THE HEALTHY COLLIE: DENTITION
The Basics of Teeth and the Oral Cavity in the Dog
by Dr. David Hansen
The purpose of this article is to acquaint the reader with
the basic anatomy and terminology of the oral cavity in the
dog. There are many abnormalities that can occur in the oral
cavity or with the dentition at different ages. It is important
for breeders to know what normal looks like, so that at key
ages they can recognize a potential problem. Many abnormalities
are very easy to treat inexpensively, if they are recognized
early. A mild abnormality may develop into a major problem if
not promptly treated. Most can still be corrected to give the
dog a comfortable and functional mouth, but it can be more difficult
and expensive. I will present a series of case reports of abnormalities
in a future article.
It is important to know the number of teeth of both the
puppy and adult dog along with the eruption times of the teeth.
Puppies have a total of 28 "deciduous" (baby or immature)
teeth. Looking only at the right side of the mouth, there are
3 upper and 3 lower incisors, 1 upper and 1 lower canine, and
3 upper and 3 lower premolars. The numbers are added together
and multiplied by 2 (right and left sides) to total 28. The
formula is written as follows:
2X (3/3 i, 1/1c, 3/3pm) = 28
All of these teeth should eventually be replaced with the mature
(adult, permanent) counterpart along with another upper and
lower premolar and 2 upper and 3 lower molars on each side (Figure
1). This results in a total of 42 teeth as indicated by the
2X (3/3I, 1/1C, 4/4PM, 2/3M) = 42
Figure: 1 Adult Teeth
The times that the deciduous and mature teeth erupt are critical,
as failure to erupt can cause major problems. The following
chart is the normal eruption times:
As the mature tooth bud develops, the deciduous tooth begins
to have its root resorbed, resulting in exfoliation (falling
off) of its crown. The exfoliation occurs as the mature tooth
crown is erupting through the gingiva.
Before discussion of dental anatomy, a general understanding
of directional and surface terminology is required (Figure:
2). The surface of the incisor and canine teeth directed toward
the lip is referred to as the "labial" surface. The
surface of the premolar and molar teeth directed toward the
cheek is the "buccal" surface. The surface of all
of the lower (mandibular) teeth directed toward the tongue is
referred to as the "lingual" surface. The surface
of all of the upper (maxillary) teeth directed toward the palate
is referred to as the "palatal" surface. The surface
of the premolars and molars facing the teeth of the opposite
jaw during closing of the mouth is called the "occlusal"
surface. The term "distal" (caudal, posterior) is
referring to the surface of the tooth furthest away from the
middle (1st) incisor or median line. The opposite direction
or surface is called "mesial" (anterior, cranial).
Figure: 2 Lower Jaw
The tooth can be broken down into the crown (above the gingival
or gums) and the root (below the gingiva)(Figure: 3). The incisor,
canine, and first premolars have 1 root. The upper fourth premolars
and upper first and second molars have 3 roots. The rest of
the teeth have 2 roots. The "cusp" is the point or
tip of the crown. The opposite end from the cusp is the "apex"
or tip of the root. The term "coronal" is used to
indicate the direction toward the crown tip or occlusal surface.
The term "apical" is used to indicate the direction
toward the root tip and away from the crown tip.
Figure: 3 Upper Jaw
Anatomy of the Tooth
The tooth is covered by enamel on the crown and cementum on
the root (Figure 4). Enamel is the hardest substance in the
body. Dentin is the substance underneath the enamel and cementum.
The pulp tissue is located in the pulp cavity in the central
portion of the tooth. The pulp contains cells, blood vessels,
lymphatics, nerves and connective tissue. The pulp functions
include forming the dentin, responding to noxious stimuli, nutritional
support and perception of stimuli (pain). The space where the
pulp is located in the crown is called the pulp chamber and
in the root is called the root canal. The apex of the tooth
has multiple small openings, which allow for communication between
the contents of the root canal and periapical tissues. The periodontium
generally refers to the supporting apparatus of the tooth and
includes the gingiva, periodontal ligament, cementum and alveolar
bone. The periodontal ligament has fibers embedded in the cementum
and alveolar bone, which hold the tooth in the alveolus (socket).
The junction of the cementum and enamel is referred to as the
cementoenamel junction (CEJ). The attachment of the gingiva
to the tooth is at the level of the CEJ. In the normal healthy
mouth the shallow gingival sulcus created between the tooth
and the unattached gingival tissue is considered to have a normal
depth of 1-3 mm in the dog.
Figure: 4 Upper jaw
The other structures in the oral cavity include the hard and
soft palate, tongue and floor of the mouth. The hard and soft
palate serves to separate the oral cavity from the nasal cavity.
The hard palate is the anterior portion of the roof of the mouth
between the right and left side that has soft tissue overlying
bone. The soft palate extends caudally after the bone ends.
The teeth are in sockets in the incisive, mandible and maxillary
I'm sure that this is enough of the "boring" facts.
Keep this information handy for the future case reports. The
first one will have to deal with problems that can develop when
there is a "missing" tooth.
David E. Hansen, DVM, FAVD, graduated from Kansas State
College of Veterinary Medicine in 1987. In 1989 he and his wife,
Krista, formed Camloch Collies. He developed an interest in
advanced veterinary dentistry in 1990 and in 2001 became one
of only 69 Fellows of the elite worldwide organization, Academy
of Veterinary Dentistry.