Fig. 9.1 Radiograph of the rostral teeth: lateral view. The canine teeth are large in this horse (probably a male). The first premolar teeth (wolf teeth) are not present.

Fig. 9.2 Radiograph of the cheek teeth: lateral view. Compare the roots of P₄ (erupts c. 4 y) with those of M₁ (erupts c. 9–12 m).

Fig. 9.3 Radiograph of the mandible: lateral oblique view. Dentally immature horse. The developing crowns of the permanent mandibular premolar teeth (P₂–P₄) lie beneath the roots of the temporary premolar teeth (p₂–p₄). They produce palpable bony prominences on the ventral borders of the mandibles in chronological sequence, between the ages of 1½ and 3–4 years. Each prominence disappears after each temporary premolar tooth is lost and the crown of the permanent premolar tooth comes into wear.

A similar developmental sequence of palpable prominences in the maxillary bone occurs, between the ages of 2 and 5 years, at the level of the infraorbital foramen, when the upper permanent maxillary premolar teeth (P²–P⁴) develop and eventually replace the temporary maxillary premolar teeth. At about 2 years of age, the palpable infraorbital foramen lies dorsal to the prominence related to p³ and the developing P³ tooth. At about 3½ years of age, all three maxillary prominences are in line with the supraorbital foramen. See Fig. 1.55 and compare the positions of p² and p³ and the infraorbital foramen in the foal with those shown for P², P³ and the infraorbital foramen in the adult horse (Fig. 1.44). None of these mandibular or maxillary bony prominences are seen in the horse at 6 years of age (Fig. 1.44).