Dental Radiography in Cattle: Technic and Application for Age Determination’

J. L. sTOWATER,2 J. J. FRANCIS,3 and J. R. PICKARD4

INTRODUCTION

The use of dental radiography in cattle is not wide- spread because of technical difficulties and its appar- ently limited application. Recent interest in using dental radiography as a means of age determination in show cattle served as a stimulus for investigating the feasibility of this procedure.

The present report describes a technic for obtaining high quality radiographs of the mandibular incisor and canine teeth in untranquilized, nonanesthetized cattle, and discusses possible application of this procedure for age determination.

LITERATURE REVIEW

Postnatal tooth development in cattle has been in- vestigated radiographically for the purpose of evaluat- ing the effects of various systemic factors such as fluo- rosis, nutritional deficiencies, and infectious diseases (3). Broad guidelines for the chronology of tooth de- velopment were established with respect to initiation and completion of the crown, completion of the root, intraosseous eruption, and emergence of the tooth into the oral cavity (3). Differences due to sex and breed were not significant. The technic for obtaining dental radiographs in live cattle was described in another re- port (4). More recently, two reports described further refinement of the criteria for radiographic age deter- mination (1, 2 ) . Crown and root formation were sub- divided into stages as was deciduous root resorption. Radiographs were obtained of the disarticulated mandibles from slaughtered cattle. The author con- cluded that the age of a group of cattle could be defined, but the age of individual animals could not be estab- lished accurately.

MATERIALS AND METHODS

Radiographs of the mandibular incisor and canine teeth were obtained from 144 live cattle of known age.

Twenty-nine additional radiographs were taken of the disarticulated rostral mandibles from slaughtered cat- tle. The birthdates of all animals radiographed were known. The age range was 188 to 916 days. Several breeds of cattle were radiographed, the majority being Angus. All animals had been fed similar rations.

The live cattle were restrained in a squeeze chute for radiography. A portable x-ray unit5 with standard settings of 20 mA, 90 kVp, and 0.08 sec was used for all exposures. The focal-spot-to-film distance was ap- proximately 45 cm. Nonscreen film6 was cut into ap- proximately 8 X 10 cm pieces in the darkroom and the cut edges of the paper wrapper sealed with black plastic tape. The film was inserted into a holder and placed inside the animal’s mouth over the rostral mandible but beneath the tongue. Two types of film holders were used. The first type was constructed of two polyeth- ylene sheets which were glued and stapled together on three sides. An elastic band was attached to secure the film holder to the mandible. This model did not pro- tect the film sufficiently from saliva or the pressure of chewing, and was largely responsible for the technical inadequacy of 29 radiographs. A second film holder (Fig. 1) was constructed with a 0.38-cm thick piece of plexiglass to which a similar sized sheet of polyethylene was secured with small bolts and sealed with waterproof glue on three sides. A piece of rubber tire inner tubing was attached to short extensions from two sides of the plexiglass plate for the purpose of securing the film holder to the mandible. Personnel wearing leaded gloves and aprons were needed to help position the film holder and restrain the animals (Fig. 2). The x-ray beam was restricted to the area of interest to prevent exposure to the individual positioning the film holder. A pocket dosimeter was used to monitor radiation ex- posure to personnel.

The developed radiographs were examined for tech- nical quality. Those in which the anatomic details of the deciduous and developing permanent incisor and canine teeth could not be evaluated were discarded. Deciduous mandibular incisor and canine teeth were

This study was supported by a grant from the American Angus Association, St. Joseph, MO. Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL. Department of Animal Science, College of Agriculture, University of Illinois, Urbana, Illinois. Present address Joliet, IL. Department of Veterinary Continuing Education, Public ServicelExtension, University of Illinois, College of Veterinary Medicine, Urbana,

Phillips Super Practix, Phillips Medical Systems, Holland. IL.

ti Kodak NS-ZT, Eastman Kodak, Rochester, NY.

