What Is Dentin Dysplasia Type I 

Overview

Dentin dysplasia type I, also known as radicular dentin dysplasia, is a genetic disorder that causes abnormal development of the dentin, one of the tooth’s tissues.¹ Although the teeth might appear normal at first glance due to the enamel (the outermost layer of the teeth) being normal, people affected by this disease have weak teeth that are prone to mobility, and they are at extreme risk of tooth loss, as their teeth have abnormally short and malformed roots.¹ Let’s understand more about this rare condition in the sections below.

Causes

Dentin dysplasia, as stated, is a genetic disorder affecting the development of dentin.² But what is dentin? It is one of the tooth’s tissues, and it sits in between the enamel and the pulp.³ 

The enamel is the outermost layer that covers the teeth’s crowns, a hard mineralised tissue; the dentin sits directly below it, acting as a bridge between the enamel and the pulp: the dentin is also mineralised, although to a lesser extent, and is filled with microscopic tubules that connect to the pulp; and finally, the pulp is the soft tissue inside the tooth, that contains nerves and blood vessels.³

Patients with dentin dysplasia have an abnormal development of the dentin, which leads to an abnormal development of the pulp as well.¹ In type I, the radicular type, the aberrant dentin obliterates the pulp chamber either partially or completely, the pulpal tissue being replaced with more mineralised tissue.³ While the excess of abnormal dentin makes the teeth more resistant to cavities (as the dentin lacks normal tubules, being more dense and compact), the loss of pulp tissue results in the formation of radicular cysts and granulomas that leads to premature tooth loss.²

We understand currently that dentin dysplasia type I is caused by an autosomal dominant genetic mutation.³ What that means is that it is transmitted regardless of sex (as autosomal mutations are not contained in the X or Y chromosomes that determine biological sex) and it is dominant, so it only takes one copy of the mutated gene in an individual to develop dentin dysplasia. Unlike dentin dysplasia type II or dentinogenesis imperfecta, which are other diseases that affect the dentin, dentin dysplasia type I is very heterogeneous: there hasn’t been one specific gene linked to its cause, but a few different genes that, once mutated, can lead to radicular dentin dysplasia.⁴ 

Three genes have been identified as potential causes: VPS4B, SSUH2, and SMOC2.

VPS4B controls root formation, among many other things, in the body. Experiments have shown that loss of this gene or a defective copy leads to short, malformed teeth roots, but more studies need to be done in humans to completely understand the relationship.⁴

SSUH2 is a gene that produces a nuclear protein that controls the transcription of genes related to tooth formation: what that means is that this protein signals what genes should or should not be made into proteins, controlling tooth development.⁴

SMOC2 has many functions, mainly related to wound healing and embryogenesis, like promoting the proliferation of epithelial cells and angiogenesis (formation of new blood vessels). Though its relationship to tooth formation in specific is still unknown, mutations of SMOC2 have generated dental anomalies like short roots, fewer teeth (oligodontia) and smaller teeth (microdontia).⁴

Theories on how these mutations influence dentin formation have been proposed:³

• During the formation of the roots of the tooth’s germ, an epithelial mutation induces an early start and early stop of the invagination of Hertwig’s root sheath.³ This premature development leads to the formation of an incomplete, aberrant dentin.
• Alternatively, it has been proposed that the mutations affect the odontoblasts, the cells responsible for producing dentin. A problem in the differentiation of the odontoblasts leads to abnormal cell functions, and the mutated odontoblasts produce defective dentin.³

Signs and symptoms

Dentin dysplasia type I affects both primary dentition (deciduous or baby teeth) and secondary dentition (permanent or adult teeth).³ 

Common signs and symptoms of radicular dentin dysplasia include:

• The teeth generally appear to be normal but can appear to have either blue, brown, grey or amber discolouration in some cases.³
• Tooth mobility²
• Tooth loss²
• Radiographically, the roots are short and malformed; there can be presence of radiolucent lesions like radicular cysts and granulomas affecting the root apex²
• Additionally, radiography can show the pulps are either partially or completely obliterated by dentin in a crescent or half-moon aspect.²

Diagnosis

Diagnosis is made through clinical examination by a dentist and analysis of radiographic exams. More importantly, a professional should investigate other possibilities beyond dentin dysplasia type I. 

