American Association of Equine Practitioners 

GlIlDr roll. DEHH.MII\IING TilE AGE OP TII~ HORS( 

American Association of Equine Practitioners 

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. 

Considered to be the most accurate of all indicators and is the only indicator used in horses under five years of age. Permanent teeth generally 

corne into wear three to six months after eruption. In this photograph, 

the left upper central deciduous incisor ("cap") is being pushed off by the 

underlying permanent. The Eruption Table is shown on page iv. A recent 

publication suggests that shedding of the incisors may have a wider range 

tha n conventionally taught and generally incisors may be shed later than 

reported in the literature. 

2 

The shape of the permanent upper corner incisor has been used recently 

to categorize a horse's age into one of three groups from five to twenty 

years of age. Between five and nine years of age this tooth is generally wider 

than tall. At ages nine to ten the upper corner incisor appears square in 

most horses and then progresses to taller than wide as age increases. 

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American Association of Equine Practitioner 

GUIDI: FOR D[TlRMINING TilL AGE or Till HOR<;r 

American Association of Equine Practitioners 

Gumf lOR D[HRMlNING Till AGE OI'IIIE HORSE 

Shape Changes of the LoW'er 

Incisor Table Surfaces 

Disappearance of the Infundibular 

"Cups" 

The sha pe of the table surfaces of the central incisors has traditi onally 

been described as changing from oval to triangular to biangular. Although 

these shape changes are gradual and somewhat subjective in their assessment they are considered fairly relia ble. The oval to round shape is consistent with the age of five to nine. Round to triangula r shape is indicative of 

the age range of 10-15 and tria ngula r to bi angu lar (l ong in the labiolingual 

direction) in the J6-20 age range. 

The infundibulum is an enamel infolding in the occlusal surface of the 

equine incisor. The "cup" is the hollow upper segment of this infolding and 

has a dark brown appearance, especially in horses eating grass. Older references show the disappearance of the cup to occur in II' ~ & 13 at six, seven 

and eigh t years. Recent studies have found more variability with the II cup 

disappearing as ea rly as five years. I3 cups can linger as remnants and not 

disappea r in some individuals until 12-15 years of age . Generally, however, 

cups are a useful indicator in the five to ni ne year age range. 

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AmerJcan Association of Equine Practitioners 

GUJDl rOR D 1:HRMIN I NG T l lr 1\(,1 or T I I[ H ORSF 

American Association of Equine Practitioners 

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 

appears as a yellow brown linear structure on the occlusal surface between 

the labial edge of the incisor and the "cup." Recent studies on aging suggests the dental star can appear in II at five years, 12 at six years and I at J 

seven to eight years. With age the dental star becomes oval and then round 

and moves toward the center of the tooth. The dental star becomes the only 

structure in the table surface of the centrals at 15-18 years of age . 

The lower half of the infundibulum that is filled with cement is called 

the enamel ring or "mark." When the "cup" disappears the remaining 

enamel ring goes through shape changes similar to the changes in the occlusal surface of the incisors. These shapes change from oval (side to side) to 

triangular to round and vary a great deal between breeds. In the central 

incisor the shape of the "mark" changes from oval to round in the five to 

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 followed one to three years later in 12 and 13 • 

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American Association of Equine Practitioners 

GUIOL FOrt DLrLRMINING T IH AG[ or TilE II OltsE 

American Association of Equine Practitioners 

GUIDi: I'OR DLTEltMIN I NG Till' AGr or lH[ IloitSL 

Appearance and Position of 

Galvayne's Groove 

Changes in Direction of Upper and 

Lower Incisor Arcades 

Galvayne's groove is descri bed as a " longitudinal depression on the 

labial su rface of the upper corner inc isor. " Cementum may rema in in part 

or all of the groove and mayor may not have a dark stain. The groove is 

said to first appear at dle gumline at nine to ten years of age and extends 

the full length of the tooth at eighteen to twenty years of age. The presence 

of Galvayne's groove is varia ble and even when present the length in relation to the age of rhe horse may be inexact. 

B 

This indicator may only be useful in comparing a young horse to a very 

old horse. In profile the upper and lower arcades of a young horse are very 

close to a straight line (1 80°) from gum of the upper arcade to the occlusal 

surfaces and down to d1e gumline of the lower arcade. As aging occurs this 

angle becomes more acute (near 120° or less) and usually is significantly 

noticea ble around twenty years of age. The lower arcade generally takes up 

the most o bJjque position first. 

