Congenital Deformed Premolars

Case History

A 3-year-old Quarter horse gelding was referred to the wet lab with a history of unusually shaped second premolars and facial swelling above the 206 which was becoming increasingly larger with time (Fig. 7).



Oral examination revealed normal eruption and shedding of premolars except for the second premolars. The 106 had erupted but was deformed and mobile (Fig. 9).


Radiographs of the 106 showed a small deformed tooth that was displaced slightly anteriorly (Figs. 10 and 11).


After removing the remaining portion of the 606, the crown of the 206 could not be seen or palpated (Fig. 8). Radiographs showed a nonerupted 206 that was misaligned (Figs. 12 and 13).


The direction of the tooth was a 45 degree plane from buccal to palatal with the root being buccal and the crown pointing toward the hard palate. The facial swelling was an eruption cyst caused by the impacted 206 which was unable to erupt due to the misalignment. As seen in figure 7, the facial swelling is not where a normal eruption cyst for a 206 would be expected to be found. This cyst is more buccal and ventral due to the misalignment of the apical root of the 206.



After removing the 508, 608, and the partial 606, the 106 was extracted. Due to the mobility, reduced size, and infection of the 106 (Figs. 10, 11, 12), the extraction was not difficult.
Due to the misalignment causing impaction of the 206 and to prevent any further complications that the direction of the eruption may cause, we decided to extract this tooth. However, there was no visible crown and the direction of the tooth would make repulsion difficult.

An incision was made over the eruption cyst, and the soft tissue and periosteum were undermined and retracted, providing exposure to the underlying bone (Fig. 15).

Figure 15: Incision and separation of tissue to expose bone

A small section of bone was removed over the eruption cyst, exposing the apical root of the 206. An elevator was placed on the palatal side of the 206, which was used to force the unexposed crown ventrally while the tooth was repulsed with a hammer and punch from the apical root. This was necessary to prevent the tooth from being forced into the palatal area during repulsion and doing damage to the hard palate and underlying vessels.

Post extraction radiographs (Fig.14) revealed that there were several tooth fragments still remaining in the alveolus, which is commonly seen after repulsions. These were removed manually with a curette, and the area was flushed and packed with antiseptic gauzes from the oral cavity. The periosteum, subcutaneous tissue, and skin were individually sutured with a simple continuous pattern. The pack was removed in 2 hours and the horse was sent home with instructions to flush the mouth twice a day with copious amounts of tap water from a garden hose and feed a soft pellet ration for 2 weeks. Oral antibiotics were prescribed and the horse was injected with 10cc of Banamine and inoculated with tetanus toxoid.

Figure 14: Post extraction radiographs of 206

The prognosis is good for healing of the extraction sites, however, with 2 teeth absent in the upper arcades there will be lack of opposition and pressure for the lower second premolars, which will require regular dental maintenance to correct imbalances of the arcades.


These abnormal premolars are believed to have been caused by a congenital defect. The infected 106 had empty pulp cavities that were packed with feed (Fig.8), which was causing periodontal disease. Extraction was the only option in this case. The 206 was extracted to prevent the tooth from erupting into the palate causing further structural damage. Also, it is likely that this impacted tooth would abscess eventually and produce a drain tract through the maxilla. Extractions are always the last option due to the complications they cause to the integrity of the arcades and should only be performed if absolutely necessary.

Follow up

Troy Walck examined this horse 3 months after the extractions. He reported that the lower second premolars were protuberant due to lack of wear, and that he removed 2 small tooth fragments at the extraction site
of the 106. Also, there was a small seam between the gingiva and palate at the level of the extraction site that was trapping a small amount of feed, but no odor or signs of infection were present. He suggested another followup in 6 months.

By B.W. Fletcher, DVM


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