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 CMC joint of the thumb allows a wide range of motion while maintaining stability for grasp and pinch.With this in mind, failure to properly recognize and treat the Bennett fracture will not only result in an unstable, painful, arthritic CMC joint with diminished range of motion: it will also result in a hand with greatly diminished overall function.In the case of the Bennett fracture, the proximal metacarpal fragment remains attached to the anterior oblique ligament, which in turn is attached to the tubercle of the trapezium bone of the CMC joint. This ligamentous attachment ensures that the proximal fragment remains in its correct anatomical position.The distal fragment of the first metacarpal bone possesses the majority of the articular surface of the first CMC joint. Unlike the proximal fracture fragment, strong ligaments and muscle tendons of the hand tend to pull this fragment out of its correct anatomical position.Specifically:

tension from the abductor pollicis longus muscle (APL) subluxates the fragment in a dorsal, radial, and proximal direction
tension from the APL rotates the fragment into supination
tension from the adductor pollicis muscle (ADP) displaces the metacarpal head into the palmTension from the APL and ADP muscles frequently leads to displacement of the fracture fragments, even in cases where the fracture fragments are initially in their proper anatomic position. Because of the aforementioned biomechanical features, Bennett fractures nearly always require some form of intervention to ensure healing in the correct anatomical position and restoration of proper function of the thumb CMC joint.