Fig 1.
Permanent dentition of an Eastern Atlantic harbor seal (Phoca vitulina vitulina).
The teeth in the maxillary (upper image) and mandibular (lower image) dental arcades are identified by anatomical terms and the numbering of the modified Triadan system frequently used in veterinary dentistry.
Fig 2.
Overview of examined Eastern Atlantic harbor seals (Phoca vitulina vitulina).
Numbers of males and females in three age classes are given.
Fig 3.
Numbers of Eastern Atlantic harbor seals (Phoca vitulina vitulina) in the study sample exhibiting numerical dental anomalies.
The criteria for classifying cases of missing teeth are given in the text.
Fig 4.
Distribution of intravital tooth loss in the study sample of Eastern Atlantic harbor seals (Phoca vitulina vitulina).
Absolute numbers for the different tooth loci are given. The teeth are identified both by anatomical terms and the numbering of the modified Triadan system (see Fig 1).
Fig 5.
Skull of an anodont 5-year-old male Eastern Atlantic harbor seal (Phoca vitulina vitulina, specimen ZIK 4626).
(a) Ventral view of incisive and maxillary bones. (b) Radiograph of anterior skull region (laterolateral projection). (c) Dorsal view of left mandible. (d) Radiograph of left mandible (mediolateral projection). Note that the (tooth-dependent) alveolar structures are also missing.
Fig 6.
Example of congenital tooth absence in an Eastern Atlantic harbor seal (Phoca vitulina vitulina).
Dorsal view of the mandibles of a 1-year-old male (specimen ZIK 24885). The left P1 is missing, there is no indication of an alveolus (arrowhead), and the distance between canine and P2 is shorter on the left than on the right side.
Fig 7.
Examples of supernumerary teeth in the permanent dentition of Eastern Atlantic harbor seals (Phoca vitulina vitulina).
(a) Dorsal view of the mandibular tooth rows of a 2-year-old female (specimen ZIK 24806). There are two supernumerary teeth (located between P3 and P4) in the left and one supernumerary tooth in a corresponding position of the right mandible (arrowheads). Due to the formation of the supernumeraries, both teeth at the normal P3 position are rotated approximately 45 degrees. The condition is interpreted as the result of a splitting of both the P3 and the P4 tooth germs on the left side and of the P3 tooth germ on the right side. (b) Ventral view of maxillary and incisive bones of a 3-year-old female (specimen ZIK 28942) showing a (two-rooted) supernumerary tooth (arrowhead) situated palatal to the left P2. The cause of the hyperodontia is most probably a splitting of the P2 tooth germ. (c) Lateral view of the right maxilla of a 1-year-old male (specimen ZIK 28170), showing a peg-shaped and mesially inclined supernumerary tooth (arrowhead) located buccal to the P2 (mesial to the right). (d) Ventral view of left maxilla of a 10-year-old female (specimen ZIK 29485), showing a peg-shaped, mesially inclined supernumerary tooth (arrowhead) located palatal to the P3 (mesial to the right).
Fig 8.
Simplified crown shape and elongated tooth roots in a 2-week-old male Eastern Atlantic harbor seal (Phoca vitulina vitulina, specimen ZIK 27251).
(a) Premolar with simplified (tricuspid) crown and elongated roots. Arrows: periradicular bands. (b) Dorsal view of the mandibles, with identification of the alveoli for the canine, the premolars and the M1. Note abnormally wide interdental septa.
Fig 9.
Abnormal crown and root morphology in an 11-year-old female Eastern Atlantic harbor seal (Phoca vitulina vitulina, specimen ZIK 29115), diagnosed as a case of gemination.
(a) Radiograph (mediolateral projection) of left maxillary postcanine tooth row. Note bifid crown and occurrence of three roots in the P2, and presence of a small supernumerary root arising from the bifurcation area in the P3. (b) Buccal view of left P2. Buccally, the notch in the tooth crown does not extend onto the central root. (c) Palatal view of left P2. Palatally, the notch extends onto the central root. Arrowheads: vertical furrow on the central root.
Fig 10.
Abnormal crown and root morphology in an 18-year-old male Eastern Atlantic harbor seal (Phoca vitulina vitulina, specimen ZIK 29091), diagnosed as a case of incomplete fusion of P1 and P2.
(a) Radiograph (mediolateral projection) of maxillary right canine and postcanine teeth. Asterisk: incompletely fused right P1 and P2. Note hypercementosis on the roots of the postcanine teeth. (b) Buccal view (mesial to the right) of incompletely fused right P1 and P2 (crowns separate). (c) Palatal view (mesial to the left) of incompletely fused right P1 and P2. Arrowhead: shallow furrow on the central root.
Fig 11.
Incompletely fused right P1 and P2 in a 1-month-old male Eastern Atlantic harbor seal (Phoca vitulina vitulina, specimen ZIK 27291).
(a) Buccal view (mesial to the right) of the incompletely fused teeth (crowns separate, only roots fused). Note small cusps (some marked by arrows) at the mesial and distal crown edges of both teeth. (b) Palatal view of the incompletely fused teeth (mesial to the left). (c) Radiograph of the specimen, showing that the crowns of the two teeth are separate and only the roots are partly fused. (d) Alveolar pattern of right maxillary postcanines. The number of alveoli is normal, as the fused root is situated in the anterior (mesial) socket of the P2. The septum marked by the arrow must be classified as an interradicular septum rather than an interdental septum normally present in this location.
Fig 12.
Examples of tooth fracture and sign of periapical lesion in Eastern Atlantic harbor seals (Phoca vitulina vitulina).
(a) Fractured right mandibular canine of a 22-year-old female (specimen ZIK 28104). This is a case of complicated crown fracture as the pulp cavity has been opened (arrowhead). The right I2 had been lost intravitally. Also note signs of advanced periodontitis (porosity of alveolar bone due to numerous vascular foramina, and horizontal and vertical loss of alveolar bone) and pronounced signs of wear on the teeth. (b) Right mandible of a 23-year-old male (specimen ZIK 28745). The alveolar bone shows a focal osteolytic area, diagnosed as the opening of a draining tract for pus discharge. This is considered indicative of a periapical lesion associated with the P1. The alveolar bone shows signs of advanced periodontitis in the form of porosity of the alveolar bone (denoting increased vascularity), alveolar exostosis (arrow), and loss of alveolar bone. Note also pronounced wear signs on the teeth.
Fig 13.
Distribution of periapical lesions visible on external inspection in the permanent dentition of the studied Eastern Atlantic harbor seals (Phoca vitulina vitulina).
The first premolar was the most frequently affected tooth position. The teeth are identified both by anatomical terms and the numbering of the modified Triadan system (see Fig 1).