Lesson 1: Dental nomenclature, anatomy, and charts
This lesson emphasizes the dental nomenclature, anatomy, and charts as it relates to the dog and cat.
Understand the meaning and use of common dental terminology
Know the basic tooth classifications seen in domestic animals
Recognize the normal oral structures of the dog and cat
Understand the clinical significance of dental anatomical structures
Be able to estimate the age of a puppy or kitten using tooth eruption information
Recognize the difference between deciduous and permanent dentition
Know how to read and write a dental formula
Use the anatomic and modified Triadan numbering systems
Be familiar with the various styles of clinical dental charts
It sounds like a lot of pages but there are a lot of nice pictures in the book taking up space so don’t panic!
Chapter 1 pp. 1-23
Veterinary Dentistry A Team Approach 2nd ed (Holmstrom)
There is a writing assignment at the end of each chapter in the textbook for you to use as a self review.
There is also a writing assignment at the end of each lesson in the online lesson. Please submit your answers to the writing assignment to the Blackboard dropbox.
Key words Chapter 1
Mucogingival line, Mucosa, Gingiva
Apical delta, apical foramen
Enamel, dentin, cementum, CEJ
Pulp chamber, root canal,
Free gingiva, attached gingiva
Alveolus, alveolar bone, periodontal ligament
Continuously growing teeth
Primary teeth, deciduous, baby teeth
Secondary, adult, permanent teeth
Incisors, Canines, Premolars, Molars
Mesial, distal, labial, buccal, palatal, lingual
Nomenclature, basic anatomy, and dental charts
Several criteria are used to evaluate an animal’s oral examination and include the identification of the head type, tooth type, occlusion, and condition of the teeth, bone, and soft tissues. Most dental terms used to describe various conditions have been borrowed from the human field, but also there are some terms that have been developed within the veterinary profession that your dentist or dental hygienist probably have not heard of!
The three main head shapes are mesaticephalic, brachycephalic, and dolichocephalic.
Mesaticephalic refers to a medium or average head shape where the width and length of the head is in balance, so that (in dogs) the skull is about twice as long as it is wide. The majority of dogs are mesaticephalic.
Brachycephalic animals have short and wide heads. Even though the mandible is also shorter than normal, the relationship of the upper and lower jaw is such that the lower jaw often is longer than the upper jaw. This conformation results in crowded, rotated teeth, and sometimes a malocclusion, meaning the upper and lower teeth do not fit well together when the animal closes his mouth.
Dolichocephalic animals have long, narrow heads and tapered muzzles. Sometimes this narrow head conformation is associated with malocclusions in which the upper teeth do not overlap the lower teeth properly.
What is the head shape classification of the following breeds?
-Rhodesian ridgeback, Pekingese, Saluki
-Oriental shorthair, Devon Rex
Upper vs. Lower
The teeth residing in the maxillary and incisive bones of the maxilla are referred to as the upper teeth, while the maxilla itself is referred to as the upper jaw. Two soft tissue structures of interest on the hard palate are the rugae and the incisive papilla. Between the rugae are crevices that can sometimes collect quite a bit of debris or hair in some animals (especially brachycephalic breeds). You must remember to check and clean these areas between the rugae if needed during dental prophylaxis. The incisive papilla is a small round bump just caudal to the upper incisors. Sometimes owners get a glimpse of the incisive papilla and assume it is a wart or some kind of tumor, which it is not. The incisive papilla is a normal structure.
Sometimes the opening to the ducts of the parotid or zygomatic salivary glands are very prominent and you may mistake the openings for a lesion. An opening for a salivary gland duct is usually easily seen just above the area around the upper fourth premolar and first molar.
