Congenital hypodontia in three horses diagnosed by computed tomography

Abstract

Summary Dental agenesis is a congenital disease defined as failure of formation of one or more teeth, which has been extensively described in human literature and that has been documented in several other species including cats, dogs, seals and sea lions, mice, and ungulates. The aim of this study was to review the clinical and computed tomographic (CT) features of tooth agenesis in a population of horses. Retrospective review of the imaging records from the Langford Equine Hospital was performed, including all horses that underwent head CT between January 2015 and June 2017. Of a total number of 167 CT scans, three horses with hypodontia were found. All three cases had agenesis of the maxillary 08s and one case had additional agenesis of the 307 and 308 teeth. Delayed resorption of the corresponding deciduous teeth was reported in all cases. The empty space left by the absent teeth was filled either by heterogeneous bone tissue alone (two cases) or by a combination of bone and soft tissue (one case). Alignment between teeth was preserved, and there was no displacement of the neighbouring teeth adjacent to the agenesis site. All three horses presented a symmetric pattern of dental agenesis within the maxillary arcades. The maxillary 08s, which are the latest to erupt, were the most affected teeth. This was similar to that reported in human literature, where the teeth that form later during development are the most vulnerable to dental agenesis.

The prevalence and risk factors of dental disease found in 100 miniature horses

“…The missing teeth were attributed to hypodontia. This diagnosis was based on the radiographic appearance, i.e., absent or reduced dental drift into the vacant alveolus, unlike the situation following extraction ( 21 ) as well as history (no known extractions) and the age of the affected animals ( Figure 5 ). Two of the affected horses were >15 years and age-related loss could not be definitively ruled out but was deemed to be unlikely ( 21 ).…”

The Role of Computed Tomography in Imaging Non-neurologic Disorders of the Head in Equine Patients

“…Hypodontia, oligodontia and anodontia, which describe the lack of one tooth to multiple teeth, can cause abnormal occlusion and therefore abnormal ware of other teeth. In a study of 3 horses with hypodontia, the maxillary fourth premolar was missing in all three horses ( 59 ). In polydontia, which is the presence of extra or supernumerary teeth, the teeth may have a normal anatomical shape or can be malformed.…”

Equine developmental dental disorders

“…The limited number of recorded cases of equine cheek teeth hypodontia has been in permanent rather than deciduous cheek teeth (Dixon 2011; Giavitto and Meehan 2021), and a further case with hypodontia of two permanent mandibular cheek teeth associated with a mandibular cyst is shown in Fig . A deciduous tooth needs the presence of the underlying permanent tooth to resorb its apex by activity of its odontoclast cells and also to displace the deciduous tooth remnant (‘cap’) into the oral cavity.…”

“…2008) leading to a shorter cheek teeth row and the later development of overgrowths on the peripheries of the opposing row. It is very interesting that in the cases reported by Giavitto and Meehan (2021) that alveoli where the permanent teeth did not develop (i.e. agenesis sites) became fully or partially filled with bone‐like material that along with the prolonged retention of the deciduous teeth remnants restricted drifting of adjacent teeth into the alveolar space of the missing tooth.…”

“…hypodontia or anodontia, is the rarest equine dental developmental disorder with a prevalence of 0.25% in one study of 400 horses (Dixon et al 1999). Consequently, the accompanying article by Giavitto and Meehan (2020) with excellent computed tomographic imaging is a very worthwhile addition to both the equine clinical and imaging literature.…”