The beam is aimed at the chin and there is about a 90 degree angle from the IR to the tube.

Question 18

OPG - Orthopantomogram

AKA dental panoramic x-ray (DPR)
Panoramic scanning dental x-ray of the upper and lower jaw
2D view of the view from ear to ear
Tomographic technique

What anatomy and pathology could you see using this?

Answer 18

Anatomy – Demonstrates the nasal area, maxillary sinuses, TMJs, teeth, maxilla, mandible and surrounding bone
Pathology – Can demonstrate cysts, tumours, bone irregularities, impacted teeth, amongst other pathologies
Trauma

Question 19

Pros and Cons of OPG

Answer 19

Pros
Minimal exposure
Quick and simple to perform
Patient cooperation is good
Useful in patients with strong gag reflex

Cons
Should not be used as a replacement for intra-oral imaging which are better at detecting caries/cavities
Overlapping of teeth in pre-molar region
Tomographic blur
Magnification
Shadow of cervical spine
Cost of equipment

Question 20

What is the frankfort plane

Answer 20

Frankfort plane passes through the floor of the orbit and the external auditory meatus.

Question 21

Patient Preparation and Positioning for dental imaging OPG

Answer 21

-Any bulky clothing or metallic objects around the head and neck should be removed
Consider scarves, chunky coats, glasses, hair clips, hearing aids, tongue studs, nose jewellery, necklaces and earrings

-Equipment should be in start position and raised to an appropriate height for patient
-Explanation of the procedure including length of exposure should be given clearly
-Bite-block or chin rest should be positioned on the equipment
-Patient should walk straight into the machine, holding onto handles if necessary.
-Patient’s head should be tilted down towards the floor so that the Frankfurt plane is parallel to the floor

-Positioning lights should now be turned on – you may like to ask the patient to close their eyes;
-Sagittal plane line should be down the MSP of the face
-Antero-posterior light should be centred distal to the upper lateral incisor

-Patient should bite onto the bite-block groove with upper and lower incisors (if patient has an underbite, upper incisors should be in the groove)
-Standing behind the patient, check the symmetry of their position – adjust if necessary by moving shoulders
-Close head restraints
-Make any fine adjustments to position
-Patient should now close their mouth and press their tongue to the roof of their mouth (prevents a readiolucent shadow of air appearing over the upper teeth)
-Remind patient they must stay still for about 20 seconds and then expose

Question 22

Lateral Cephalogram Patient Preparation and Positioning

Answer 22

SID fixed between 150-200cm to minimise magnification
-Bulky or metallic objects over area of interest should be removed
-Patient sits or stands within the unit with the sagittal plane vertical and parallel to the image receptor
-Frankfort plane parallel to the floor
-Head is immobilised using earpieces which are carefully inserted into the EAMs
-Nose support positioned against the nasion
-Patient is instructed to close the mouth and bite together on their back teeth (known as in centric occlusion)
-Lips should be relaxed
-Direction of central ray is fixed HB

Question 23

Examples of justification for OPG

Answer 23

Impacted teeth
Assessment of unerupted teeth
Assessment of lesions
Evaluation of Trauma
Evaluation Post-Operatively
Dental Caries
Dental Abscess