Differential diagnoses include:¹

• Dentin dysplasia type II: affects the primary teeth, causing discolouration of the crowns, but does not affect the secondary dentition nor causes tooth mobility¹
• Dentinogenesis imperfecta: affects both permanent and deciduous teeth, causing discolouration and a bulbous aspect to the crown, without mobility¹
• Odontodysplasia: non-hereditary, it affects only a few teeth, causing mobility and formation of a thin layer of both enamel and dentin, with a radiographic aspect of “ghost teeth” (due to enlarged radiolucent pulp)¹
• Vitamin D‐dependent rickets type I (VDDR‐I) and vitamin D‐resistant rickets (VDRR): systemic diseases that cause defective calcification of bone and teeth, with bowing legs, impaired growth and teeth with short roots and large pulp chambers⁴
• Familial tumoral calcinosis: a systemic condition that causes calcification of soft tissue; teeth are usually short with bulbous roots and have obliterated pulp chambers⁴

Other diseases might present with teeth with similar aspects to dentin dysplasia type I: 

• Osteogenesis imperfecta²
• Ehlers-Danlos syndrome²
• Goldblatt syndrome²
• Schimke immuno-osseous dysplasia²
• Brachio-skeleto-genital syndrome²

Management and treatment

Management of dentin dysplasia type I should be discussed individually with each patient: it depends on the present complaint, as well as the age of the patient and the severity of the case.² 

Generally, the best course of action is to prevent cavities and gum disease with excellent oral health. As these teeth have partially or completely obliterated pulp chambers, a root canal treatment (RCT) is extremely difficult, if not impossible, to execute, favouring tooth extraction in case of abscess development or an unsuccessful RCT.²

Tooth wear is more prevalent in primary dentition, and it can be prevented or mitigated by placing stainless steel crowns or composite resin restorations to protect the dental tissue. While stainless steel crowns are harder and more durable, composite resin has a better aesthetic outcome. It can be used even when the tooth cannot receive a crown (like a tooth with a very short and thin root or unfavourable anatomy).²

Dentures, either partial or complete, are options to treat tooth loss. Due to the short roots, affected teeth have mobility, and extraction can be considered an option in case of extreme mobility. Dentures can be considered, even in childhood, as an alternative to dental implants before facial and bone development is complete.²

Dental implants can be done later in life once the patient has reached bone maturity and is done growing. However, in some cases due to early loss of teeth, extensive alveolar bone loss can occur and it might be necessary to perform bone grafts or a sinus lift to correctly place dental implants.²

FAQs

How can I prevent dentin dysplasia type I?

Unfortunately, there is no way to prevent radicular dentin dysplasia, as it is an inherited genetic disease. If there is a family history of dental abnormalities, a patient should seek genetic counselling to understand the risks of passing down the disease if they desire to have children.

How common is dentin dysplasia type I?

It is very rare to have this disease: it is estimated that one in every 100.000 people has dentin dysplasia type I.³

What is the difference between dentin dysplasia types I and II?

Type I affects both primary and secondary teeth, with crowns that appear normal (though discolouration is possible) and tooth mobility. Roots are short, blunt, and malformed, and there can be obliteration of the pulp chamber. Radicular cysts and granulomas can be present in the root apex.²

Type II affects the primary teeth with great discolouration(teeth appear to be yellow, brown, or grey) and normal roots, but with total pulp chamber obliteration in a thistle tube aspect. The permanent teeth can be unaffected or have a slight amber discolouration.²

Summary

Dentin dysplasia type I is a rare genetic disorder that causes abnormal development of the dentin, one of the tissues that make up human teeth. Affected teeth can appear normal in colour but have mobility that leads to loss. Radiographic exams, however, show abnormally short, blunt and malformed roots, with either partial or complete obliteration of the pulp chamber. 

Radicular dentin dysplasia has many differential diagnoses like dentin dysplasia type II, dentinogenesis imperfecta, odontodysplasia and other systemic conditions that might mimic the clinical appearance, and a health professional should use clinical and radiographic evidence to correctly diagnose the patient. 

There is no cure, but management is possible with adequate dental care: stainless steel crowns or composite restorations can be performed to aid in tooth wear, and in case of a dental abscess, a root canal can be performed - although it is difficult and often unsuccessful due to the obliteration of the pulp chamber. Tooth extractions might be necessary when root canal treatment is unsuccessful or mobility is mobility’s too extensive, and dentures (either partial or complete dentures) can be crafted to aid the patient’s oral health, as well as dental implants can be considered once the patient’s done growing.