Malocclusions What to do about them, when and why In this paper I will discuss some of the more In cats, the primary formula is 2 x i3/3, c1/1, common malocclusions affecting dogs (and less p3/2 meaning each side of the mouth has three frequently, cats), why they are of significance, primary incisors, one primary canine top and what to do about them, when to do it and why. bottom, three premolars in the maxilla and 2 There is no way I will be able to cover every premolars in the mandible. The upper premolars scenario, but I hope this paper will help you with are considered the 2nd, 3rd and 4th and the the common ones and may give you the tools to mandibular ones are considered the 3rd and 4th figure out the odd-ball cases too. primary premolars (so as well as having no primary molars and no primary 1st premolars, cats are also missing the mandibular primary 2nd Dogs and cats do not need perfect bites, premolars). but they deserve comfortable bites. The rd things that should always trigger Confusingly, the 3 primary premolar in each intervention are abnormal tooth-to-tooth quadrant has the structural anatomy and the function of the adult 4th premolar and the 4th and tooth-to-soft tissue contacts. primary premolars have the form and function of the adult 1st molars. Here is a chart of the My hope had been to keep this paper short and to primary dentition in dogs: the point. As I went through the process, Dog_Deciduous_Chart.pdf. however, I realized that a four-page bulletin would have raised more questions than it And here is a primary chart for cats: answered and realizing that a little knowledge Cat_Deciduous_Chart.pdf. can be a dangerous thing, I decided I had to dive Note that when using the modified Triadan in a bit deeper. Even so, this should be numbering system for the primary teeth, the right considered a very brief introduction to the maxilla is the 500 series, left maxilla is the 600 various subjects covered. series, the left mandible is the 700 series and the In some instances, I will mention a subject upon right mandible is the 800 series. which I have already written and so there are active hyperlinks that will take you to those papers for more detail on these issues. From the rest of this section, when I am referring to any tooth/teeth, unless stated Malocclusions of the Primary Teeth otherwise, I will be referring to the We are going to start with puppies and kittens primary tooth/teeth. and the occlusal problems you might find during the first few veterinary visits. I am talking about Classification of Malocclusions malocclusions involving the primary teeth. But first, some background information. We must abandon the use of the terms overbite or underbite. They are as confusing as the date Primary Dental Formulae and Anatomy 05-07-09 (is that May 7th or July 5th of 2009 or maybe even July 9th of 2005?). So, let us use The primary dental formula in dogs is 2 x i3/3, Angle’s classifications which are as follows: c1/1, p3/3 which means that on each side of the head, there are three primary incisors top and Normal Occlusion: proper craniofacial bottom, one primary canine top and bottom and development with appropriate jaw-length three premolars top and bottom. There are no relationships (upper and lower jaws proper primary molars ever. Neither are there ever any lengths in their own right and in relation to each primary 1st premolars. This first primary tooth other), proper jaw width relationship and all behind the canine is the 2nd premolar in each teeth present and in their proper quadrant, then the 3rd and then the 4th. position/alignment. Hale Veterinary Clinic [email protected] www.toothvet.ca Local Calls: 519-822-8598 Fraser A. Hale, DVM, FAVD, Dipl AVDC Page 1 June 2018 Long Distance: 1-866-866-8483 Class 1 Malocclusion: normal craniofacial anatomy but one or more teeth out of place within a normal skeletal framework This is considered a dental malocclusion as it is the tooth (teeth) that is at fault. In Figure 3, the jaw- length relationship is great (lower incisors just behind the upper incisors and lower canine in proper location in the rostral-caudal dimension). However, that lower primary canine tooth is lingually displaced (linguoversion aka “base- Figure 1 narrow”) and so is in traumatic contact with the maxillary tissues (note the inflammation – ouch). Figure 1 shows some features of a normal puppy mouth. We see six upper and six lower incisors. The maxillary midline is directly above the mandibular midline and there is good symmetry right-to-left. The lower incisors are just behind the upper (scissors occlusion). The width of the mandibles is also