References

1. Cell, PGH and Coombs, RRA: Clinical Aspects of Immunology. 2nd ed. FA Davis, Philadelphia. 1968.

2. Rilk, RF. AustJAgric Res 5 (1954)109.

3. Eyre, P. Vet Rec 91 (1972) 134,

4. Farrelly, CT et at. Irish Vet J 20 (1966) 42.

5. Collins, JD, Proc 1st Int Symp on Hematol,1975. p 342.

6. Francis, J: Tuberculosis in Animals and Man.Cassell, London, 1958.

7. Eyre, P. Vet Rec 90 (1972) 36.

8. Mansmann, RA el at. JAVMA 166 (1975) 673.

9. Mansmann, RA. Doctoral thesis, Univ Calif,1973.

10. McGavin, MD et al. JAVMA 160 (1972) 1632.

11. Carroll, EJ et al. JAVMA 146 (1965) 1300.

12. Gertsen, KE. Proc 16th Ann Mtg Am Assoc Eq Pract, 1970. p 309.

13. Rooney, JR: Autopsy of the Horse. Williams &Wilkins, Baltimore, 1973.

14. Gabel, AA and Koestner, A. AVMA 142 (1963) 1397.

15. Mansmann, RA. Vet Clin No Am 5 (1) (1975) 84.

16. Bur Vet Med Memo. FDA Publ No 80-6029, 1980.

17. Latour, JG etal. Am J Path 65 (1971) 189.

18. Nordstoga, K, Path Vet 4 (1967) 233.

19. Gabel, AA, Ohio St Univ: Personal communi cation, 1980.

20. Suzuki, Y et al. Proc 1st Int Symp on Hematol, 1975. p 34.

21. Stormont, CJ. Paper presented at symposium, Cornell Univ, 1979.

22. Gabel, in Catcott: Equine Medicine and Surgery. 2nd ed. American Veterinary Publications, Santa arbara, 1972.

23. Crawford, TB and Perryman, LE. Eq Pract 2 (2) (1980)17.

24. Mansmann, RA. J Eq Med Surg 3 (1979) 443.

25. Rumbaugh, GE et al. JAVMA 174 (1

437

Diseases of the teeth and paranasal sinuses by g,j. Baker

Dental Anatomy and Physiology

The Eocene ancestor of the modern horse had simple teeth. As its environment and diet changed, its browsing habit changed to graz­ing. Corresponding modifications in tooth structure subsequently occurred. These modi­fications involved the process of molarization of the cheek teeth fpremolar teeth adopting molar form), reserve crown formation and con­tinuous eruption with the development of crown cementum. This evolution of an efficient food-grinding apparatus and alimentary tract re­sulted in horses suited to a life of almost con­tinuous grazing. Their lips are selective and prehensile, and the incisor teeth form an effi­cient cutting apparatus. The cheek teeth func­tion as a serrated arcade and the temporoman-dibular joint accommodates the side-to-side movements of the mandible that grind food.

The deciduous (milk) teeth are represented by the dental formula ³⁰³₃₀₃ . Within a week of birth the first incisors erupt and within 2 weeks all 3 premolars erupt. The second inci­sors usually appear at one month and the third at 6-9 months of age. The deciduous incisors are shell-shaped compared with the rectangu­lar permanent incisors and are much smaller. A 2-year-old horse should not be confused with a 5-year-old on dental appearance (Fig 1).

The first molar (fourth cheek tooth) erupts at 9-12 months of age and the first permanent in­cisors at 2^l/2 years of age. By 5 years of age all deciduous teeth have been shed and the horse has its complete permanent arcade repre­sented by the dental formula ³¹³₃₁₃₃^{( or 4) 4} (Table 1).

The first permanent premolar may be absent or rudimentary and is popularly termed the "wolf tooth." In horses the term molar may be applied to any maxillary or mandibular teeth irrespective of the true definition of the term, ie, a molar tooth is a tooth not represented in the deciduous dentition. In this discussion, the teeth are described as cheek teeth, upper or lower, and numbered 1-6.

The canine teeth are usually absent or rudi­mentary in the mare. Like wolf teeth, canine teeth resemble a low-crowned tooth with a sim

Table 1. Tooth Eruption*

A.TEETH ERUPTION