In my May 2012 article, “The Problematic Deciduous Canine Tooth,” I described how persistent deciduous teeth could contribute to chronic linguoversion (medial displacement) of permanent mandibular canine teeth due to attempts of the permanent and deciduous teeth to occupy the same area. When this happens, the permanent teeth may cause trauma to the palatal mucosa or to the maxillary teeth.
Chronic trauma to the palate may result in development of an oronasal fistula and possible traumatic endodontic or periodontal disease of teeth meeting in abnormal occlusion (Figure 1).
This month’s article describes treatment options for relieving palatal trauma in these cases.
Malocclusions can be of skeletal origin (for example, a jaw being shorter than normal) or of dental origin (for example, a tooth erupting in an abnormal position in a jaw of normal length and width). Normally, when the mouth is closed, the mandibular canine tooth sits in a space called the diastema between the maxillary third incisor tooth and the maxillary canine tooth.
The three most common reasons for development of an abnormal relationship between these teeth are:
• Mandibular distoclusion, or a skeletal malocclusion previously referred to as mandibular brachygnathism, where the lower jaw is shorter than normal.
• Linguoversion of the mandibular canine teeth, where a mandibular canine tooth is in a normal position but is abnormally angled in a lingual direction.
• Abnormally narrow mandible, where the canine teeth diverge at the correct angle but due to the narrowness of the mandible cause palatal trauma (sometimes referred to as base-narrow canine teeth).
Whenever an orthodontic abnormality is encountered, the ethical aspects of treatment must be discussed. Although many of the genetic aspects of most canine malocclusions have not been elucidated, some conditions seem to have a breed predilection, suggesting a genetic component. Therefore, we typically recommend a spay or neuter at the time of the orthodontic procedure. Some hospitals ask clients to sign a form that ensures they are aware of the possible genetic aspects of the condition and the potential for the condition to be transmitted to offspring.
What to Do
Maloccluded permanent mandibular canine teeth have four main treatment options.
1. If the jaw length discrepancy is minimal, a conservative, readily available option may suffice. A manuscript published in the Journal of Veterinary Dentistry evaluated use of a hard rubber ball or Kong toy of appropriate size during active play for a minimum of 15 minutes three times a day to act as a passive orthodontic device to help lateralize the mandibular canine teeth. The technique showed correction in 28 of 38 cases in young dogs of various breeds and partial improvement in three additional dogs. In all the cases where the technique failed, there was not just a tooth in the wrong position, but rather a skeletal malocclusion (mandibular distoclusion).1
2. The second treatment option is a passive orthodontic device called an inclined plane, usually placed at 7 to 9 months of age (Figure 2). This is most commonly made with a composite material that can be fabricated to allow for a “sliding board” effect. The device engages the mandibular canine teeth when the mouth is nearly closed, resulting in slow, lateral movement of the canine teeth, guiding the tooth to its normal diastema.
The most common type of material used to create the device is a chemical-cured composite used for temporary crowns in humans. The material exits the mixing tip as a liquid but hardens to a solid mass within a few minutes. The teeth are etched prior to placement, which allows the composite to adhere to the teeth. Composite is placed on the etched and dried teeth to allow for retention, and the material is built up over the area of palatal trauma.
Once the material sets, it is shaped with burs to allow for the ideal angulation and divergence of the mandibular canine teeth. This device requires good home care—brushing to keep the device clean—and may become dislodged if dogs are allowed to chew on hard items while the device is in place. The device may be kept in the mouth as a retainer once the teeth have moved to their desired position, or a retainer may be placed between the mandibular canine teeth for at least a few months to prevent drifting of the teeth back to their original position. Therefore, this option requires at least two anesthetic episodes.
3. The third option for treatment of malpositioned permanent mandibular canine teeth is crown reduction. Since removal of even a small portion of the crown will result in pulp exposure, this procedure is done with an aseptic technique, and once the crown is reduced to approximately the height of the adjacent mandibular third incisor tooth, a portion of the coronal pulp is removed to create space for placement of medicament and filling material.
Also called vital pulp therapy, this procedure has a high rate of success when pulp exposure occurs aseptically2 and the duration of pulp exposure is confined to minutes rather than days or hours. The material placed directly on the pulp may be either calcium hydroxide or mineral trioxide aggregate (MTA).
Next, a glass ionomer intermediate restorative layer is placed, followed by a layer of composite to provide a seal that prevents bacteria from penetrating the previously exposed pulp. Though this procedure can be done in one anesthesia, monitoring with dental radiographs is recommended at six months postoperatively and every 12 months thereafter.
4. The final treatment option is extraction of the mandibular canine teeth that are causing palatal trauma. This is perhaps the least desirable option because the mandibular canine teeth comprise such a large part of the rostral mandible, and as a result extraction of both mandibular canine teeth leads to functional and esthetic changes.
Identifying abnormal occlusions is best done at an early age so treatment can be planned and monitored appropriately. An occlusal evaluation should be part of every puppy visit.
Dr. Lewis, FAVD, Dipl. AVDC, is a past president of the American Veterinary Dental Society and is an assistant professor of dentistry and oral surgery at the University of Pennsylvania School of Veterinary Medicine.
1. Verhaert, L. A removable orthodontic device for the treatment of lingually displaced mandibular canine teeth in young dogs. J Vet Dent 1999;16:69-75.
2.Niemiec BA. Assessment of vital pulp therapy for nine complicated crown fractures and fifty-four crown reductions in dogs and cats. J Vet Dent 2001;18:122-5.