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Veterinary Forum August 2008 (Vol 25, No 8)

Dental Dilemma — Unerupted Mandibular Canine Teeth

by Jan Bellows

    Saffron, an 8-month-old, 5.5-kg, spayed, mixed-breed dog, was referred for evaluation and treatment of generalized enamel hypoplasia. The owner's main complaint was persistent halitosis despite home care efforts. Historically, the dog had been sick as a puppy when it was adopted from an animal shelter. The vaccination history before adoption was not available.

    On physical examination, Saffron was a well-fed, playful puppy. The dog was normothermic and well hydrated. Other than dental abnormalities, all physical examination findings appeared normal.

    Oral examination revealed patchy areas of missing enamel with stained dentin on most of the teeth (Figure 1). The crown heights appeared to be reduced on several mandibular incisors, and the right mandibular second incisor crown appeared to be missing. The primary man­di­bular canines were present without evidence of secondary (adult) canine teeth (Figure 2).

    Two major dental problems that needed evaluation and care were identified after briefly examining the dog's mouth: generalized enamel hypoplasia and unerupted or missing mandibular secondary canine teeth. The findings were shared with the client. Permission was obtained for laboratory testing before anesthetizing the dog for teeth cleaning and an in-depth clinical and radiographic evaluation of all the teeth. Preoperative complete blood count and liver, kidney, and glucose testing, as well as an ECG and blood pressure testing, were within normal limits.

    The initial plan was to evaluate preanesthetic results and if within normal ranges, anesthetize the dog to evaluate all its teeth and determine the presence and appearance of the secondary mandibular canines. Following assessment, a treatment plan would be developed to care for the unerupted or missing teeth as well as the teeth affected by enamel loss.

    An intravenous catheter was placed for administration of lactated Ringer's solution during anesthesia. The patient was premedicated with hydromorphone at 0.1 mg/kg combined with acepromazine at 0.010 mg/kg IM; after waiting 20 minutes, 0.5 mg/kg of diazepam and 10 mg/kg of ketamine were administered intravenously to induce anesthesia. The dog was intubated and maintained on 2% isoflurane. The temperature was controlled in a warm-air Bair Hugger (Arizant Healthcare).

    Clinically, most of the teeth had areas of missing enamel exposing the underlying dentin. All of the mandibular incisors were markedly pitted. While scaling during tooth cleaning with an ultrasonic scaler using minimal pressure, much of the remaining enamel flaked off the crowns, leaving no apparent enamel on any tooth.

    Radiographs revealed a right mandibular second incisor root fragment, an erupted deciduous right mandibular second premolar without an underlying permanent tooth (Figure 3). The secondary mandibular canines were impacted (embedded) bilaterally beneath the first, second, and third premolars (Figure 4).

    The final assessment established two dental dilemmas: how to appropriately treat the crowns, which had marked enamel loss (exposing the sensitive dentin to the oral environment), and what to do with the large unerupted right and left mandibular canines — leave them or extract and, if so, using what approach? Extraction and crown treatment would be too time-consuming to properly complete during one procedure. While the dog was still under anesthesia, it was decided to extract the impacted canines first and treat the enamel hypoplasia in a second procedure.

    The mandibular incisors were approached using a No. 15 scalpel blade to make a circumferential incision into the sulcus around each visible tooth. A wing-tipped elevator was chosen to elevate the teeth from their alveoli, and extraction forceps were used to remove the teeth from the oral cavity. To access the mandibular incisor root fragment, perpendicular incisions were made into the over­lying gingiva and a flap developed to expose the overlying alveolus. A round bur was used to remove the rostral alveolus, exposing the root fragment. A root tip pick was used to remove the fragment.

