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How to Recognize and Clinically Manage Class 1Malocclusions in the Horse

Robert M. Baratt, DVM, MS, FAVD

Class 1 malocclusions are a frequent finding in the dentition of the horse. These malocclusions oftenresult in tooth elongations that can be detrimental to normal mastication, cause pathologic orthodon-tic tooth movements, and predispose to painful periodontal disease. Odontoplasty, the removal oftooth material with manual or motorized instrumentation, is generally used in a conservative mannerto correct the malocclusion or prevent it from becoming worse over time. Author’s address: SalemValley Veterinary Clinic, 12 Center Street, Salem, Connecticut 06420; e-mail: [email protected]. © 2010 AAEP.

1. Introduction

A malocclusion is defined as any deviation from nor-mal occlusion.1 In the horse, the normal occlusion(orthooclusion) is a level incisor bite. In humans(and many breeds of dog and cat), the incisors havea normal overbite. The hypsodont dentition, an-gled conformation of the temporomandibular joints,and anisognathism (mandibular jaw width narrowerthan the maxillary counterpart) result in the normal10–15° angle to the occlusal surface of the cheekteeth and enamel points on the lingual aspect of themandibular cheek teeth and buccal aspect of themaxillary cheek teeth.2 The normal horse has acurvature of the occlusal surfaces of the cheek teethin the longitudinal plane, called the curvature ofSpee (Fig. 1). The rostral angulation of the distalcheek teeth and the caudal angulation of the mesialcheek teeth maintain tight interproximal contactuntil very late in life.3

A class 1 malocclusion (neutroclusion) occurs inhorses with normal jaw lengths and teeth in theirnormal mesiodistal location. Abnormalities of cheek

tooth wear are frequently seen and often described aswaves, steps, hooks, and ramps.4 Although thesetypes of occlusal abnormalities have not been previ-ously classified as a type of malocclusion, their descrip-tion as a class 1 malocclusion is justified and lendscredence to the idea that occlusal adjustment is anorthodontic procedure. Similarly, abnormal incisorwear, given the descriptive terms smile, diagonal,stepped or irregular, and frown, can be consideredanother type of class 1 malocclusion.5

A malpositioned tooth, in the horse with normaljaw lengths, is another type of class 1 malocclusion.Rotations, embrications (crowding), displacements,and versions (tilting) are seen in both the incisor andcheek teeth, with the highest incidence in the Min-iature Horse. An overjet is a facial projection of themaxillary incisors, whereas an overbite is the verti-cal overlap of the maxillary incisors over the man-dibular incisors.6 The overbite (parrot mouth) ismost commonly seen in the class 2 malocclusion, inwhich the mandible is short relative to the maxilla(Fig. 2). The maxillary incisor overbite or overjetmay be accompanied by abnormalities in cheek tooth

458 2010 � Vol. 56 � AAEP PROCEEDINGS

RESPIRATORY/DENTISTRY

NOTES

wear, such as hooks on the rostral maxillary andcaudal mandibular cheek teeth. However, normalcheek tooth occlusion is often observed with theseincisor malocclusions (Fig. 3). The class 3 maloc-clusion, in which the mandible is of greater lengththan the maxilla-incisive bones, is most commonlyseen in the Miniature Horse. Mandibular incisoroverjet or overbite may occur in the absence ofcheek teeth abnormalities but is most commonlyassociated with ramped mandibular first cheekteeth (306, 406).

The etiology of class 1 malocclusions generally canbe determined by physical examination and radio-graphic imaging. Because malocclusions can be re-sponsible for poor mastication, periodontal disease,and poor athletic performance related to oral pain,proper diagnosis and management is important.

2. Materials and Methods

The equipment needed and method of performing athorough physical examination of the horse’s headand mouth have been described.7 The clinicianshould perform a brief physical examination before

sedation, noting the horse’s body score, rectal tem-perature, and in some cases, observation of thehorse’s chewing behavior and whether quidding ispresent. An extraoral examination should includethe observation of any facial swelling, nasaldischarge, malodorous breath, ocular discharge, pty-alism, painful response to palpation of the temporo-mandibular joint region, and lymphadenopathy.After sedation, and before placement of the full-mouth speculum, oral examination of the lips, oralmucosa and gingiva of the lips and incisors, incisormalocclusions, and periodontal disease and assess-ment of the lateral excursion to molar contact isperformed. After placement of the full-mouthspeculum, the diastema between the incisors andthe cheek teeth is examined, and the presence ofcanine teeth and first premolars (wolf teeth) isnoted. The examination of the cheek teeth requiresboth an overall evaluation of the occlusion for pat-terns of abnormal tooth wear and a detailed, toothby tooth examination with a good headlight, dentalmirror, dental explorer, and periodontal probe.Mobility of teeth can be assessed digitally and using

Fig. 3. Warmblood X gelding, 14-yr-old. Incisor overjet, withramp overgrowth of 206 and 311.

