Oral endoscopy as an aid to diagnosis of equine cheek tooth infections in the absence of gross oral pathological changes: 17 cases.

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1 EQUINE VETERINARY JOURNAL Equine vet. J. (2009) 41 (2) doi: / X General Articles Oral endoscopy as an aid to diagnosis of equine cheek tooth infections in the absence of gross oral pathological changes: 17 cases P. H. L. RAMZAN Rossdales Equine Hospital, Cotton End Road, Exning, Newmarket, Suffolk CB8 7NN, UK. Keywords: horse; dental; oral; endoscopy; infection Summary Reasons for performing study: Removal of cheek teeth in all but the aged horse or pony is a serious undertaking with potentially deleterious sequellae. Rigid endoscopy permits detailed examination of the oral cavity and erupted dental tissues and has the potential to assist in the correct identification of the diseased tooth. Objectives: To document oral endoscopic findings associated with infected equine cheek teeth in cases without gross oral pathological changes and thereby determine the usefulness of rigid oral endoscopy as an aid to diagnosis of such infections. Methods: Records of all cases of equine cheek tooth removal attempted under standing sedation over a 38 month period were examined. Cases were excluded from the study if apical infection was associated with gross dental fracture, malalignment, diastema/periodontal pocketing or supernumerary teeth. Endoscopic and radiographic findings were analysed and correlated to diseased tooth location. Results: Seventeen cases of apical dental infection fitting the inclusion criteria (nonresponsive to antibiotics and with no gross oral abnormality of the affected arcade) were identified in which oral endoscopy was used as an aid to diagnosis. In 15 (88%) of the 17 cases, oral endoscopy revealed abnormalities specific to the infected tooth. Focal gingival recession (10/17 cases) was the most common visible abnormality associated with infected teeth. Conclusions: In the majority of cases of apical infection of equine cheek teeth there is visible intraoral evidence implicating the affected tooth. Potential relevance: Oral endoscopy facilitates detailed examination of the mouth and should be considered along with radiography as an important aid to diagnosis in cases of equine dental infection. Introduction Exodontia is currently the treatment of choice in cases of equine cheek tooth apical infection that do not resolve with antimicrobial therapy (Tremaine 2004). In all but the aged horse or pony, removal of a cheek tooth is a potentially serious undertaking regardless of surgical technique used (Prichard et al. 1992; Dacre and Dixon 2004). Apart from the considerable risk of immediate post surgical complications, longer-term sequellae, such as focal dental overgrowth or creation of diastemata (Tremaine and Lane 2005) can cause significant morbidity. For this reason it is important that the infected tooth is identified with accuracy prior to any surgical intervention. Radiography continues to play an important role in the investigation of suspected dental sepsis in horses, although the sensitivity and specificity of equine dental radiography for infection has been shown to be limited (Gibbs and Lane 1987; Weller et al. 2001). In recent years, the quality of imaging in equine practice has been boosted by the use of computed radiography, but correct interpretation of radiographic images remains highly dependent upon the experience of the viewing clinician and does not always permit a definitive diagnosis (Dixon and Dacre 2005). Accurate diagnosis and appropriate management of apical cheek tooth infections relies therefore upon the accumulation of evidence derived from several sources, including clinical and radiographic examinations. Nasal endoscopy (Tremaine and Dixon 2001), sinoscopy (Easley 2005), gamma scintigraphy (Weller et al. 2001) and computed tomography (Henninger et al. 2003) all have a role in the diagnostic armoury of the examining clinician depending on the nature of the infection. Although external features of apical cheek tooth infection (facial/mandibular swelling or fistulation, nasal discharge from sinus empyema) are well known, very few references to the examination of dental tissues within the oral cavity as an aid to correct identification of diseased teeth exist (Tremaine and Lane 2005). Intraoral endoscopy has been shown to be of use in the investigation of some nondental oral conditions in the horse (Griss *Author to whom correspondence should be addressed. Author s address for correspondence: Rossdale and Partners, Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS, UK. [Paper received for publication ; Accepted ]

