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This is a report of a kindred of at least 181 members, of whom 35 exhibit or are reported to have dentin dysplasia type I. Six others are suspected of having the condition. Radiographic evidence that included obliterated or semilunar pulp chambers and short or undeveloped roots confirmed the diagnosis in 18 persons. The autosomal dominant mode of inheritance has been confirmed. One hundred percent penetrance has been demonstrated. There were insufficient data to determine the degree of expressivity.

Dentin dysplasia is a rare developmental disturbance of dentin affecting approximately 1:100,000 people. It has been classified as an autosomal dominant disease. Two distinct forms of dentin dysplasia have been described. As more cases of dentin dysplasia were reported these categories seemed inadequate; subclassification of type I dentin dysplasia were proposed based on root length and the presence or not of a pulpal remnant. This paper presents two cases demonstrating the classic features of type I dentin dysplasia in the mixed and permanent dentitions and discusses the suggested subclassifications. The authors suggest that while differences in root length may be useful in determining treatment options, thinking of these variables as separate types of dentin dysplasia is not warranted at this time. Justification of a subcategory of type I dentin dysplasia should be based on a different disease process, different histology, significantly different symptoms, or different etiologies, and until researchers can clearly prove from a genetic or chromosomal standpoint that the subcategories are separate entities, we should accept, as we do for many other genetic disorders, that some patients are more severely affected than others.

The literature is reviewed to determine the radiographic appearance of the reported cases of dentin dysplasia. The sometimes confusing nomenclature is rationalized. Four distinct forms of dentin dysplasia type I and one form of dentin dysplasia type II are identified. There seems to be no need to identify more than two distinct types of this relatively rare inherited defect of human dentin, but a proposed subclassification of type I dentin dysplasia could make identification of the two types easier.