213

214 J. L. STOWATER, J. J. FRANCIS, AND J. R. PICKARD 1978

Fig. 2. The film holder has been inserted into the animal’s mouth and the rubber tubing pulled over the mandible. The x-ray machine is being positioned beneath the mandible at a focal film distance of approximately 45 cm. Nose tongs were occasionally used to prevent patient movement. Prior to radiographic exposure, the nose tong rope will be secured above the animal’s head to the squeeze chute allowing the individual on the viewer’s left to remove his hand from the x-ray field. Restriction of the primary beam to the area of interest minimizes scatter radiation to the individual positioning the film holder.

Fig. 1. The second film holder was constructed with a 0.38-cm thick piece of plexiglass to which a similar sized piece of polyethylene was secured on three sides with small bolts and sealed with waterproof glue. A piece of rubber tire inner tubing was attached to the extensions on the sides of the plexiglass. The tubing was stretched over the mandible at the time of radiography to help secure the film holder. A piece of nonscreen film cut to approximately 8 X 10 cm and sealed in a lightproof wrapper has been inserted into the holder.

evaluated for degree of root resorption or exfoliation. Permanent mandibular incisors and canines were evaluated for stages of crown initiation, crown calcifi- cation, and root formation. The various stages of tooth development and their definitions are given in Table 1. These stages and their definitions were adapted and modified from previous reports (1-3).

RESULTS

The radiographs of 144 cattle were of sufficient technical quality to be included in the study. Exposure to visible light or malalignment of the subject, film, and primary x-ray beam were the main technical problems. Patient motion was a minor problem. On the average, an examination took 4 min to complete, including catching the animal in the chute, positioning, and ex- posure. Radiation exposure to personnel was not a serious problem. In one series of 125 examinations over a 2-day period, the dosimeter recorded a dose of 11 mR on the outside of the lead apron.

After evaluating each radiograph for the various stages of tooth development (Figs. 3-7), specific stages

were tabulated for mean age in days, standard deviation, range, and minimum age in days at which it was ob- served. These results are given in Table 2. Each ani- mal was classified by the most advanced stage of tooth development present. The teeth develop in an orderly sequence with the first incisor appearing first, then the second, the third, and finally the canine (3). An early form of development of a second incisor would represent a more advanced stage of overall dental development and, therefore, older chronological age than an advanced form of development in the first incisor. Therefore, an animal showing late crown calcification of the first in- cisor and early initiation of the second incisor was classified according to the latter. Deciduous root re- sorption was not tabulated because of the variability and wide range of time over which it was observed. Permanent root formation was observed at about the time crown calcification was completed, and extended over a longer period of time than crown formation. The stages of initiation and crown calcification, except for complete crown calcification, seemed to be the most definitive for establishing minimal ages at which they might be observed. Complete crown calcification represented an end point rather than a transitional

VOL. XIX DENTAL RADIOGRAPHY IN CATTLE 215

Table 1

Stages of Tooth Development Definitions

1.

2.

3.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

-

Early root resorption Late root resorption Exfoliation

Deciduous Teeth Resorption of one-third or less of

the root. Resorption of greater than one-

third of the root. Absence of the tooth.

Permanent Teeth Early crown initiation

Late crown initiation

Early crown calcification

Mid c r o w n calcification Late crown calcification Complete crown calcification

Early root formation

Midroot formation

Late root formation

Complete root formation

A small area of radiolucency in the bone adjacent to the tip of the corresponding deciduous tooth root.

approaching the size of a developed crown.

the occlusal surface of the developing crown.

Up to one-half of the crown has opacified.

Greater than one-half of the crown has opacified.

The entire crown has opacified and is as dense as the erupted teeth.

The first differentiation of the root from the crown seen as a narrower area or neck a t the base of the crown.

The root is about one-third to two-thirds the length of the crown.

The length of the root is greater than two-thirds that of the crown.

length, is as radiopaque as the

An area of radiolucency

A slight radiopacity appearing a t

The root has reached its full

crown, and has a tapered end.

stage, overlapped with initiation of the next tooth and, therefore, was not used in this tabulation.

