Dentition Flashcards
Enamel
Hard outer part projecting above gyms
Ectodermal origin
Formed by ameloblasts
Acellular can’t regenerate
Dentine
• Mesodermal in origin.
• Formed by ODONTOBLASTS
• Forms the bulk of the tooth
• 2nd hardest tooth material
• Structure is similar to bone but whereas in bone the OSTEOBLASTS stay within the bone matrix, in teeth the ODONTOBLASTS (the dentine producing cells), recede from the newly formed dentine and remain as a continuous layer on the surface of the pulp cavity. This produces SECONDARY DENTINE throughout life, which gradually reduces the size
of the dental pulp cavity.
•Secondary dentine is darker in appearance than primary dentine.
•Tertiary dentine may occur at sites of injury.
Cementum
•Mesodermal in origin
•Formed from calcified connective tissue
•Forms the outer lining of the tooth in the socket in brachydont teeth, and completely covers the tooth in hypsodont teeth
•It is the least hard of the calcified tissues of the tooth
•It is continuously, but slowly, produced throughout life, so is
thicker in older animals.
Pulp cavity
•It reflects the external shape of the tooth i.e. is present in each tooth root.
•It is open at the apical foramen.
• Central part of tooth containing nerve fibres, lymphatic and blood vessels
•Smaller in older animals as secondary dentine fills in pulp cavity.
The periodontium
This term describes the functioning unit of several anatomical
components. It consists of the Gingiva, periodontal ligament, cementum
and alveolar bone.
Its role is to anchor the tooth in the skull and provide a suspensory
apparatus to absorb stresses induced at biting.
What is the gingiva
the oral mucosa that covers the alveolar processes of the jaws and covers the neck of the teeth. It is composed of
keratinized stratified squamous epithelium
Gingiva coronal to the cemento-enamel junction = free gingiva
Gingiva tightly attached to the periosteum of the alveoulus = attached gingiva
Freely moveable mucosa = alveolar mucosa. Non keratinised epithelium.
What is the gingiva sulcus and size
Small natural space between the tooth and the gum. Less than 1 mm in cats, less than 3 mm in dogs
The periodontal
•Is made of collagen fibres
•Attaches to the cement of the tooth and the Alveolus
•These fibres are arranged in a sling formation – allowing small movements of the teeth during mastication, and acting
as shock absorbers.
Alveolar bone
Similar to other bone but the layer of bone lining the socket – i.e. the layer next to the PDL is very dense. It
is radiographically noticeable as a thin white line. Its called the lamina dura. Note that in teeth with more
than 1 root the white and dark lines of the different roots may become superimposed.
Dark line = periodontal space =periodontal ligament
White line = lamina dura
Innervation teeth
All teeth are innervated by branches of the TRIGEMINAL NERVE - cranial nerve V.
The upper teeth are supplied by the MAXILLARY (or superior) ALVEOLAR NERVE (from the maxillary division of the Trigeminal Nerve).
The lower teeth are supplied by the MANDIBULAR (or inferior) ALVEOLAR NERVE (from the mandibular division of the
Trigeminal nerve).
regular mammal dental formula
I 3/3 C 1/1 P 4/4 M 3/3 x2 = 44
Hypsodont
those of horses, high or long crowned with unerupted crown lying beneath the gum in all but very aged
animals. The root of the tooth is generally shorter than the crown.
Brachydont teeth
those of the dog and cat (and human), are low crowned - where all of the crown has erupted by
adulthood. The root of the tooth is generally longer than the crown.
Aradicular/elodont
teeth grow throughout life and never develop true roots. Always hyposodont.
Radicular/Anelodont
teeth with a true anatomical root structures and do not continuously grow throughout life. Can be
hypsodont or brachydont.
Clinical crown
this is the exposed part of the tooth, regardless of structure.
Anatomical crown
this is the enamel covered part of the tooth regardless of location.