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American Association of Equine Practitioners 

GUIDE FOR DETERM INING THl AGE OF THI: I I ORSE 

Upper Corner Incisor Hook 

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 reasonable explanation of the wide age range and high ly inconsistent presence of 

this indicator is the changing obliquity of the incisors (see direction changes 

of incisors indicator). The inconsistent presence of this indicator dictate 

that it be considered too wlreliable to be useful in aging. 

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American Association of Equine Practitioners 

GUlDl rolt DLTLRMI NING TIlE AGL 01" rill: HOR)E 

Section II 


Ages One Week 


to Twenty Years 


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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) 

covers the other incisors. Viewed from in front, the labial border of the 

centrals is visible in both jaws. The dental table (masticatory or occlusal 

surface) shows the labial (anterior border) of the central incisors. 

Viewed from in front, the deciduous centra ls (II) are in contact, the 

lower with the upper (superior with the inferior). The labial surface of 

the crown presents deljcate vertical ridges and grooves. The intermediates 

(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. The in termediates are 

emerging through the gum witb the labial edge showing th e most exposure. 

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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 incisors (12 ) are in contact and the crown of each is full y exposed. In profile, the 

corner incisors (I) have emerged from the gums but are not in contact. Tbe 

dental ta bles of the centrals and intermediates show wear; tbe cup is shallowe r in the centrals than in the intermediates in this individ ual. 

14 

Viewed from in front, all deciduous incisors are visi ble, the crown of 

the centrals and intermediates is fully exposed. In profile, the upper and 

lower corner incisors are partiall y or completely in contact (depending on 

the time of year). The dental tables of the centrals show considerable wear. 

The dental star is seen usuall y in the centra ls and intermedia tes as a dark 

or yellowish-brown transverse line in the dentin on the labial side of the 

infundibulum. 

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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 a re fr ee from the gum and the 

neck ma y be visible (depending on time of year). In profile, the co rners are 

in full wear. The dental tables of the lower incisors are smooth, the intermediates show decided wear and the corners are in full wear. T he dental 

star is clearly visible in the lower centrals and intermediates. 

Viewed from in front, the four permanent central incisors are seen in 

fu ll wear. They appear more solid, have vertica l. ri dges and grooves and are 

larger than adj acent decid uous teeth. In profile, the deciduous intermediate ma y be inactive or show signs of being shed (depending on the time of 

year). The dental table of each centra l incisor has a deep cup and the borders of these teeth are sharp. The lower intermedia tes a re deciduous in this 

individual and are smooth . The lower corners (deciduolls) have little central 

enamel. 

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American Association of Equine Practitioners American Association of Equine Practitioners

GUIDI: fOR DETERMIN ING THE AG[ or T i lE HORSE GUIDE FOR DETERMINING TI l E Ali[ Or- Ti l E HORSE 

Four Years Five Years

Viewed from in front, the permanent upper central and intermediate incisors a re 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 profil e, the corners (deciduous) appear 

small and may show signs of shedding (dependi ng on the time of year). The 

dental ta bles of the centrals (permanent) show wear but their cups are deep. 

The intermediates are permanent and a re in wear. 

is 

Permanent dentition is complete; all teeth are in wear. In profile the 

upper corner incisor is rectangular in shape (long side horizonta l). The 

dental ta bles of the centrals and intermediates are wide transversely and 

show wear. Their cups are readily visible and completely encircled by the 

central enamel. The dental star is present labia l to the cup on the centrals. 

The corners ar e beginning to wear at their labial border. 

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American Association of Equine Practitioners 

GUID~ I-OR DETEIU"IINING 1HI: AGE O~ TII I- IloRSf 

Six Years 

Viewed from in front, the jaws present the same features as at 5 yea rs. 

The upper centrals are either larger or of a similar size to the intermediates. 

In profile, the upper corner is still wider than tall and may show a small 

hook, especially if no overbite is present. The incisive angle is at its least 

acute angle (approaches 180°). T he dental tables of the lower centrals are 

usually smooth and not as wide transversely as at 5 years (tend to be oval). 

The surface of the intermediates may still show a cup (or remnant thereof) 

w hile the corners should have well defi ned cups that arc in full wear. 

Denta l stars are present in both centrals and intermediates in this individual. T he enamel rings in the centrals are oval in shape. 

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American Association of Equine Practitioners 

GUJrJr POR [)nrIU..tINING TilE ACt 01 n lr HORsr 

Seven Years 

from in front no significant change is evident from the six-year-old 

mouth. The corner incisor on profile should still be wider than tall but may 

be approaching square. The dental tables of the centrals appear oval, while 

the enamel ring is somewhat triangular in this individual. The "white spot" 

in the dental star is visible. T he intermediates show some cup present (usually worn down to enamel ring at this age). The surface of the corner shows 

a well defined cup that ma y take several years to completely disappear. The 

disappearance of the cups in the six- and seven-year-old examples demonstrate the normal viability between horses. 

