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The Veterinary Journal 178 (2008) 307–310

TheVeterinary Journal

Introduction

Establishing a scientific basis for equine clinical dentistry

This issue of The Veterinary Journal provides a uniquecollection of original papers on equid dentistry that willbe of fundamental value to equine clinicians and research-ers and will be an important literary resource for all inter-ested in this rapidly growing subject. We are particularlyindebted to Professor Padraic Dixon of the University ofEdinburgh for editing this Special Issue and to The Veter-

inary Journal for publishing it.Merillatt (1906) commented that ‘the principal objective

of dentistry is to promote the general health (of the horse)

by improving mastication and by relieving pain’. Mostequine clinicians would agree that the current goal of den-tistry remains the same. Merillatt’s text, published in 1906,described how to float enamel points, manage deciduousteeth, and extract terminally diseased teeth. With theexception of the outstanding clinical work of Becker andcolleagues some 40 years later (Becker, 1962), the standardof equine dental care saw minimal change through most ofthe 20th century, with many of the procedures described byMerillatt, such as wolf tooth extraction, canine teeth reduc-tions and bit seat application, still commonly practicedwithout scientific validation of their merit.

Ironically, the limited literature investigating the relation-ship between floating and mastication or work performancefails to show any clinically significant correlation (Carmaltet al., 2004a, 2006). While we know horses perceive pain sen-sation through the dental nerves, dental pain, which is themost common presenting complaint in human dentistry, isnot clinically measurable in the horse (Brunson et al.,1987). Exposure of dentine and dentinal processes to the oralenvironment would cause great pain in other species, yetsuch exposure occurs on the occlusal surfaces of equine teeth(Kilic et al., 1997) without apparent pain or infection of theunderlying pulp via the open dentinal tubules – and this isjust one example of many fundamental questions to be an-swered in equine dentistry. Nevertheless, the work of AnnaTell et al. (2008), published in this Special Issue, conclusivelyshows that riding horses in a bit and bridle can cause buccalulceration, which is very likely to cause pain.

Veterinary dentistry began with (and was once synony-mous with) equine dentistry, as the horse was the foremost

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domesticated animal treated by veterinarians in past centu-ries. Currently, however, equine dental practice lags behindthose of other companion animals by approximately20 years. Several reasons for the delayed development ofequine dentistry have been suggested, including the paucityof basic research and even of clinical case reports (Dixon,1993), the lack of formal dental education (Schumacher,2001), limitations on early diagnosis of dental disease dueto difficulties in clinically examining and imaging the largeequine head, and the lack of translational application ofhuman dental surgical techniques to equine dental disease(Pascoe, 2006).

Interestingly, the current growing pains of equine prac-titioners are similar to those experienced by small animaldentists in the past. In an editorial in the Journal of Veter-

inary Dentistry aptly termed ‘All saddled up, but where are

we headed?’ Harvey (1997) commented ‘To those of us in

small animal dentistry, this is a familiar story – recognition

of the clinical need by practitioners, lack of interest in the

schools, and the sterling efforts by several individuals to ele-

vate their own knowledge followed by a willingness to share

their experiences and hard-won expertise with fellowpractitioners’.

However, the need for formal equine dental educationhas at last been recognized and dental training opportuni-ties for veterinarians are now available through multipleoutlets. Many national and international equine and veter-inary dental associations now organize lectures and practi-cal classes. For example, in 2006 the American Associationof Equine Practitioners and the British Equine VeterinaryAssociation held a joint equine dental conference with 49papers presented by international speakers, a feat thatwould have been impossible 10 years earlier (see ‘Focuson Dentistry’; http://www.ivis.org).

The current renaissance of equine dentistry began in themid-1990s when Paddy Dixon recognized the need for spe-cies-specific, basic research (Dixon, 1993). His team atEdinburgh University has since made the most significantcontribution to the body of equine dental knowledge todate, by publishing multiple studies including morphologi-cally describing equine dental tissues in health and disease.

