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J Dent Res 45(3): 575-583, 1966
© 1966 International and American Associations for Dental Research
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Geminated Odontome—Connation of the Incisors in the Dog—Its Etiology and Ontogeny

A. D. HITCHIN 1 and I. MORRIS 1

1 Dundee Dental School University of St. Andrews, Dundee, Scotland

Connation of the maxillary and mandibular incisors is inherited in the strain of Lakeland Terriers studied.

A large number of variants occur, including the appearance of connation of a first incisor with a supernumerary tooth.

The primary developmental abnormality in connation is persistence of the dental lamina between the tooth germs. Persistence of this interdental lamina in the maxillae and mandible is controlled by the same genes.

The appearance of two teeth united is usually described as "gemination," but the term "connation" is preferred. The evidence for its hereditary basis in man has been reviewed.

By inbreeding a strain of Lakeland Terriers in which the condition had been observed, it was established that connation of the first and second incisors in dogs is inherited; connation was produced in at least 1 dog of each litter. A large number of variant forms of connation were observed.

Material from dogs obtained at the 34th day of gestation to 13 days after birth was submitted to serial sectioning. From a study of the dogs with unilateral involvement, it was shown that persistence of the interdental lamina is the primary developmental abnormality and that this is controlled by the same genes in the maxillae and mandible.

Based on these observations, a new theory regarding the mechanism of connation is advanced; that is, herniation of the enamel organs occurs between the two layers of persistent interdental lamina to effect their union; whereas, if the persistent lamina breaks near one tooth germ, its neighboring enamel organ may suddenly burst between the two layers of lamina and produce the appearance of connation with a supernumerary tooth.




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