Fig. 1. Quarter Horse gelding, 7-yr-old. Normal development of sharp enamel points on the buccal side of the maxillary cheek teethand the lingual aspect of the mandibular cheek teeth (left). Buccal mucosal lacerations (arrows). Normal curvature of Spee givesthe false impression of a hook on the lower third molars (311, 411). Conservative management: floating of the enamel points; notethat very little rasping of the occlusal surface has occurred.

Fig. 2. Quarter Horse mare, 11-yr-old. Class 2 malocclusion(short mandible). Incisor overbite in conjunction with a normalcheek tooth occlusion.

AAEP PROCEEDINGS � Vol. 56 � 2010 459


a variety of forceps. It is important to carefullyexamine the tooth opposite from any overly longtooth. Although crown reduction of the overlongtooth may be indicated, the pathology is generally inthe opposing tooth (Fig. 4).

The pulp horn numbering system devised by Da-cre has been generally adopted.8 Particular atten-tion to the presence of pulpar exposure in all cheekteeth is important. Any “catch” of the dental ex-plorer on the occlusal aspect of a pulp horn should benoted. The depth of pulp horn and infundibularcavities can sometimes be assessed using 25- to 27-gauge hypodermic needles, but computed tomogra-phy studies have shown that these estimatesgenerally underestimate the apical extent of the le-sions.9 Recording of these findings on a dentalchart is recommended and should be kept as part ofthe medicolegal records. Fewer errors and omis-sions will be made if an assistant records the find-ings that are dictated by the clinician as he performsthe oral examination. The use of standard abbre-viations approved by the Academy of VeterinaryDentistry10 and the American Veterinary DentalCollege11 will facilitate communication with col-leagues and specialists.

Meticulous evaluation of any sites of feed impac-tion is important. A variety of instruments may berequired to accomplish the removal of impacted feedmaterial and cleansing and sounding of the diastem-ata and periodontal pockets. Long-handled straightand right-angled alligator forceps, long-handledpicks and scalers, marked (in millimeters) periodon-tal probes, and irrigation devices are often needed.Accurate periodontal disease assessment requiresthe introduction of sharp instruments into thehorse’s mouth and therefore adequate sedationneeds to be used to prevent iatrogenic injury to theoral soft tissues. Radiographic evaluation is cer-tainly indicated when probing depths exceed 10 mmor there is significant tooth mobility or clinical evi-dence of apical infection.12 Techniques for obtain-ing diagnostic dental radiographs have beendescribed.13 There have been several papers docu-

menting the efficacy of widening the diastema be-tween cheek teeth in cases where feed impaction isthe cause of painful periodontal disease.14,15 Bursof various sizes and shapes are available from themanufacturer of some models of motorized dentalfloats.

Instrumentation for the reduction of tooth over-growths is largely a matter of personal preference.Although there is no substitute for direct visual oralexamination, some practitioner’s prefer to use in-struments (floats) to rasp tooth overgrowths withdigital rather than visual guidance and assessment.In the author’s opinion, the use of motorized instru-mentation allows easier direct visualization of theodontoplasty procedure and a more precise adjust-ment of occlusal abnormalities. The procedure isgenerally faster with motorized equipment, andoften the ergonomics are improved. A scanningelectron microscopy study indicated that live odon-toplastic processes were exposed by routine odonto-plasty procedures and that motorized floats resultedin less trauma to the treated surface of the tooth.16

Of course, the two types of instrumentation can beused in conjunction with each other. Regardless ofthe instrumentation used, care must be taken not tocause iatrogenic trauma to soft tissues or teeth.Removal of excessive tooth material can cause irre-versible pulpitis either from direct pulp exposure orthermal damage.17,18 The clinician should alwaysbear in mind that the equine hypsodont tooth isa vital structure, which continuously erupts.Although removal of sharp enamel points on a young(�15 yr old) horse may be necessary at 6- to 12-mointervals, the older horse may require this only ev-ery 2 yr or even less frequently. Tooth wear is alsosignificantly affected by the horse’s access to pasture

Fig. 5. Quarter Horse gelding, 27-yr-old. Wave complex withtooth overgrowth of 408 (left) and excessive wear and diastemabetween 107 and 108, with food packing and periodontal disease(center). Conservative odontoplasty of 408 (right) takes thistooth out of occlusion. In a younger horse, this would permitclosure of the diastema and resolution of the periodontal disease.In this geriatric horse, the diastema will persist, and re-evaluationof periodontal disease will be necessary to determine whether fur-ther management is needed.

