Dental building blocks: Anatomy, charting and cleaning (Proceedings)

Skeletal Anatomy: Skull Types

There are 3 common head shapes in the dog and cat.

Mesocephalic or mesaticephalic - the most common head shape. Cephalic means head. Meso or mesati means medium. Typical mesocephalics are poodles, corgis, Labrador retrievers, and domestic shorthair cats.

Brachycephalic - brachy means short. Brachycephalic animals have a short and wide skull. This commonly results in crowded and rotated premolars. Typical brachycephalic animals are boxers, pugs, bulldogs, and Persian cats.

Dolichocephalic - dolicho means long and straight. These animals have long, narrow heads with an extremely long and thin mandible. Typical dolichocephalic animals are greyhounds, borzois, and sealpoint Siamese cats.

Maxillary

Incisive Bone

The rostral part of the maxilla. Within the body of the incisive bone are the six incisor teeth and the oval palatine fissures.

Dorsal aspect

• Nasal aperture: This is composed of 2 symmetrical halves separated by the nasal septum

Ventral aspect

• Incisivomaxillary suture

• This articulates the incisive bone with the maxilla.

• Incisive foramen : This is the opening to the incisivomaxillary canal

Maxillary Bone

The main body of the maxilla. Within the body of the maxilla are the premolars and molars.

Dorsal aspect

• Infraorbital foramen: The most prominent feature of the dorsal maxilla. It is the opening to the cranial end of the infraorbital canal through which passes the infraorbital nerve, artery and vein.

• Maxillary foramen: Opening to the caudal end of the infraorbital canal.

• Pterygopalatine fossa : this is where the pterygoid and the palatine bones meet. Located in the rostral part of this fossa are two foramina.

• Sphenopalatine foramen: This opens into the sphenopalatine canal which carrys the caudal nerves and vessels to the nasal cavity

• Caudal palatine foramen: This is located ventral to the sphenopalatine foramen. This opens into the palatine canal which carries the anterior and posterior nerves and vessels to the hard and soft palate

• Alveolar bone: This is the bone in which the tooth roots sit.

• Alveolar jugae: The bony prominences on the buccal wall the alveolar bone

Ventral aspect

• Palatine suture: midline of the hard palate

• Palatine sulcus: These are the bony troughs that sit on either side of the palatine suture. The major palatine nerves and vessels pass along this sulcus to supply the tissues of the hard palate

• Major palatine foramen: This is located palatal to the upper fourth premolar

• Minor palatine foramen: This is located palatal to the upper first molar

• Interradicular septa: This is the bone that separates the roots of an individual tooth

• Interalveolar septa: This is the bone that lies between teeth

Mandibular

The lower teeth are embedded in the mandible. The mandible is made up of symmetrical bilateral bones. The areas of the mandible are divided into three areas – the symphyseal, the body and the ramus.

Symphyseal Region

This contains the incisors and canine teeth

Mandibular symphysis: The strong fibrous joint that fuses the two bones of the mandible at the rostral aspect

Anterior mental foramen: These are located just below and between the first and second incisor.

The Body of the Mandible

This contains the premolars and molars.

Middle and posterior mental foramina: These are located on the buccal aspect of the mandible apical to the second premolar and third premolar respectively. The mental nerves run through the anterior, middle and posterior mental foramina innervating the lower lip and chin.

The Ramus of the Mandible is the perpendicular portion of the bone.

Masseteric fossa: This is located on the buccal aspect of the ramus. It is a depression which serves as a point of insertion for the masseter muscle.

Mandibular foramen: This is located on the lingual aspect of the ramus. The inferior alveolar nerve passes through this foramen into the mandibular canal and innervates the mandibular teeth.

Anatomy of the Periodontium

Attached gingiva: This is the gum tissue that is attached to the outer layer or periosteum of the alveolar bone.

Marginal or Free gingiva: Coronal to the attached gingiva at the cemento-enamel junction.

Gingival Sulcus: The space between the tooth and the free gingiva

Mucogingival Line (MGL): The line that separates the attached gingiva from the free gingiva.

Dentition And Tooth Classifications

Heterodont - teeth of mixed form and function

Diphyodont - having a set of primary (deciduous) teeth and secondary (permanent) teeth

Anelodont - having a limited period of growth as they develop roots

Brachyodont - having a root that is longer than the crown

Hypsodont - having a long crown and a short root, much of the crown is held in reserve subgingivally in the alveolar bone.