2 102 Oral endoscopy as an aid to diagnosis of equine cheek tooth infections and Simhofer 2006) and is becoming increasingly popular as a diagnostic aid for equine dental disease. Intraoral imaging is widely used in human dental practice and has been shown to enable improved detection of carious lesions compared to unaided visual examination (Erten et al. 2005). Rigid oral endoscopy permits the identification (and recording) of defects of the erupted dentition and associated soft tissues in the standing sedated horse and, in some cases, can be a key diagnostic aid in the investigation of dental infection. The aim of the current study was to document abnormalities observed using oral endoscopy in cases of confirmed apical cheek tooth infection in a referral hospital and thereby determine the usefulness of the technique as a diagnostic modality. Materials and methods Case selection Hospital records for all horses admitted to the Rossdales Equine Hospital over a 38 month period (December 2004 to February 2008) for standing cheek tooth removal due to dental infection nonresponsive to antibiotic therapy were reviewed. Cases were excluded from further analysis if oral examination had revealed the apical infection to be associated with any of the following: gross fracture of the clinical crown; gross cheek tooth malalignment; large diastema with periodontal pocketing; or supernumerary cheek teeth. Radiography All cases included for analysis underwent radiography of the head. Radiography was performed on standing, sedated animals in a radiographic suite using a ceiling-mounted 700 ma, 175 kv x-ray unit and computed radiography system (Agfa ADC) 1. For cases with suspected maxillary cheek tooth infection, laterodorsal-lateroventral oblique projections of each maxillary arcade were obtained; a lateral projection of the head was also obtained if a sinusitis was present or suspected. For cases of suspected mandibular cheek tooth infection, lateroventrallaterodorsal oblique projections of the mandibular arcades were obtained. If an external mandibular draining tract was present a blunt metal probe was introduced to assist with identification of any infected tooth. In some cases, additional views such as stressed dorsoventral projections (Gibbs 2005) or open-mouth oblique projections (Barakzai and Dixon 2003) were obtained to provide additional information. Oral endoscopy Cases were subjected to detailed intraoral examinations following sedation with a combination of 12 µg/kg bwt detomidine hydrochloride (Domosedan) 2 and either 25 µg/kg bwt butorphanol tartrate (Torbugesic) 3 or 0.3 mg/kg bwt morphine sulphate 4. Horses were restrained in stocks. The oral cavity was lavaged to remove all loose food material, then a full-mouth speculum fitted and the head supported from a ceiling-mounted head sling. A sideviewing flexible videoendoscope 5 sheathed in a rigid protective bracket was used from December 2004 to January A 45 cm long, 8 mm diameter 70 forward-viewing rigid industrial borescope with C-mount camera and metal halide lightsource 6 was used from February 2006 onwards. With the full-mouth speculum open, endoscopic examinations of the oral cavity were undertaken in systematic fashion. In each horse, both the maxillary and mandibular arcades were examined, with each arcade viewed from the occlusal, buccal and lingual aspects. Dental picks were used to remove food from infundibular cavities and diastemata but were not used routinely to assess pulp horn secondary dentine at the occlusal surface. A cheek retractor ( Stubbs speculum) was used during examination of the mandibular arcades to permit the lingual and buccal aspects of the cheek teeth to be viewed unimpeded by the tongue and cheeks. Images were recorded on videotape. Exodontia The decision to extract any diseased tooth was made only following a full diagnostic investigation, assessment of response to antibiotic therapy and consideration by the owner of the risks and potential deleterious sequellae of surgery. In all cases, exodontia was attempted in the first instance per os under standing sedation with or without regional