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Summary
Tooth eruption and exfoliation are the technical terms for the process by which deciduous or primary teeth (also referred to colloquially as "baby" teeth or "milk" teeth) erupt (emerge) and are exfoliated (shed) to make room for the permanent teeth (commonly called "adult" teeth), which arise between three and six months of age in both puppies and kittens.
The process by which deciduous teeth are exfoliated involves the resorption of their roots and the subsequent shedding of the crown. When this process fails to occur normally, the permanent tooth erupts in the same location, causing it to become abnormally positioned.
The four canine teeth in dogs are the most common sites of deciduous tooth retention in companion animal medicine. The incisors and premolars are next most common. Molars, it bears noting, are never retained as deciduous molars are never present in dogs and cats.
Genetic factors account most often for the retention of deciduous teeth. Environmental, infectious and traumatic factors are considered distant possibilities in these cases.
Symptoms and Identification
The clinical signs of retained teeth are obvious: Any deciduous teeth retained after six months of age are deemed abnormally persistent.
Diagnosis of retained deciduous teeth is typically undertaken via visual inspection of the mouth during routine physical examination. Dental x-rays under anesthesia are recommended to assess the length of the root, the degree of resorption of the root (if any), and the relationship to and integrity of the adjacent permanent teeth.
Affected Breeds
All breeds of dogs are susceptible to retained deciduous teeth but small breed dogs are especially susceptible.
Treatment
The ideal treatment of retained deciduous teeth involves the immediate removal of the abnormally persistent tooth. Because the permanent tooth may be seriously compromised as a result, the earliest possible extraction date beyond six months of age is strongly advised.
The problem, however, is that extraction of deciduous teeth is a far more delicate procedure than it might initially appear. For example, if the procedure is brusquely undertaken, damage to the adjacent permanent teeth resulting in compromised integrity is a distinct possibility, as is the possibility of deciduous tooth root fracture.
Extraction of these teeth typically requires either a closed or open extraction technique. The selection of either procedure is based on the degree of resorption visible on X-rays. Closed extraction requires no surgical incision and is typically indicated in cases where no evidence of resorption is visible. Open extraction is recommended if X-rays reveal the presence of resorption. (This is by way of decreasing the chance of root fractures, which can yield painful abscesses).
Veterinary Cost
The cost of retained deciduous teeth is limited almost exclusively to expenses incurred as a result of their initial detection and subsequent extraction. The cost of anesthesia and dental X-rays (if deemed necessary) should also be factored in (typically between $200 and $400).
The timing of treatment is another factor. If performed early, before any root resorption or damage to adjacent teeth occurs, simple closed extraction can be relatively inexpensive, typically less than $100 per tooth. If more complicated surgery is in order, the cost may double or even triple.
Of course, the cost of treating any permanent damage to adjacent teeth must also be considered when calculating the potential cost of deciduous teeth retention.
Prevention
Since the retention of deciduous teeth is largely considered a genetic trait, prevention is not feasible except by means designed to limit the inheritance of this developmental disorder.
In cases where environmental, infectious and traumatic factors are in play, any efforts aimed to reduce these possibilities represent possible means of prevention.
References
Amimoto A, Iwamoto S, Taura Y, et al. Effects of surgical orthodontic treatment for malalignment due to the prolonged retention of deciduous canines in young dogs. J Vet Med Sci 1993;55(1):73-79.
Hale FA. Juvenile veterinary dentistry. Vet Clin North Am Small Anim Pract 2005;35(4):789-817.
Harvey CE, Emily PP. Occlusion, occlussal abnormalities, and orthodontic treatment. In: Harvey CE, Emily PP, eds. Small animal dentistry. St. Louis, Mo: Mosby, 1993;278-280.
Reiter AM. Dental surgical procedures. In: Tutt C, Deeprose J, Crossley DA, eds. BSAVA manual of canine and feline dentistry. Gloucester: BSAVA, 2007;178-195.
Wiggs RB, Lobprise HB. Oral anatomy and physiology. In: Wiggs RB, Lobprise HB, eds. Veterinary dentistry: principles and practice. Philadelphia, Pa: Lippincott-Raven, 1997;69 and 169-174.