Dental caries in dogs are reported to affect around 5% of the population. Most of the cases we see are in Labradors - by far the worst affected breed. We do see it occasionally in other breeds though. Often we find them as an incidental finding when treating a dog for another unconnected dental problem.
In addition it almost always only affects the molar teeth. The images below show caries in the most common location - the occlusal pits and fissures of the upper first molar. Radiographs are a vital tool in selecting good cases. The radiograph below right, shows a lower second molar that is clearly non-viable with large lucencies round both root apices from pulp death. The larger carnassial is a better subject despite losing much of the distal crown.
They can be treated with fillings but our general advice to vets that contact us is that if the caries are clearly visible to the naked eye the tooth is probably best extracted. The reason is that caries that are already large are enormous once we finish removing all the carious (rotten) dentine. Teeth with this much structural loss are rarely viable and will often need root filling in addition as the pulp will be exposed.
The best subjects for filling are those that present as a black dot on the tooth surface. We distinguish caries from other black dots by probing with a sharp explorer. If it feels like probing chewing gum it is probably a carie. We can confirm using a caries detecting dye such as "Snoop". To prove they also affect other molar teeth the image below left shows a carie in the lower left second molar.The radiograph shows the extent of the fill and the final image, on the right, shows a good result.
This article from Dr Fraser Hale in Canada coves the problem very well