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A 7-year-old mare presented with facial deformities associated with oral discomfort and weight loss was found to have bilateral, palatal, developmental displacements of the maxillary 08s, with secondary diastema. Following repulsion of both displaced teeth, the horse regained weight and resumed training. Bony deformities remained visible 9 mo after discharge.
Un cas de déformation faciale suite à un déplacement développemental bilatéral de dents molariformes chez un cheval adulte. Une jument de 7 ans présentée avec des déformations faciales associées à de l’inconfort oral et à une perte de poids a montré, après examen, des déplacements développementaux, bilatéraux, du coté palatal des 4e prémolaires supérieures, avec un diastème secondaire. Après répulsion des 2 dents déplacées, le cheval a regagné de l’état et repris l’entrainement. Les déformations osseuses étaient toujours visibles 9 mois après la sortie de la jument.
(Traduit par les auteurs)
A 7-year-old French warmblood mare was presented to the Equine Clinic of the National Veterinary School of Lyon, France so that bilateral facial deformities against the maxillary arcades could be investigated. These had been present for at least 1 y, since the horse was purchased, and had increased in size. Concurrent oral pain was reported by the owner. Following significant weight loss, the referring veterinarian performed an intra-oral examination which revealed anomalies in cheek teeth (CT) positioning. He suspected bilaterally persistent deciduous maxillary third premolars (teeth 507 and 607 in the modified Triadan system) (1), removed impacted food particles in a diastema on the right arcade, and prescribed oral phenylbutazone for 10 d and trimethoprim-sulfamethoxazole for 3 wk. With this treatment the chewing ability of the mare improved and she regained weight. However, the mare later had difficulty chewing and exhibited a defensive reaction against the bit, motivating further examination and referral.
On admission, the horse was alert, heart rate was 32 beats/min, respiratory rate 8 breaths/min and rectal temperature 37.5°C. Physical examination revealed the horse to be in poor body condition (428 kg, body score condition 2/5). Symmetrical, hard, painless swellings were present rostro-dorsal to the rostral aspects of the facial crests (Figure 1). After administration of romifidine (Sedivet; Boehringer Ingelheim, Reims, France), 0.04 mg/kg body weight (BW), IV, as a sedative and positioning the horse in stocks, an intra-oral examination was performed using a Haussmann mouth gag. Oral examination findings were palatal displacement of a maxillary cheek tooth on each side that lay medial to the 107 and 207, and a food-filled diastema on the right maxillary arcade (Figure 2); the juxtaposed teeth were in contact on the left maxillary arcade (Figure 3).
A radiographic examination of the teeth was performed, and dorso-ventral, latero-medial, sinistrodorsal-dextroventral, and dextrodorsal-sinistroventral views were assessed. On the dorso-ventral view (Figure 4), a buccopalatal displacement of both 108 and 208 was suspected. Tooth 108 seemed to be medial to both 107 and 109, whereas 208 seemed to be medial to 207. Because of these displacements, 107, 207, and 209 were rotated and pushed laterally. Against these displaced teeth, the cortices of the maxillary bones appeared to be deformed and thickened on both sides, with irregular periosteal reaction on the right side. On the oblique projections (Figures 5 and and6),6), severe periapical lucency and an increased opacity of the alveolar bone were visible, surrounding every maxillary premolar root. These radiographic signs of severe periapical osteolysis and osteocondensation were compatible with periapical and possible periodontal disease (2). In addition, 106 and 206 seemed to be inclined caudally, and 306 started to show rostral overgrowth.
Based on oral examination and radiographic findings the following diagnoses were made: buccopalatal displacement of both 108 and 208 with a secondary diastema on the right arcade; subsequent rotation and outward positioning of 107, 207, and 209; periapical disease of the maxillary premolars; overgrowth on 306; and probable periodontal disease.
