Morphologic features of the modern

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3 CREDITS Article 1 features important topics on equine dentistry The First Premolar Teeth Cleet Griffin, DVM, DABVP Texas A&M University NEW Important topics on equine Abstract: The first premolar

Through study of the fossil record, it has been determined that wolf teeth are dental vestiges from ancestors of the modern horse.

performance, and bitting problems. Rationale exists for veterinarians to remove wolf teeth when necessary to alleviate discomfort and bitting problems.

1 In the Eocene period, the first ancestor of the horse a small, leaf-eating mammal called Hyracotherium had four toes on each front foot and three toes on each hind foot 2 and bore little

Fossils show that Hyracotherium had three incisors; one canine tooth; and seven primitive, short-crowned cheek teeth (four premolars and three molars) in each side of the upper and lower jaws.

1 3 CREDITS Article 1 features important topics on equine dentistry The First Premolar Teeth Cleet Griffin, DVM, DABVP Texas A&M University NEW Important topics on equine Abstract: The first premolar teeth (wolf teeth) of horses are considered a component of the permanent dentition and may be identified as Triadan 05. Through study of the fossil record, it has been determined that wolf teeth are dental vestiges from ancestors of the modern horse. Although wolf teeth may not be problematic for the horse, many believe that harm arising from the presence of wolf teeth in some horses may account for oral discomfort, abnormal behaviors during performance, and bitting problems. Rationale exists for veterinarians to remove wolf teeth when necessary to alleviate discomfort and bitting problems. dentistry Morphologic features of the modern horse s teeth represent adaptations to ecologic changes. 1 In the Eocene period, the first ancestor of the horse a small, leaf-eating mammal called Hyracotherium had four toes on each front foot and three toes on each hind foot 2 and bore little resemblance to modern horses. Fossils show that Hyracotherium had three incisors; one canine tooth; and seven primitive, short-crowned cheek teeth (four premolars and three molars) in each side of the upper and lower jaws. 3 Over time, the second, third, and fourth premolars as well as the three molars progressively became (through molarization ) long-crowned, complex, well-developed grinders as the horse adapted to prolonged periods of grazing. 1,3 The first premolar progressively became smaller and is now small, cone shaped, and usually situated just rostrally to the first well-developed cheek tooth 3 5 (figure 1). Thus, the first premolar (wolf tooth) is a functionless remnant from ancestors of the modern horse. 1 5 FIGURE 1 At a Glance Triadan Tooth Numbering System Page 70 Anatomy and Eruption Page 71 Rationale for Removing Wolf Teeth Page 75 The maxillary dental arcades. Upper wolf teeth (arrows; Triadan 105 and Triadan 205) are just rostral to each row of the upper cheek teeth. 68 Compendium Equine: Continuing Education for Veterinarians March 2009 CompendiumEquine.com

FREE Wolf teeth are functionless dental remnants from ancestors of the modern horse. There are several possible origins of the term wolf tooth, some of which appear to be based on superstition.

