Normal Radiographic Anatomy

Question 1

List the tissue involved in anchorage of the
tooth to the bone of the jaw?

Answer 1

• Gingiva
• Periodontal ligament
• Alveolar Bone
• Cementum

Question 2

What creates the
distinct lamina dura on radiographs?

Answer 2

The radiographic shadow of the Cribriform
plate (bone lining the alveolus)

Question 3

What varies significantly
with the angle of the incident x ray beam?

Answer 3

The shape and size of teeth

Question 4

When x-raying 3 rooted teeth what can help to distinguish roots?

Answer 4

With three rooted teeth, change the angle of incident beam to separate and distinguish different roots and
associated pathology

Question 5

The age of a patient can be estimated by?

Answer 5

The size of the root canals: ongoing
deposition of dentin by odontoblasts,
creates progressively narrower root
canals as an animal ages.

Question 6

What is often superimposed on especially the
third and fourth maxillary premolar?

Answer 6

The zygomatic arch.

Question 7

How long is the infraorbital canal in the cat?

Answer 7

The infraorbital canal is very short in cats (2-3
mm)

Question 8

The infraorbital foramen in cats is very close to what?

Answer 8

The orbital margin (and the orbit) Dorsal the
maxillary third premolar

Question 9

The infraorbital foramen in dogs is where?

Answer 9

The infraorbital foramen in dogs is dorsal to distal aspect of the third premolar

Question 10

Discuss how the palatal shelf appears on radiographs?

Answer 10

• The angle within the nasal cavity between the body of the
  maxilla and it’s perpendicular palatal process created is
  prominent radiographic landmark.
• The position of this radiopaque line on radiographs is closely
  associate with the mid portion of the ipselateral maxillary
  canine tooth.
• This relationship with the canine on radiographs, does not
  change much with the position of the incident x-ray beam

Question 11

What are the palatine fissures?

Answer 11

The palatine fissures are slit like openings in the bone of the palate,
on both sides of the palatal midline.

Question 12

What is the function of the palatine fissures?

Answer 12

Allows communication of the neurovascular supply between the
oral and nasal cavities.

Question 13

Where do the mandibular canals run and how are they viewed on radiographs?

Answer 13

The mandibular canals run parallel to the ventral margin of the mandibles, and occupies the ventral third of the mandibles. They are clearly
visible on radiographs.

Question 14

Do dogs and cats have maxillary sinuses?

Answer 14

Dogs and cats do not have true maxillary sinuses but open recesses in the caudo-lateral aspects of the nasal cavities.

Question 15

How do the nasal turbinates attach to the nasal cavity?

Answer 15

The nasal turbinates are attached via the chonchal crests to the to the lateral walls the nasal cavity.

Question 16

How do the conchal crests appear radiographically?

Answer 16

• Radiographically a radiopaque line closely associated with the apex of the canine
• Position does not change when the incident x-ray angle changes

Question 17

What are the characteristics of deciduous dentition radiographically?

Answer 17

Both Deciduous and permanent dentition
are present in the image.
Deciduous teeth are often more slender and the ratio between crown height and root length exaggerated.

Question 18

What is the ratio of crown height to root length in deciduous teeth?

Answer 18

Crown: root length ration up to 1:4-6

Question 19

What is standardised organisation of dental radiographs?

Answer 19

Images of mandibular premolar and molar teeth should face
upwards and those of maxillary premolar and molar teeth downwards.
Dorsoventral radiographs of the maxillary incisors and canine teeth, should be
orientated with that incisor teeth facing downwards.
Radiographs obtained from ventrodorsal exposure of the mandibular incisor and canine
teeth should be displayed with the incisor teeth facing upward.

Question 20

What is the Lamina Dura?

Answer 20

This layer of bone adjacent to the periodontal ligament, appears as a denser line more
radiopaque zone. This is caused by an end-on visualisation of the laminae cribrosa that
appears more dense than the surrounding trabecular bone.

Question 21

What is Cancellous bone?

Answer 21

This trabecular bone occupies the space between adjacent dental alveoli and the
cortical bone of the jaw

Question 22

How should radiographs of the teeth be mounted?

Answer 22

To aid systematic evaluation of radiographs, it is ideal to present images in a standardised
orientation. Images of mandibular premolar and molar teeth should have the roots facing
downwards and those of maxillary premolar and molar teeth the roots facing upwards.
Dorsoventral (occlusal) radiographs of the maxillary incisors and canine teeth, (occlusal
views) should be orientated with the incisor teeth crowns facing downwards.
Radiographs obtained from ventrodorsal exposure (occlusal views) of the mandibular incisor
and canine teeth should be displayed with the incisor teeth facing upwards

Question 23

Look at this:

Answer 23

Question 24

What can very rarely be distinguished on a radiograph?

Answer 24

Only at the very few specific sites and angles can the various components of the hard tissue
of a tooth (enamel, dentin) occasionally be distinguished. Cementum can rarely, if ever, be
radiographically distinguished from dentin

Question 25

How does the lamina dura appear radiographically?