308 Introduction / The Veterinary Journal 178 (2008) 307–310

Some of the most recent studies of this group describe thedentition of the donkey, which shows minimal differencesbetween the teeth of the two equid species (du Toit et al.,2008a), and provides conclusive evidence that dental dis-ease is associated with colic and weight loss (du Toitet al., 2008b).

Also from the Edinburgh group and published in this is-sue is a detailed pathological study of dental caries andocclusal pulpar exposure in donkeys (du Toit et al.,2008c), and this work is equally applicable to equine teeth.Then there is a series of five fundamental studies on prob-ably the most significant equine dental disease (cheek teethapical infections) presented by Dacre et al. (2008a,b,c,d,thisissue), and Shaw et al. (2008) that initially reclassifies andquantifies equine dentine in normal equine teeth and quan-tifies dentine in infected cheek teeth. Two of the papers ex-plore the multiple aetiologies of cheek teeth apicalinfections and describe the gross and histological changespresent in these infected teeth (Dacre et al., 2008c,d).

Researchers at the University of Ghent added to thebody of knowledge by publishing several studies describingnormal equine dentine (see, for example, Muylle et al.,2000). Workers at the University of Hannover have pub-lished descriptive studies on the equine periodontium(Masset et al., 2006; Staszyk and Gasse, 2007; War-honowicz et al., 2006) and, in this issue, they report the firstsignificant pathological study on the enigmatic odontoclas-tic incisor/canine syndrome of horses (Staszyk et al., 2008).The Ghent team published the first studies on equine alve-olar bone grafting and the use of alveolar prostheses (Vla-minck et al., 2006) to prevent post-extraction dental drift, atopic further explored by Townsend et al. (2008) in thisissue.

The first decade of the 21st century has been marked byexponential changes in equine dental practice. While float-ing teeth (‘occlusal equilibration’) remains the primary pro-phylactic procedure, and exodontia is a necessary salvageprocedure in many dental cases, the scope of equine carehas expanded to include all dental disciplines (endodontics,orthodontics, periodontics and restorative dentistry).Although these disciplines are currently being practiced,formal case reporting remains limited, documentation oflong-term case follow-up is essentially lacking, and con-trolled studies to validate the merit of most of these ad-vanced dental procedures in horses are totally absent.Klugh et al. (2001) first described the restoration of infun-dibular cavities, and numerous practitioners have per-formed this with anecdotal success; however, the bondingof restorative materials to equine dental tissues has notbeen documented, nor has the bonding to cementum inany species been investigated. This latter research is criticalfor equine dentistry since cementum is a peripheral struc-

tural tissue, which is currently being stripped from teethto provide an enamel bonding surface. Likewise the greatdepth, variable width, and complex anatomical shape ofequine cheek teeth infundibula, with the frequent presenceof damaged or absent infundibular cementum up to 7 cm

beneath the occlusal surface (Fitzgibbons, 2007) needs tobe addressed when attempting to restore such lesions occlu-sally within the limited confines of the equine oral cavity.

Limited success continues to be reported with equineendodontic therapy performed from the apical aspect ofthe tooth, including the most comprehensive account todate of this procedure by Simhofer et al. (2008a), publishedin this issue. Reasons for failure include the complexity andlack of knowledge of equine endodontic anatomy, tech-nique sensitivity and poor adaptation of human endodon-tic instruments and materials to the complex equineendodontic system. The studies of Dacre et al. (2008c,d,thisissue) showed the presence of clinically unrecognized peri-odontal disease, fissure fractures and pulpar exposures inextracted, infected cheek teeth that, if clinically detected,may have influenced the treatment protocol. The techniqueof oral endoscopy as described by Simhofer et al. (2008b)should help detect such subtle lesions.

