W
hen a dog or cat ends up at an animal shelter, how does anyone estimate how old that dog or cat might be? If the deciduous, or baby, teeth are still in the mouth than an accurate estimate of age can be given. The deciduous teeth erupt and are then shed as the permanent teeth erupt, according to a fairly defined schedule. By seven months of age both dogs and cats should have all of the permanent teeth erupted. Permanent teeth are much larger than the deciduous teeth and have a somewhat different shape. Dogs and cats are also growing in size and weight from birth through the first year of life, which is also a clue as to the age of the pet. But what happens if all of the permanent teeth are in place? Is there Sandra L Waugh VMD, MS any accurate or even reasonably accurate way to assess the age of the pet? It is tempting to think that the condition of the teeth should be a good clue, as we know that without intervention teeth will accumulate plaque and tartar which tends to become worse over time and that gingivitis and periodontal disease also become more prevalent over time. Can the physical condition of the teeth and gums be useful in estimating age? Unfortunately, no. The amount of tartar, for instance, is highly variable with some very young pets having advanced periodontal disease and some quite old pets having reasonably healthy mouths even without any dental care. With the aid of a dental x-ray, a much better estimate of the age of the pet can be made. The inside of the tooth changes with age in a standard and predictable way.
“How Much (err, Old) is That Doggy in the Window?�
Anatomy of a tooth: The visible part of the tooth is the crown and is covered with enamel, a shiny white substance. The root, which is not normally visible, is covered with cementum, which is slightly off-white in color and has a rough surface. Underneath the cementum and enamel is dentin, which provides support for the enamel and cementum. As the permanent tooth erupts, the amount of dentin is fairly thin and the pulp chamber and root canal are quite large. As the pet ages, the dentin grows circumferentially toward the center of the pulp chamber and root canal. On an X-ray the thickness of the dentin is readily apparent. Dentin grows continuously through life as long as the tooth remains vital.
Red area is the pulp chamber in the crown and root canal in the root. It is really all one chamber.
Blue area is dentin
Root, covered by cementum (yellow)
Crown, covered by enamel (white)
Root Canal
Pulp Chamber Dentin Enamel
Let’s look at some real life examples. The following are radiographs of the lower jaw canine teeth in similarly sized dogs.
6 month old Maltese Notice the very wide pulp chamber and root canal. The bottom of the root has not yet formed.
42 4 Legs & a Tail
5 yr old Toy Poodle The dentin has grown quite a bit. The pulp chamber and root canals are readily visible from top to bottom of the tooth.
12 yr old Cairn Terrier/Shih Tzu. The pulp chamber and root canals are very narrow at this age.
13.5 yr old Yorkie The root canal at the bottom of the teeth is barely visible. In an older dog it can disappear at the bottom of the root.
Spring 2018