|Oral photographs from an individual with Dentinogenesis imperfecta|
Dentinogenesis imperfecta (DI) is a genetic disorder of tooth development. This condition is a type of dentin dysplasia that causes teeth to be discolored (most often a blue-gray or yellow-brown color) and translucent giving teeth an opalescent sheen. 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.
Consequently, teeth are also weaker than normal, making them prone to rapid wear, breakage, and loss. These problems can affect both primary (deciduous) teeth and permanent teeth. This condition 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 to 8,000 people.
Clinical appearance is variable with presentation ranging from gray to yellowish brown, but the characteristic feature is the translucent or opalescent hue to the teeth.
In Type I, primary teeth are more severely affected compared to the permanent dentition which has more varied features, commonly involving lower incisors and canines. Primary teeth have a more obvious appearance as they have a thinner layer of enamel overlying dentine, hence the color of dentine is more noticeable.
In Type II, both the dentitions are equally affected.
Enamel is usually lost early because it is further inclined to attrition due to loss of scalloping at the dentinoenamel junction (DEJ). It was suggested that the scalloping is beneficial for the mechanical properties of teeth as it reinforces the anchor between enamel and dentine. However, the teeth are not more susceptible to dental caries than normal ones.
However, certain patients with dentinogenesis imperfecta will suffer from multiple periapical abscesses apparently resulting from pulpal strangulation secondary to pulpal obliteration or from pulp exposure due to extensive coronal wear. They may need apical surgery to save the involved teeth.
These features are also present in dentine dysplasia and hence, the condition may initially be misdiagnosed.
Dentinal tubules are irregular and are bigger in diameter. Areas of uncalcified matrix are seen. Sometimes odontoblasts are seen in dentin.
Type I and II have similar radiographic features
- Total obliteration of the pulp chamber and root canals due to deposition of dentine
- Bulbous crowns with apparent cervical constriction
- Reduced root-length with rounded apices
Type III shows thin dentin and extremely enormous pulp chamber. These teeth are usually known as "shell teeth".
Periapical radiolucency may be seen on radiographs but may occur without any apparent clinical pathology.
Type I: DI associated with Osteogenesis Imperfecta (OI). Type of DI with similar dental abnormalities usually an autosomal dominant trait with variable expressivity but can be recessive if the associated osteogenesis imperfecta is of recessive type.
Type II: DI not associated with OI. Occurs in people without other inherited disorders (i.e. Osteogenesis imperfecta). It is an autosomal dominant trait. A few families with type II have progressive hearing loss in addition to dental abnormalities. Also called hereditary opalescent dentin.
Type III: Brandywine isolate. This type is rare with occurrences only in the secluded populations in Maryland, USA. Its predominant characteristic is bell-shaped crowns, especially in the permanent dentition. Unlike Types I and II, it involves teeth with shell-like appearance and multiple pulp exposures.
Mutations in the DSPP gene have been identified in people with type II and type III dentinogenesis imperfecta. Type I occurs as part of osteogenesis imperfecta.
Preventive and restorative care are important as well as esthetics as a consideration. This ensures preservation of the patient's vertical face height between their upper and lower teeth when they bite together. The basis of treatment is standard throughout the different types of DI where prevention, preservation of occlusal face height, maintenance of function, and aesthetic needs are priority. Preventive efforts can limit pathology occurring within the pulp, which may render future endodontic procedures less challenging, with better outcomes.
- Challenges are associated with root canal treatment of teeth affected by DI due to pulp chamber and root canal obliteration, or narrowing of such spaces.
- If root canal treatment is indicated, it should be done in a similar way like with any other tooth. Further consideration is given for restoring the root-treated tooth as it has weaker dentine which may not withstand the restoration.
Preservation of occlusal face height may be tackled by use of stainless steel crowns which are advocated for primary teeth where occlusal face height may be hugely compromised due to loss of tooth tissue as a result of attrition, erosion of enamel.
In most cases, full-coverage crowns or veneers (composite/porcelain) are needed for aesthetic appearance, as well as to prevent further attrition. Another treatment option is bonding, putting lighter enamel on the weakened enamel of the teeth and with many treatments of this bonding, the teeth appear whiter to the eye, but the teeth on the inside and under that cover are still the same. Due to the weakened condition of the teeth, many common cosmetic procedures such as braces and bridges are inappropriate for patients with Dentinogenesis imperfecta and are likely to cause even more damage than the situation they were intended to correct.
Dental whitening (bleaching) is contraindicated although it has been reported to lighten the color of DI teeth with some success; however, because the discoloration is caused primarily by the underlying yellow-brown dentin, this alone is unlikely to produce normal appearance in cases of significant discoloration.
If there is considerable attrition, overdentures may be prescribed to prevent further attrition of remaining teeth and for preserving the occlusal face height.
Management of DI associated with OI
Bisphosphonates have recently been introduced to treat several bone disorders, which include osteogenesis imperfecta.
A recognized risk of this drug relevant to dental treatments is bisphosphonate-associated osteonecrosis of the jaw (BRONJ). Occurrences of this risk is associated with dental surgical procedures such as extractions.
Dental professionals should therefore proceed with caution when carrying out any dental procedures in patients who have Type 2 DI who may be on bisphosphonate drug therapy.
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This article incorporates public domain text from The U.S. National Library of Medicine