2 FREE Wolf teeth are functionless dental remnants from ancestors of the modern horse. There are several possible origins of the term wolf tooth, some of which appear to be based on superstition. In one publication from the 1700s, the term wolves teeth was used as a general description of teeth with sharp edges that could prick and wound the oral mucosa or tongue while eating. 6 At about the same time, Daubenton 7 described the horse s first premolars as supplementary premolars, 8 and some early 20th-century texts suggested that the term wolf teeth may have originated from the resemblance of these teeth to the incisors of carnivores. 8,9 Merrillat 10 used the terms remnant teeth and supernumerary teeth as synonyms for wolf teeth. He suggested that these Box 1. Triadan Tooth Numbering System Using the three-digit nomenclature system, the first digit designates the quadrant of the mouth and whether a tooth is deciduous or permanent. The numbering sequence for permanent teeth is right maxilla, 1; left maxilla, 2; left mandible, 3; and right mandible, 4. The deciduous teeth are designated as quadrants 5 through 8 in the same order. The subsequent digits in the numbering system designate each tooth within the quadrant, starting with the central (first) incisor, which is designated as 01. The incisors are designated as 01 to 03; the canine teeth, 04; the premolars, 05 to 08; and the molars, 09 to 11 (e.g., the central incisor of the upper right arcade is 101, the intermediate incisor of the same arcade is 102) 21,22 (Figure 2). teeth were retrogressive representatives of prehistoric horses premolars that were degenerating under the influence of selection. He further theorized that the use of the bit over many generations had rid the interdental space of premolars. 10 Easley 11 retold a remarkable story about a 16th-century military general s horse that had turned and reared, refusing to move forward into a battle. According to the story, removal of a small tooth in the area of bit contact alleviated the embarrassing behavior of the general s horse, which became a favorite mount for battle. Unable to leave well enough alone, the general s horseman concluded that the horse had sensed the presence of wolves when the bit was worked against the tooth, which instinctively caused the horse to shy in order to protect the general. 11 In some older publications, the first premolar teeth were blamed for eye problems, including excessive watering, inflammation, and blindness. 12,13 It was even speculated that wolf teeth adversely influenced ophthalmic branches of the fifth cranial nerve. 12 Therefore, wolf teeth were commonly removed from horses to alleviate eye ailments, resulting in use of the synonym eye tooth. 5,10,12,13 Apart from these myths and misconceptions, the presence of wolf teeth in horses remains an area of importance and interest to veterinarians. In general, wolf teeth are not considered to serve a useful purpose. Although wolf teeth may not be problematic for the horse, many horsemen and horsewomen believe that harm caused by the presence of wolf teeth FIGURE 2 Triadan classification of equine teeth. (From Floyd MR. The modified Triadan system nomenclature for veterinary dentistry. J Vet Dent Reprinted with permission from Baker GJ, Easley J, eds. Equine Dentistry. 2nd ed. Philadelphia: Elsevier; 2005) 70 Compendium Equine: Continuing Education for Veterinarians March 2009 CompendiumEquine.com

The First Premolar Teeth FREE FIGURE 3 The upper wolf tooth (green arrow; Triadan 205) is near the erupting second premolar (black arrow; Triadan 206).

) may account for oral discomfort, problems with the bit, and abnormal behavior of some horses at work.

3 The First Premolar Teeth FREE FIGURE 3 The upper wolf tooth (green arrow; Triadan 205) is near the erupting second premolar (black arrow; Triadan 206). A deciduous premolar cap (blue arrow; Triadan 606) is present. A small lower wolf tooth (yellow arrow; Triadan 305) is present. (Skull specimen.) may account for oral discomfort, problems with the bit, and abnormal behavior of some horses at work. 11,14 20 Anatomy and Eruption Anatomically, the wolf tooth is a component of the permanent dental formula of the horse and is designated as Triadan 05. Because practitioners are using the modified Triadan tooth numbering system more frequently to identify specific teeth, a review of the numbering system is provided 21,22 (Box 1 and Figure 2). The first premolars have a simple shortcrown (brachyodont) structure 22 and are composed of enamel, dentine, cementum, and a pulp chamber. 23 These teeth usually erupt between 6 and 12 months of age and may be present in up to 90% of yearlings. 11,22 When horses are approximately 3 years of age, supporting structures of the wolf tooth become sclerosed and calcified and the pulp chamber starts to obliterate with secondary dentine. 23 Wolf teeth are usually no more than 1 to 2 cm in length and have a single root of variable length and substance, ranging from short, loose attachments to the gingiva to 30 mm in length. 4,14,22 During eruption of the adjacent second premolar (which occurs at approximately 30 months of age), some wolf teeth may undergo root resorption or be shed. 4,24,25 This normal shedding process may account, in part, for the 13% to 32% reported incidence of wolf teeth in mature horses 22,25,26 (Figure 3). In my experience, the incidence of mandibular wolf teeth (Triadan 305 and Triadan 405) is very low; however, it has been reported that these teeth may be more common in some lines of Standardbred horses. 27 Lower wolf teeth are usually very small but can be FIGURE 4 An erupted lower wolf tooth (arrow; Triadan 305). Wolf teeth were once superstitiously and incorrectly associated with a variety of conditions. CompendiumEquine.com March 2009 Compendium Equine: Continuing Education for Veterinarians 71

FREE FIGURE 5 FIGURE 6 The upper left interdental space of a 3-year-old Quarter horse gelding.