Given the observed dental displacement, the signs of oral pain, the periapical osteolysis, the associated weight loss, and non-responsiveness to previous medical treatment, a bilateral exodontia of the displaced teeth via repulsion was recommended. The mare was hospitalized and a 2-step surgical procedure under 2 episodes of general anesthesia was elected.
Prior to surgery, phenylbutazone (Phenylarthrite; Vetoquinol, Lure, France), 2.2 mg/kg, BW, IV; gentamicin (G4; Virbac, Carros, France), 6.6 mg/kg, BW, IV; and procaine penicillin (Depocilline; Intervet, Beaucouze, France), 22 000 U/kg, BW, IM; were administered. Following premedication with acepromazine (Vetranquil; CEVA, Libourne, France), 0.04 mg/kg, BW, IV; romifidine (Sedivet; Boehringer Ingelheim), 0.04 mg/kg, BW, IV) and morphine (Morphine Aguettant; Aguettant, Lyon, France), 0.1 mg/kg, BW, IV, anesthesia was induced with diazepam (Valium Roche; Roche, Neuilly-sur-seine, France), 0.05 mg/kg, BW, IV, and ketamine (Imalgene 1000; Merial, Villeurbanne, France), 2.2 mg/kg, BW, IV and maintained with isoflurane vaporized in oxygen in a circle system with assisted ventilation. A bolus (1.5 mg/kg, BW, IV) followed by an infusion (0.05 mg/kg, BW, IV mg/kg, BW, IV per minute) of lidocaine (Lurocaine; Vetoquinol, Lure, France) were given to the horse in order to reduce the minimum alveolar concentration of isoflurane and to provide supplementary analgesia.
The horse was positioned in left lateral recumbency. The right maxillary area was clipped and prepared for aseptic surgery. The gingiva was elevated with a periosteal elevator around tooth 108. An elliptical skin incision was performed on the bony deformation in order to effect a repulsion of the most axial tooth. The periosteum was elevated and a maxillary osteotomy was performed. The root of the tooth to be removed was located by positioning an unscrubbed assistant’s hand inside the horse’s mouth. A mallet and a burr were used in order to repulse the tooth orally. Curettage of the alveolus was performed and then an orthodontic polyacrylic paste (Speedex Putty; Coltène, Altstätten, Switzerland) was positioned in the oral 1/3 of the alveolus, overlying the gingival margins on the palatal and buccal sides. Iodoform mesh was packed in the remaining alveolar space and brought out of the incision. After repositioning the maxillary flap, subcutaneous tissues were closed using 2-0 lactomer in a simple continuous pattern and skin was apposed using 2-0 polypropylene interrupted horizontal mattress sutures. The wound was protected using a non-adherent absorbent dressing.
Following surgery, the horse was maintained on procaine penicillin and gentamicin for 3 d, and phenylbutazone (Equipalazone; Dechra Veterinary Products, Suresnes, France) was given for 7 d (5 d at 2.2 mg/kg, BW, q12h, then 2 d 2.2 mg/kg, BW, q24h). The iodoform mesh was removed 3 d after the surgery, the wound was cleaned with saline and the dressing was changed. Six days after the surgery, cutaneous necrosis was observed on the surgical wound. Two skin sutures were subsequently removed.
Concurrently, thrombophlebitis developed on the left jugular vein, where the intravenous cathether had been inserted. It was treated with topical application of dimethyl sulfoxide (DMSO) and prednisolone (Ekyflogyl; Audevard, Clichy, France), and fucidic acid (Fucidine; Léo pharma, Saint Quentin en Yvelines, France) for 1 wk.
One week after the first surgery, the second surgery was performed. Prior to surgery, phenylbutazone (2.2 mg/kg, BW, PO) and trimethoprim-sulfamethoxazole (TMS; 30 mg/kg, BW, PO) (Avemix; Vetoquinol, Lure, France) were administered. Premedication, induction, and maintenance were identical to the first procedure. The horse was positioned in right lateral recumbency and the left maxillary area was clipped and prepared for aseptic surgery as for the first surgery. Tooth 208 was removed using the same repulsion technique. Cystic structures were observed against the removed tooth root and were excised. An iodoform mesh was used, as was the orthodontic paste in the same manner. The skin was closed with stainless steel staples.