Two patterns of intraosseous movement of teeth or prefunctional eruption were also identified (3). Rota- tion was observed, especially in the first permanent incisor. The tooth initially develops in a position ro- tated 90 degrees on a longitudinal axis to its final posi- tion in the dental arch. This mechanism appears to compensate for the narrow mandible of the growing animal. Migration is the movement of the tooth towards the occlusal plane with eventual eruption into the oral cavity. These movements occurred over a broad time span and did not lend themselves to chro- nological staging.

The data show a substantial range of time for each developmental stage in which a sufficient number of

Fig 3. A 188-day-old Polled Hereford with early initiation of the permanent first incisors. The circular radiolucent areas adjacent to the root tips of the deciduous first incisors are the initiating crowns. Early resorption of the de- ciduous first incisor roots can also be seen

Fig. 4. A 41 lday-old Angus with complete crown calcification and early root formation of the permanent first incisor teeth and late initiation of the second permanent incisor teeth. The larger area of radiolucency, approximating the size of a developed crown, distinguishes late initiation from early initiation. Compare the lateral radiograph of the permanent first incisors to the rostrocaudal radiograph seen in older animals (Figs. 5, 6, and 7). This demonstrates the rotational-type movement seen as the tooth erupts.

animals are present to make evaluation meaningful (Table 2). Two stages which seem to show extreme ranges are early initiation of the second incisor and late initiation of the third incisor. In the former instance, one of the five animals showing early initiation of the second incisor was 465 days old, while the other four

216 J. L. STOWATER, J. J. FRANCIS, AND J. R. PICKARD 1978

Table 2. Age Characteristics for Stages of Tooth Development

Age (days) Range Minimum Stage of Development n* Xt S.D.t

First incisor Early initiation Late initiation Early crown calcification Late crown calci-fication

Early initiation Late initiation Early crown calcification Midcrown calcification Late crown calcification

Early initiation Late initiation Early crown calcification Late crown calcification

Late initiation Early crown calcification

Second incisor

Third incisor

Canine

5 14 25 39 23

7 11 4 7

3 1

144 -

188 214 215 336

389 444 464 480 498

547 617 565 570

884 914

0 0 0 0.71

39.30 20.45 27.22 20.60 21.32

21.89 87.00

7.53 2.79

44.86 0

108 76 99 79 70

57 221

17 a

a3 0

188 214 215 336

357 411 416 434 459

512 516 556 566

833 914

* = number of cattle. + = mean age. 1 = standard deviation.

averaged 374 days old, covered a range of only 29 days, and showed a standard deviation of 14.08 days. The one older animal might have been excluded had a larger population been sampled and a more critical statistical analysis performed. The eleven cattle showing late initiation of the third incisor represent two distinct age ranges, including seven Holstein steers averaging 562 days of age covering a 61-day range, and 4 beef cows with an average age of 724 days representing a 37-day range. This might be attributed to differences in breed and sex. With the exception of this stage, however, the dental development patterns appeared consistent re- gardless of breed or sex, and coincided with a previous study (3).

Angus Breeders Association utilizes the independent estimations of three veterinarians to determine age if it is disputed. Questions concerning the reliability of this technic have prompted the search for a more ac-

DISCUSSION

Accurate age data on show cattle is necessary to as- sure proper grouping of animals for judging purposes. Falsification of birth dates, or in some instances lack of knowledge of an animal’s birthdate, might result in placement in an improper age category. Unethical cattle owners might attempt to place an over-age animal into a group with younger animals hoping to gain ad- vantage. For these reasons, the currently practiced technic of “mouthing,7 to determine age was developed. “Mouthing” is age estimation by visual inspection based on the eruption and wear of the teeth. The American

Fig. 5. A 479-day-old Polled Hereford with complete crown calcification and early root formation of the permanent first incisors, and midcrown calcification of the permanent second incisors. Various degrees of root resorption are seen on the deciduous incisors.

VOL. XIX DENTAL RADIOGRAPHY IN CATTLE 217

Fig. 6. A 546-day-old Polled Hereford with complete crown calcification and late root formation of the permanent first incisors. The permanent second in- cisors show late crown calcification.

