What Is Dentinogenesis Imperfecta Type III?

Overview

Dentinogenesis imperfecta (DGI) is a disorder of the tooth that causes discolouration and weakening of the teeth. Sounds like a rare disorder? Yes, it is a relatively rare occurrence, inherited in an autosomal dominant way. If left untreated, it causes a progressive distortion of tooth form and permanent discolouration, which cannot be corrected by mere toothbrushing. There are three types of DGI, according to Shield: Type I, Type II and Type III.

Continue reading as we briefly discuss the different types and further explore Type III DGI in more depth.

Classification of dentinogenesis imperfecta

The most common classification of the disorder is from Shields (1973), categorised as the following:

Type I DGI

This is when the teeth disorder is coupled with the bone disorder, osteogenesis imperfecta. The tooth disorder consists of discoloured teeth (amber), which are translucent and weak. The bone disorder also has, as one of its features, a bone deformity due to weakened bone tissues. This can occur in both primary and adult teeth. Further investigation with a radiograph will confirm short constricted dental roots, with dentine hypertrophy and pulpal obliteration.

Type II DGI

This presents in a very similar way as Type I but without the bone defect. It also has a higher penetrance. It has a spectrum of expression in individuals with the gene, with a distinguishing feature being crown bulbosity. Radiographically, the teeth have bulbous crowns and short roots with obliterated pulp.¹ So next time you see an abnormally bulbous and discoloured tooth with a constricted neck, suspect a Type II Dentinogenesis Imperfecta. It has also been found to be associated with some form of hearing loss, according to some literature. It has, however, not been established to be syndromic. 

Type III DGI

This type is also known as the Brandywine isolate in Wiktop’s classification, as it was first identified in the Brandywine tri-racial isolate in southern Maryland. This isolate has also been identified in a Jewish family.^2,5 The clinical features are variable but similar to those found in Type I and II. However, it has a distinguishing feature of rapid wear with multiple exposures of the pulp of the teeth just post-eruption. Radiographic investigations show very large pulp chambers and root canals at initial eruption (shell teeth), which progressively reduce in size with age. It is also not syndromic and can occur in both primary and permanent dentitions.

Albeit being the most widely acknowledged classification, some authors have also proposed a new classification of the condition as the genetic study of the disorder has shown that the disease may be a variation of the same disease with differing severity.³ Type I is however viewed as a different disorder as it involves mutation of a different gene and now classified by the Mendelian Inheritance in Man (MIM) database as osteogenesis imperfecta.⁴

Cause and genetics of dentinogenesis imperfecta type III (DGI-III)

Genetic mutation is the primary cause of DGI-III, as with other cases of the disorder. The defective gene is the Dentine Sialophosphoprotein (DSPP), which is responsible for encoding the non-collagenous proteins of the dentin.³

The inheritance pattern is autosomal dominant, which means that if an individual inherits the defective gene from one or both of their biological parents, they will develop this disorder regardless of their gender.

Clinical features

The three layers of the coronal part of the teeth, arranged from the outermost to the innermost, are enamel, dentine, and pulp.

DGI-III results in the abnormal development of the middle layer of the teeth, the dentine. This leads to the following features:⁴

Discoloured teeth 

The teeth are usually discoloured and translucent. These colours range from amber, grey, and purple to bluish.

Rapid wear and tear

Individuals with this disorder tend to have teeth that are weaker than normal due to an altered dentin-enamel junction (the junction between the middle and outermost layer of the teeth). 

This may cause rapid teeth wear which may lead to chipping, teeth fractures, and small holes in the enamel. 

Dentine pulp exposure

As a result of the rapid wear of the outermost layer of the teeth, the dentine and the innermost coronal part of the teeth–the pulp–are exposed. DGI-III in primary teeth is distinguished by the feature of multiple pulp exposures. 

Malocclusion

Misalignment of the teeth can occur as they progressively get worn out and sometimes lost.

Early tooth loss

The inevitable end of an unrestorable, worn-out tooth. 

Diagnosis

To make a diagnosis of DGI-III, one has to visit a dental professional who will follow the steps below:

1. Clinical history: The dental professional will review the patient’s medical, dental, and family history. A higher index of suspicion is raised if relative features are reported and if a first-degree relative has a similar disorder. It is also important to exclude any bone disorder that may point to osteogenesis imperfecta and DGI-I.
2. Clinical examination: the features enumerated above are being identified to aid in diagnosis.
3. Radiographic imaging: Radiographic imaging in DGI-III gives the classical “shell teeth”, with the characteristic large central radiolucency of the pulp with reduced width of dentine radiopacity due to dentine hypotrophy.¹

Differential diagnosis

Some other tooth disorders that can present similarly are dentine dysplasia, DGI-I, and DGI-II.

Management and treatment¹

For primary dentition (baby teeth)

• Stainless steel crown: used to crown the back teeth to prevent wear due to chewing and to maintain tooth height
• Composite facing or strip crown: Improves aesthetics in the front teeth 
• Overdentures: If the teeth have undergone severe wear, overdenture might suffice to restore function and aesthetics
• Extraction: extraction of the symptomatic teeth may be the best solution, as pulp therapy is not usually favourable in teeth that have developed abscesses 

For mixed dentition 

This is a period when both primary and permanent dentition, or baby teeth and adult teeth, are present simultaneously in the mouth. 

• Monitor tooth wear: Regular monitoring of permanent dentition wear and restoration if necessary
• Cast occlusal onlays: To be placed on first permanent molars and eventually premolars
• Minimal tooth preparation
• Removable partial denture: considered for replacement of lost teeth before growth completion

For permanent dentition 

When all teeth in the mouth are permanent, or adult teeth.

• Full mouth rehabilitation: To be considered if clinically indicated. 
• Overdentures: An option for a patient with severe tooth wear dental implants: Considered for replacement of lost teeth after 18 years of age when growth is complete. Ridge augmentation may be required if the bulk of the bone support for the lost tooth is reduced

In all cases, regular dental check-up is required. It is also important to prevent tooth decay. 

Prognosis

The outcome of DGI-III is significantly dependent on when the stage of development the diagnosis was made and how soon treatment is received. When the diagnosis is early, and treatment aligns with the aforementioned recommendations, satisfactory aesthetics and functionality can be achieved. This helps in reducing emotional stress and nutritional imbalances that might be caused if left untreated.¹

Summary 

Dentinogenesis imperfecta type III (DGI-III) is a rare tooth disorder that results in weakened and discoloured teeth, with the consequent effects of rapid wear and, ultimately, tooth loss. 

DGI-III, though, can lead to aesthetic and functional limitations, but it can be managed if discovered early. It is therefore necessary to regularly visit the dentist for early diagnosis of such a rare disorder and adequate management and treatment if diagnosed.