Answer 25

This layer of bone adjacent to the periodontal ligament, appears as a denser, more radiopaque zone. This is caused by an end-on visualisation of the laminae cribrosa that appears denser than the surrounding trabecular bone.

Question 26

Vertical or horizontal bone loss can be identified how on a radiograph?

Answer 26

Deviations in the shadow of the alveolar crest is a very good indication of periodontal health. As a general rule, the margin of the alveolar crest should be level with the neck of the adjacent tooth. In cases of periodontitis, radiographic signs of vertical or horizontal bone loss can be identified.

Question 27

Where is Cancellous bone?

Answer 27

This trabecular bone occupies the space between adjacent dental alveoli and the cortical bone of the jaw

Question 28

Where is the Cortical bone?

Answer 28

Cortical bone forms the dense, superficial layer of bone of the upper and lower jaws. The best radiographic demonstration of the structure is the ventral margin of the mandible.

Question 29

Specific anatomical features of teeth should be recognised e.g:

Answer 29

* Superimposition of cusps in the crown. * Superimposition of roots of multirooted teeth especially the maxillary fourth premolars, on the crown or other roots of both the same and adjacent teeth. gerhard.putter@drw.co.uk ©Gerhard Putter * Tram lines on radiographs indicate developmental grooves on the roots of some premolar and molar teeth. These features are commonly encountered on the furcational aspects (distal aspect to mesial roots and the mesial aspects of distal roots) of the mandibular first molars, but it can occur elsewhere. This complicates the extraction of these teeth.

Question 30

If dentine production slows down or ceases, because of pulpitis or pulp necrosis, the pulp canal of the affected tooth might appear what?

Answer 30

Larger than an unaffected contralateral side.

Question 31

Look at this x-ray of mixed dentition and what does mixed dentition mean?

Answer 31

Mixed dentition indicates that both deciduous and permanent teeth are present.

Question 32

How do deciduous teeth appear?

Answer 32

more slender roots and the ratio between crown and root is usually much larger than in permanent teeth. It is not uncommon for the root of a deciduous permanent canine to be 4 to 5 times longer than the length of the crown. In deciduous incisor teeth this relationship could be even higher (up to 1:8)

Question 33

What is a succedaneous tooth?

Answer 33

The succedaneous teeth are the permanent teeth that replace the deciduous teeth.

Question 34

Deciduous teeth not replaced by a permanent succedaneous tooth, might fulfil the role of?

Answer 34

The absent permanent tooth but they remain more fragile and might resorb later.

Question 35

What indicates the end of eruption of the tooth?

Answer 35

Apexogenesis. The formation of the apex of the tooth root indicates the end of eruption.

Question 36

When does apexogenesis occur in adult canine teeth of dogs?

Answer 36

In the permanent canine teeth of dogs, this happens at about eight months of age. In animals younger than this, the apices of teeth would remain open and are not completely formed.

Question 37

When is the enamel of permanent crowns formed?

Answer 37

The enamel of crowns of the permanent teeth are completely formed by about two months of age. These structures can be identified on radiographs of very young patients, and it is important to identify them as such.

Question 38

What is often superimposed on premolar and molar teeth especially in feline maxillary premolar and molar teeth?

Answer 38

Zygomatic arch

Question 39

Discuss the palatine sutures?

Answer 39

The interface between the various bony structures that forms the hard palate are called palatine sutures. These could occasionally be identified as lines on radiographs of the maxilla and maxillary teeth. As discussed elsewhere, changing the angle of the incident x-ray beam could clarify these structures

Question 40

What are the Palatine fissures?

Answer 40

These large slit-like openings at the rostral aspects of the hard palate can be superimposed on radiographic images of maxillary incisors, canines and rostral most premolars. It is important that these structures are not confused for pathological changes associated with teeth.

Question 41

What forms the palatal shelf and where is it seen on x-rays?

Answer 41

The Junction of the Vertical and Horizontal aspects of the Maxilla. The angle formed inside the nasal cavity, where the above mentioned two aspects of the maxilla meet to form the palatal process of the maxilla. This is known as the palatal shelf and forms a clear radiopaque line visible on all lateral radiographs of maxillary premolar and molar teeth. This line is closely associated with the apices of the maxillary premolar and molar teeth Labelled 3 in attached image

Question 42

What is the closed arrow pointing towards?

Answer 42

The Chonchal Crest This anatomical structure appears on radiographs of maxillary canine and premolar teeth as a curved radiopaque line, closely associated with the apex of the canine tooth. In the attached image A and B demonstrate the anatomic variability in appearance of the conchal crest (arrow) and nasal surface of the alveolar process (open arrow) in a long-nosed (A) and a short-nosed (B) dog.

Question 43

Where can the infraorbital foramen be identified on radiographs of cats and dogs?

Answer 43

In dogs the infra-orbital canal is very closely associated with the apices of the distal root of the of the maxillary third premolars. In cats the infra-orbital canal is extremely short (2 to 3 mm) and can occasionally be identified as a single structure on radiographs of maxillary premolar teeth