The mandible is known as the lower jaw, and the teeth within the mandible are called the lower teeth. The mandible is comprised of two halves that join together at the symphysis. Normally this is a very tight joint with essentially no movement, but in some breeds (especially brachycephalic toy breeds) the symphysis may have some joint laxity present. If this occurs, you will notice the laxity is present between the middle lower incisors. You should make note if this condition is present before you start your work on the animal and discuss it with the veterinarian. Then you would establish that it was a pre-existing condition and that you did not cause it during any of your manipulations for dental treatments. A soft tissue structure of interest on the mandible of both the dog and cat is the frenulum, which is a band of tissue that attaches the lip to the mandible in the area of the lower canine tooth.
Another soft tissue structure you will see on the mandible of cats is a bulge of salivary tissue next to the lower molar on the side next to the tongue. It may be quite prominent in older cats and can get in the way and flop around when you are cleaning the tooth in this area. Many veterinarians will use the structure as a flap of tissue to close the extraction site of the molar.
There are differences between the dog and the cat regarding the structure of the tongue. The tongue of the dog has a soft surface and a prominent crease down the middle of it. This crease may accumulate hair and debris in some dogs, especially those with skin conditions in which the animal licks the coat excessively. During dental prophylaxis, don’t forget to check this area of the tongue for any foreign material.
The tongue of the cat is normally quite rough on the surface due to numerous projections that cover the surface. Anyone who has ever been licked by a cat can attest to the sandpaper-like quality of the tongue. Veterinary technicians learn very quickly that gauze pads or cotton swabs used to wipe out the mouth during dental treatments easily catch and leave fibers on these projections of the cat tongue.
In our common domestic animals, we find 3 basic types of teeth that are classified according to their anatomy and development: continuously growing, continuously erupting (reserve crown), and brachyodont teeth.
The continuously growing tooth is one that continuously grows and erupts throughout the animal’s life, in the same sense that a nail or hoof will continuously grow. The continuously growing tooth is essentially rootless but has germinal cells at the base of the tooth that continue to produce tooth structure. What prevents the tooth from becoming excessively long is that it is worn down through use, that is, mastication and occlusion against the opposing teeth. An example of this type of tooth is seen in the rabbit. For more information, refer to chapter 14 in “Veterinary Dentistry for the Technician and Office Staff”.
The continuously erupting tooth is one that has a very long crown and little short roots. The tooth only erupts as far as is needed for function, and the rest of the tooth crown remains submerged until eruption of that part of the tooth occurs. The part of the tooth that is submerged is called the reserve crown. As the teeth are worn down through use, that is, mastication and occlusion against the opposing teeth, the teeth continue to erupt slowly to maintain the dentition needed for function. This occurs throughout the life of the animal. If the animal lives long enough, eventually the teeth are worn down to the point where there is no reserve crown left. The teeth by this time are just little nubs with short roots that eventually exfoliate. Horses are an example of an animal with teeth that have reserve crown structure, and we will discuss more aspects of horse dentistry in another lesson.
The brachyodont tooth is one in which there is a long root and relatively short crown. Once erupted, the crown length is fully formed and there is no replacement of the crown by the body if the tooth becomes worn or damaged. An example of animals that have this type of tooth structure is the dog and cat. The majority of this dentistry unit will concentrate on dentistry of the dog and cat, which means that any dental anatomy and physiology will be about the brachyodont type of tooth, unless otherwise stated.
Topographically, the tooth is divided into regions of the crown, neck, and root. The entire tooth is largely made up of a hard, mineralized substance called dentin, which is a pale yellow color. The part of the tooth that is visible in the mouth is the crown, which is covered with enamel, a mineralized substance similar to dentin but harder and it is white. The root is the part of the tooth that is anchored in the bony socket of the jaw and is covered with cementum, which is also a mineralized substance similar to dentin and enamel. Cementum allows attachment of the periodontal ligament that holds the tooth in place in the bone. It is slightly softer than enamel and is not as white.
The neck region is where the crown meets the root, or where the cementum meets the enamel. There is often a slight enamel bulge just above the neck and then a slight indentation where the enamel stops at the neck, but it is often not very prominent in some teeth of the dog and cat. You may have to rely on identifying enamel vs. cementum by the color and consistency of the tooth surface. You must be able to identify this neck region on your dog and cat patients because it is an important observation in assessing if there has been gingival recession. Also, since the root surface is softer, you must be careful when cleaning any exposed roots to avoid damaging the tooth structure or making your patient sensitive afterwards.
