Animal Dentistry/ dental anatomy

The oral cavity; Carnivore dental anatomy; Comparative dental anatomy;

What are the boundaries of the oral cavity

Lips
Cheeks
Commissure
Vestibule

vomeronasal organ

involved in scent and pheromone detection

What bones make up the hard pallet

Incisive bine
maxilla
Palatine bone

Why is the hard pallet covered in thick ridged mucosa

to help guide food backwards into the caudal area of the oral cavity and into the oesophagus

what are the 3 layers of the lips

skin
muscle, tendons, salivary glands
oral mucosa

Philtrum

a slit that goes from the nose to the lips
common in carnivores and ruminants

Platysma

Longitudinal Fibres that run to the back of head and neck

Mimetic Muscles

Transverse Fibres that control facial expressions
e.g. blinking, twtching of the nose and movement of the lips

Infraorbital nerve

Gives sensation to the muzzle, lips and teeth
- it exits the head through the infra orbital foramen

What type of epithelium lines the whole oral cavity

Stratified squamous

What is seen on the interior of the lips on a histological exam

no hairs
no sebaceous or sweat glands
skeletal muscle and connective tissue

What is seen on the exterior of the lips on a histological exam

hair follicles
sebaceous glands and sweat glands
skeletal muscle and connective tissue

What are the 3 parts of the pharynx

Oropharynx, Nasopharynx, Laryngopharynx

What are the boundaries of the pharynx

Skull base and C1-2 dorsally
Larynx ventrally- leading to the respiratory system
Mandible, Pterygoideus, Hyoid Laterally

what additional structure would you find in a horse pharynx

Guttural pouches

Nasopharynx

at the back of the nose

Oropharynx

at the back of the oral cavity

Laryngopharynx

around the epiglottis

Dorsal aspect of the soft pallet mucosa type

Respiratory

Ventral aspect of the soft pallet mucosa type

Oral

Arches that connect the tongue

Palatoglossal Arches – tongue base
Palatopharyngeal Arches – Lateral wall of pharynx

What is the hyoid apparatus

a series of linear bones that suspends the base of the tongue and the larynx from the skull

What are the names of the linear bones
Some Elephants Came By Train

Stylohyoid
Epihyoid
Ceratohyoid
Basihyoid
Thyrohyoid

Basihyoid bone

the only one that isn't a pair, it connects the left and right arches

2 types of muscles in the tongue

intrinsic- within the tongue
extrinsic- originate from structures out with the tongue and then go in

5 forms of papillae

Filiform
Conical papillae
Fungiform, foliate, vallate

4 extrinsic tongue muscles

Styloglossus
Hyoglossus
Genioglossus
Geniohyoideus

Styloglossus

originates from the stylohyoid bone and runs down the rostral and attaches to the apex of the tongue
when it contracts it will pull the tongue both backwards and upwards

Hyoglossus

originates from the basihyoid bone and attaches to the intrinsic part of the tongue
when it contracts it will pull the tongue in a caudal direction into the back of the mouth

Genioglossus

Originated on the area behind the incisors but then fans up and inserts onto the body of the tongue
when muscle contracts it pulls the tongue in a ventral direction

Geniohyoideus

from back of incisors to hyoid apparatus
when muscle contracts this pulls the tongue forward

Frenulum-

connects the tongue to the floor of the mouth

Sublingual caruncles

areas of opening for salivary ducts for mandibular and sublingual salivary glands

innervation of sensation to the tongue

supplied by the Lingual Branch of Mandibular Nerve (V) and the Glossopharyngeal (IX) and Vagus (X)

innervation of taste to the tongue

supplied by the Chorda tympani from Facial Nerve (VII) and the Glossopharyngeal (IX) and Vagus (X)

innervation of motor function to the tongue

supplied by the Hypoglossal Nerve (XII)

What is the main artery to the tongue

Lingual artery

what form of papillae do equine tongues have the most of

filiform

Lingual Tonsil

immune/ lymphoid tissue

what about the ruminant tongue makes it more susceptible to infection

torus linguae as it has a thinner mucosa

what is different about the papillae in ruminants

rostrally there is harsh filiform
at the back of the tongue at the torus linguae there will be conical and lenticular papillae

lingual papillae histology

consists of a connective tissue core covered with stratified squamous epithelial

What are the 4 forms of papillae

filiform/ coniform/lentiform
fungiform
vallate
foliate

filiform/ coniform/lentiform papillae features

slender conical structures
purely mechanical function- no sensory structures
coniform most common in cats
lentiform is more common in ruminants

Fungiform

project above the epithelium

foliate

rare in domestic- seen in rabbits

vallate

largest and most prominent, sitting in a deep trough at the root of the tongue

sequence of events when swallowing

Bolus formed in oral cavity
Pushed into oropharynx by tongue (voluntary)
Epiglottis and interpharyngeal ostium (to nasopharynx) closed/ Soft Palate elevated
Bolus moved through pharynx into oesophagus by sequential contraction of constrictor muscles, while larynx and hyoid apparatus moved rostrally
Bolus passes into oesophagus

3 centres of lymphoid drainage

Parotid
Mandibular
Retropharyngeal

parotid

One or more on each side of the head
Masseteric region
Drain dorsal head – dorsal skull, orbit, dorsal masticatory muscles

Mandibular

1-3 on each side of the head
Caudal intermandibular space, angle of jaw
Drain muzzle, salivary glands, intermandibular space (incl. tongue), ventral masticatory muscles

Retropharyngeal

Medial – roof of pharynx
Lateral – atlantal fossa (first vertebrae)
Drain pharynx/larynx, deep structures of head, cranial neck
Medial – collection for other centres (Parotid and Mandibular).
Lateral in Cattle