analgesia. The extraction technique consisted of gingival elevation, rostro-caudal spreading and bucco-lingual twisting to loosen the tooth prior to vertical elevation (Tremaine 2004). Repulsion of affected teeth was undertaken if extraction per os was unsuccessful for any reason, e.g. in the event of clinical crown fracture. Image analysis Endoscopic video recordings, radiographs and dental charts for all cases were subjected to review. All abnormal endoscopic findings were documented and assessed in relation to the affected tooth and radiographic findings. The reviewer was not blinded from related case details having been the primary investigating clinician, although in most cases any potential hindsight bias was limited by the availability of contemporaneous notes from oral endoscopic examinations (some of which preceded radiographic assessment). Results During the period of study, 54 horses underwent attempted extraction per os of infected cheek teeth. In 48 cases, standing extraction was successful, with 6 requiring repulsion of the tooth under general anaesthesia. A total of 62 cheek teeth were removed; 37 horses having gross abnormalities upon examination of the oral cavity that readily identified the cheek tooth/teeth requiring extraction were eliminated from the study. These abnormalities included obvious fracture of clinical crown (18 cases), cheek tooth malalignment (12 cases), large diastema associated with deep periodontal pocketing (4 cases) and supernumerary maxillary cheek teeth associated with maxillary sinusitis (3 cases). Seventeen horses fitting the inclusion criteria were identified. Extraction per os was successful in 15/17 horses; one horse required repulsion under general anaesthesia due to breakdown of the clinical crown during standing extraction and, in another horse, repulsion under standing sedation was performed in the final stages of the extraction procedure. In every case, correct identification of the infected cheek tooth was confirmed by gross examination by the treating clinician following successful exodontia, typically by the observation of focal reactive fibrous or cemental change (with or without malodour) associated with a diseased apex or root (Fig 1). Histopathology was not performed.

3 P. H. L. Ramzan 103 Although follow-up information was not analysed in the present study, at the time of writing none of the cases had been re-presented due to recurrence of clinical signs of dental infection. All 17 cases presented with signs of periapical dental infection which antibiotic therapy had not successfully abolished. Age ranged from 4 13 years (median 8 years). Maxillary cheek teeth (4 x 07, 4 x 09, 2 x 08) were involved in 10 cases and mandibular cheek teeth (3 x 07, 3 x 08, 1 x 06) in 7. At the time of examination all cases had radiological changes consistent with apical dental infection, or had draining tracts permitting the introduction of a metal probe to assist tooth identification: the radiological findings were specific to the infected tooth in 15 of the 17 cases. In Cases 1 and 9 radiological changes were observed in the region of the apices of 2 adjacent maxillary cheek teeth and it was not possible to differentiate by radiographic interpretation alone which tooth was implicated. Case details are summarised in Table 1. Video recordings of the endoscopic examinations of the oral cavity were available for all 17 cases. Abnormalities specific to the infected cheek tooth were observed in 15 of the 17 cases and are detailed in Table 1 (the 2 cases without endoscopic evidence of abnormality differed from the 2 cases with ambiguous radiological findings noted above). These included focal gingival recession with or without visible discharge of purulent material (10 cases), apparent pulpar compromise (4 cases) and supragingival calculus deposition (2 cases). Combinations of TABLE 1: Details of age, sex, breed, presenting signs, radiographic findings, tooth number and endoscopy findings in 17 cases Affected Endoscopy: occlusal surface 1 / Case Age Sex Breed Presenting signs Radiographic findings tooth gingival margin 2 Other 1 12 M WB Left-sided facial swelling Increased periapical Hairline fissure extending axially radiopacity caudal from pulp horn 4 to peripheral 208/rostral 209 cementum 2 11 F TB Thickening and draining Increased periapical Gingival recession entire lingual tract right ventral mandible radiopacity