The incisor tooth is an example of a single rooted tooth. The crown is at the top of the photo. Note the features of the tooth regions. Many teeth have a slight bulge in the contour of the enamel that is visible near or at the cementoenamel junction.
When referring to the crown area of the tooth, we use the term coronal. If we are moving an instrument in a coronal direction, we are moving towards the crown end of the tooth. When referring to the end of the root, we use the term apex. So if we are moving an instrument in an apical direction, we are moving towards the root end of the tooth.
Teeth that have more than one root are termed multirooted. The area where the roots branch off from the crown near the neck is referred to as the furcation. It is an important landmark to note because normally the furcation is covered by bone and gingiva and so it is not normally exposed to the oral cavity. If you can see or feel the furcation with an instrument, it is exposed and this is abnormal, indicating gingival recession.
The endodontic system of the tooth is the soft tissue inside the tooth and is referred to as the pulp. The pulp is comprised of the vessels and nerves that supply the cells that produce dentin and line the inner compartment of the tooth. The space in the crown where the pulp resides is the pulp chamber and the space in the root portion where the pulp resides is the root canal.
The pulp vessels and nerves usually enter the tooth in the region of the root apex. In some instances there is a single large opening allowing the entrance and exit of the pulp, referred to as an open apex. This is common in young animals.
In some instances the pulp enters the tooth via numerous small openings that may not be visible to the naked eye, a formation referred to as an apical delta. The root apex appears solid, but it is actually not. This is common in a mature animal, and explains why a tooth from an older animal does not appear to have an opening at the apex, either radiographically, or upon inspection of the tooth after extraction.
View of the apices of a molar from a mature dog. The apex of many teeth of the mature dog and cat appear completely closed, but are actually open for the pulp structures to enter/exit at the apex through numerous microscopic openings called the apical delta
All teeth have pulp tissue, and since the pulp enters and exits out the apex, any disease of the pulp will tend to affect the tissue near and around the end of the root.
From the following photo of the endodontic system you can appreciate that any infection of the pulp can travel through the inside of the root, out the apex, and cause inflammation in the bone around the apex of the affected tooth wherever the pulp tissues enter and exit the tooth. You can also see that the pulp in a multirooted tooth is continuous from one root to another through the pulp chamber. So in a multirooted tooth, if one root canal is diseased, the other root canal of the tooth as well as the pulp chamber will also be affected, even if the original problem involved initially only one root.
The periodontal tissues are those tissues surrounding and supporting the tooth in its place. The teeth reside in a bony socket in the jaw called the alveolus. Usually the bone surrounds the root and extends all the way to the cementoenamel junction. The periodontal ligament attaches the bone to the tooth by attachment to the cementum. If bone support is lost, the periodontal ligament attachments are lost, and the tooth will become loose.
The soft tissue covering the bone around the tooth is the gingiva and the mucosa. Both the gingiva and mucosa can have varying degrees of pigmentation. If it is not pigmented, it is normally a coral pink color. The gingiva is tightly attached to the bone around the teeth and is very tough thick keratinized tissue. A small area of the gingiva is also attached to the tooth near the cementoenamel junction, which protects the periodontal ligament attachments in the bone beneath. A little flap of unattached gingival tissue may extend over the crown surface, forming a little tiny space around the tooth, called the sulcus. The sulcus normally is not noticeable, but may form pockets around the tooth with periodontal disease. The mucosa is very loosely attached to the bone and it is thinner, more delicate tissue than gingiva. You can easily see the difference between gingiva and mucosa simply by lifting the lip of a dog or cat (or yourself for that matter!) and examining the tissue lining the mouth around the teeth. There is an obvious line of demarcation between the gingiva and the mucosa called the mucogingival line. This is an important anatomical landmark because if there is gingival recession and the gingiva is lost up to the mucogingival line, the chance for successful periodontal treatment is poor.
