American Association of Equine Practitioners American Association of Equine Practitioners GlIlDr roll. DEHH.MII\IING TilE AGE OP TII~ HORS( GU I DE rGR. DlIER.MINING rilE AGE or- TilE HORSE Eruption Length vs. Width of Upper Corner Incisor Emergence of tooth (either deciduous or permanent) at gum. The shape of the permanent upper corner incisor has been us ed recently Considered to be the most accurate of all indicators and is the only indi­ to categorize a horse's age into one of three groups from five to twenty cator used in horses under five years of age. Permanent teeth generally years of age. Between fiv e and nine years of age this tooth is generally wider corne into wear three to six months after eruption. In this photograph, than tall. At ages nine to ten the upper corner incisor appears square in the left upper central deciduous incisor ("cap") is being pushed off by the most horses and then progresses to taller than wide as age increases. underlying permanent. The Eruption Table is shown on page iv. A recent publication suggests that shedding of the incisors may have a wider range than conventionally taught and generally incisors may be shed later than reported in the literature. 2 3 American Association of Equine Practitioner American Association of Equine Practitioners GUIDI: FOR D[TlRMINING TilL AGE or Till HOR<;r Gumf lOR D[HRMlNING Till AGE OI'IIIE HORSE Shape Changes of the LoW'er Disappearance of the Infundibular Incisor Table Surfaces "Cups" The shape of the table surfaces of the central incisors has traditi onally The infundibulum is an enamel infolding in the occlusal surface of the been described as changing from oval to triangular to biangular. Although equine incisor. T he "cup" is the hollow upper segment of this infolding and these shape changes are gradual and somewhat subjective in their assess­ has a dark brown appearance, especially in horses eating grass. Older refer­ ment they are considered fairly relia ble. T he oval to round shape is consis­ ences show the disappearance of the cup to occur in II' ~ & 13 at six, seven tent w ith the age of five to nine. Round to triangular shape is indicative of and eigh t years. Recent studies have found more variability with the II cup the age range of 10-15 and triangular to bi angular (l ong in the labiolingual disappearing as ea rl y as five years. I3 cups can linger as remnants and not direction) in the J6-20 age range. disappear in some indiv iduals until 12-15 years of age. Generall y, however, cups are a useful indicator in the five to ni ne year age range. 4 5 AmerJcan Association of Equine Practitioners American Association of Equine Practitioners GUJDl rOR D 1: HRMIN I NG T l lr 1\(,1 or T I I[ H ORSF GUIDr lOR DnERMINING TilE AGE 0 1 TilE H ORSE Appearance of the Dental Star Disappearance of the Enamel Ring (Mark) The dental star is secondary dentine that occludes the pulp cavity and The lower half of the infundibulum that is filled with cement is called appears as a yellow brown linear structure on the occlusal surface between the enamel ring or "mark." When the "cup" disappears the remaining the labial edge of the incisor and the "cup." Recent studies on aging sug­ enamel ring goes through shape changes similar to the changes in the occlu­ gests the dental star can appear in II at five years, 12 at six years and IJ at sal surface of the incisors. These shapes change from oval (side to side) to seven to eight years. With age the dental star becomes oval and then round triangular to round and vary a great deal between breeds. In the central and moves toward the center of the tooth. The dental star becomes the only incisor the shape of the "mark" changes from oval to round in the five to structure in the table surface of the centrals at 15-18 years of age. twelve year age range in most breeds. The disappearance of the "mark" is also highly variable, ranging from 12-18 years from the central incisor fol­ • lowed one to three years later in 12 and 13 6 7 American Association of Equine Practitioners American Association of Equine Practitioners GUIOL FOrt DLrLRMINING T IH AG[ or TilE II O ltsE GUIDi: I'OR DLTEltMIN I NG Till' AGr or lH[ IloitSL Appearance and Position of Changes in Direction of Upper and Galvayne's Groove Lower Incisor Arcades Galvayne's groove is descri bed as a " lo ngitudinal depression on the T his indicator may only be useful in comparing a young horse to a very labial su