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American Association of Equine Practitioner 

GUIDL rOR DLHRM1NING TH[ AGL or H I [ (-jOR.S~ 

Eight Years 

There is still no significant change in the front view from the previous 

two years. In profile, the upper corner may now begin to appear somewhat square. The lower dental tables are smooth and all cups will be gone 

(although remnants may remain, especially on the corners). Due to natural 

variation no differences in the dental stars or enamel rings may occur from 

the previous age. 

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Amerjcan Association of Equine Practitioners 

GUIDE lOR DL HRMIN ING I Hr. AG[ OF Tlle IIOlt$[ 

Nine Years 

Viewed from in front the upper centrals will still be similar in size to 

larger than the adjacent intermediates. In profile, the upper corners will 

us ually be somewhat square. The gum line (area where tooth emerges from 

gum) will start to lose its straight appearance and begin to drop down 

where Galvayne's groove will appear. The dental tables of the centrals are 

now round with the enamel rings triangular. All lowers in this individual 

show a dental star, with the centrals and intermediates having a "white 

spot " in the middle of the star. The corners show remnants of a cup in this 

individual. 

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American Association of Equine Practitioners American Association of Equine Practitioners 

GUIDE rOR DETeRMINING TilE AGE or T I I[ HOR.SE G\Trnr Wit DnrRMININC TH[ AGf OF THI I loRSr 

Ten Years Eleven Years 

No change has occurred in the front view of the incisors. The upper 

corner on profile will be square and likely will show evidence of the beginning of Galvayne's groove. The dental tables of the centrals remain round 

while the dental star is shorter in length and a ppea rs to be moving more 

central in the tooth. This individual shows remnants of cups in all lower 

incisors at this age (could be attributed to a naturally occurring deeper 

cup). 

24 

No obvious changes from the front view should occur at this age. In 

profile, the upper corne r is still somewhat square or slightly tall er than 

wide. The gW11 !tootb margin should show a v-effect where Galvayne's 

groove has started (see section on indicators). This individual has a distinct 

hook on the posterior ventral aspect of this tooth (also see indicators). The 

den ta l tables of the lower centrals are round. The central enamel of each 

[ower incisor forms a small ring close to the lingual border; the dental stars 

arc narrower transversely and near the center of the denta l table. 

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American Association of Equine Practitioners American Association of Equine Practitioners 

GUJOF rOR DrnRMININli 1111 Mil-' OF THt: HOR~E GU I D[ roR DEHRMINING THE AGr or Tl I [ H ORSt 

Twelve Vears Thirteen Years 

This individual's centrals appear slightly shorter than the adjacent intermediates when viewed from in front. In profile, the upper corner should 

be slightly taller than wide and have evidence of a Galvayne's groove at its 

apex. The dental tables of the centrals should be round to triangular. The 

central enamel may be disappearing and the dental star is seen as a darker 

stained area of secondary dentine near the center of the tooth. 

Viewed from in front, the appearance is similar to that of 12 years. 

M any individuals at this age begin to exhibit a shrinking of the size of 

the upper centrals as compared to the intermediates. In profile, the upper 

corner is definitely taller than wide with a Galvayne's groove extending 

approximately 1/3 down from the apex (see indicators for accuracy). The 

dental tables of the lower centrals resemble a triangle in shape. The central 

enamel should be disappearing from the centrals. The dental star is similar 

to age 12. Remnants of cups are still evident in the corners of this 

individual. 

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American Association of Equine Practitioners American Association of Equine Practitioners 

GUIDI' FOR DETERMIN ING H I[ AGE or Ti ll HORse GUIDf I-OR D r TERM IN I NG T 11[ AGF OF lI ~ H ORSE 

Fourteen Years Fifteen Years

Changes in all views become gradual and more variable as horses age 

through [he next fi ve to seven years which affects accuracy negati vely. 

From in front the upper centrals LlsuaIly are now sho rter. In profil e, the 

upper corner may resemble age 13 but should be slightly tall er and may 

have a Ga lvaync's groove that is near halfway down the labial surface. The 

denta l tables may be unchanged from age 13. This individua l appea rs to 

have remnants of cups in all six lower incisors. 