The format of the dental formulas is standardized and is a convenient way to relate the dentition of any species as an equation. Each tooth type has a specific letter designation accompanied by the number for each tooth type. Incisors are designated by an “I”, canines by a “C”, premolars by a “P”, and molars by an “M”. Deciduous teeth are given lower case letters. The upper and lower counterparts of each tooth type are expressed as a fraction by expressing the upper teeth in the numerator and the lower teeth in the denominator. Since the teeth types and numbers are symmetrical with regards to the left and right sides of the head, the formula is only written for one side of the head.
So, for example, in the upper left (or right) quadrant of the mouth, the dog has 3 incisors, 1 canine, 4 premolars, and 2 molars. In the lower left (or right) quadrant of the mouth, the dog has 3 incisors, 1 canine, 4 premolars, and 3 molars. The list of tooth letters with the correct numbers in the numerator and denominator is added together like an equation, and then the information looks like this:
3/3I + 1/1C + 4/4P + 2/3M
But since there are 2 sides to the head, the whole formula is multiplied by 2 to give the total number of teeth. So the final dental formula for the adult dog looks like this:
2 ( 3/3I + 1/1C + 4/4P + 2/3M) = 42
Knowing how to decode the dental formula will enable you to develop a dental chart for any species of animal.
Lateral view: The adult dog dentition 2 (3/3I + 1/1C + 4/4P + 2/3M) = 42
Lateral view: The adult cat dentition 2 (3/3I + 1/1C + 3/2P + 1/1M) = 30
The timetable of eruption can be quite variable depending on the breed and even differ among individuals within a breed. However, knowing common eruption times will help you estimate the age of a puppy or kitten.
Generally, by the time a puppy or kitten is 6 weeks of age, all of the deciduous, or “baby”, teeth are present. The permanent, or “adult”, teeth erupt as the deciduous teeth are shed, and are easily identified because they are much larger and a more bright white color than the deciduous precursors.
The permanent teeth that seem to be fairly consistent on eruption times and easily examined in the squirmy puppy or kitten are the incisors and canines. Basically, the incisors erupt starting around 3 to 3 and ½ months of age. The incisors to erupt first are usually the lower central incisors. There will be a sequence of eruption from the central incisors (upper and lower) to the adjacent incisors over the period of 3 to 5 months of age. The canine teeth typically erupt around 4 to 4 and ½ months of age, but only the tip will be visible at first. The crown is completely erupted by around 6 to 7 months of age. During this time, the premolars and molars are also erupting, so that by the time the animal is 7 months of age, the complete permanent dentition should be present. Recently erupted teeth are normally very large, white and clean looking.
Fun Factoid: Note that there are no deciduous precursors for the first premolar of the adult dog.
When observing the deciduous dentition of a puppy or kitten, note that there are no molars, which is also apparent in the dental formula. Molars have no deciduous precursors. This means that the most caudal deciduous tooth you see in the dental arch is designated a premolar and is the precursor for the permanent fourth premolar. Sometimes the shape of the last deciduous premolar you see in the arch resembles the first molar tooth of the adult. This can be confusing, but remember that the deciduous teeth are much smaller than the permanent teeth, and watch for the molar to erupt caudal to that last deciduous premolar and you will see the difference.
It is important to be familiar with the basic root structure of each tooth for the purposes of recognizing and treating periodontal disease, and for extractions. The photos in the textbook on pages 9 and 10 illustrate the number of roots in the dog or cat. Important points to remember is that in both the dog and the cat, all canine and incisor teeth are single rooted. There are normally no three rooted teeth in the mandible. In the maxilla, the first three-rooted tooth in the maxilla as you move caudally from the front of the mouth, is the upper fourth premolar.
Multirooted teeth do not always have roots that are equal in size, nor is the furcation always centrally located. For example, the lower molar of the tooth in the cat has one large wide root and one thin root (see figure 1-11 on page 10).
