Developmental abnormalities happen when genetics, trauma or illness effects developing dental structures altering adult dentition. This can happen when deciduous (baby) teeth do not fall out, when jaws are to short or too long, teeth erupt in abnormal positions or when teeth do not erupt at all. Intervention in these abnormalities is only required if the abnormality will lead to disease or cause the pet pain.
Retained deciduous teeth
This is when deciduous or baby teeth do not fall out. In normal development the adult tooth erupts right underneath the corresponding deciduous tooth. During this process the roots of the deciduous tooth dissolve from the pressure of the erupting adult tooth. With no root support structure the deciduous tooth it will fall out during normal chewing. The deciduous tooth remains in the mouth if the adult tooth does not erupt in the correct position and the deciduous tooth will remain with a full root structure. If these teeth are left in place they result in crowding of the adult dentition and early onset periodontal disease. They can sometimes push the adult teeth into abnormal positions that may require orthodontic intervention
Retained deciduous teeth are most common in small breed dogs. Over time humans have selectively bred these dogs to accentuate desired characteristics represented by the diversity of the different dog breeds we see today. In a sense we have selected for abnormal anatomy and in some cases this affects development of normal dentition.
All retained deciduous teeth are considered abnormal; they usually cause early onset periodontal disease and require extraction. In most dogs and cats all adult teeth should be erupted by 6 months of age and retained deciduous teeth can be extracted at spay and neuter time.
Sometimes adult dogs will be missing some adult teeth. If the tooth is not present at all then that is just a variation of normal anatomy and usually does not cause any problems. However if a tooth has not erupted and is just present under the gums then this can cause a significant problem. The tissues surrounding an unerupted tooth will produce a fluid that over time will cause a cyst to form. This cyst(dentigerous cyst) will result in the loss of bone around that tooth and if we do not intervene can end up affecting surrounding teeth or even cause a broken jaw
If discovered early a procedure called an operculectomy can be performed where the overlaying gingival tissue is removed and the tooth may erupt normally. If discovered later in life and a dentigerous cyst has already formed then surgical intervention is required. The cyst needs to be opened and the tooth removed. The lining of the cyst needs to be removed to prevent recurrence. If the bone loss is significant then the cyst should be filled with a material that will aid in the growth of bone to fill in the defect. For this reason we recommend taking radiographs of any missing teeth to ensure that they are truly missing.
Sometimes teeth erupt in the wrong place or at the wrong angle. As long as these teeth are not causing pain or disease then they can be left as is. If they are causing discomfort then they require intervention. That intervention can be orthodontics, crown reduction, or extraction. Any of these options are appropriate with the end result being a pain free mouth. Due to the genetic influence on these abnormalities we need any animals that require orthodontic intervention to be spayed or neutered, so this problem is not passed on to future generations.
The most common developmental defect we see is base narrow canines. This is where the lower canines (fangs) are too close together and are traumatizing the hard palate (stick into the roof of the mouth). This can happen with adult or deciduous canines. The younger the animals are at the time of treatment the better. Orthodontic options are an acrylic incline plane where we place acrylic on the upper canines and incisors and make a ramp to guide the lower canines out where they need to be.
Another option is a crown extension where we make the lower teeth longer using acrylic and angle the extension so that the tooth will be guided into its normal position.