    The mandibular canines were approached ventrally. After surgical preparation, a No. 15 scalpel blade was used to make a ventral midline incision over the mandible, beginning at the level of the first premolar and extending back to the third premolar. A Molt periosteal elevator was used to expose the ventral mandible (Figure 5). A No. 2 round bur in a water-cooled, high-speed dental handpiece was used to remove an oval of bone, which exposed the embedded canine (Figure 6). A wing-tipped elevator helped loosen the tooth, which was removed from the mandible with the help of extraction forceps (Figure 7 and Figure 8). The skin incision was moved over to the left mandible, where the procedure was repeated (Figure 9). Osteoplasties were performed to remove rough and sharp bony projections in the extraction sites using a No. 3 round bur.

    Radiographs confirmed extraction, with areas of enamel still present in the surgical sites (Figure 10). Before closure, bone-grafting material (Consil Dental, Nutramax Laboratories, Inc.) was used to fill the defects left after removal of the mandibular canines. Penrose drains were placed before subcutaneous and skin closure (Figure 11). The patient was released after the second hospital day with instructions for the client to feed a gruel mixture of Hill's Prescription Diet a/d Canine and canned puppy food. Tramadol at 2 mg/kg PO bid, firocoxib (Previcox, Merial) at 5 mg/kg q24h for 4 days, and clindamycin at 5 mg/kg q24h for 7 days also were dispensed. The drains were removed on the fourth postoperative day.

    One month after surgery, the dog was anesthetized for follow-up radiography and therapy for generalized enamel loss.a Follow-up films showed bone growth in the surgical defects. There were no apparent areas of lucency surrounding the enamel present in the extraction sites. The mandibular premolars also appeared normal (Figure 12).

    Discussion

    Eruption is the continuous process of movement of a tooth from its developmental location to its functional position. Teeth that cease to erupt before emergence are impacted. These unerupted teeth can be further subdivided into those that are obstructed by a physical force, such as an adjacent tooth (impacted), or those that have lost their eruptive forces (embedded).

    Abnormalities in the eruption process may be inherited or caused by traumatic displacement of a tooth bud or mechanical obstruction by retained deciduous, supernumerary teeth, heavy fibrous tissue, or sclerotic bone. Bittegeko and Arnbjerg reported enamel and dentin hypoplasia and impacted mandibular canine teeth in a puppy that had previously been infected with canine distemper. The influence of canine distemper virus interfering with dental bud growth, leading to failure of dental eruption should be considered in similar cases. Canine distemper virus has a preference for the enamel-forming cells of the tooth bud. If infection occurs during the time that the enamel layer of the tooth is being laid down, the mature tooth will develop surface irregularities characterized by underdevelopment or incomplete development of the enamel.

    Removal of the impacted teeth was indicated in this case to prevent cyst and tumor formation and destruction of the adjacent bone, to alleviate pain, and to preserve the vitality of the overlying premolars. The most common technique used to extract the mandibular canine teeth is the buccal (lateral) approach, in which a mucoperiosteal flap is developed by incising through the frenulum to expose the underlying alveolus. Alternatively, the lingual approach for mandibular canine extraction can be used to avoid disruption of the lip attachment and the mental neurovascular structures.

    In this case, a ventral approach was chosen after examination of the lateral radiographs confirmed that the mandibular canines were located ventrally in the mandibular body. The mandibular incisors were extracted because of the poor long-term prognosis. Consil, a synthetic particulate, was chosen to encourage bone formation in the oral defect bordered by bony walls.

    Future clinical progress examination and follow-up radiography are planned.

    For more information:

    Bittegeko SB, Arnbjerg J, Nkya F, Tevik A. Multiple dental developmental abnormalities following canine distemper infection. JAAHA 1995;31(1):42-45.

    Cahill DR. Tooth eruption: evidence for the central role of the dental follicle. J Oral Pathol 1980;9(4):189-198.

    Gorski JP, Marks SC Jr. Current concepts of the biology of tooth eruption. Crit Rev Oral Biol Med 1992;3(3):185-189.

    aTreatment of this dog's generalized enamel loss will be presented in the October Dental Dilemma column.

    NEXT: Doctor to Doctor — Polishing your policies

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