Most dogs have 42 permanent teeth with 20 teeth on the upper jaw and 22 on the bottom jaw. To be precise, the dog's upper jaw has two canines, six incisors, eight premolars and four molars, while the lower jaw has two canines, six incisors, eight premolars and six molars. In some dogs though, there may be variations, and in particular there is a dog breed that is known for missing teeth. So today's trivia question is:
What dog breed is known for missing teeth?
A The Mexican hairless dog
B The German shepherd
C The Rottweiler
D The great dane
The correct answer is: drum roll please...
The correct answer is A, the Mexican hairless dog.
The Missing Teeth
The technical term for a dog who is missing a few teeth (usually between one and five) is "hypodontia." Generally, hypodontia is quite common in small dog breeds and the teeth that are more commonly missing are the premolars, especially the first and the second ones, the incisors and the mandibular third molars, explains Brook Niemiec a board-certified veterinarian specializing in veterinary dentistry.
In some cases, the premolars may be missing in some large dog breeds too but in those cases (unless they are missing because of an accident,) a lack of teeth is often considered a serious fault.
The Mexican hairless, also known as xoloitzcuintli is a breed that is often missing teeth, however, not all specimens miss them.
The Xolo's Teeth
According to the American Kennel Club's standard for the xoloitzcuintli breed, this dog's teeth must meet in a scissor bite. In the hairless variety, the absence of premolars is acceptable, and while a complete set of incisors is preferred, missing incisors are not considered a fault to be penalized.
This is considered normal for this dog, and the missing teeth do not interfere with the dog's ability to eat. On the other hand, the coated variety of this breed is required instead to have a complete set of teeth.
A Matter of Genes
One may wonder at this point, why does the hairless variety have a tendency to miss teeth while the coated variety does not? It appears to be a matter of genes. There are two types of genetic hairlessness in dogs: dominant and recessive.
The Mexican hairless has a dominant gene for hairlessness which means that this breed has a genetic disposition to pass down the lack of hair to their offspring. Dental, skin or other health conditions are often associated with the dominant gene for hairlessness and this includes the missing teeth in the hairless variety. Because the coated variety doesn't have the dominant hairless gene, it's therefore not affected and boasts a complete set of teeth.
Did you know? The Xolo's unique dentition, with its lack of premolars has made the remains of this breed easy to identify at archaeological sites.
- Flickr Creative Commons, Mariposa Veterinary Wellness Center in Lenexa, KS, Periodontal disease apparent only in dental xray-Luce Mae, CCBY2.0
Mexican hairless dog Alfredo&Sara Aguirre - originally posted to Flickr as Behold: The Xoloitzcuintle. CCYBY2.0