Additionally, some of the apically infected cheek teethdescribed by Dacre and colleagues (Dacre et al., 2008c,d),had such extensive changes to their calcified dental tissuesthat they would have been poor candidates for endodontictreatment. The detection of such dental changes by modernimaging techniques should be another future priority. Tra-ditionally, endodontic therapy has been reserved for ma-ture horses; however, apexification of an immaturepermanent incisor has been recently reported (Baratt,2008). The use of mineral trioxide aggregate (MTA), themost popular endodontic filling material in human den-tistry, has been proposed as a retrograde filling materialin a horse, but the case report lacks long-term follow-up(Earley, 2006). MTA is of particular interest for equinedentistry because of its properties, which includes its abilityto be used in a wet environment and the induction ofcementogenesis. Steenkamp et al. (2005) have publishedthe only in vitro study reporting the effective apical sealingof equine cheek teeth.

Interceptive orthodontic therapy in adolescent horses, inthe form of deciduous teeth management, is well described,but like many other aspects of equine dentistry, the subjectof equine orthodontics has received no critical review. Thedescription of orthodontic treatments in the literature hasbeen limited to the correction of Class II and Class III mal-occlusions using acrylic bite plates with and without theapplication of tension bands (DeBowes and Gaughan,1998; Easley, 1999; Klugh, 2004). However, the first casereport describing the corrective orthodontic treatment ofan equine cheek tooth malocclusion was reported by Gal-loway (2008).

Periodontal disease is the primary cause of tooth loss inmammals and was described in the horse by Aristotlearound 333BCE (Carmalt, 2007). Becker (1962) describeda categorization system for equine periodontal disease(based on oral examination findings), which is still widelyused today. Since reattachment of the periodontium wasconsidered impossible, direct periodontal treatment duringthe second half of the 20th century was limited to irrigation

Introduction / The Veterinary Journal 178 (2008) 307–310 309

of periodontal pockets and extraction of mobile teeth(Baker, 1999). Carmalt et al. (2004b) introduced mechani-cal widening of cheek teeth diastemata as a direct treatmentof periodontal disease and Dixon et al. (2008) reportedlong-term clinical success with this technique.

Traditionally, radiographic imaging of the horse’s denti-tion has not been adequately used as a diagnostic tool, butrather as a means to confirm a physical examination find-ing. Based on this philosophy, conservative medical treat-ment with antibiotics has been routinely suggested forhorses with dental diseases. Retrospective study of antibi-otic therapy for horses with clinical signs consistent withcheek tooth apical infection, however, showed this treat-ment to be ineffective and Dixon et al. (2000) concludedthat ‘radiographic misinterpretation of early dental lesions

was a common cause of misdiagnosis’.Equine dentistry is a science that requires the early

radiographic recognition of dental disease in order to pre-serve the horse’s dentition. During the 20th century, veter-inarians were significantly handicapped by the availableimaging systems and the accepted radiography techniques.Contemporary digital radiograph systems allow practitio-ners to take diagnostic quality dental radiographs in thefield (Baratt, 2006), and the development of intra-oral radi-ography techniques allows the detailed study of dental tis-sues required for advanced dental procedures (Klugh,2005). Most experienced practitioners would agree thatmany dental procedural failures and complications are of-ten not caused by material or technique failures but bypoor case selection and treatment planning due to incom-plete diagnostic investigations. The increased availabilityof computed tomography (CT), with its superior imagingcapabilities of the equine head, has made this imagingmodality a valuable tool for both research and clinicaldiagnostics (Henninger et al., 2003; Pulchalski, 2006).Although CT traditionally requires general anesthesia(some newer CT units can image standing sedated horses),the cost and risk of the diagnostic procedure is often com-pensated for in advanced dental procedures by improvedtreatment planning, reduced surgery time, and fewercomplications.

