Persistent Deciduous Teeth
Usually, as the permanent tooth erupts, resorption of the deciduous tooth root occurs and the deciduous tooth is lost.
A deciduous tooth is considered persistent when it is present in the mouth together with its permanent counterpart. The permanent tooth does not need to be fully erupted for the deciduous tooth to be considered persistent.
The most common cause for a persistent deciduous tooth is an incorrect eruption path of the permanent tooth. This means that there will be no impetus for the root of the deciduous tooth to be resorbed, and the permanent tooth will erupt alongside it.
Another potential cause is primary impaction or ankylosis of the deciduous tooth. There will then be either impaction or improper eruption of the permanent tooth, creating a persistent deciduous tooth.
This is thought to be an inherited problem and occurs most commonly in small and toy breed dogs and also in cats.
Potential problems associated with this condition include:
- overcrowding of the dental arch, and permanent teeth in abnormal locations leading to malocclusion
- abnormal development of the roots and periodontal support around the permanent tooth, leading to early loss
- accumulation of plaque leading to the development of periodontal disease
The teeth most commonly affected are the canines, and the condition is often bilateral.
There will be additional teeth in the arcades, which appear crowded. The permanent teeth may be in an abnormal position, and this may have lead to tooth, gingival or palatine trauma and damage.
There is weakened periodontal attachment and periodontal disease, often seen as gingivitis, tartar and loosening of the tooth.
A thorough oral examination should enable the persistent deciduous teeth to be found.
Radiographs help distinguish deciduous from permanent dentition, determine the location of the developing permanent tooth/teeth, and the integrity of the deciduous tooth root structure.
There should never be two teeth of the same type in the same place at the same time.
Any persistent deciduous teeth should be extracted as soon as possible to avoid all the sequelae of the condition.
The time of permanent dentition eruption is between 3 and 6 months, and therefore waiting to extract the teeth at the same time as neutering is not acceptable.
Extraction can be difficult as the deciduous teeth have thin walls and are of considerable length. There is also sometimes resorption and ankylosis of the tooth. The extraction should be gentle and careful to avoid damaging the permanent tooth.
Closed extraction is usually sufficient, and it is the fastest method causing the least trauma.
Root fracture commonly occurs, and every effort should be made to remove the remaining piece, as a retained root tip can act as a nidus of infection and inflammation.
Dental radiographs should be taken post-extraction to confirm complete removal of the deciduous tooth and to document the condition of the permanent tooth.
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Tutt, C. (2006) Small Animal Dentistry: a manual of techniques Wiley-Blackwell
Bellows, J. (2010) Feline Dentistry: oral assessment, treatment and preventative care John Wiley and Sons
Niemiec, B. (2010) A colour handbook of small animal dental and oral maxillofacial disease Manson Publishing
This article was expert reviewed by Lisa Milella BVSc DipEVDC MRCVS.
Date reviewed: August 4, 2014
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