rostral 408 margin F TB Right-sided nasal discharge Maxillary sinusitis Peripheral caries entire caudal Increased periapical margin 109 with visible compromise radiopacity 109 to pulp horns 2 and F TB Right-sided facial swelling Periapical radiolucency Focal gingival recession/ulcer and right-sided nasal 108 buccal margin 108. Evidence of discharge drainage of malodorous exudate at site 5 7 F XB Left-sided facial swelling Increased periapical Visual evidence of drainage of radiopacity and apical exudate at buccal margin 207 lysis M XB Right-sided facial swelling Increased periapical Grade 2 caudal infundibular radiopacity 209 caries 209 Focal gingival recession rostral buccal margin M pony Thickening and draining Probe to 407; ventral Focal gingival recession lingual Subtle tract right ventral mandible cortical thickening margin 407 malalignment 406/ M WB Left-sided facial swelling Periapical radiolucency 207 NAD rostral F WB Right-sided nasal discharge Increased periapical Small rostral buccal sliver fracture radiopacity caudal 108; apparent involvement pulp 108/rostral 109 horn M XB Left-sided nasal discharge Maxillary sinusitis and Pulp horn 2 increased periapical blackened/compromised appearance radiopacity 209 Grade 2 caudal infundibular caries M pony Thickening right ventral Apical blunting 407; Focal gingival recession lingual mandible ventral cortical thickening margin M pony Draining tract left ventral Probe to NAD Minor interproximal mandible diastema 308/9 (same as contralateral side) 13 8 F TB Thickening left ventral Periapical radiolucency Focal gingival recession caudal mandible 308; ventral cortical lingual margin 308 thickening 14 8 F WB Thickening left ventral Apical blunting rostral 306; Focal gingival recession buccal Supragingival mandible ventral cortical thickening margin 306. Evidence of drainage calculus rostral and of malodorous exudate at site buccal aspects M pony Right-sided facial swelling Periapical radiolucency Focal gingival recession rostral caudal 107 buccal margin 107. Evidence of drainage of malodorous exudate at site 16 7 M WB Draining tract left ventral Probe to 307; ventral 307 NAD mandible cortical thickening F TB Right-sided facial swelling Probe to Focal gingival recession Small area and draining tract mid-buccal margin 107 supragingival calculus at site of gingival recession

4 104 Oral endoscopy as an aid to diagnosis of equine cheek tooth infections these abnormalities were noted in 2 animals. In all cases in which gingival recession, pulpar compromise or supragingival calculus deposition was observed, these findings were specific to the infected tooth and were not present on any other cheek tooth in either the ipsilateral or contralateral arcades. Infundibular caries (2 cases), minor interproximal diastema (one case) and subtle malalignment (one case) were also observed; however, these latter abnormalities were not exclusive to the diseased teeth. Focal gingival recession was defined as an area of obvious proximal deviation of the gingival margin with associated exposure of reserve crown (Fig 2), relative to adjacent teeth (or adjacent sites on the diseased tooth). Typically, the affected gingival margin had a slightly dimpled or puckered appearance. In several of these cases it was possible to visualise discharge/ exudate at the gingival defect; this was usually scant and once detected endoscopically was found typically to be malodorous when palpated. Of the 7 cases presenting with mandibular cheek tooth infection, 5 were found to have gingival recession of the infected tooth (4 with lesion on lingual aspect, one on buccal aspect). Of the 10 cases with maxillary cheek tooth infection, 5 had gingival recession of the infected tooth: in all of these the gingival lesion was located buccally. In no case was generalised gingival recession of the affected tooth observed. Gross examination of several diseased teeth following exodontia revealed evidence of communication between the affected gingival margin and the diseased tooth root: this typically took the form of a narrow well-defined tract of disrupted periodontium, sometimes appearing as a groove flanked by hypercementosis (Fig 3). Underlying exposed dental tissues in these cases were not marked by staining. Findings felt to be consistent with possible pulpar compromise were noted in 4 cases (all maxillary teeth). These consisted of carious, fracture or