Developmental Structural Tooth Defects in Dogs - Experience From Veterinary Dental Referral Practice and Review of the Literature

Abstract

Developmental tooth abnormalities in dogs are uncommon in general veterinary practice but understanding thereof is important for optimal management in order to maintain masticatory function through preservation of the dentition. The purpose of this review is to discuss clinical abnormalities of the enamel and general anatomy of dog teeth encountered in veterinary dental referral practice and described in the literature. More than 900 referral cases are seen annually between the two referral practices. The basis of the pathogenesis, resultant clinical appearance, and the principles of management for each anomaly will be described. Future research should be aimed toward a more detailed analysis of these conditions so rarely described in the literature.

Keywords: concrescence; enamel hypoplasia; fusion; gemination; odontogenesis; tooth abnormalities.

Figure 1

The micrograph represents a deciduous tooth germ in the developing mandible (MDB) of a dog fetus. The primary dental lamina (PL) is breaking up to form the small epithelial rests of Serres (SR), and the successional dental lamina (SL) for the permanent tooth is developing next to the deciduous tooth germ. The inner enamel epithelium (IEE) gives origin to the enamel-producing ameloblasts (AB) seen as tall cylindrical cells with prominent subnuclear vacuolization. The odontoblasts (OB) that developed from the papilla mesenchyme have already formed a layer of dentin (asterisk) and are moving toward the developing pulp (P). The IEE and outer enamel epithelium (OEE) come together at the Herwig root sheath (HERS) where the tooth root formation will take place.

Figure 2

A left maxillary canine (A) and left mandibular first molar (C) present with FEH, affecting the labial/buccal surfaces, respectively. The photograph in (D) is an example of FEH affecting two adjoining maxillary incisor teeth and (E) a right mandibular first molar with enamel hypoplasia that is so extensive that the distal cusp is completely distorted. The radiograph in (F) represents the enamel changes seen in a case of FEH. Radiographic changes may be so subtle that they can go unnoticed. The photograph marked as (B) was taken after restoration with a dental compomer of the tooth shown in (A).

Figure 3

The photographs represent two examples of DEH in different patients with circumferential hypoplastic lines present on almost all the teeth in (A). There is, however, still enamel present on all the crown surfaces, thus the unstained appearance. More severe enamel hypoplasia with dentin exposure and resultant staining is shown in (B). The lesions must have been caused by systemic insults such as infectious disease with episodes of severe pyrexia associated.

Figure 4

Both patients (A,B) presented with extensive enamel hypoplasia affecting the entire dentition with obvious loss of dental structure (arrows). One can appreciate the involvement of all the surfaces of all the teeth with a variety of defects and color.

Figure 5

The photograph is an example of the bright-yellow discoloration of the teeth in a patient that was on confirmed tetracycline treatment as a puppy. Apart from the discoloration, there were no structural defects of the enamel on clinical examination.

Figure 6

The diagram presents a summary for the definitions of gemination, twinning, fusion, and concrescence.

Figure 7

The photographs exhibit examples of gemination encountered in an incisor (A), canine (B), and premolar tooth (C) of dogs. (D) represents a case of bilateral permanent maxillary first incisor tooth gemination, and (E) was a case of gemination of a deciduous premolar tooth in a Dachshund. (F) is a radiograph of a geminated second maxillary incisor tooth demonstrating a single root with two crowns.

Figure 8

The patient presents with a good example of fusion between teeth 201 (left maxillary first incisor) and 202 (left maxillary second incisor) resulting in a double tooth in their place.

Figure 9

The photograph (A) shows an example of concrescence between a canine and supernumerary tooth in the left maxilla. The pathogenesis in this case was uncertain. Both were surgically removed. On examination of the excised teeth (B), they shared only a cementum bridge but not dentin or any other dental hard tissue.

Figure 10

The diagram aims to explain the pathogenesis of a dens invaginatus tooth. During development, there is invagination of the inner enamel epithelium into the tooth pulp (P), resulting in a deep infolding of enamel (E) into dentin (D) and pulp (P). Radiographically, this may give the impression of a tooth within a tooth.

Figure 11

Photograph (A) demonstrates an example of dilacerations of both roots of a left mandibular first molar, and photograph (B) is a good example of dilaceration of the crown of a right maxillary canine (tooth 104).