Fig. 4. Quarter Horse gelding, 18-yr-old. Tooth overgrowth of408, with expired 108 (center). Odontoplasty of 408 (right).



and the proportion of concentrate to roughage in thediet. Because an unopposed cheek tooth will eruptmore quickly and has less wear than a normal cheektooth, occlusal adjustment, in the form of crownheight reduction, may be required at frequent (6 mo)intervals in a young horse and yearly in an olderhorse.

Once a diastema has formed between adjacentcheek teeth, an excessive transverse ridge tends toform on the opposing cheek tooth (Fig. 5). Thisdental overgrowth acts as a wedge, perpetuating oreven increasing the diastema width.19 In someearly cases, the associated feed packing and peri-odontitis may be adequately addressed by removalof the excessive transverse ridge/tooth overgrowthat shorter intervals (3–6 mo) than the routine re-moval of sharp enamel points. Removal of thetooth overgrowth will often allow closure of the di-astema (by mesial drift) and resolution of the peri-odontal disease. Similarly, a hook on the mesialaspect of the maxillary second premolar will some-times result in mesial orthodontic movement of thistooth that will correct when the hook is removed.

It is not possible to predict with any degree of cer-tainty how much tooth overgrowth can be removedwithout the risk of pulp exposure. Conservativeodontoplasty, the removal of �4 mm of clinicalcrown at any time, can be performed at 2-mo inter-vals when large tooth overgrowths must be cor-rected. The apical retraction of the vital pulp andcoronal deposition of secondary dentine in the pulphorns will occur in response to this staged odonto-plasty procedure. The coronal extend of the mesialpulp horn (#6) of the first maxillary and mandibularcheek teeth is not likely to extend beyond the occlu-sal surface of the body of the premolar. If the baseof the hook is narrow, the entire hook can be re-moved at one visit, because the #6 pulp horn is not atrisk (Fig. 6). However, if the base of the hook isbroader, a more conservative crown reduction is jus-tified (Fig. 7).

Once the cheek teeth overgrowths have been ad-dressed, the full-mouth speculum should be re-moved, and the excursion to molar contact should bereassessed. If there is excessive excursion to molarcontact, conservative incisor crown reduction can beperformed.20 Some diagonal incisor malocclusionshave recently been shown to have accompanyingdeformation of the incisive bone.a In the author’sopinion, it is not necessary and potentially deleteri-ous (inadvertent pulp exposure) to perform occlusaladjustments of these cases in an effort to recreate alevel bite. Odontoplasty of incisors is generally notneeded if there is normal excursion to molar contact(Fig. 8).

3. Results

Sharp enamel points are normal in the horse.Although there is no doubt they are occasionallythe cause of painful buccal or lingual lacerationsin the horse, removal of enamel points (floating)has not been shown to affect either feed digestibil-ity or performance in a limited number of stud-ies.21,22 However, it is generally accepted that,for many performance horses, the removal ofsharp enamel points on the cheek teeth results in

Fig. 6. Thoroughbred, mare, 11-yr-old. The large hook, with anarrow base, was reduced in one session.

Fig. 7. Quarter Horse gelding, 7-yr-old. 106 hook with a broad base (left). Odontoplasty of �5 mm (center). Further odontoplastyof �5 mm the following year (right).



improved “rideability.” The author believes thatthis procedure should be conservative and in gen-eral should not reduce the occlusal surface of thecheek tooth (Figs. 1 and 9).

Conservative management of class 1 malocclu-sions has, in the author’s experience, been success-ful in the vast majority of cases presented in generalpractice for a “routine float” (Fig. 10). With theexception of the geriatric patient, conservative man-agement of diastema between cheek teeth is proba-bly preferred over diastema widening, because therisk of iatrogenic pulp exposure is significant.23

Removal of the opposite tooth overgrowths and ad-dressing any tooth overgrowths that are exertingorthodontic forces that tend to create the diastemashould be attempted before diastema burring inmost cases. In the author’s experience, mesial driftwill often close the diastemata in horses �20 yr ofage, if tooth overgrowths are corrected.