FIGURE 7 A small, lower wolf tooth (arrow) is adjacent to the first cheek tooth. (Skull specimen.

the horse s performance. Oblique radiograph of the upper left interdental space (of the same horse in Figure 6).

4 FREE FIGURE 5 FIGURE 6 The upper left interdental space of a 3-year-old Quarter horse gelding. The commissure of the lips is retracted by the clinician to demonstrate the location of a nodular submucosal enlargement (arrow) that was detected by palpation of the interdental space. FIGURE 7 A small, lower wolf tooth (arrow) is adjacent to the first cheek tooth. (Skull specimen.) It is generally accepted that wolf teeth probably do not cause problems for most horses; however, in some cases, discomfort due to the presence of wolf teeth may cause bitting problems and affect the horse s performance. Oblique radiograph of the upper left interdental space (of the same horse in Figure 6). An unerupted wolf tooth is situated at an angle (within the white circle) just rostral to the larger first cheek tooth. large with a sharp point 25 (Figure 4). Careful examination is required to detect short, small, splinter-like lower wolf teeth because they can be positioned close to the second premolar and may be partially concealed by the mucosa of the cheek and gingiva (Figure 5). The upper wolf teeth usually erupt in a vertical plane close to the first cheek tooth. Occasionally, the crown of the upper wolf tooth may be positioned further rostral to or palatal or buccal to the second premolar. The crown may also be angled slightly in some instances. 22 Wolf teeth have been reported to be quite large and even molarized in Clydesdale horses or other draft breeds. 16,25 In some horses, a wolf tooth can be large, rostrally displaced, and mistaken for a supernumerary canine tooth. 28 Supernumerary wolf teeth are reported to be rare; however, small, superficial remnant portions of the deciduous second premolar may occasionally be found just rostral to the first cheek tooth and may be erroneously identified as a supernumerary wolf tooth. 14,19,28 Unerupted wolf teeth are occasionally detected in the upper arcades. Synonyms for unerupted wolf teeth include blind or impacted wolf teeth. 27 An unerupted wolf tooth is positioned along the maxilla several centimeters rostral to the first cheek tooth in a relatively horizontal orientation within the submucosa of the interdental space. Because of this orientation, the crown fails to erupt vertically through the mucosa. With careful palpation, a blind wolf tooth can usually be detected as a firm, nodular, submucosal enlargement. These teeth are generally small, so radiography can be useful for confirming their presence 25 (Figures 6 and 7). Unerupted wolf teeth of the mandible are reported to be rare and are probably very difficult to detect without the use of radiography Compendium Equine: Continuing Education for Veterinarians March 2009 CompendiumEquine.com

The First Premolar Teeth FREE Rationale for Removing Wolf Teeth Horses may experience oral pain as a result of pressure from the bit forcing the cheeks against sharp dental points.

14,16,17 Behaviors associated with oral discomfort caused by wolf teeth include bitting problems, head tossing, and head shaking.