The horse was maintained under TMS for 5 d and phenylbutazone for 4 d (2 d at 2.2 mg/kg, BW, q12h, then 2 d at 2.2 mg/kg, BW, q24h). Two days after the second surgery, the bandage was changed and a complete dehiscence of the right surgical wound was observed. All cutaneous and subcutaneous sutures were removed, saline solution was used to lavage the wound and it was left to heal by second intention. The iodoform mesh was removed from the left surgical wound and a new dressing was applied. Surgical wounds were kept bandaged until removal of the skin staples, 14 d after the second surgery. The mare was discharged from the hospital 6 d after the second surgery.
Following discharge, the surgical wounds were cleaned daily and they healed uneventfully with a good cosmetic result; the thrombophlebitis resolved without additional treatment. Three weeks after discharge, the horse was starting to gain weight and was ridden again. Nine months later, phone contact revealed the owner to be satisfied with the results of the treatment. Even though facial deformities were still present, the horse had a good body condition and was not reluctant to eat and to work. Unfortunately, the mare was not rechecked at our clinic, so resolution of the periapical disease of the maxillary premolars as well as the condition of the prosthesis were not reassessed.
According to Gieche (3), the differential for facial deformities includes tooth-root issues, sinus pathologies, and tumors. Intra-oral examination revealed the presence of a displaced tooth on both maxillary arcades at the level of the third premolars [107 and 207 in the modified Triadan system (1)]. These teeth are thought to be responsible for the periapical osteolysis observed on the radiographs, for the subsequent bony remodeling leading to the bilateral deformities over the maxillary arcades, and for oral discomfort. Secondary pathological changes, such as a diastema on the right maxillary arcade, laterally displaced teeth, focal overgrowth and abnormally angulated teeth were visible as well.
The rows of CT function as single units with all 6 molariform teeth in contact, owing to the caudal angulation of 06s and rostral angulation of 10s and 11s (4). Disparity of the rows’ length can result in dental overgrowths, as observed in our case because of the teeth displacement.
Weight loss was observed, although it is reported to be uncommon in dental diseases (4). In contrast, facial swelling is commonly observed lateral to the affected apex. After the intra-oral exam and before performing the radiographs, which are often needed to diagnose a developmental dental abnormality (5), the differential diagnosis included retained deciduous teeth, which was considered likely by the referring veterinarian, supernumerary teeth, and an abnormal dental eruption.
Cheek teeth displacements can be developmental or acquired (4,6). As in the present case, developmental displacements seem to be more common (70%) (6). They can be due to dental rows overcrowding during eruption, often bilaterally, with rotation of the affected teeth. Overgrowths are common secondary findings. In cases where large diastemata are observed between displaced and adjacent CT, abnormal positioning of the tooth bud could explain the displacement. Sometimes, displaced CT lay horizontal in the mandible or maxilla and never erupt (7). Acquired displacement develops in older horses. Degree of displacement and overgrowths are smaller and seem to be caused by wear abnormalities. According to Dixon et al (6), maxillary CT displacement is less common (22.7%) than mandibular ones. Protruding areas of displaced CT and secondary overgrowths can be responsible for oral discomfort and biting problems. The sequence of eruption of equine check teeth shows an overlap in the time sequence so that the 08s tend to be impacted between the 07s and 09s around 4 years of age (8,9). This may result in inflammation of the periapical structures, dental fistula, periradicular disease or sinusitis. Impaction of 108 and/or 208 may result in palatal displacement, possibly leading to food pocketing and periodontal disease. This latter condition, particularly painful (3) and prevalent in tooth displacement (87%) (6), is likely responsible for the observed oral discomfort. Usually, dental impactions and maleruptions occur more commonly in ponies and miniature horses (8).
