Osteogenesis imperfecta (OI) results from various gene mutations leading to defects in type I collagen, which is the major component of both bone and dentin. Yet dentinogenesis imperfecta (DI) is found only in half of the patients with OI. Here we document patients from three families with OI and DI lacking the clinical and radiographic features of DI in permanent teeth. However, light and transmission electron microscopic studies of dentin of deciduous and permanent teeth revealed various changes in the morphology of the dentinal tubules and collagen fibers. In one family, diagnosis of DI preceded that of OI. The grade of severity of dentinal manifestations in patients with OI apparently forms a continuum from normal dentin structure to severe DI, and the marked difficulty in diagnosing mild DI may have led to underestimating its frequency. Furthermore, patients with DI should be carefully examined for the possible presence of OI.

Heritable dentin defects have been divided into 2 main categories: dentinogenesis imperfecta (DI) and dentin dysplasia (DD). Recent studies have shown that they share many features in common. Of the connective tissue diseases, only osteogenesis imperfecta (OI) has been linked to these disorders. So far, no definitive relation between the type of OI and the dental involvement can be established. Familial occurrence of DI with OI cannot be comprehensively explained by mutations in type I collagen genes. No information about the gene defects in DD is available. At the ultrastructural level, the organization of the normally cross-striated collagen fibers in the dentin matrix varies markedly in patients affected by DI.

Types I, V, and VI collagen were immunohistochemically localized in frozen and paraffin sections of human permanent teeth, periodontal ligament, and alveolar bone, by means of polyclonal antibodies. Hyaluronidase was effective in exposing epitopes of the various collagen types. The expression of type I collagen in predentin was strong in frozen sections, whereas the dental pulp stained relatively weakly. Staining intensity in the dentin matrix decreased toward enamel and cementum. Reactivity in the periodontal ligament was moderate, and it was weaker in the alveolar bone and also in cementum, which stained more intensely in paraffin sections. Staining for type V collagen was strong in the pulp. Weak reactivity in predentin became uniformly evident in frozen sections only, and dentin was negative. The periodontal ligament stained with moderate intensity, and a weak staining reaction was seen in cementum and bone. Staining for type VI collagen in the pulp and periodontal ligament was strong, whereas predentin and dentin were negative. The alveolar bone stained moderately, and non-uniform reactivity was present in cementum. In non-mineralized dental tissues, the use of frozen material enabled good immunohistochemical localization of the distinct collagen types to be carried out. Their distribution patterns in dental tissues not only differed, but the relative staining intensities for each collagen type in the pulp and predentin were inversely related. However, differences may exist in the exposure of the epitopes of collagen(s) between soft and mineralized tissues.

We used transmission immunoelectron microscopy and polyclonal antibodies to study the reactivities of Types III and VI collagen in dentin of normal human permanent and primary teeth and in primary teeth from five patients with dentinogenesis imperfecta (DI) associated with osteogenesis imperfecta and occurring as a single trait. In the normal permanent tooth, reactivity of Type III collagen was occasional and, where present, peritubular. Staining of normal primary teeth was less occasional but still rare, whereas the abnormal dentin stained more uniformly. Atypical, non-striated fibrillar structures that also showed Type III collagen reactivity were observed in dentin of two of the three patients with DI as a single trait. Later, these two patients proved to be first cousins. Unlike antibodies to the N-terminal pro-peptide of Type I pro-collagen, antibodies to the C-terminal telopeptide of Type I collagen, used for comparison stained the affected dentin homogeneously. Reactivity of Type VI collagen, not detected in normal teeth, was seen in the dentin of all abnormal teeth, in association with non-fibrillar delicate material. This study also shows that although readily detectable in dentin affected by DI, Type III collagen is a minor constituent of normal human dentin matrix.

Dentin matrix of deciduous teeth from two patients affected by dentinogenesis imperfecta (DI) associated with types IB and IVB osteogenesis imperfecta (OI) displayed previously undescribed structures in transmission electron microscopic examination. Vesicles were seen in dentin of both patients, and abnormally thick collagen fibers (hyperfibers) were found in dentin of the patient with the rare type IB OI. Both vesicles and hyperfibers were situated in abnormal, atubular areas of dentin. Matrix vesicles, which have normally been identified in mantle dentin only, were abundant in selected areas of the affected dentin, thereby supporting the concept that dentin matrix in OI is elaborated by successive cell generations. The hyperfibers, not previously described in either normal or abnormal human dentin, have possibly been formed by fusion of several collagen fibers. Further ultrastructural studies of dentin in DI with OI may help to clarify the marked clinical variation in teeth of patients affected by OI.