Surface next to the lips
Labial
Surface next to the cheeks
Buccal
Surface next to the tongue
Lingual
Surface touching the tooth in front
Mesial
Surface touching the tooth behind
Distal
Masticatory surface
Occlusal
Carnivore Dentition
•Radicular/Anelodont brachydont
•Incisors for grooming and nibbling
•Canine teeth adapted to piercing flesh to kill and hold prey,
•Premolars/molars adapted to cutting like a scissor – carnassials.
•Molars – cutting/crushing. In some species used for crushing e.g. bones, to extract marrow, in other species reduced in
number.
Approximate tooth eruption times
All deciduous 6 weeks
All permanent dog-7 months, cat 6 months
Dog dental formulae
I 3/3 C1/1 P4/4 M2/3=42
What are carnassials
Teeth found in carnivorous mammals designed for shearing and slicing meat
Cat dentition formulae
Cat I3/3 C1/1 P 3/2 M 1/1 x2 = 30
Normal oral pH in dogs and cats
7.5
What is plaque
a biofilm on the teeth that is formed by bacteria colonizing the dental pellicle
(the protein film on the surface of the teeth formed by saliva and food). The most
important strategy in prevention of periodontal disease is plaque control. Mechanical
prevention – chewing coarse textured food and tooth brushing.
Inorganic substances from saliva are deposited into bacterial plaque and form calculus
(commonly called tartar). The surface of calculus is readily colonised further by
plaque.
Periodontal disease
The most common oral disease seen in small animals - very common in domestic carnivores. Possibly
the most common disease in in small animal practice.
First stage is gingivitis - inflammation of the gingiva
Second stage - early periodontitis – inflammation of gingiva and periodontal ligament
Third stage - further breakdown of support tissues, tooth mobility, tooth loss. Advanced periodontal
disease in the upper dental arcade, especially of the canine teeth, can lead to oronasal fistulas.
Tooth decay and abscesses
Tooth decay-caries, caused by bacteria, much less common in carnivores
Abscesses may result in periodontal disease or factures
Congénital malocclusions
Malocclusion – different head shapes – esp brachycephalic, but also sometimes
seen in dolicocephalic breads.
Prognathism = lower jaw too long (brachycephalic)
Brachygnathism = lower jaw too short (dolicocephalic)
Différence between radicular and aradicular teeth?
Radicular teeth have a true root and as such are a complete tooth with only a finite amount of
wear.
Aradicular teeth have no true root – are open rooted and can continue growing throughout the
animals life.
• Horses have radicular hyposodont teeth – i.e. they are long crowned but with true roots
• Ruminants have brachydont incisors and canines and radicular hypsodont premolars and molars
• Species with aradicular dentition include some lagomorphs and rodents (diverse species course)
Dental formulae of domestic large herbivores
2 x (I3/3, C0/0 or 1/1, PM 3/3 or 4/4, M3/3) = 36 to 44 teeth
Horse dentition
• Radicular hypsodont dentition
• Cellulose is digested in herbivores by micro-organisms in gut. Ideally
this is made available by crushing and grating vegetation. This
causes considerable wear so teeth designed to permit this.
• Teeth continue to erupt through life. i.e. as the tooth wears it moves
outwards and the bone grows underneath to fill in the socket (all
lower teeth mandible, upper incisors, canines, UPM1, UPM2 and
UPM3) or the maxillary sinus expands (UPM4, UM1-3 in teeth in the
maxilla).
• The cementum initially covers the crown and creates a ridging due
to the different hardness of cement, enamel and dentine.
Horse tertiary dentine
formed as a response to injury and is
also found in some horse teeth
What’s incisor hook
Due to incomplete occlusion.
Occurs at around 5-7 years, may
recur at 11-13years.
Only present in 60% of horses
NOT RELIABLE!
Galvayne’s groove
Galvayne’s groove
Occurs in horses over 10 years.
Half way down tooth at 15 years,
fully down at 20, then starts to
‘grow out’. Again, not reliable
Horse cheek teeth
Premolars and molars (PM2 – M3) very similar to each other in the horse
and form a continuous row both in the upper and lower dental arcades.