Dental extraction remains the most frequently performed oral surgery in the horse (10). It should be considered only, as in our case, when conservative treatment has failed. The technique for extracting a CT often depends on the surgeon’s preference, as well as the tooth involved. Oral extraction, with the horse standing or under general anesthesia, lateral buccotomy, vertical alveolar osteotomy, and repulsion are the classically described techniques. The repulsion technique has remained unchanged since the beginning of equine general anesthesia (10). It comprises an osteotomy directly over the apex of the diseased tooth before driving it into the mouth. Osteotomy can be limited to a trephine hole or more extended, with a maxillary flap, to approach the roots of the upper molar teeth. Repulsion is suggested as the surgical option of choice for extraction of maxillary 09s to 11s. Buccotomy extraction involves a horizontal incision through the cheek, removal of the buccal crest of the alveolar bone, division of the tooth and subsequent lateral withdrawal. It is recommended for removal of premolar teeth. Vertical alveolar osteotomy involves an incision parallel to the linguofacial vein and artery and to the parotid duct. This method is satisfactory for removal of mandibular 09s and 10s.
Although periodontal disease may facilitate oral extraction (6), and even though fewer complications are reported with this technique compared to repulsion (11), it can be difficult, namely with dental crowns which are difficult to access, and may lead to fracture of the affected tooth. Three of 11 oral extraction failures occurred with displaced teeth in Dixon’s study (11). In our case, the crown of the teeth to be extracted was placed directly adjacent to the normal teeth, so that it would not have been possible to grasp the affected crown firmly with instruments for oral extraction. Furthermore, repulsion is the most frequently performed technique in our clinic.
After tooth extraction, the alveolus and adjacent structures may be protected from ingesta and saliva with dental wax, impression compound, polymethyl methacrylate, bone cement, plaster of Paris, or a gauze swab impregnated with antimicrobials, until the granulation tissue pushes it away (10,12,13). The prosthesis is molded to fill 1/3 of the alveolar cavity, overlying the gingival margins. The polyvinylsiloxane orthodontic paste we used is easy to work with in the horse’s mouth and has good stability after positioning.
Dental drift usually occurs in the affected arcade to close the gap resulting from exodontia. It has been reported that the extraction space is indeed reduced by more than 70% in 2 y (14), even if the rate of dental drift is negatively related to the time since extraction (15). In our case, upper 07s and 09s were already in contact because of this drift, with a caudal orientation of the cranial part of the maxillary arcade, as described by Vlaminck et al (14) following 08s maxillary extraction.
After tooth removal, advice regarding dental control and rasping should be given to the owner, to prevent focal overgrowth and step-mouth from occurring on the opposite arcade (10). A 6–12 monthly dental inspection is thus recommended (3,15,16). In this case, this control was performed by the referring veterinarian.
Diastema is a significant, and often under diagnosed, cause of oral pain in horses because of the food impaction occurring, leading to secondary periodontal disease with lysis of the alveolar bone (4,6). These diastemata can be primary, due to inadequate rostro-caudal compression, or secondary, as in our case, to other dental abnormalities. Dixon et al (17) described an efficient widening technique of these diastemata to treat periodontal pocketing. However, most of the secondary diastemata require more than 1 treatment before improvement, and this method is technically difficult. So, we decided to treat the underlying cause rather than the diastema itself.
This case illustrates an uncommon cause of bilateral facial deformity treated surgically. It is in accordance with Dixon et al (6) who relate excellent immediate and long-term response to treatment of tooth displacement, without later dysfunction. Even though the cosmetic result was not perfect 9 mo after surgery, it allowed an arrest in growth deformity and permitted the mare to regain weight and resume training, making the owner satisfied. The question remains whether or not the radiographically observed periapical disease resolved with time.
The authors thank Drs. Marianne Depecker and Jean-Luc Cadoré for their friendly and helpful reviews. CVJ
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