Regardless of the study, science progresses in a contin-uum which can be divided into four historical ‘Phases of

Knowledge’ (Bader and Shugars, 2006). Through Phase 1,the ‘Age of Experts’ knowledge is accumulated throughexperience and uncontrolled observation, and is sharedinformally from person to person through apprenticeships.During Phase 2, the ‘Age of Professionalism,’ the opinionsof the experts are disseminated through textbooks. InPhase 3, the ‘Age of Science,’ knowledge is acquiredthrough clinical trials and literature reviews. Scientificstudy allows an investigator to question the opinions of ex-perts, and literature review exposes scientific investigationto peer scrutiny. This process is essential to define ‘factual’information. Once a body of factual information is estab-lished, practitioners can move to Phase 4, the ‘Age of Evi-

dence,’ where individual patient care decisions can be made

based on the current best scientific evidence available (Bad-er and Shugars, 2006). Our review of the literature showsthat equine dentistry is in the early stages of Phase 3; there-fore, most of the knowledge that is being taught and ac-cepted as fact is the unproven opinion of ‘experts.’

In order to remedy the current situation, the equine vet-erinary profession needs to continue to look to academiafor help, and hopefully from a wider group of universitiesthan have contributed to date, including the American uni-versities that so far have virtually ignored scientific equinedental studies. These institutions should provide more fun-damental basic and clinical research as well as perform(and help practitioners perform) retrospective and (prefer-ably) prospective structured clinical studies. Field practitio-ners need to document meaningful and measurable datafrom cases and disseminate this information to theprofession.

There is a ‘grassroots’ demand for more information inthe equine dental field that needs to be conveyed toresearchers and grant awarding bodies that will hopefullybring funds for research and thus lead to developments inthis field. With such funding and more scientific research,such as is provided so excellently in this issue of The Veter-

inary Journal, the care of our equine patients could be dri-ven by evidenced-based principles.

Stephen S. GallowayAnimal Care Hospital,

8565 Highway 64,

Oakland, TN, USAE-mail address: achvet@yahoo.com

Jack EasleyEquine Veterinary Practice LLC,

P.O. Box 1075, Shelbyville,KY 40066, USA

E-mail address: easleydvm@aol.com

References

Anna Tell, A., Egenvall, A., Lundstrom, T., Wattle, O., 2008. Theprevalence of oral ulceration in Swedish horses when ridden with bitand bridle and when unridden. The Veterinary Journal 178 (3), 405–410.

Bader, J.D., Shugars, D.A., 2006. The evidence supporting alternativemanagement strategies for early occlusal caries and suspected occlusaldentinal caries. Journal of Evidence Based Dental Practice 6, 91–100.

Baker, G.J., 1999. Abnormalities of wear and periodontal disease. In:Baker, G.J., Easley, J. (Eds.), Equine Dentistry, first ed. W.B.Saunders, London, pp. 295–302.

Baratt, R.M., 2006. How to use computed equine dental radiography inambulatory practice. In: Proceedings of American Association EquinePractitioners Focus on Dentistry, Indianapolis, pp. 293–303.

Baratt, R.M., 2008. Equine incisor endodontic therapy. In: Proceedings ofthe 22nd Annual Veterinary Dental Forum, Jacksonville, Florida, pp.113–123.

Becker, E., 1962. Dental disease in the horse. In: Joest, E., Parcy, P. (Eds.),Handbook of Special Pathology of the Domestic Animals. Verlag PaulParey, Berlin, pp. 642–651.

310 Introduction / The Veterinary Journal 178 (2008) 307–310

Brunson, D.B., Collier, M.A., Scott, E.A., Majors, L.J., 1987. Dentaldolorimetry for the evaluation of an analgesic agent in the horse.American Journal of Veterinary Research 38, 182–196.

Carmalt, J.L., Townsend, H.G., Janzen, E.D., Cymbaluk, N.E., 2004a.Effect of dental floating on weight gain, body condition score, feeddigestibility, and fecal particle size in pregnant mares. Journal of theAmerican Veterinary Medical Association 225, 1889–1893.

Carmalt, J.L., Rucker, B.A., Rach, D.J., 2004b. Treatment of periodon-titis associated with diastema formation in the horse – an alternativeapproach. In: Proceedings of the American Association of EquinePractitioners, vol. 50, p. 1407.

Carmalt, J.L., Carmalt, K.P., Barber, S.M., 2006. The effect of occlusalequilibration on sport horse performance. Journal of VeterinaryDentistry 23, 226–230.