appropriate compared to the maxilla. Figure 2 is a side view of the same pup (just happens to be a 13-week-old Lab). It shows how the lower canine tooth is centred in the space between the upper third incisor and canine teeth Figure 3 and is tipped labially at enough of an angle that it is not in direct contact with the maxillary soft Class 2 Malocclusion: the mandibles are too tissue. We can also see how the lower incisors short compared to the maxilla as in Figure 4. are tucked up right tight behind the upper Note the wide gap between the upper and lower incisors. incisors and how the lower canines are now trapped to the palatal side of the upper canines. This is a serious skeletal deformity and would be considered a skeletal malocclusion. Figure 2 I do not seem to have any photos showing the relationship of the primary premolars but they are relatively small and well-spaced apart. I do not recall seeing clinically relevant occlusal issues with the primary premolars in the past. Figure 4 Hale Veterinary Clinic [email protected] www.toothvet.ca Local Calls: 519-822-8598 Fraser A. Hale, DVM, FAVD, Dipl AVDC Page 2 June 2018 Long Distance: 1-866-866-8483 Craniofacial development is under genetic push on the back of the lower canine and drag control and virtually all malocclusions are the mandibles along with it. If the mandibles are going through a spurt, the lower canine and genetic and heritable. One possible exception incisors will push on the palatal aspect of the would be a “wry-bite” or facial asymmetry upper incisors and push the maxilla along for the secondary to a known trauma during ride. In this manner, whichever is growing development. In the absence of a known actively (maxilla or mandibles), the other is trauma that could reasonably be expected to carried along by the interlock and so the have caused the deformity, all malocclusions desirable jaw length relationship is maintained. should be considered genetic and heritable. With a class 2 malocclusion in which the lower Affected individuals should not be bred and canines are penetrating the palatal mucosa, this neither should their parents. It might even be effectively staples the mandibles to the maxilla best to avoid breeding their litter mates. in that relationship (an abnormal dental interlock). Even the lower incisors can be a Class 3 Malocclusion: the maxilla is too short problem as they can get hung up behind the relative to the mandibles. Sadly, this serious palatal rugae and incisive papilla. This abnormal craniofacial abnormality is considered breed dental interlock can act as a mechanical standard for a great many breeds of dog and impediment to the desirable growth of the several breeds of cats (the brachycephalics) mandibles. This could mechanically prevent the despite this anatomy being associated with a mandibles from catching up. Or if the mandibles great many liabilities that negatively impact are determined to grow longer but the front health and quality of life. For more of my soap- cannot move forward because of the interlock box ranting on this have a look at these papers: and the back cannot move backward because it is www.toothvet.ca/PDFfiles/Stop_Brachy.pdf held up at the TMJ, then the only option is for www.toothvet.ca/PDFfiles/Stop_Brachy_2.pdf the mandible to bow (bend ventrally) causing more problems. The bend usually occurs in the I could not find a photo of a class 3 malocclusion area between the lower adult 4th premolar and 1st in a young puppy in my records but picture a molar. boxer pup and you will know what I mean. The upper incisors are behind the lower incisors and In a class 3 malocclusion (maxilla too short), the often in traumatic contact with the floor of the upper incisors will be behind the lower incisors, mouth. creating a different abnormal dental interlock. In this case the interlock would mechanically Class 4 Malocclusion: refers to asymmetry of prevent the maxilla from catching up, even if the the maxilla and/or mandibles when comparing animal had the genetic potential to make that the right side to the left side. The lay-term for happen. class 4 malocclusions is “wry bite”. More detailed descriptions of the classifications of malocclusions can be found on the The growth of the maxilla and the nomenclature page of the American Veterinary mandibles are under the control of Dental College’s website different genes. The maxilla tends to (Nomenclature/Nomen-Occlusion). grow faster initially but the mandibles soon catch up. Maintenance of a proper Dental Interlock jaw-length relationship depends on a Another term I would like to introduce at this proper dental interlock.