4. Discussion

The hypsodont dentition of the horse is always in astate of eruption and wear. Although class 1 mal-

occlusions are commonly observed in the horse, thepractitioner should bear in mind that the vast ma-jority of these horses have an occlusion that is quitefunctional, with a normal excursion to molar con-tact. In these cases, the goal of intervention is asfollows: reduce dental overgrowths that are causingorthodontic movement of teeth, diastemata, feed

Fig. 8. Arabian gelding, 20-yr-old. Diagonal incisor malocclusion with normal cheek tooth occlusion and normal excursion to molarcontact in both directions. This diagonal bite form of malocclusion has resulted in acquired skeletal deformation of the incisive boneand/or rostral mandible.

Fig. 9. Oldenberg gelding, 11-yr-old. Neutrocclusion; sharpenamel points, buccal lacerations; before (left) and after (right)floating.

Fig. 10. Thoroughbred gelding, 19-yr-old. Initial exam andodontoplasty of 411 step (upper left and right). Over the next 3yr, the tooth overgrowths were addressed on four visits. Thelower photos are the before (left) and after (right) on the occasionof the last odontoplasty, which returned the 411 to a nearlynormal crown height.



packing, and periodontal disease and reduce dentalovergrowths that are the cause of traumatic softtissue contacts or excessive wear of opposing dis-eased teeth.

With mesial drift and continued eruption of cheekteeth, conservative management of many class 1malocclusions will be enough to eliminate the mal-occlusion in young horses with undamaged cheekteeth. The frequent occurrence of asynchronouseruption of the maxillary and mandibular fourthpremolars is presumed to be a common etiology ofthe wave complex in which there is relative toothovergrowth of the mandibular fourth premolars.In the horse �15 yr of age, correction of this maloc-clusion may be possible with several crown reduc-tions of 3–4 mm over the course of 1–2 yr, becausethe short (infracluded) maxillary cheek tooth eruptswithout the occlusal contact of the opposite mandib-ular cheek tooth. On the other hand, in the olderhorse, there may not be significant reserve crowneruption of the infracluded maxillary cheek tooth topermit correction of the wave malocclusion. Again,very conservative odontoplasty is generally all thatis needed.

Complex malocclusions, such as waves, should notbe corrected to a theoretical normal anatomical con-dition by trying to reduce the height of all overgrownteeth in an effort to create a “textbook” occlusion.This results in unnecessary removal of crown, runsthe risk of iatrogenic irreversible pulpitis, wouldoften require excessive incisor crown reduction toallow normal excursion to molar contact, and mayresult in quidding or even anorexia (Fig. 11). In thecase of a mild to moderate wave, when the mostovergrown tooth is opposed by a diseased tooth, thenannual reduction of 3–5 mm of this “peak” of thewave is enough to keep the weakened tooth out ofocclusion and to protect it from traumatic contact.This degree of crown reduction is not associated withquidding or a measurable change in excursion tomolar contact

Another proposed etiology is the presence of in-fundibular cemental hypoplasia of the maxillary

premolars or molars. This may predispose to in-fundibular caries and a crown that is relativelyweaker than the mandibular counterpart. Exces-sive wear is recognized as a prematurely expired(cupped) crown opposite the overgrown mandibulartooth. In this case, regular reduction of the man-dibular cheek tooth overgrowth will be needed forthe life of the horse.

Step overgrowths, ramps, and large hooks oncheek teeth not only impede normal mastication,they exert orthodontic forces that move the over-grown teeth, with creation of diastemata. The re-sultant feed impaction in turn causes periodontaldisease. Some hooks are so large that they causesignificant trauma to the opposite soft tissues.In the author’s experience, removal of large hooksback to the level of the normal occlusal surface mayneed sequential reduction to avoid pulp exposure.Pulp exposure has been documented when removingthe normal occlusal surface along the mesial aspectof the second premolars (the so-called “bit seat”).24

Basic dental principles dictate that the occlusal ta-bles should be preserved. In regard to large toothovergrowths, until more scientific evidence is avail-able, a conservative reduction of 3–4 mm every 2–3mo is recommended. The use of molar cutters isnot recommended, because these instruments cancause vertical tooth fracture. In cases where themandibular third molar has a very large distal hook,a motorized float can still be used by placing theinstrument cutting disc on the lingual or buccalaspect of the tooth overgrowth and pressing it coro-nally until enough space is created so the float canbe placed on top of the tooth overgrowth.

In the author’s opinion, if there is normal excur-sion to molar contact, diagonal incisor bite malocclu-sions need not be corrected. In these instances,there has likely been adaptive remodeling of theincisive bone and/or rostral mandible (axial rotationand/or lateral deviation). Shortening of overgrownteeth will not change this skeletal adaptation. Onthe other hand, if incisor overgrowth has precludedmolar contact, crown reduction of the overlong inci-

Fig. 11. Thoroughbred mare, 12-yr-old. Chief complaint of dysphagia, anorexia, and rapid weight loss after teeth were floated.Full lateral excursion of the mandible with no molar contact (left); overfloated cheek teeth with flat occlusal angles (right).



sors can be done in a conservative manner (3–4 mm,every 2 mo).

