Dentinogenesis imperfecta (DI) is a genetic disorder of tooth development. It is inherited in an autosomal dominant pattern, as a result of mutations on chromosome 4q21, in the dentine sialophosphoprotein gene (DSPP). It is one of the most frequently occurring autosomal dominant features in humans. Dentinogenesis imperfecta affects an estimated 1 in 6,000-8,000 people.This condition can cause teeth to be discolored (most often a blue-gray or yellow-brown color) and translucent, giving teeth an opalescent sheen. Teeth are also weaker than normal, making them prone to rapid wear, breakage, and loss. These problems can affect baby (primary/deciduous) teeth alone, or both baby teeth and adult (permanent) teeth, with the baby teeth usually more severely affected.Although genetic factors are the main contributor for the disease, any environmental or systemic upset that impedes calcification or metabolisation of calcium can also result in anomalous dentine. Classification
Shield classification (1973)
This is the most widely used classification for dentinogenesis imperfecta, and sub-divides the condition into 3 types:

Type I
DI associated with Osteogenesis Imperfecta (OI).
The DPP protein is thought to contribute to hydroxyapatite crystal formation and growth, a fundamental crystal which is widely distributed in mineralised dentine and enamel. The function of the DGP and DSP proteins is not well understood.Genetic studies have shown that type II and III may be the same sub-type of dentinogenesis imperfecta, differing only by the severity. de La Dure-Molla, Foruner and Berdal (2015)
de La Dure-Molla, Foruner and Berdal (2015) have proposed a new classification to supersede the Shield Classification (1973). This new classification is designed to overcome the shortcomings of its predecessor, mainly the clinical difficulty in using the Shield classification due to the overlapping signs & symptoms between the sub-types.In this classification, the authors propose that the DSPP (dentine sialophosphoprotein) diseases, that is dentinogenesis imperfecta and dentine dysplasia, are jointly named "Dentinogenesis imperfecta", and sub-types are determined according to the severity of the condition. There are a few exceptions:

Shields Dentine Dysplasia type I - this condition is unique in that it only affects root development, and is separately termed "radicular dentin dysplasia" in the new classification. Shields Dentinogenesis Imperfecta type I - this sub-type is not acknowledged in this new classification as the authors deem it a different disease since it is a syndrome of osteogenesis imperfecta

Mild type
Primary (baby) teeth are moderately affected. Permanent (adult) teeth are not discoloured, or the discolouration is mild (grey colour). Little or no attrition (tooth wear) is evident. The crown of the teeth may be bulbous and markedly constricted at the cemento-enamel junction (CEJ).