One Year
Viewed from in front, all deciduous incisors are visible, the crown of the centrals and intermediates is fully exposed and the neck may be discernible. In profile, the upper and lower corner incisors are not in contact. The dental tables of the centrals show considerable wear. The dental star is seen usually in the centrals and intermediates as a dark or yellowish-brown transverse line in the dentin on the labial side of the infundibulum. The corner incisors are sharp.

Three Years
Viewed from in front, the four permanent central incisors are seen just coming into wear. They appear more solid, have salient vertical ridges and grooves and are larger and broader than adjacent deciduous teeth. In profile, the deciduous intermediates appear pushed out and short. The neck is distinct on the intermediates and corners. The dental table of each central incisor has a deep cup and the borders of these teeth are sharp. The lower intermediates are smooth. The lower corners have little central enamel.

Four Years
View from in front, the permanent upper central and intermediate incisors are in contact with corresponding lower teeth. The jaws have acquired so much width for the centrals and intermediates that the deciduous corners can scarcely be seen. In profile, the corners appear very small; the upper corner is shown being pushed from its alveolus. In the lower jaw the canine is seen cutting the gum. (Canines may erupt as early as three and one-half years but usually at four years and three  months and as late as five years.) The Dental tables of the centrals show wear but their cups are deep. The intermediates are in wear but sharp; the deciduous upper corners show a portion of their roots exposed.

Five Years
Permanent dentition is complete; all teeth are in wear. Viewed from in front, the jaws appear convex in both directions. In profile, they have a similar disposition. The canines have erupted completely. The dental tables of the centrals and intermediates are wide transversely, show wear, but their cups are readily visible and completely encircled by the central enamel. The corners are commencing to wear at their labial border. (It is imperative that the form and dimensions of the central enamel be considered carefully.)

Seven Years
Viewed from in front, the teeth may appear whiter due to wearing of the cement although some teeth remain stained. In profile, the dental table of the lower corner incisor is narrower than that of the upper; this results in a notch upon the upper corner incisor, the seven year hook or notch. The incident angle of the incisive arcades is less perpendicular than at six  years. The dental tables of the lower centrals and intermediates are smooth, cups for practical purposes are no longer present. The ring of central enamel is narrower from side to side and nearer the lingual border. The lower corners still retain their cups.

Fifteen Years
Viewed from in front, the lower incisors may appear shorter than the uppers depending upon the angle from which they are observed. (This will vary depending upon height of horse and examiner.) In profile, the incisors appear to be about the same length. Galvayne’s groove extends  halfway down the labial surface of the upper corner incisor; the corner notch is often present. The dental tables of the lower centrals appear triangular, the intermediates are round to triangular and all lower incisors show in their center a dark, distinct, round dental star.

Appearance of the table (occlusal) surface at different
stages of wear.

1. Shortly after eruption its breadth (transverse, long
diameter) marked by a-b, its thickness (short diameter) c-d.

2. Shows the table surface as it appears at the age of six years, the breadth a-b, begins to decrease, and the thickness, c-d, increases slightly; the tooth appears oval.

3. Shows a round surface of nine to twelve years. The two
diameters become equal.

4. Shows a triangular surface of fourteen to seventeen years. The long diameter, c-d, in the labiolingual direction.

5. Shows surface of animal over twenty in which breadth,
a-b, measures only half as much as thickness, c-d.

6. Depicts exposed incisor.