Morphology of the Cementoenamel Junction in Permanent Teeth of Dogs: A Scanning Electron Microscopic Study.

In human teeth, the cementoenamel junction (CEJ) can have different morphologies, known as Choquet cases or types: in type 1, the cementum overlaps the enamel; in type 2, the enamel overlaps the cementum; in type 3, the relationship between the cementum and enamel is edge-to-edge; and in type 4, there is a gap between the enamel and the cementum, with exposed dentin. Since little is known on the morphology of the CEJ in animals, the aim of this study was to characterize the structure of the CEJ of dog teeth by SEM. We studied 82 permanent teeth extracted from 4 dogs of similar size, aged from 7 months to 2 years. Teeth were grouped according to their size, sectioned and prepared for SEM. The teeth evaluated showed the 4 CEJ types. Type 3 was the most prevalent, being present, either alone or in combination, in 90.79% of the samples, followed by type 4 (present in 31.58% of the samples). Of the samples, 65.13% showed only one type, while 34.87% presented a combination of them. Types 3 and 4 were the only ones present alone (in 55.92% and 9.21% of the samples respectively), whereas the combinations between types 3 and 4 (20.40%) and types 1 and 3 (9.87%) were the most frequent. In all combinations, type 3 was predominant. The CEJ of the dogs evaluated showed a high degree of variability in the different types of teeth, within a same tooth, within the dentition of a single individual, and among individuals.

Scanning electron microscopy of pulp cavity dentin in dogs.

Dentin morphology and tubule diameter and density of peripulpal dentin were evaluated in 36 teeth from 12 adult dogs, aged between 2.5 and 13-years. The right maxillary canine and third premolar and right mandibular first molar teeth were extracted from euthanized dogs. The teeth were prepared and photomicrographs (n=108) were taken of the radicular and coronal dentin. Dentinal tubule density (tubules/mm2) was determined and tubular diameter and luminal area were measured in 3240 randomly chosen tubules using measurement software. Results from group 1 dogs (< 7-years-old) were compared with group 2 dogs (> 7-years-old). The majority of dentinal tubules were round or oval in shape and had uniform distribution at the radicular coronal third, and coronal levels. Dentin surfaces showed morphological differences at different levels of the tooth. Group 1 dentinal tubule diameter (1.87 +/- 0.44 microm) and area (1.91 +/- 0.83 microm2) were significantly different compared with Group 2 dentinal tubule diameter (1.53 +/- 0.39 microm) and area (1.22 +/- 0.50 microm2). There was no significant difference in tubular density between groups 1 (74,692 +/- 25,991 tubules/mm2) and 2 (72,938 +/- 24,646 tubules/mm2). Site-specific differences were observed in the pulp cavity dentin in the same tooth. These results provide a reference for future research in dogs or where dogs are used as a model for investigations in human dentistry.

Furcation canals of the maxillary fourth premolar and the mandibular first molar teeth in cats.

The furcation region morphology was evaluated in 103 mature feline carnassial teeth (54 maxillary fourth premolar and 49 mandibular first molar teeth). Patent furcation canals were present in 27.2% of teeth. No significant difference (p = 0.88) in distribution of this anatomical variation was found between maxillary fourth premolar and mandibular first molar teeth. The mean width of these furcation canals was 104.0 microns with two-thirds of the canals having a buccal orientation. The presence of furcation canals could be a factor in the etiopathogenesis of feline dental resorptive lesions, as well as a characteristic to be considered in the diagnosis, prognosis, and treatment of endodontic or periodontic-endodontic lesions in cat teeth.