Some terms for surfaces of the teeth are related to the other anatomical structures that are nearby. As you look at an animal’s mouth, the surfaces of the teeth immediately facing you are informally called “outside” surfaces of the teeth. The accepted term for the "outside" surface is vestibular. Specific terms for these surfaces are labial (facing towards the lips) and buccal (facing towards the cheeks). Less commonly, some veterinarians also use the term facial (towards the face) when referring to the outside surfaces.
As you look on the inner surfaces of the teeth of the maxilla, you are then looking at the palatal surfaces because these surfaces are facing the palate. As you look at the inner surfaces of the teeth of the mandible, the tongue is next to these surfaces and so that is called the lingual surface. The lingual surface may also be used when describing the inside surface of the palatal teeth.
The term mesial refers to those surfaces of the tooth that are closest to the midpoint of the dental arch, which is between the central incisors. The term distal refers to that surface of the tooth that is farthest away from the midpoint.
Where the various types of surfaces meet is termed a line angle.
The area in between the teeth is called the interproximal area. When there is a large space between teeth, it is called a diastema. A diastema is normal for certain regions of the mouth in many animals, such as between the upper third incisor and upper canine in the dog and cat. The space is needed for the lower canine to fit when the animal closes the mouth.
Dental numbering systems
There are several numbering systems developed for dentistry notation, but the 2 most common systems used that you need to be familiar with are the anatomical and modified Triadan systems. These numbering systems are used in recording clinical findings on the medical records and help to shorten the amount of writing that is required while at the same time making the record very exact. Most technicians find that they prefer one system over the other.
Both systems use the concept of quadrants to designate the nomenclature of each tooth. A quadrant divides the oral cavity into left and right halves, and also upper and lower halves so that there are a total of four sections, or quadrants.
Anatomic system for notation
The anatomic system uses a letter to designate the tooth group: I for incisors, C for canine, P for premolar, and M for molars. Deciduous teeth are designated with a lower case letter. Then each tooth is assigned a number within its group type to designate its position in the arch. The numbering starts at the midpoint of the dental arch, between the central incisors, and then progresses caudally. There are 6 incisors total, but if we start at the midline, and work caudally through the mouth along the arch, we find there are 3 incisors in a quadrant. So incisors are then numbered 1, 2, and 3.
The quadrant that the tooth is in determines where the number is placed next to the letter. If the tooth is from the right side, the number is put on the right side of the letter, and vice versa. So, for example, the second incisor encountered from the midpoint is incisor 2 and if we were on the right side of the animal’s head, then the designation would be “I2”. However, the number is also placed in a subscript or superscript position depending on if the tooth is from the upper or lower jaw. So if the tooth is from the maxilla, the number will be put in a superscript position next to the letter. Then the designation for the upper right second incisor is “I2”.
As we move caudally through the dental arch, we find that there is only one canine in each quadrant, so the only number used for the canine is “1”.
Premolars in carnivores are numbered according to the carnassial tooth group. The carnassial teeth are the fourth upper premolar and the lower first molar. The upper fourth premolar overlaps the lower first molar in a sectorial type of occlusion, so that the food is processed on the sides of the teeth in a chopping fashion. You can easily identify the fourth upper premolar by observing the teeth caudal to the canine tooth. The largest triangular shaped tooth in the maxilla caudal to the canine is the upper fourth premolar. The mandibular tooth that is overlapped by the upper fourth premolar is the lower first molar and also happens to be the largest tooth caudal to the canine in the mandible.
Now you can figure out the number designation of the premolars for any carnivore. The number designation of the premolars is determined by their relationship to the carnassial teeth. The premolars in the maxilla are numbered according to their position related to the upper fourth premolar. The tooth immediately in front of the upper fourth premolar is the third premolar, and so on. Since the dog has a total of four upper premolars, the premolars are numbered 1, 2, 3, and 4, with the fourth upper premolar being a carnassial tooth. The premolars in the mandible are numbered according to their position related to the lower first molar, which is the mandibular carnassial tooth. The tooth immediately in front of the lower first molar is always designated the fourth premolar in the mandible. Since the dog has a total of 4 premolars between the canine and the mandibular first molar, the premolars are numbered 1, 2, 3, and 4.