References and Footnote1. Wiggs RB, Loprise HB. Basics of orthodontics. In: Veteri-

nary dentistry, principles & practice. Philadelphia: Lip-pencott-Raven, 1997;435–481.

2. Carmalt JL. Observations of the cheek tooth occlusal angleof the horse. J Vet Dent 2004;21:70–75.

3. Dixon PM. Dental anatomy. In: Baker GJ, Easley J, eds.Equine dentistry, 2nd ed. Edinburgh: Elsevier, 2005;25–48.

4. Baker GJ. Abnormalities of wear and periodontal disease.In: Baker GJ, Easley J, eds. Equine dentistry, 2nd ed. Edi-nburgh: Elsevier, 2005;111–119.

5. Easley J. Corrective dental procedures. In: Baker GJ, Eas-ley J, eds. Equine dentistry, 2nd ed. Edinburgh: Elsevier,2005;221–248.

6. Wiggs RB, Loprise HB. Basics of Orthodontics. In: Veteri-nary dentistry, principles and practice. Philadelphia: Lip-pencott-Raven, 1997;442.

7. Gieche J. How to assess the equine periodontium, in Pro-ceedings. 56th Annual Meeting of the American Associationof Equine Practitioners 2010; 441–449.

8. Dacre IT. Equine dental pathology. In: Baker GJ, EasleyJ, eds. Equine dentistry, 2nd ed. Edinburgh: Elsevier,2005;91–109.

9. duToit N, Burden FA, Kempson SA, et al. Pathological in-vestigation of caries and occlusal pulpar exposure in donkeycheek teeth using computerised axial tomography with his-tological and ultrastructural examinations. Vet J 2008;178:387–395.

10. American Veterinary Dentistry. http://www.fvvds.com/files/Equine_Application_2010.docx. Accessed August 30, 2010.

11. American Veterinary Dental College. http://avdc.org/abbreviations.pdf. Accessed August 30, 2010.

12. Klugh DO. Equine periodontal disease. Clin Tech EquinePract 2005;4:135–147.

13. Baratt RM. How to obtain equine dental radiographs inambulatory practice, in Proceedings. 53rd Annual Meeting

of the American Association of Equine Practioners 2007;460–465.

14. Dixon PM, Barakzai S, Collins N, et al. Treatment of equinecheek teeth by mechanical widening of diastemata in 60horses (2000–2006). Equine Vet J 2008;40:22–28.

15. Collins NM, Dixon PM. Diagnosis and management ofequine diastemata. Clin Tech Equine Pract 2005;4:148–154.

16. Kempson SA, Davidson MES, Dacre IT. The effect of threetypes of rasps on the occlusal surface of equine cheek teeth:a scanning electron microscopic study. J Vet Dent 2003;20:19–27.

17. Wilson GJ, Walsh LJ. Temperature changes in dental pulpassociated with use of power grinding equipment on equineteeth. Austr Vet J 2005;83:75–77.

18. Allen ML, Baker GJ, Freeman DE, et al. In vitro study ofheat production during power reduction of equine mandibu-lar teeth. J Am Vet Med Assoc 2004;224:1128–1132.

19. Easley, J. Corrective dental procedures. In: Baker GJ, Ea-sley J, eds. Equine dentistry, 2nd ed. Edinburgh: Elsevier,2005; 221–248.

20. Rucker BA. Utilizing cheek teeth angle of occlusion to de-termine length of incisor shortening, in Proceedings. 48thAnnual Meeting of the American Association of Equine Prac-tioners 2002;448–452.

21. Ralston SL, Foster DL, Divers T, et al. Effect of dentalcorrection on feed digestibility in horses. Equine Vet J 2001;33:390–393.

22. Carmalt JL, Carmalt KP, Barber SM. The effect of occlusalequilibration on sport horse performance. J Vet Dent 2006;23:226–230.

23. Rucker BA, Carmalt JL. Measurement of equine cheekteeth pulpcavities from mesial and caudal tooth edges, inProceedings. 50th Annual Meeting of the American Associ-ation of Equine Practioners 2004;41–46.

24. Klugh DO. Principles of occlusal equilibration. In: Prin-ciples of equine dentistry. London: Manson, 2010;75.

aEarley E. Unpublished data, 2009.



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