Carmalt, J.L., 2007. Evidence-based equine dentistry: preventivemedicine. Veterinary Clinics of North America: Equine Practice 23,519–524.

Dacre, I.T., Kempson, S., Dixon, P.M., 2008a. Pathological studies ofcheek teeth apical infections in the horse: 1. Normal endodonticanatomy and dentinal structure of equine cheek teeth. The VeterinaryJournal 178 (3), 311–320.

Dacre, I.T., Kempson, S.A., Dixon, P.M., 2008b. Pathological studies ofcheek teeth apical infections in the horse: 2. Quantitative measure-ments in equine dentine in apically infected cheek teeth. The VeterinaryJournal 178 (3), 321–332.

Dacre, I.T., Kempson, S., Dixon, P.M., 2008c. Pathological studies ofcheek teeth apical infections in the horse: 4. Aetiopathological findingsin 41 apically infected mandibular cheek teeth. The Veterinary Journal178 (3), 341–351.

Dacre, I.T., S Kempson, S., Dixon, P.M., 2008d. Pathological studies ofcheek teeth apical infections in the horse: 5. Aetiopathological findingsin 57 apically infected maxillary cheek teeth and histological andultrastructural findings in apically infected cheek teeth. The VeterinaryJournal 178 (3), 352–363.

DeBowes, R.M., Gaughan, E.M., 1998. Congenital dental disease ofhorses. In: Gaughan, E.M., DeBowes, R.M. (Eds.), Veterinary Clinicsof North America: Equine Practice, vol. 14, pp. 273–289.

Dixon, P.M., 1993. Equine dental disease: a neglected field of study.Equine Veterinary Education 5, 285–286.

Dixon, P.M., Tremaine, W.H., Pickles, K., Kuhns, L., Hawe, C.,McCann, J., McGorum, B.C., Railton, D.I., Brammer, S., 2000.Equine dental disease. Part 4: A long-term study of 400 cases: apicalinfections of cheek teeth. Equine Veterinary Journal 32, 182–194.

Dixon, P.M., Barakzai, S., Collins, N., Yates, J., 2008. Treatment ofequine cheek teeth by mechanical widening of diastemata in 60 horses(2000–2006). Equine Veterinary Journal 40, 22–28.

Du Toit, N., Kempson, S.A., Dixon, P.M., 2008a. Donkey dentalanatomy. Part 2: Histological and scanning electron microscopicexaminations. The Veterinary Journal 176, 345–353.

DuToit, N., Burden, F.A., Dixon, P.M., 2008b. Clinical dental examin-ations of 357 donkeys in the UK. Part 2 – Epidemiological studies onthe potential relationships between different dental diseases, andbetween dental diseases and systemic disorders. Equine VeterinaryJournal.

Du Toit, N., Burden, F.A., Dixon, P.M., 2008c. Pathological investigationof caries and occlusal pulpar exposure in donkey cheek teeth usingcomputerised axial tomography, histological and ultrastructuralexaminations. The Veterinary Journal 178 (3), 387–395.

Earley, E.T., 2006. Pulp disease in mandibular cheek teeth. In: Proceed-ings of the 20th Annual Veterinary Dental Forum, Portland, Oregon,pp. 117–126.

Easley, J., 1999. Basic equine orthodontics. In: Baker, G.J., Easley, J.(Eds.), Equine Dentistry, first ed. W.B. Saunders, London, pp. 249–266.

Fitzgibbons, C., 2007. Equine Infundibular Anatomy. MSc thesis,University of Edinburgh, Edinburgh, pp. 18–40.

Galloway, S.S., 2008. An expansion screw device to facilitate eruption of amandibular premolar in a horse. In: Proceedings of the 22nd AnnualVeterinary Dental Forum, Jacksonville, Florida, p. 105.

Harvey, C.E., 1997. All saddled up, but where are we headed? Journal ofVeterinary Dentistry 14, 50.