Viewed from in front all the lower incisors may appear shorter than 

the uppers. The upper centrals will usua lly be smaller but not yet half the 

height of the intermediates. In profile, the upper corner is taller-than-wide 

with a Galvayne's groove that is somewhere near halfway do.vn the tooth 

(variable). The shape of the dental tables of the lower central incisors 

should have a rriangular appearance. The intermediates are rOllnd to triangular and the dental star is taking a central position in the lower central 

InClSOr. 

28 29 
American Association of Equine Practitioner American Association of Equine Practitioners 

GUIDE FOR DETER.MIN ING filE AGE OF THE H ORSE GUID[ rOR DETERMINING I'I"IE AGF or TH E" II ClR~[ 

Sixteen Years Seventeen Years 

From in front, this individual's lower incisors are smaller than the 

uppers and have a significant space between each tooth (aging change). 

In profile the incisive angle should begin to drift toward a less than 180" 

angle. As the upper corner becomes taller it may appear narrower (front to 

back) with increasing age. Galvayne's groove is highly variable but should 

extend past the mid-point of the corner. The surface of all lower dental 

tables will generally lack color except for the centrally located dental star. 

The dental star gradually replaces the enamel ring from central to corner 

InCISOr. 

Viewed from in front, the upper centrals are definitely shorter than 

the intermediates. In profile, the upper corner is taller than wide and 

Galvayne's groove (if evident) should extend about 3/4 of the way down 

rhe tooth. The dental tables of the lower centrals and intermediates should 

appear triangular to biangular (see Indicators section). Each dental star is 

round and near the center of the tooth. Teeth may begin to appear more 

widely spaced (not evident on this individual). 

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American Association of Equine Practitioners American Association of Equine Practitioners

GUIDI: rOR O[HltMINING THf- AGE or TilE IloRsr GUll")!' Inlt [)nflU."IININCl 1'1-11'. Atil Of HIE HORS[

Eighteen Years Nineteen Years

Changes in all indicators in the ages 15 to 20 will be gradual causing 

age estimation to be less accurate than in ages under ten. Viewed from in 

front, the LIpper centrals are smaller tha n th e adjacent intermediates. In 

profile, the upper corner is tall with a Galvayne's groove that is past halfway and approaching th e ta ble surface. T he dental tables are similar to 

the 17-year-old (usually exhibit min imal color) an d show a single centrally 

located den tal star. 

The front and profile views will be simiJar to the I8-year-old. The most 

useful changes in the indicators may be in Galva yne's groove and the shape 

of the dental ta bles. T he groove should extend nearly the full length of the 

corner tooth (mayor may not have color). T he dental tables of the centrals 

will no longer appea r tria ngular but will have a more biangular (long lingual to labia l) shape. 

32 33 
American Associat.ion of Equine Practitioners 

GUID[ lOR D[TERMIN ING TilL Acl.: Of ll-IF HORSI 

Twenty Years 

Viewed from in front, the upper centrals should be obviously smaller 

than the intermediates. In profile, the upper corner tooth is tall with a 

Galvayne's groove extending the full length of the tooth. The incisive angle 

will be much less than 1800 (see Indicators section). The dental tables of 

the lower incisors will have little or no co]or and the centrals will be oval to 

biangular in shape (labial to lingual). A single round shaped dental star w.ill 

occupy the center of the tooth. 

American Association of Equine Practitioners 

GUID[ rOR DETeRMINING TilE Alj[ cJ[ rHE HURSL 

Glossary of Terms 

Cup - The da r k or dark-brown to black cavity in the infundibulum surrounded by 

enamel ring. 

)cdduous Teeth - Temporary, fetal, milk or baby teeth. They are characterized 

primarily by their small er si ze, constricted neck, and shallow cup. 

)cnt~J Star - The darker dclltin that fills the pulp cavity as the tooth wears. It is 

&Jrk yell ow to yellowish-brown. 

Iknta] T ahh .. - T he tahle, lll~l ticato y or occlusal surface. 

~ rupliun - l'l'rLli n, to th e period when a tooth breaks through the gum. 

Galvnync'\ Gronve - T he longitud inal depression on the labial surface of the upper 

co rner (l ;) in ()r. The cementu lll remains in the groove as a dark line; the rest of 

the surface is worn to expose the white enamel. 

Inci~or rccrh - Starting at the midline incisors are designated as centrals (1 ), inter­ 1

mediates (Ie) and corners (I). 

Infundibulum - The deep invagination of enamel which is filled with a variable 


um ount of cement. Commonly referred to as the "cup." 


l.;lbi~l Surface - Surface toward the lips. 


Ungual Surface - Surface toward the tongue. 


I'.:rmanenl Teelh - Second dentition or adult teeth. 


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