5 The First Premolar Teeth FREE Rationale for Removing Wolf Teeth Horses may experience oral pain as a result of pressure from the bit forcing the cheeks against sharp dental points. 29 In some horses, a wolf tooth may cause discomfort as a result of the bit working against the tooth and forcing cheek mucosa into the sharp point of the tooth. 14,16,17 Behaviors associated with oral discomfort caused by wolf teeth include bitting problems, head tossing, and head shaking. 14,30 The presence of a wolf tooth also makes it difficult to adequately float and bevel the rostral portion of the second premolar (i.e., creating bit seats ). Wolf teeth that are enlarged, displaced, loose, fractured, or diseased are considered to be a source of pain. 14,18,25,30 Blind wolf teeth may cause discomfort when the mucosa is hit and compressed against the tooth by the bit. 27 Erupted and unerupted lower wolf teeth have also been associated with bitting problems in horses. 14,22 Therefore, I prefer to remove wolf teeth from young riding horses and from horses of any age with a history of performance problems that may be related to oral discomfort. On occasion, erupted upper wolf teeth may be present in mature horses that are being ridden successfully with a bit and have no history of oral discomfort. 14,31 If wolf teeth are detected during examination of this type of horse, the owner should be made aware of potential behavioral problems related to the teeth. Extraction is not recommended in these horses unless the wolf teeth begin to cause a problem. Acknowledgment The author acknowledges the following individuals at Texas A&M University s College of Veterinary Medicine for their assistance in preparing this article: Kathrin R. Burke, DrMedVet, Department of Veterinary Pathobiology; Kyle Westfall, veterinary technician, Veterinary Medical Teaching Hospital; Betsy McCauley, veterinary radiologic technologist, Veterinary Medical Teaching Hospital; and Larry Wadsworth, medical photographer, College of Veterinary Medicine Media Resources. TO LEARN MORE Watch for an upcoming article on extraction of the first premolar teeth. Upper and lower wolf teeth can be removed by a veterinarian to help the horse perform more comfortably. References 1. Soana S, Gnudi G, Bertoni G. The teeth of the horse: evolution and anatomo-morphological and radiographic study of their development in the foetus. Anat Histol Embryol 1999;28: Matthew WD. Evolution of the Horse. New York: Guide Leaflet Series; 1932: MacFadden BJ. Equine dental evolution: perspective from the fossil. In: Baker GJ, Easley J, eds. Equine Dentistry. 2nd ed. Philadelphia: Elsevier; 2005: Sisson S, Grossman JD. Anatomy of Domestic Animals. 4th ed. Philadelphia and London: WB Saunders; Jones WE. The Teeth of the Horse. Fort Collins, CO: Caballus Publishers; 1972: Bartlet J. The Gentleman s Farriery: or, a Practical Treatise on the Diseases of Horses. 8th ed. London; 1773: Based on information from English Short Title Catalogue. Eighteenth Century Collections Online. Accessed May 2008 at 7. Daubenton LJM. Histoire Naturelle, Générale et Particulière, avec la Description du Cabinet du Roi. Paris: Imprimerie Royale; 1763: Huidekoper RS. Age of the Domestic Animals. Chicago: Alexander Eger; 1903: Goubaux A, Gustave B. The Exterior of the Horse. 2nd ed. London: JB Lippincott; 1904: Merrillat LA. Animal Dentistry and Diseases of the Mouth. Chicago: Alexander Eger; 1905: Easley KJ. Equine canine and first premolar (wolf) teeth. Proc AAEP 2004;50: Korinek CJ. The Veterinarian. 2nd ed. Cedar Rapids, IA: The Veterinarian Publishing Company; 1916: Baker AH. Livestock and Complete Stock Doctor, A Cyclopedia. St. Louis: ND Thompson Publishing Company; 1916: Dixon PM, Dacre I. A review of equine dental disorders. Vet J 2005;169: Lane JG. A review of dental disorders of the horse, their treatment and possible fresh approaches to management. Equine Vet Educ 1994;6: Linkous MB. Performance dentistry and equilibration. Clin Techniques Equine Pract 2005;4(2): Easley J. Guidelines to extracting wolf teeth. Vet Pract News 2002: Gaughn EM. Dental surgery in horses. Vet Clin North Am 1998;14(2): Dixon PM. Equine dental disease, part 1: a long term study of 400 cases: disorders of incisor, canine, and first premolar teeth. Equine Vet J 1999;31: Scrutchfield L, Schumacher J. Examination of the oral cavity and routine dental care. Vet Clin North Am 1993;9(1): Easley KJ. Dental and oral examination. In: Baker GJ, Easley J, eds. Equine Dentistry. Philadelphia: WB Saunders; 1999;(1): Dixon PM. Dental anatomy. In: Baker GJ, Easley J, eds. Equine Dentistry. 2nd ed. Philadelphia: Elsevier; 2005: Stelzer P. Die Extraktion des Wolfszahnes beim Pferd (Extraction of the wolf tooth in horses). Der Praktische Tiearzt 2004;85(3): Nickel R, Schummer A, Seiferle E. The Viscera of Domestic Mammals. New York: Springer-Verlag; 1979;2: Easley KJ. Corrective dental procedures. In: Baker GJ, Easley J, eds. Equine Dentistry. 2nd ed. Philadelphia: Elsevier; 2005;2: Dixon PM. The gross, histological, and ultrastructural anatomy of equine teeth and their relationship to disease. Proc AAEP 2002;48: Scrutchfield WL. Dental prophylaxis. In: Baker GJ, Easley J, eds. Equine Dentistry. Philadelphia: WB Saunders; 1999;1: Dixon PM, Easley J, Ekmann A. Supernumerary teeth in the horse. Clin Techniques Equine Pract. Philadelphia: Elsevier; 2005;4: Manfredi J, Clayton HJ, Rosenstein D. Radiographic study of bit position within the horse s oral cavity. Equine Comp Exerc Physiol 2005;3: Lowder M. Dental conditions affecting the young horse birth to 2 years. Focus Dent Proc AAEP 2006: Scrutchfield WL. Wolf teeth: how to safely and effectively extract and is it necessary. Focus Dent Proc AAEP 2006: CompendiumEquine.com March 2009 Compendium Equine: Continuing Education for Veterinarians 75

