INTRODUCTION TO DENTITION AND
AGEING OF HORSES
The age of the horse determined
by the appearance of Incisor teeth. The use of the examination of teeth to
determine age is of value in non-pedigree animals. Further it is impossible for
the following reasons.
o
To issue
soundness certificates
o
For
valuation of livestock
o
For
selection and purchase
The surface which bites the food
or its fellow on the opposite jaw is the TABLE OR WEARING SURFACE of the
tooth. The mark of infundibulum is the blackened depression seen on the
table. It is lined by distinct narrow pearly white ring of enamel.
The crown of the tooth is that
part which is above the gum and the point where the gum and tooth meets is the
neck. The fang is that part within the jaw, hollowing its cavity contains the
blood vessels and nerves which nourishes and sensitize the tooth.
DEFINITIONS OF TEETH
·
Alveolus: The
bony cavity in which the fang of the tooth is embedded.
·
Buccal Surface:
The outer surface of tooth that is next to the cheek.
·
Central Incisors:
The 2 incisors immediately on each side of middle line
·
Cheek Teeth:
Premolars and molars are often spoken off collectively as cheek teeth
·
STRUCTURE OF TOOTH
The pulp is the soft gelatinous
tissue occupying the pulp cavity in the centre of the tooth. The pulp is well
supplied with blood vessels and nerves.
Dentine: Covers the pulp and is hard
and yellowish white in colour.
Enamel: Hardest tissue in the body
and covers the dentine of the crown. It is clear and bluish white in colour.
Cement: Covers the dentine of the
roof. The embedded portion of tooth is firmly attached to the alveolus,
periosteum by layers of connective tissue.
There are 2 complete sets of
incisors,
Temporary, milk or Foal teeth and permanent or
horse teeth. The difference between temporary and permanent teeth are as
follows.
The temporary teeth is small and
white , has a distinct neck, and a short fang which practically disappears as
the tooth gets older. The permanent teeth are longer, stronger and brown in
colour and has no marked neck or distinct neck and has a stout long
fang.
DENTAL FORMULA AND ERUPTION OF
TEETH
TEMPORARY DENTAL
FORMULA (Horse)
I 3/3 C0/0 PM 3/3 M 0/0
PERMANENT DENTAL FORMULA
I3/3C1/1PM3or4/3M3/3
The variation in the number of
premolar depends upon whether wolf teeth are present or not.
ERUPTION OF TEETH IN HORSE
·
9 days -
Central incisors (temporary)
·
9 weeks -
Lateral incisors (temporary)
·
9 months
- Corner incisors (temporary)
9 months - Corner incisors (temporary)
WEARING OF TEMPORARY TEETH
·
1 Year -
Central incisor .
·
1 ½ Year
- Lateral incisor
·
2 Years -
Corner incisor
ERUPTION OF PERMANENT TEETH
·
2 1/2
Years - Central incisors
·
3 ½ Years
- Lateral incisors
The variation in the number of
premolar depends upon whether wolf teeth are present or not.
ERUPTION OF TEETH IN HORSE
·
9 days -
Central incisors (temporary)
·
9 weeks -
Lateral incisors (temporary)
·WEARING OF TEMPORARY TEETH
·
1 Year -
Central incisor .
·
1 ½ Year
- Lateral incisor
·
2 Years -
Corner incisor
ERUPTION OF PERMANENT TEETH
·
2 1/2
Years - Central incisors
·
3 ½ Years
- Lateral incisors
4 1/2 years - Corner incisors
DISAPPEARANCE OF DENTAL MARK
6th Year -
Central incisors
7th Year -
Lateral incisor takes in lower jaw
8th Year - Corner incisors
9th Year - Central incisors
10th Year -
Lateral incisors takes in upper jaw
11th Year -
Corner incisors
When the dental mark disappears,
the dental star reappears.
ERUPTION OF TEMPORARY INCISORS
At birth: The foal usually has two
temporary central incisors in each jaw through the gums, or just appearing.
At 1 month: The two temporary lateral
incisors erupt. At about this age the first three temporary molars cut through
the gums.
At 6 months: The foal’s mouth has a neat and
compact appearance. The central and lateral incisors being well developed and
are in wear upon their anterior edges.
At 9 months: The foal has two temporary corner
incisors cut through the gums, but these are only touching along their anterior
edges.
At 1 year: The temporary central and lateral
incisors start wearing due to the friction with lower teeth. The temporary
corner incisors are still shell like and only touching along their anterior
edges.
At 1 year 6 months: The temporary corner incisor
starts wearing all along their edges, and the centrals and laterals have become
large and well formed. At about this age the 5th molars erupts.
At 2 years: The temporary corner incisors are
well in wear, and all the incisor teeth have well formed tables.
At 2 years 3 months: The temporary central incisors
are often loose, and the gums are receding from their necks and may appear to
be inflamed. The teeth are only held in position by a short portion of fang or
root.
At 2 years 6 months:
The two temporary central
incisors fall out and are replaced by permanent central incisors. At the same
time the first 2 temporary molars in each jaw are shed, and the corresponding
permanent molars get erupted.
At 15-16 years
The tables of the teeth are
becoming broader and in the centre of the dental star a cleft or depression
usually appears.
Galvayne’s groove has grown about
half way down to the free edge in the upper corner teeth.
·
The angle
formed between the teeth of the two jaws is almost a right angle, and the
tables of teeth are getting much smaller.
A distinct depression appears in the centre of
the dental star. Galvayne’s groove has almost reached the free border.
20-30 years
·
The teeth
gradually appear older and more worn and the teeth are huddled together with no
space between them.
·
Galvayne’s
groove is practically the only definite guide, and even it may be indistinct or
absent.
BISHOPING
It is attempting to make an old
mouth to look younger. The teeth are rasped and levelled.
A false mark is gouged out of the
centre of the table and blackened with caustic (usually with silver nitrate
crystals).
This can be found out by
observing,
o
The angle
of teeth,
o
The
absence of enamel rim and
Occasionally the traces of rasp being used to
shorten the teeth.
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