fissure lesions in which the lesion was seen to encroach upon the secondary dentine of one or more pulp horns. It was not possible to determine pre-extraction whether the affected pulp horns were indeed compromised; however, sectioning of 2 of these extracted teeth (from Cases 1 and 3) was undertaken at a later date. This confirmed devitalised pulp horns corresponding to the endoscopically observed lesions in each case (pulp horn 4 in Case 1, pulp horn 2 in Case 3). The teeth from Cases 9 and 10 were not available for sectioning hence, in these cases, it was not determined whether the oral lesions were truly associated with pulpar exposure or had a causal relationship with the apical dental infection. However, in both cases no other similar lesions were observed in the ipsilateral or contralateral arcades. Discussion Fig 1: Typical appearance of diseased apex of an extracted cheek tooth with focal inflammatory fibrous tissue (arrows). Infection of equine cheek teeth is a serious condition that demands accuracy in diagnosis and proficiency in treatment. Correct identification of the diseased tooth often depends on the accumulation of a body of evidence using several diagnostic aids, although diagnosis has traditionally relied heavily upon the radiographic imaging of the apical and alveolar portions of the cheek tooth arcade of interest. The interpretation of radiographic images of the equine head has, for some time, been considered difficult and somewhat inaccurate (Gibbs and Lane 1987) prompting utilisation of other imaging modalities, such as Fig 2: Focal gingival recession with small adjacent area of supragingival calculus deposition (arrows) on the mid-buccal aspect of tooth 107 in Case 17. Fig 3: Buccal aspect of extracted tooth 107 from Case 15 with tract (arrows) delineating disrupted periodontium between infected caudal apex and the site of gingival recession at rostrobuccal aspect of clinical crown. Note attrition of clinical crown caused by extraction forceps (arrowheads).

5 P. H. L. Ramzan 105 scintigraphy (Weller et al. 2001) and computed tomography (Tietje et al. 1996; Henninger et al. 2003). Although much information exists to guide the clinician on the radiographic and scintigraphic features associated with equine cheek tooth infections, very little consideration has been given in the literature to the detailed visual examination of intraoral structures. The increasing use of rigid side-viewing endoscopic equipment has permitted a rapid advancement in the documentation and understanding of many conditions of the equine mouth in vivo that had previously been investigated only through post mortem studies (Griss and Simhofer 2006). Oral endoscopy facilitates close scrutiny of features of the occlusal surface, such as the maxillary infundibulae and the secondary dentine of the pulp horns, as well as the interproximal spaces and parts of the clinical crown difficult to access by other means (Easley 2005). Images are highly detailed and superior to those achievable by examination with a dental mirror, primarily due to favourable magnification. This indeed is the basis for the widespread use of intraoral imaging in human dental practice (Erten et al. 2005). In many cases of equine dental infection, the precipitating cause is readily apparent on gross examination of the mouth using digital palpation and visualisation aided by a lightsource and dental mirror (Tremaine and Lane 2005). Examples include loose teeth in aged horses, teeth with obvious fracture of the clinical crown, gross malalignment of cheek teeth (with or without diastemata) and supernumerary cheek teeth. In such circumstances it is not usually necessary to utilise oral endoscopy to achieve a diagnosis, although endoscopy may have a role in defining and archiving the findings. Oral endoscopy is of particular use in cases in which the presence of apical infection is suspected or known but in which there is some doubt about the identity of the tooth involved, either due to radiographic ambiguity or absence of gross abnormalities of the affected arcade on oral examination. For this reason, the present study excluded cases of dental infection associated with obvious crown fracture, gross malalignment or diastemata, or supernumerary cheek teeth. This permitted an investigation of dental arcades that were ostensibly grossly normal on oral examination but which were known to house an