The cat is missing some premolars when compared to the dog. The cat has a total of 3 upper premolars and these are designated premolars 2, 3, and 4. (See figure 1-11 on page 11). Remember we number the upper premolars according to the upper fourth premolar. Therefore, the cat is said to be missing the first premolar in the maxilla. The first tooth you encounter in the upper arch caudal to the canine tooth in the cat is premolar 2, also called the second premolar. In the mandible, the cat has a total of 2 premolars and these are designated premolars 3 and 4, because of their relationship to the lower first molar. Therefore, the cat is said to be missing the first and second premolars in the mandible.
Modified Triadan system for notation
The modified Triadan system labels each tooth by a code of 3 numbers, starting at the midpoint of the arch in each quadrant. The first number designates the quadrant. The upper right quadrant uses the number 1, the upper left quadrant uses 2, the lower left quadrant uses 3, and the lower right quadrant uses 4 as the quadrant designation. Deciduous teeth use the series 5-8 for the quadrants.
The second 2 numbers are determined by the tooth position counting back from the midline of the arch in each quadrant. Incisors are numbered 01, 02, 03 canine is 04, premolars 05, 06, 07, 08 and molars 09, 10, 11, etc. So for example, the Triadan number for I2 is 102. Refer to figures 1-14 on page 16 and 1-15 on page 17 for the complete Triadan numbering of the dog and cat.
The Triadan system is adaptable to any species regardless of how many teeth are normally present for that species, or not. However, in order to assign the Triadan numbers to species that are normally missing teeth in the dental formula, you need to know the anatomic number designations, especially for the premolars. Since the cat is missing the upper first premolar, you should have noticed on the Triadan chart in the book that there are no 105 or 205 teeth. Likewise for the mandibular premolars, since the cat is missing the first and second premolars, there are no 305, 306 or 405 or 406 teeth. You can always remember the rule of 4 and 9 to help keep you oriented when determining the Triadan numbers. The canine tooth always ends in a 4, and the first molar always ends in a 9. Then you can count forward or backwards in the dental arch as needed.
Dental charts for medical records are most often some type of picture diagram of the dentition. Some dental charts use lateral views, open mouth views, or panoramic views. Most records have only the permanent dentition represented, but occasionally there is a need for a chart that shows the deciduous teeth as well. Findings are marked on the diagram or in boxes assigned for each tooth using abbreviations and marks on the tooth diagrams. A key should always be present on the chart so that future operators may know what the markings mean and be able to figure out the animal’s history.
An example of a panoramic chart using the anatomical system is seen in figure 1-16 on page 18 and in figure 1-17 on page 19. The panoramic view looks as if the animal is smiling widely at you.
Do not record normal findings, as that would severely clutter the record. Abnormal findings regarding missing or extra teeth and lesions of the gingiva or crown are the items most commonly noted on the chart. Treatments are also recorded. Some veterinarians keep two separate charts for each treatment session that an animal has. One chart is for oral examination before treatment begins, and then the other chart is for a description of the actual treatment. Using two dental charts per session is useful for complicated cases when there otherwise would not be enough room on the chart to write all the information.
Please answer these questions in complete sentences and submit your answers to the assignment in Blackboard:
Acknowledgement: Many thanks to the students, staff, and faculty of NVCC for allowing me to photograph their pets for these dental lessons.
Baker GJ and Easley J: “Equine Dentistry” WB Saunders Company, Philadelphia, 1999, p. 3.
Evans HE: Miller’s Anatomy of the Dog third edition WB Saunders Company, Philadelphia, 1993, pp. 132-133, 385-393
Holmstrom SE: Veterinary Dentistry for the Technician and Office Staff” WB Saunders Company, Philadelphia, 2000, pp. 293-323
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