Fig. 7. A 734-day-old Polled Hereford with emergence of the permanent first incisors into the oral cavity. The permanent second incisors are also completely calcified and show midroot formation. The permanent third incisors are in a stage of late initiation, seen as the large radiolucent area adjacent to the roots of the deciduous third incisors and deciduous canines.

curate and legally defensible means of age evaluation. Dental radiography would seem to offer a more tangible and objective method for determining an animal’s age. The broad age ranges over which some stages of tooth development are seen would make it difficult to assign an exact age to an individual animal. By establishing minimum ages at which certain radiographic criteria are present, this approach could be applied to grouping animals of similar age for show purposes. For example, on the basis of the results obtained thus far, an animal showing late initiation of the second incisor could be no less than 411 days old. Larger numbers of animals, especially in the younger and older categories, are needed to make the results more meaningful and ap- plicable to all ages of show cattle. Further investigation

of this approach to age determination in cattle is an- ticipated.

SUMMARY

A technic for obtaining good quality dental radio- graphs in nontranquilized, nonanesthetized cattle is described. Radiographs of the mandibular incisor and canine teeth were obtained from 144 live cattle and 29 slaughtered cattle. The stages of tooth development were tabulated and each animal classified as to the most advanced stage present. The mean, standard deviation, range, and minimum age in days for each stage of tooth development were determined. While each stage ap- pears to show a broad range, it may be possible to es- tablish minimum ages for each stage, thereby providing a means of determining proper age classification for show cattle.

College of Veterinary Medicine University of Illinois Urbana, IL 61801

REFERENCES

1. Andrews, A. H.: Age Detection by Radiography in Hereford Cross Friesian Steers. Vet. Rec. 97: 244, 1975.

2. Andrews, A. H.: The Visual and Radiographic Examination of Mandibular Cheek Teeth and Their Relationship to Age in a Group of Aberdeen Angus x Friesian Steers. Br. Vet. J. 132: 9, 1976.

3. Brown, W. A., Christofferson, P. V., Massler, M., and Weiss, M. R.: Postnatal Tooth Development in Cattle. Am. J. Vet. Res. 21: 7, 1960.

4. Christofferson, P. V. and Weiss, M. B.: Technique for Dental Radiography in Cattle. JAVMA 1 3 3 496, 1958.

ZUSAMMENFASSUNG

Eine Methode fuer Zahn-Roentgenaufnahrnen von hoher Qualitaet von nichtberuhigten und nichtbetaeubten Rindern wird beschrieben. Es wurden Roentgenaufnahrnen der unteren Schneide- und Eckzaehne bei 144 lebenden und 29 geschlachteten Rindern gemacht. Die Stufen der Zahnentwicklung wurden tabellarisch angeordnet und jedes Tier nach seiner hoechsten Entwicklungsstufe eingeteilt. Es wurden der Mittelwert, die Normalabweichung, der Bereich und das Mindestalter in Tagen fuer jede Stufe der Zahnentwicklung bestimrnt. Waehrend es scheint, dass jede Stufe einen weiten Berich urnspannt, ist es dennoch rnoeglich, das Mindestalter fuer jede Stufe festzus- tellen, und sornit kann die richtige Alterseinteilung fuer Vor- fuehrrinder erzielt werden.

RESUME

II s’agit d’un procedi. pour obtenir des radios dentaires de bonne qualiti. avec du betail auquel l’on n’a administri. ni skdatif, ni anks- thksie. Ces radios des incisives et des canines de la rnschoire i n f b ieure proviennent de 144 t&tes de betail vivantes et de 29 t&tes de betail abattues. Les phases de croissance dentaire ont 6% ritpertorikes et chaque animal a r e y une classification suivant la phase la plus avancke atteinte. L’on a dbtermini. l’bge rnoyen, sa dkviation stan-

6 6

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dard, son dtendue et 1Pge minimal comptk en jours pour chaque phase de croissance dentaire. Bien que chaque phase semble offrir une Btendue considkrable, il semble que I’on puisse arriver B ddfinir un Bge minimal correspondant B chaque phase, offrant de cette faCon un moyen de determiner une classification acceptable de 1’5ge pour Mtail de concours.

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