infected cheek tooth. The most common abnormal oral endoscopic finding associated with infected cheek teeth in the present study was that of focal gingival recession, found in 10 of 17 cases either on the buccal (6 cases: predominantly maxillary teeth) or lingual (4 cases: all mandibular teeth) aspect of the infected tooth. In each case following the detection of gingival recession by endoscopy, the site was palpated digitally; in many instances malodour (sometimes with discharge) of the type often associated with dental infection was detected specifically at the affected gingival margin. In particular the buccal location of the maxillary gingival lesions was felt to hamper the detection of this finding by traditional oral examination, as the close proximity and tautness of the cheek particularly in the mid-arcade region is less suitable to placement of a mirror than a rigid endoscope. In view of the observation of a channel of disrupted periodontium linking gingival lesion and infected root in several extracted teeth, it was considered likely that the focal gingival recession noted in the presented cases was linked to drainage into the oral cavity of inflammatory exudate originating from apical abscessation. It is less likely that any communication may have been a causal mechanism in the seeding of these infections, as the selection criteria ensured no gingival lesion was associated with any obvious oral lesion such as deep periodontal pocketing. It was also considered unlikely that the gingival lesions in the present study were the result of tooth devitalisation as, in all cases, the periodontal attachments were strong and gingival lesions were focal rather than generalised. It is interesting to note that gingival recession was observed across the entire spectrum of cases including those displaying facial and mandibular swellings, discharging tracts and sinusitis; the reasonably young profile of the study population also meant that alveolar depth in many cases was considerable. This confounds the common assumption that the path of least resistance for purulent material to exit the head is necessarily anatomically closest to the infected apex. As the inclusion criteria for the study necessarily resulted in overrepresentation of cases with longstanding apical infection, it is possible that the duration of pathological change was sufficient for drainage into the oral cavity to become established. The significance of the supragingival calculus that was observed in Cases 14 and 17 was not determined in this study. In man, supragingival calculus is more typically seen to precede gingival recession than result from it, but the nature of the findings in the present study was felt to be more compatible with focal calculus deposition secondary to exposure of reserve crown or to chronic exudation of purulent material at the site. Aside from gingival lesions, oral endoscopy aided the detection of defects of the occlusal surface in several cases. Some of these (infundibular caries, minor interproximal diastemata), are common findings in asymptomatic equine mouths and were considered in the present study to be of doubtful clinical relevance. Four cases, however, displayed some evidence of possible disease involving one or more pulp horns of the infected tooth. Although dental probes were not used during the examinations to explore these defects, it is often difficult in vivo to determine the true extent of any pulpar exposure using such instrumentation. Sectioning of the teeth from 2 of these cases was possible following extraction and confirmed the gross presence of devitalised pulp chambers in both instances. Recent work on the histopathology of fractured cheek teeth (Dacre 2005; Dacre et al. 2007) has confirmed that damage to pulp horns (through fracture or caries) can lead to pulpitis and loss of tooth vitality and it would seem that further investigation into the correlation between occlusal defects detected in vivo and histopathological evidence of pulpar disease is warranted. The unblinded structure of the study may have introduced some bias with regard to documentation of oral endoscopic findings relating to infected cheek teeth. It should be noted, however, that detailed records from the original diagnostic investigations (including oral endoscopy) were available and that the retrospective analysis of endoscopic images was intended more to ensure lesions