Henninger, W., Frame, E.M., Willmann, M., Simhofer, H., Malleczek, D.,Kneissl, S.M., Mayrhofer, E., 2003. CT features of alveolitis andsinusitis in horses. Veterinary Radiology and Ultrasound 44, 269–276.

Kilic, S., Dixon, P.M., Kempson, S.A., 1997. A light and ultrastructuralexamination of calcified dental tissues of horses: dentine. EquineVeterinary Journal 29, 206–212.

Klugh, D.O., Basile, T., Brannan, R., 2001. Infundibular decay in equinemaxillary teeth. Journal of Veterinary Dentistry 18, 26–27.

Klugh, D.O., 2004. Acrylic bite plane for treatment of malocclusion in ayoung horse. Journal Veterinary Dentistry 21, 84–87.

Klugh, D.O., 2005. Intraoral radiology in equine dental disease. ClinicalTechniques in Equine Practice 4, 162–170.

Masset, A., Staszyk, C., Gasse, H., 2006. The blood vessel system in theperiodontal ligament of the equine cheek teeth – Part 2: The micro-architecture and its functional implications in a constantly remodellingsystem. Annals of Anatomy 188, 535–539.

Merillatt, L.A., 1906. Animal Dentistry and Diseases of the Mouth,Veterinary Surgery, vol. 1. Alex Eber, Chicago, pp. 18–204.

Muylle, S., Simoens, P., Lauwers, H., 2000. Tubular contents of equinedentin: a scanning electron microscopic study. Journal of VeterinaryMedicine A, Physiology, Pathology Clinical Medicine 47, 321–330.

Pascoe, J.R., 2006. Advances in equine surgery. Veterinary Surgery 35,587–588.

Pulchalski, S., 2006. Computed tomographic and ultrasonographicexamination of equine dental structures: normal and abnormalfindings. In: Proceeding of American Association of Equine Practitio-ners, Focus on Dentistry, Indianapolis, pp. 173–180.

Schumacher, J., 2001. The present state of equine dentistry. EquineVeterinary Journal 33, 2–3.

Shaw, D., Dacre, I.T., Dixon, P.M., 2008. Pathological studies of cheekteeth apical infections in the horse: 2. Quantitative measurements innormal equine dentine. The Veterinary Journal 178 (3), 321–332.

Simhofer, H., Griss, R., Zetner, K., 2008a. A long-term study ofapicoectomy and endodontic treatment of apically infected cheekteeth in 12 horses. The Veterinary Journal 178 (3), 411–418.

Simhofer, H., Griss, R., Zetner, K., 2008b. The use of oral endoscopy fordetection of cheek teeth abnormalities in 300 horses. The VeterinaryJournal 178 (3), 396–404.

Staszyk, C., Gasse, H., 2007. Primary culture of fibroblasts and cemento-blasts of the equine periodontium. Research in Veterinary Science 82,150–157.

Staszyk, C., Bienert, A., Kreutzer, R., Wohlsein, P., Simhofer, H., 2008.Equine odontoclastic tooth resorption and hypercementosis. TheVeterinary Journal 178 (3), 372–379.

Steenkamp, G., Olivier-Carstens, A., van Heerden, W.F., Crossley, D.A.,Boy, S.C., 2005. In vitro comparison of three materials as apicalsealants of equine premolar and molar teeth. Equine VeterinaryJournal 37, 133–136.

Townsend, N.B., Dixon, P.M., Barakzai, S.Z., 2008. Evaluation of thelong term oral consequences of equine exodontia in 50 horses. TheVeterinary Journal 178 (3), 419–424.

Vlaminck, L.E., Huys, L., Maes, D., Steenhaut, M.L., Gasthuys, F., 2006.Use of a synthetic bone substitute to retard molariform tooth driftafter maxillary tooth loss in ponies. Veterinary Surgery 35, 589–595.

Warhonowicz, M., Staszyk, C., Rohn, K., Gasse, H., 2006. The equineperiodontium as a continuously remodelling system: morphometricalanalysis of cell proliferation. Archives of Oral Biology 51, 1141–1149.