Use of crown height of the maxillary first molar tooth to approximate the age of horses

Abstract

OBJECTIVE To identify whether age, sex, or breed is associated with crown height of the left and right maxillary first molar tooth (M1) measured on CT images, to develop a mathematical model to determine age of horses by use of M1 crown height, and to determine the correlation between M1 crown height measured on radiographic and CT images. SAMPLE CT (n = 735) and radiographic images (35) of the heads of horses. PROCEDURES Crown height of left and right M1 was digitally measured on axial CT views. Height was measured on a lateral radiographic image when available. Linear regression analysis was used to identify factors associated with crown height. Half the data set was subsequently used to generate a regression model to predict age on the basis of M1 crown height, and the other half was used to validate accuracy of the predictions. RESULTS M1 crown height decreased with increasing age, but the rate of decrease slowed with increasing age. Height also differed by sex and breed. The model most accurately reflected age of horses < 10 years old, although age was overestimated by a mean of 0.1 years. The correlation between radiographic and CT crown height of M1 was 0.91; the mean for radiographic measurements was 2.5 mm greater than for CT measurements. CONCLUSIONS AND CLINICAL RELEVANCE M1 crown height can be used to predict age of horses. Results for CT images correlated well with those for radiographic images. Studies are needed to develop a comparable model with results for radiographic images.

A Retrospective Observational Cohort Study on the Expiration of Maxillary Cheek Teeth Infundibula in 217 Horses

“…The lack of inclusion of gender in the model contrasts with other reports which include gender as a factor in the eruption pattern of maxillary premolars in Thoroughbreds, and it is in contrast with a previous study investigating the use of the height of the first maxillary molar tooth as an indicator of age. 2,20 Again, this discrepancy may be due to the fact that the current study sample group had an overrepresentation of geldings (castrated males) compared to other studies having intact females and only one intact male.…”

“…Our statistical model did not include horse breed in the number of factors affecting age of infundibular senescence in contrast to previous reports. 17,20 It is likely a statistical power issue due to the overrepresentation of 5 breeds in our study group, and the fact that 21 of the 35 breeds were represented by 3, or fewer, individuals. The lack of inclusion of gender in the model contrasts with other reports which include gender as a factor in the eruption pattern of maxillary premolars in Thoroughbreds, and it is in contrast with a previous study investigating the use of the height of the first maxillary molar tooth as an indicator of age.…”

“…In a second study, the same research group used computed tomography (CT) of cheek teeth to show that the crown height of the maxillary first molar could be used to predict the age of horses from ages 1 to 39.8 years. 20 The difficulty in using these aging methods routinely is that they are not useful in a clinical practice setting.…”

Three-Dimensional Segmentation of Equine Paranasal Sinuses in Multidetector Computed Tomography Datasets: Preliminary Morphometric Assessment Assisted with Clustering Analysis

“…In young horses (<5 years of age), the RMS and CMS are largely filled with embedded parts of the four maxillary cheek teeth (Triadan 108/208–111/211 and 208–211 [ 1 ]) [ 7 ]. With prolonged eruption, the reserve crown length of the maxillary cheek teeth decreases with age by 2.2 to 4.7 mm each year [ 10 , 35 , 36 ]. The rate of reserve crown shortening, and the associated increase in related sinus volume, decreases with age, so the rate of clinical crown eruption slows as horses age [ 35 , 36 ].…”

“…With prolonged eruption, the reserve crown length of the maxillary cheek teeth decreases with age by 2.2 to 4.7 mm each year [ 10 , 35 , 36 ]. The rate of reserve crown shortening, and the associated increase in related sinus volume, decreases with age, so the rate of clinical crown eruption slows as horses age [ 35 , 36 ]. Moreover, cheek teeth drift with age in a rostral direction, which is contributed to by the continued eruption of rostrally angulated clinical crowns and additionally increases the volume of the related sinuses [ 10 ].…”