associated with clinically normal teeth and cheek tooth arcades had not been missed rather than to find retrospective evidence that implicated the teeth known to be infected. There is certainly a need to corroborate the findings presented here through future blinded studies. However, at the time of original investigation in most of the presented cases it was felt that intraoral endoscopy was diagnostically helpful in confirming the identity of the infected cheek tooth. The cases in the present study were selected for the absence of gross oral pathology and therefore comprise a small subset of horses treated for cheek tooth infection. These cases are, however, often the most diagnostically challenging when attempting to determine the location and viability of a cheek tooth suspected to

6 106 Oral endoscopy as an aid to diagnosis of equine cheek tooth infections be diseased. Any clinical evidence that assists the interpretation of radiographic findings can reduce the risk of misdiagnosis. In the present study, it was found that oral endoscopy facilitates the detection of subtle pathology in the majority of cases of apical cheek tooth infection in which there is no gross evidence of loss of cheek tooth integrity, and should therefore be considered along with radiography as an important diagnostic modality. Acknowledgement The author would like to thank Lorraine Palmer for her assistance with the manuscript. Manufacturers addresses 1 Agfa-Gevaert, Brentford, Middlesex, UK. 2 Pfizer Ltd., Sandwich, Kent, UK. 3 Fort Dodge Animal Health, Southampton, UK. 4 Martindale Pharmaceuticals, Romford, Essex, UK. 5 Pentax (UK), Langley, Berkshire, UK. 6 Everest VIT (UK), Burford, Oxfordshire, UK. References Barakzai, S.Z. and Dixon, P.M. (2003) A study of open-mouth oblique radiographic projections for evaluating lesions of the erupted (clinical) crown. Equine vet. Educ. 15, Dacre, I.T. (2005) Equine dental pathology. In: Equine Dentistry, 2nd edn., Eds: G.J. Baker and J. Easley, Elsevier Saunders, Philadelphia. pp Dacre, I. and Dixon, P. (2004) Oral extraction of cheek teeth in the standing horse: Indications and techniques. Proc. Am. Ass. equine Practnrs. 50, Dacre, I.T., Kempson, S. and Dixon, P.M. (2007) Equine idiopathic cheek teeth fractures. Part 1: Pathological studies on 35 fractured cheek teeth. Equine vet. J. 39, Dixon, P.M. and Dacre, I. (2005) A review of equine dental disorders. Vet. J. 169, Easley, J. (2005) Dental and oral examination. In: Equine Dentistry, 2nd edn., Eds: G.J. Baker and J. Easley, Elsevier Saunders, Philadelphia. pp Erten, H., Uctasli, M.B., Akarslan, Z.Z., Uzun, O. and Baspinar, E. (2005) The assessment of unaided visual examination, intraoral camera and operating microscope for the detection of occlusal caries lesions. Oper. Dent. 30, Gibbs, C. and Lane, J.G. (1987) Radiographic examination of the facial nasal and paranasal sinus regions of the horse, Part II: Radiological interpretation. Equine vet. J. 19, Gibbs, C. (2005) Dental imaging. In: Equine Dentistry, 2nd edn., Eds: G.J. Baker and J. Easley, Elsevier Saunders, Philadelphia. pp Griss, R. and Simhofer, H. (2006) Erstmaliger endoskopischer nachweis von Gasterophilus-larven in der mundhohle bei 14 Warmblutpferden. Berl. Munch. Tierarztl. Wochenschr. 119, Henninger, W., Frame, E.M., Willmann, M., Simhofer, H., Malleczek, D., Kneissl, S.M. and Mayrhofer, E. (2003) CT features of alveolitis and sinusitis in horses. Vet. Radiol. Ultrasound 44, Prichard, M.A., Hackett, R.P. and Hollis, N.E. (1992) Long-term outcome of tooth repulsion in horses: a retrospective study of 61 cases. Vet. Surg. 21, Tietje, S., Becker, M. and Bockenhoff, G. (1996) Computed tomographic evaluation of head diseases in the horse: 15 cases. Equine vet. J. 28, Tremaine, W.H. (2004) Oral extraction of equine cheek teeth. Equine vet. Educ. 16, Tremaine, W.H. and Dixon, P.M. (2001) A long-term study of 277 cases of equine sinonasal disease. Part 1: details of horses, historical, clinical and ancillary diagnostic findings. Equine vet. J. 33, Tremaine, W.H. and Lane, J.G. (2005) Exodontia. In: Equine Dentistry, 2nd edn., Eds: G.J. Baker and J. Easley, Elsevier Saunders, Philadelphia. pp Weller, R., Livesey, L., Maierl, J., Nuss, K., Bowen, I.M., Cauvin, E.R.J., Weaver, M., Schumacher, J. and May, S.A. (2001) Comparison of radiography and scintigraphy in the diagnosis of dental disorders in the horse. Equine vet. J. 33,