• Usually referred to as ‘cheek teeth’
• 6 on the upper arcade (plus maybe a wolf tooth UPM1)
• 6 on the lower arcade (LPM1 usually absent, if present may be unerupted)
• Tooth attrition is approx. 2-3 mm of wear per year.
• Each cheek tooth erupts with one large pulp cavity. As the horse ages
these separate into between 5 and 8 separate pulp cavities with varying
degrees of intercommunication.
Describe the upper tooth row in horses
The whole upper tooth row is slightly curved
out toward the cheek, the lower tooth row is
straighter.
Both tooth rows also curve up at the caudal
end of the oral cavity (curve of Spee).
What is a cheek tooth occlusion
Upper cheek teeth wider and
squarer, lower cheek teeth
narrower and more rectangular
So as the upper arcade is wider,
and the teeth in it are also wider,
when the mouth is closed about
1/3 of the occlusal surface of the
upper cheek teeth is in contact
with about half of the occlusal
surface of the lower cheek teeth.
Also, the occlusal surface is
angled in a linguo-buccal
direction - around 15 degrees
rostrally and 30 degrees
caudally in the normal animal.
Upper cheek teeth and lower cheek teeth characteristics
In the upper cheek
teeth there are 2
infundibula totally
surrounded by
dentine.
In the lower cheek
teeth there are
infoldings of the
enamel rather than
true infundibulae.
These are open on
the lingual surface.
What are transverse ridges?
raised enamel structures that run across the occlusal (chewing) surface of the upper and lower cheek teeth.
These ridges help horses efficiently grind down fibrous plant material (like hay and grass).
They are a natural part of equine dentition and contribute to their hypsodont teeth, which continuously erupt throughout their lives.
The wear is such that along each cheek tooth row there are around 12
transverse ridges. In occlusion the ridges of the upper arcade
interdigitate with those of the lower arcade
Permanent premolars erupt…..,… , permanent molars…………
Permanent premolars erupt 2.5 to 4 years, permanent molars 1 month – 3.5 years
What’s the relationship between upper cheek teeth and maxillary sinus?
Tooth Roots Extend Into the Maxillary Sinus
The last three or four upper cheek teeth (specifically PM4, M1, M2, and M3) have roots that project directly into the maxillary sinus.
As horses age, their teeth continue to erupt, and the roots gradually extend deeper into the sinus.
Dental Disease Can Lead to Sinus Infections
If an upper cheek tooth becomes infected (due to decay, fractures, or periodontal disease), the infection can spread into the maxillary sinus, causing sinusitis (inflammation and infection of the sinus).
Signs of sinusitis include nasal discharge (often foul-smelling), swelling, and difficulty breathing.
Tooth Extractions Can Affect the Sinus
When a deeply rooted upper cheek tooth is extracted, it can leave an open connection (fistula) between the oral cavity and the maxillary sinus.
This can require surgical closure to prevent food and bacteria from entering the sinus.
Age-Related Changes
In younger horses, the maxillary sinus is smaller, as the teeth are still growing and occupy more space in the skull.
As the horse ages, the sinuses become larger, and the roots of older cheek teeth extend higher into the sinus cavity.
How to extract a tooth horse?
Per os– through the
oral opening – incisors,
wolf teeth, premolars.
By buccotomy– surgical
approach through the soft
tissue structures of the cheek
then removing some bone
overlying the lateral side of the
tooth - premolars
By repulsion – surgical
approach through the skull
or mandible. The tooth is
driven out from the root
using a metal punch. –
caudal premolar and
molars.
What are the structures to avoid when approaching the upper cheek teeth
Infraorbital teeth, parotid duct, dorsal and ventral buccal nerves
Nasolacrimal duct and infraorbital canal
Formulae for cattle and sheep and when do they come oit
I0/3 C0/1 P3/3 M3/3 =32
=20 deciduous
DECIDUOUS cattle: 3 weeks Sheep: 4 weeks
Permanent cattle: 3.5 years Sheep:2.5 years, canines by 4 years