rface of the upper corner incisor. " Cementum may remain in part old horse. In profile the upper and lower arcades of a young horse are very or all of the groove and mayor may not have a dark stain. The groove is close to a straight line (1 80°) from gum of the upper arcade to the occlusal said to first appear at dle gumline at nine to ten years of age and extends surfaces and down to d1e gumline of the lower arcade. As aging occurs this the full length of the tooth at eighteen to twenty years of age. The presence angle becomes more acute (near 120° or less) and usually is significantly of Galvayne's groove is variable and even when present the length in rela­ noticea ble around twenty years of age. The lower arcade generally takes up tion to the age of rhe horse may be inexact. the most o bJjque position fi rst. B 9 American Association of Equine Practitioners American Association of Equine Practitioners GUIDE FOR DETERM INING THl AGE OF THI: I I ORSE GUlDl rolt DLTLRMI NING TIlE AGL 01" rill: HOR)E Upper Corner Incisor Hook Section II Ages One Week to Twenty Years H istorically the "hook" that is sometimes visible on the caudal border of the upper corner incisor was thought to occur at the age of seven years and aga in at 11-13 years. This hook represents a lack of wear on the caudal aspect of the upper tooth by the opposing lower incisor. The most reason­ able explanati on of the wide age range and highly inconsistent presence of this indicator is the changing obliquity of the incisors (see direction changes of incisors indicator). T he inconsistent presence of this indicator dictate that it be considered too wlreliable to be useful in aging. '10 11 American Association of Equine Practitioners Alnerlcan Association of Equine Practitioner GUIDE mR DfHllMINING H II AGE 0 1: Ti l t: l·l oR.)t GUID I: FOR Dr l fRMIN ING T l lr AGE Of II IE H ORSE Birth to Two Weeks Four to Six Weeks The deciduous central incisors (II) have erupted; the gum (gingiva) Viewed from in front, the deciduous centrals (II) are in contact, the covers the other incisors. Viewed from in front, the labial border of the lower with the upper (superior with the inferior). The labial surface of centrals is visible in both jaws. The dental table (masticatory or occlusal the crown presents deljcate vertical ridges and grooves. T he intermediates surface) shows the labial (anterior border) of the central incisors. (1 ) have emerged through the gums. T he dental tables of the centrals are 2 in wear and show a defi nite cup in this individual. T he in ter mediates are emerging through the gum witb the labial edge showing the most exposure. 12 13 American Association of Equine Practitioners American Association of Equine Practitioners GU I DE FOR DETERMINING TIIf AGE OF TllE l·IORSF GUIDE FO I"\ DETrRMIN ING Tllf AGf o r THf HOllSE Six to Ten Months OneVear Viewed from in frOnt, the central (It) and intermediate deciduous inci­ Viewed from in front, all deciduous incisors are visi ble, the crown of ) sors (12 are in contact and the crown of each is full y exposed. In profile, the the centrals and intermediates is fully exposed. In profile, the upper and corner incisors (I) have emerged from the gums but are not in contact. Tbe lower corner incisors are partiall y or completely in contact (depending on dental ta bles of th e centrals and intermediates show wear; tbe cup is shal­ the time of year). The dental tables of the centrals show considerable wear. lower in the centrals than in the intermediates in this individ ual. The dental star is seen usuall y in the centrals and intermedia tes as a dark or yell owish-brown transverse line in the dentin on the labial side of the infundibulum. 14 15 American Association of Equine Practitioner American Association of Equine Practitioners GUID[ fOR DlTEI~I\'ININ(j Tllr AGr OF TII[ HORSl; GUIDI: lOR DETERMIN ING T i lE A('E OF T i ll IJ O ltSE Tw'oYears Three Years Viewed from in front, the central incisors are fr ee from the gum and the Viewed from in front, the fo ur permanent central incisors are seen in neck may be visible (depending on time of year). In profile, the corners are fu ll wear. They appear more solid, have vertical. ri dges and grooves and are in full wear. The dental tables of the lower incisors are smooth, the inter­ larger than adjacent deciduous teeth. In profile, the deciduous intermedi­ mediates show decided wear and the corners are in full wear.