Elodont - teeth that grow throughout life and never develop roots

Dogs and Cats - Heterodont, diphyodont dentition with anelodont, brachyodont teeth

Horses - Heterodont, diphyodont dentition with anelodont, hypsodont teeth

Rabbits - Heterodont, diphyodont dentition with elodont teeth, the deciduous teeth are not functional and are exfoliated shortly before or after birth

Dental Anatomy: Tooth Anatomy

Crown: That part of the tooth that is visible above the gumline

Enamel: The outermost layer of the crown. It is the hardest body substance. It prevents the tooth from being invaded by bacteria and acids. Is not a living substance, so if damaged it will not regrow.

Dentin: Layer under the enamel. It is less calcified than enamel. It is continuously secreted by the odontoblasts which are located on the dentinal side of the pulp chamber. It has a porous structure made up of tubules which run from the pulpal tissue to the cementodentinal junction.

Root: The tooth structure below the gumline.

Cementum: Layer of bony tissue which covers the root

Periodontal Ligament: Attaches to the cementum on one side of the tooth, and the alveolar bone of the jaw on the other.

Pulp Chamber (crown)/ Root Canal (root): Is located in the center of the tooth. It is made up of connective tissue, nerves, blood, and lymphatic vessels. The pulp has four main functions: 1. Forms the dentin. 2. Gives nutrition to the dentin through the tubules. 3. Supplies nerve sensitivity to the dentin. 4. Protects itself through the secretion of reparative dentin in response to injury. It appears as shiny black or brown over the surface of worn teeth.

Tooth Types

Incisor: There are six incisors in the maxilla and six incisors in the mandible. The function of the incisor is for tearing, nibbling and grooming. Each incisor has one root.

Canine: There are two canine teeth in the maxilla and two canine teeth in the mandible. The function of the canine is for grabbing and tearing food and protection. Each canine has one root. The root is longer than the crown to protect against trauma. Because of the amount of trauma this tooth is subjected to, it is most prone to fracture.

Premolar: The premolars are located behind the canine teeth. The function of the premolar is to hold and cut food into digestible pieces. In the dog, there are eight premolars in the maxilla and eight premolars in the mandible. In the cat, there are six premolars in the maxilla and four premolars in the mandible. The premolar can have one, two, or three roots in the maxilla and one or two roots in the mandible.

There are no three rooted teeth in the mandible.

Molar: The molars are located behind the premolars. The function of the premolar is to grind food. In the dog, there are four molars in the maxilla and six molars in the mandible. In the cat, there are two molars in the maxilla and two molars in the mandible.

In the dog, the molar can have two or three roots. The cat molars have one or two roots.

Carnassial Teeth: Carnassials are the cheek teeth found in carnivorous animals. Their large and pointy appearance allows them to shear flesh and bone. In the dog and cat the carnassial teeth are the upper fourth premolar and the lower first molar.

Permanent Dentition

Adult Dog

The adult dog has a total of 42 permanent teeth.

Dental Formula for the Adult Dog

2x (3/3 I, 1/1 C, 4/4 P, 2/3 M) = 42

Adult Cat

The adult cat has a total of 30 permanent teeth.

Dental Formula for the Adult Cat

2x (3/3 I, 1/1C, 3/2P, 1/1M) = 30*

*the upper first premolar and the lower first and second premolar are absent

Deciduous Or Primary Dentition and Eruption

Incisor and canine deciduous teeth are smaller in size than their permanent counterparts. There is no deciduous counterpart for the first premolar or the molars. The deciduous maxillary fourth premolar is anatomically similar to the maxillary first molar.

Deciduous Formula for the Dog

2x (3/3 I, 1/1 C, 3/3 P) = 28

Deciduous Formula for the Cat

2x (3/3 I, 1/1 C, 3/2 P) = 26

Tooth Eruption Timetable*

Tooth Maturation

The enamel of the tooth is completed at the time of eruption. During the dog or cat's life, the only way the structure of the enamel changes is through dental abrasion or tooth fracture. The layer beneath the enamel called the dentin is produced by the odontoblasts lining the pulp chamber. Dentin is produced throughout the life of the dog and cat. When a permanent tooth has first erupted the apex of the root is open and the pulp chamber almost takes up the entire width and length of the tooth. As the dog or cat ages, closure of the apex, known as apexogenesis occurs by the continuous deposition of dentin along the walls of the pulp chamber. Radiographically you can see a narrowing of the pulp chamber as the animal ages.