FREE 3 CREDITS Test 1 This article qualifies for 3 contact hours of continuing education credit from the Auburn University College of Veterinary Medicine.

6 FREE 3 CREDITS Test 1 This article qualifies for 3 contact hours of continuing education credit from the Auburn University College of Veterinary Medicine. Subscribers may take individual tests online and get real-time scores at CompendiumEquine.com. Those who wish to apply this credit to fulfill state relicensure requirements should consult their respective state authorities regarding the applicability of this program. 1. Lower wolf teeth are reported to a. never cause bitting problems and should not be removed. b. be important for proper mastication of roughage. c. occur more frequently in some lines of Standardbred horses. d. none of the above 2. Which of the following has been associated with the presence of unerupted upper wolf teeth? a. nasal discharge b. behavioral problems when a bit is used c. lingual ulcers d. unilateral epistaxis 3. Which statement regarding wolf teeth in horses is correct? a. The terms wolf teeth and canine teeth are synonymous. b. Wolf teeth are functionless structures. c. Wolf teeth are necessary for proper mastication. d. Wolf teeth are composed entirely of enamel. 4. Upper wolf teeth usually erupt a. during the first year of life. b. in 100% of yearlings. c. only in some lines of Standardbred horses. d. none of the above 5. Unerupted upper wolf teeth are also called a. canine teeth. b. impacted wolf teeth. c. blind wolf teeth. d. b and c 6. Abnormal bitting behavior associated with the presence of wolf teeth in some horses includes a. head tossing. b. head shaking. c. vision problems. d. a and b 7. According to the modified Triadan system of dental nomenclature for horses, the first premolar of the left maxillary dental arcade is designated Triadan a c b d A veterinarian detects a firm, nodular, submucosal enlargement in the interdental space of the right side of the maxilla during examination of a 3-year-old Thoroughbred mare with bitting problems. The enlargement is 2 cm rostral to the first cheek tooth (Triadan 106). Which statement(s) is/are correct? a. An unerupted or blind wolf tooth should be suspected. b. Blind wolf teeth cannot cause bitting problems because they are padded by the gingiva. c. Radiography can be useful for confirming the presence of a blind wolf tooth. d. a and c 9. Lower wolf teeth (Triadan 305 and Triadan 405) may be a. associated with bitting problems. b. present in horses. c. very small. d. all of the above 10. During eruption of the permanent second premolar, some wolf teeth may a. undergo root resorption. b. be shed. c. a and b d. none of the above 76 Compendium Equine: Continuing Education for Veterinarians March 2009 CompendiumEquine.com

Our Teeth. History Of Equine Dentistry EQUINE DENTISTRY. Who Should Do Equine Dentistry? Some Facts To Know About Teeth

Our Teeth. History Of Equine Dentistry EQUINE DENTISTRY. Who Should Do Equine Dentistry? Some Facts To Know About Teeth EQUINE DENTISTRY Mike Black, DVM Nebraska Equine Veterinary Clinic Omaha NE History Of Equine Dentistry Some evidence of equine dentistry dates back to 2,000 B.C. Bit-Seats: Information on bit-seats dates