What are tonsils made of

lymphoid tissue

What is the key species difference in tonisls

they tissue may be diffuse (equine) or compact masses (ruminants and gogs)

tridant numbering system

the most common form used for equine

Crown can be split into

clinical crown
anatomic crown

4 directional terms for the tooth

Vestibular
Lingual
mesial (rostral)
distal (caudal)

4 layers of tooth structure in carnivores

Enamel
Dentine
Cement
Pulp cavity

Enamel

Hard, highly calcified material
Acellular= cannot be repaired

Dentine

Calcified, collagen-rich matrix (similar to bone). Odontoblasts remain on pulp surface, continue production. Greater part of tooth

Cement

similar to bone, collagen fibres anchor tooth in socket. Resistant to pressure erosion (unlike bone)

Pulp cavity

follows the external form of tooth into multiple roots

Apical foramen

where the nerves and vessels exit the tooth via

3 key periodontal structures

Gingivae
Periodontal ligament
alveolar bone of jaw

Gingivae in carnivores

Attach to teeth at ginigival sulcus
Contains saliva as protectant

Periodontal disease in carnivores

the depth of the gingival sulcus is often going to become deeper due to breakdown of tissue around the tooth
(normal

Periodontal Ligament

Strong collagen (Sharpey's fibres) fibres connecting cement to alveolar bone

Thecodonty

when there is a separate alveolus for each tooth

where are the teeth sockets found

in trabecular bone

Arterial supply to the teeth in carnivores

Mandibular teeth-Inferior Alveolar (from Maxillary artery) – enters mandibular foramen, exits mental foramen

Maxillary teeth- Branch from Maxillary artery

Nervous supply to the teeth in carnivores

Mandibular teeth-Inferior Alveolar Nerve (branch from Mandibular Nerve (V))

Maxillary teeth-Infraorbital Nerve (branch from Maxillary Nerve (V))

Heterodonty

obvious variations in tooth structure
e.g. shape, occlusal surface and enamel folding, and the number of roots

what other ways can teeth vary

the amount of crown exposed
this increases with age

Diphyodonty

any animal who has two successive sets of teeth. The deciduous and the permanent ones

deciduous teeth in carnivores

allow for adaptation to larger and more powerful adult jaws, these temporary teeth erupt before the root is formed.
there are no molars with these teeth

For eruption to occur we need a combination of (in carnivores )

Root growth
Bone growth
Pulpal proliferation
Tissue pressure
Periodontal traction

Process of eruption of the tooth in carnivores

as the permanent tooth grows into the violas the temporary tooth is going to get eroded at the root. Once the root is completely eroded the tooth becomes loose and pops out. the permanent tooth then grows into the vacated space.

Carnivore dentation heterodonty reflection of diet

Incisors
Canines
Cheek teeth

Incisors in carnivores

cutting edge, grooming
fairly loosely attached
upper - 3 cusps
lower- 2 cusps
in older animals the incisors are worn down

Canines in carnivores

aggression, restraint of food- long root
large and curved
root is longer than the crown

Cheek teeth in carnivores

Premolars, molars, alignment allows shearing
Carnassial Teeth – Upper PM4, Lower M1- strongest cutting point
Some crushing action from molars (less so in cat)

Temporary dental formula for dog

3-1-3
---------
3-1-3

Permanent dental formula for dog

3-1-4-2
-----------
3-1-4-2

What affects the alignment of teeth

Skull type
e.g. they are bunched in brachycephalics

Pre-molars in carnivores

increase in size 1-4
3 cusps- large central, smaller mesial and a large distal
PM1- 1 root
PM2-3 - double root
PM4- three roots- carnassial
the multiple roots require splitting prior to extraction

Molars in carnivores

decrease in size in 1-3 (1-2 in upper jaw)
flatter crowns than premolars which leads to crushing rather than slicing
upper- 3 roots and 3 cusps, transverse orientation
lower- 2 roots, rostrocaudal orientation

Teeth occlusion in canines

Upper PM4 lies lateral to M1
Lower canines lie rostral to upper canines

Temporary dental formula for cats

3-1-3
--------
3-1-2

Differences in dentation of cats

no upper PM1 or 2
no lower PM1,2 or M2,3
Only upper PM4 has 3 roots
Reduced molars means there is:
Reduced crushing ability
Shearing bite only (Secodont)

Permanent dental formula for cats

3-1-3-1
-----------
3-1-2-1

Secodont

where the teeth have really sharp cutting edges and rely on shearing action

What features of equine dentition relate to their diet and why?

Premolars are enlarged to match the molars - this gives an even, continuous grinding surface.
High crowns - gradual extrusion of teeth allows them to be worn down by fibrous diet.

What is the diastema?

The large gap between the incisors and premolars.

Describe the occlusal surface of an equine tooth...

The occlusal surface:

alternating enamel and dentine
consists of multiple folds - increased surface area for abrasion.

What is the "wolf tooth"?

First upper premolar (PM1)

How can you tell the difference between the deciduous teeth and the permanent teeth?

The deciduous teeth are smaller in size than the permanent teeth.

What are the temporary and permanent dental formulae for horses?

Temporary:

3-0-3
---------
3-0-3

Permanent:

3-1-3(4)-3
---------------
3-1-3- 3

What is the infundibulum?

The funnel-like centre that is filled with cement and capped with enamel. The funnel is widest at the top (crown) which is the grinding (occlusal) surface. It is also known as the dental cup.

Describe equine incisors...

shape
occlusal surface
cup
dental star

continuous arch
made up of inner and outer enamel rings, inner ring encloses infundibulum
cup has a cement centre with a small cavity
formed as wear increases

What is a dental star?

A dental star is when dentine forms over the surface to prevent pulp exposure as the tooth is worn down