Directional Terminology

Maxillary: Relating to the upper jaw

Mandibular: Relating to the lower jaw

Lingual (mandible)/Palatal (maxilla) Surface: Toward the tongue or the hard palate

Labial (lips): Surface of the incisors facing the lips

Buccal (cheek): Surface of the premolars and molars facing the cheek

Occlusal Surface: Chewing surface of a posterior tooth

Interdental/Interproximal: In between teeth

Coronal: In direction of the crown tip

Apical: In direction of the root tip

Mesial: Closest to the midline

Distal: Away from the midline

Subgingival: The area below the gum line.

Supragingiva: The area above the gum line on the crown.

The Dental Cleaning Procedure

Getting Ready

Lay out dental instruments, gauze sponges, antibacterial flush, prophy polish and prophy cups. Turn on and prime the power scaler per the manufacturer's instructions. Gather the supplies needed for anesthetic induction. Look over the bloodwork and see if any changes to the anesthesia protocol need to be adjusted to best match the patient. Perform a TPR on your patient, figure up doses for anesthetic induction.

Preparing the Patient

Once general anesthesia has been induced, the patient is intubated to ensure that no water or debris is aspirated. Position the patient in lateral recumbency with the head slightly lower than the tail. This allows drainage of water and other irrigation solutions.

Prepare Yourself

Scaling and polishing aerosolizes bacteria and debris. You must protect your eyes and mouth. It does not feel good to get prophy paste or bits of dental calculus in your eye or worse yet, behind a contact lens. You should wear goggles or a face shield, surgical mask and exam gloves.

Dental Instruments for the Cleaning and Polishing

As in human dentistry, veterinary dentistry uses a combination of power and hand instrumentation. Periodontal therapy and exodontics are the primary procedures done in the small animal practice. The technician's knowledge of the instruments needed for these procedures is crucial in order to quickly diagnose and treat the dental patient.

Types of Hand Instruments

Scalers – This instrument has a sharp tip and three sharp edges. The blade can be straight or curved. If you look at the instrument with the tip pointing towards you, it looks like a triangle. It is used only for the removal of supragingival calculus. While there is a myriad of different types of scalers, the most common are the Townsend sickle, the Jacquette, and the Morse.

Curettes – This instrument has one or two sharp edges, a rounded back and a blunt tip or toe. They are used to remove calculus and debris from below the gumline both on the root surface called root planing, and to remove calculus and debris from the opposing surface of the gingival tissue called gingival curettage. The two most commonly used curettes are the Universal (Columbia, Barnhart) which can be used throughout the mouth and the Gracey which has one cutting edge and are area specific. The lower numbers are for incisors and canines and the higher numbers are used on premolars and molars.

Explorers – This instrument is used to examine the tooth surface. It's delicate and flexible steel tip is used to detect any abnormalities using the handlers sense of touch and/or hearing. The most common type of explorer is the Shepherd's hook. There is also a finer tipped explorer when you need more tactile sense to find smaller defects.

Periodontal Probes – This instrument is used to measure the depth of the gingival sulcus or it can measure gingival recession, which ascertains the stage of periodontal disease. Periodontal probes are calibrated in 1-3mm intervals using notches or color changes.

Power Instruments

Ultrasonic Power Scalers

Magnetorestrictive – This is the most commonly used scaler in practice. The insert fits into a handpiece. The insert is made up of stacked strips of laminated nickel or a ferroceramic rod a.k.a ferromagnetorestrictive. The metal strip insert vibrates causing the tip to move in an elliptical pattern. The ferromagnetorestrictive has a circular tip action. Water cools the tip by flowing into the handpiece and out through the tip. The magnetorestrictive operates at either 25 or 30 kHz. The ferromagnetorestrictive operates at 42 kHz.

Piezoelectric – This scaler has quartz crystals in the handpiece that expand and contract at a constant frequency. The tip has a back and forth motion and oscillates at 45 kHz. The tips screw into a metal base.

Because ultrasonic scalers operate at such a high frequency, they can generate significant heat. Leaving the tip on a tooth for too long or not having a constant water flow can cause thermal damage to the pulp. But when compared to the sonic scalers, the circular motion and the higher frequency decrease the working time.

Sonic Scalers

Sonic scalers are usually air driven. The compressed air has a cooling effect and is also irrigated with water at the tip. Because of the presence of the compressed air, they are less likely to cause heat related damage to the teeth that the ultrasonic units can do. The water primarily flushes debris which allows for better visualization. These units operate below 20 kHz and at 30-40 psi of air pressure. The tips for these units also screw into a metal base in the handpiece.

Scaler Tips

Tips are available for both the ultrasonic and the sonic scaler for subgingival and supragingival use. The tips do wear down and should be replaced per manufacturer's instructions or sooner depending on use.

Lowspeed Handpieces and Attachments

Lowspeed handpieces are used primarily in this application for polishing teeth. They run from 5,000 to 20,000 rpm.

Prophy Angle – This attaches to the lowspeed handpiece. A soft rubber prophy cup fits onto the angle either with a screw or snaps directly on to the angle. The prophy cup is filled with prophy paste and the teeth are polished. Thermal damage to the pulp can occur if the prophy cup is left on the tooth too long.

Dental Charting Systems

There are two commonly used systems – the Anatomic System and the Modified Triadan System

Anatomic System – Incisor = I, Canine = C, Premolars = P, Molars = M, Upper = U, Lower, Left = L, Right = R. The deciduous teeth are noted in lower case. This system is readable by all clinicians

Modified Triadan System – It uses three numbers – the first number identifies the quadrant, the second and third numbers identify the tooth. The mouth is divided into 4 quadrants – 1 = right maxillary, 2 = left maxillary, 3 = left mandibular, 4 = right mandibular. The numbering of the teeth begins in the front of the mouth. The central incisor = 01, the intermediate incisor = 02, the third incisor = 03. So when you put the parts of this system together, a left upper third incisor is 203. The deciduous teeth quadrants are noted as 5,6,7,8. There is the rule of 4s and 9s – the canine tooth is always designated by 04 and the first molar is always 09. The teeth can be counted backwards from either a 04 or 09.

The Oral Exam and Charting

When the patient is under anesthesia, these are the conditions certain conditions need to be noted on the dental chart. Notations can be made either written out in long hand or using shorthand. Some dental charts will provide a legend for the shorthand notations.

Missing or extra (supernumerary) teeth: These teeth are colored in or circled on your chart. Supernumerary teeth are drawn in on the chart and noted as SN.

Gingival health: This is noted as a general condition of the whole mouth as either mild, moderate or severe gingivitis or using the abbreviation GI, GII or GIII

Plaque and calculus level: This is noted as a general condition in the mouth as either slight, moderate or heavy or using the abbreviations C/S, C/M or C/H

Mobile teeth: Touch the top of your tooth with your periodontal probe and attempt to move the tooth. There are 3 grades of mobility – M1 = < 1mm movement side to side, M2 = 1mm movement or greater side to side and M3 = >1mm movement side to side and up and down in the socket

Gingival recession and hyperplasia : Gingival recession is the shrinking back of the free gingival in the presence of bacteria, plaque and dental calculus. Using your periodontal probe, measure the distance from the cementoenamel junction to the gingiva. Note it as GR with the number of mm of recession. Hyperplasia is the excessive growth of gingival tissue. It causes false pockets. With your periodontal probe, measure the false pocket from the top of the hyperplastic tissue to where the free gingiva would start. Note it as GH with the number of mm of hyperplasia.

Furcation exposure: The furcation is the junction where the roots meet at the cementoenamel junction. Using your periodontal probe, gently insert into the exposed furcation. F1 = furcation can just be detected by the probe, F2 = probe can pass halfway into the furcation and F3 = probe can pass all the way through the furcation to the palatal or the lingual aspect of the tooth.

Fractured teeth: This is noted on the dental chart as FX. Check the fracture for pulpal exposure. If there is pulpal exposure, the explorer will stick like you are sticking it into candle wax. If there is pulpal exposure, it will be noted as PE.

Enamel loss (from fracture, wear or abnormal development)

Masses or ulcerative lesions (don't forget the palate and under the tongue) : measure the size and note the location and shape. Note whether a biopsy was taken and from where.

Abnormal pocket depth found with your periodontal probe : The periodontal probe is gently inserted into the gingival sulcus. Any abnormal depths are noted on the chart in mm next to the tooth in question on the aspect of the tooth where it was found.

Caries, cervical neck (resorptive) lesions : Any lesion on the enamel will be picked up with your explorer. Again, it will stick like you are sticking it into wax and catch on the edge of the lesion. Caries are usually seen on the occlusal surface of premolar 4 and the molars and are noted as CA. Resorptive lesions are graded RL I-V depending on how deep into the tooth they are and how much crown destruction there is.

Steps of the Dental Cleaning

Gross Calculus Removal

Heavy calculus can be gently cracked off the tooth surface using extraction forceps. Position each jaw of the extractor on each side of the tooth above the gumline. Press the jaws together till the calculus cracks and gently pull the calculus coronally.

Power Scaling

Place a couple of gauze sponges at the back of the mouth. This will prevent any debris from flying into the trachea. DON'T FORGET TO REMOVE THE GAUZE AT THE END OF THE PROCEDURE. Contact the side of the scaler tip to the tooth surface and using a feather light touch, use overlapping short strokes over the tooth surface until the calculus is removed. Do not stay on the tooth longer than 5 seconds. This can cause thermal heat buildup of the pulp which can lead to pulpal necrosis. You can always come back to that tooth again. Scale the buccal surface of the up side and the lingual/palatal aspect of the down side of the patient. Repeat these steps when the patient is turned over.

Hand Scaling

Supragingival scaling – Thoroughly rinse the debris out of the mouth. Remove the gauze and replace it with dry ones. Blow air on the scaled tooth surfaces above and below the gumline. The leftover calculus deposits will turn a chalky white. Using your hand scaler, remove any leftover calculus. Use the sides of the scaler for along the surface and the tip in the developmental grooves. Repeat the rinsing and blowing until you are satisfied that the calculus is gone.

Subgingival Scaling and Root Planing – The dental curette is gently placed beneath the gingiva, making sure the rounded side of the instrument is towards the gum. Adjust the instrument so that the cutting edge is under the calculus and pull up on the calculus. Repeat these strokes until the deposits are removed and the tooth surface or root surface feels smoother. Turn the curette around and using a gentler pull up stroke, remove any calculus and debris that has collected on the tissue.

Polishing

Power and hand scaling leave permanent etching on the teeth. This gives a place for plaque and calculus to hold. You must polish the teeth to remove the etching.

You attach a prophy angle to a lowspeed handpiece. On the tip of the prophy angle you attach the prophy cup. The prophy cup is made of soft rubber with webbing inside to hold the prophy paste. There are two types of prophy cups, the screw in and the snap on. Make sure the type of cups you buy match the prophy angle. There are also disposable prophy angles which have the prophy cup built in. You then throw the whole prophy angle away after each patient.

Prophy paste comes in fine, medium or coarse grit. Fine or medium is sufficient for dogs and cats. The paste can be purchased in a bulk jar or in individual cups. Place a small amount of prophy paste in your prophy cup. Spread the paste along 3-5 teeth. Place more prophy paste in your cup. Run your polishing head along the teeth. Spend only a few seconds on each tooth. Apply enough pressure on the cup to flare the edges. This will allow you to gently place the cup as close to the gingiva as possible. Thoroughly rinse all the prophy paste out of the mouth, paying close attention to the hard palate and under the tongue. At this time you can apply a solution containing chlorhexidene 0.02% and a fluoride treatment

Final Treatments and Charting

Report your final findings on the dental chart and report the findings to the doctor and gather your instruments and supplies for the doctor's portion of the treatment.

Once all the treatments have been done to the patient, clean all the hand instruments in disinfectant using a brush, test for dullness and sharpen if necessary. Sterilize your instruments. Clean and lubricate your handpieces and dental units. Write up send home instructions.

References

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Gioso, MA, Carvalho VGG. Oral anatomy of the dog and cat in veterinary dentistry practice. Vet Clin Small Anim 35 (2005), 763-780.

Gorrel C, Derbyshire S. Anatomy of the teeth and periodontium. In: Veterinary dentistry for the nurse and technician. Edinburgh: Elsevier Butterworth Heinemann; 2005, 25-29.

Holmstrom SE. Introduction. In: Veterinary dentistry for the technician and office staff. Philadelphia: WB Saunders Co.; 2000, 1-22.

Orsini P, Hennet P. Anatomy of the mouth and teeth of the cat. Vet Clin Small Anim 22 (1992), 1265-1277.

Verstraete, FJM. Self assessment color review of veterinary dentistry. Ames: Iowa State University Press; 1999, 9-10.