Introduction

Dentin dysplasia type I (DDI) is a rare inherited condition that primarily affects the teeth, specifically the root formation. The dental crowns may appear normal, but the roots are often short, conical, or absent, with a destroyed tooth pulp chamber. Periapical lesions are commonly seen along with this condition. DDI affects both primary and permanent teeth, resulting in instability and early loss of teeth.

Differentiating DDI from similar dental conditions is crucial because an accurate diagnosis allows practitioners to avoid mismanaging their patients, provide appropriate treatment planning, and positively affect long-term dental outcomes. DDI has common clinical features with dentin dysplasia type II and dentinogenesis imperfecta (DGI), and using clinical examinations, radiographs, and genetic testing, it will supply valuable clinical evidence to support the diagnosis.¹

In this article, we will explore what DDI is, what other dental disorders we have to rule out while diagnosing dentin dysplasia type 1, and what treatment strategies to manage this condition.

Clinical features

Tooth appearance

In DDI, crowns are typically normal in shape, size, and colour, making it difficult to detect early on. There may be minor variations in discolouration or isolated white spots, but they can be inconsistent. The tooth enamel (the protective layer over the tooth) usually looks normal, although there can be some variation in terms of thinner dentin.^1,2

Root abnormalities

The roots can be short, blunted, malformed, or completely absent, which earns DDI the nickname of "rootless teeth". Radiographs frequently reveal destroyed or crescent-shaped pulp chambers, pulp stones, and periapical radiolucencies. The condition possesses subtypes (Ia–Id) based on the overall degree of root and pulp development.^1,2

Dental function

It is common for teeth to be highly mobile in DDI; therefore, they often are lost prematurely, either during childhood or as a late adolescent. Additionally, a compromised function of teeth due to a lack of root support and difficulty chewing. 

Even non-decayed teeth can present with spontaneous abscesses and/or cysts, leading to further need for treatment with prosthetic restoration or orthodontic management.^1,2

DDI subtypes

DDI has four subtypes, which include the following: 

• Subtype 1a: has no roots and pulp chambers, and has many periapical lesions
• Subtype 1b: has no roots and pulp chambers with few periapical lesions
• Subtype 1c: has approximately normal-length roots with pulp stones and has many periapical lesions
• Subtype 1d: has approximately normal length roots and pulp stones with few periapical lesions

Although rooted in the same condition for dentin development, there are differences in the severity of root and pulp problems between the four subtypes.²

Dentinogenesis imperfecta (DGI)

Clinical presentation

Dentinogenesis imperfecta (DGI) is a genetic disorder characterised by abnormal dentin production, affecting primary and permanent teeth, with primary teeth often being more severely affected. The teeth appear discoloured (blue, brown, amber, or grey) with a translucent or opalescent appearance. 

The tooth's enamel is fragile and can easily chip away, leading to quick deterioration. Radiographs typically demonstrate short roots, a bulbous (or a strong deviation from the normal) crown, cervical constriction, and early destruction of the pulp chamber.³

Genetic basis

Most cases of non-syndromic DI are due to mutations in the DSPP gene. If DI is associated with osteogenesis imperfecta (OI), then it is due to mutations in either the COL1A1 or COL1A2 genes. In some cases, others may be due to mutations in other genes, such as FKBP10.³

Distinguishing features

DGI shows features such as:

• Discoloured (blue, brown, amber, grey) bulbous crowns with a small occlusal appearance
• Cervical constriction
• Short, thin roots
• Rapid dental wear
• Early pulp obliteration

Meanwhile, DDI may demonstrate:

• Normal or only slightly affected crowns
• Frequently with “rootless” or very short roots (as in DD-I again)
• Pulp chambers may be obliterated or crescent-shaped

Although the genetic causes differ, common mutations in the DSPP gene are found across both disorders. However, other gene mutations may be present in one disorder but not the other, even in rare cases.^3,4

Other dental anomalies to consider

Regional odontodysplasia (RO)

Regional odontodysplasia (RO) is characterised generally by the presence of a few teeth affected by a local disorder, hence the name regional. It is characterised by thin and hypoplastic enamel and dentin, large pulp chambers, and a unique appearance of the tooth as a "ghost tooth" on radiographs.⁵

Amelogenesis imperfecta (AI)

Amelogenesis imperfecta (AI) is a disease causing generalised enamel defects such as hypoplasia or hypocalcification, but has normal roots and pulp.⁵

Other root anomalies

Other root anomalies can include root fusion, taurodontism, and pulp calcification, among others, that may be associated with systemic conditions such as Ehlers-Danlos syndrome (EDS) or osteogenesis imperfecta.^6,7

Genetic testing and molecular diagnosis

Genetic markers for DDI

DDI is a genetically autosomal dominant disorder. Mutations in the genes SSUH2, VPS4B, and SMOC2 related to DDI were identified in different families. The SSUH2 gene mutation disrupts tooth development in humans and animals. In some of the cases, the inheritance pattern was autosomal recessive, and no alterations in DSPP or SMOC2 genes were found, suggesting that there were other genetic factors yet to be identified. Next-generation sequencing (NGS) advances our ability to correctly identify DDI by providing the ability to screen these target genes.^7,8,9

Treatment and management

DI treatment strategies

Conservative management aims to preserve teeth and delay loss through good oral hygiene, regular dental visits, and preventive strategies. ¹ Endodontic treatment, also known as root canal treatment, is also available, but they are difficult to carry out due to the presence of variable root malformations.

The use of newer methods, such as 3D-guided techniques, can increase the likelihood of success.¹⁰ Teeth that are severely affected have other options available, such as extraction, followed by prosthetic rehabilitation, including an implant, once jaw growth is complete. Cases with higher classification levels may require a multidisciplinary approach to meet aesthetics and function.¹¹

Long-term prognosis

Prognosis varies depending on the timing of diagnosis, the severity of root involvement, and the degree of compliance with preventive care.⁸ Early loss of teeth is common but may be acceptable if appropriately managed with timely intervention, ongoing maintenance, and monitoring. The use of implant-supported prostheses provides a significant qualitative benefit to an adult patient once the growth of the jaw is complete.¹¹

Summary

Dentin dysplasia type I (DDI) is a rare inherited disorder mainly affecting teeth, particularly the formation of their roots. While the crowns may look normal, the roots are usually short, conical, or even absent, leading to issues like unstable teeth and early tooth loss. It is important to identify DDI correctly to avoid mismanagement and plan proper treatment.

DDI can share features with other dental conditions, such as dentin dysplasia type II and dentinogenesis imperfecta (DGI). Diagnosis can be supported through clinical exams, radiography, and genetic testing. In DDI, the crowns appear normal, but there can be slight discolourations. The roots may be very short or missing, leading to the term "rootless teeth. " X-rays often show damaged pulp chambers or other issues. Teeth affected by DDI tend to be loose and may be lost prematurely, causing functional difficulties like trouble chewing.

There are four subtypes of DDI, varying in root and pulp development severity. Dentinogenesis imperfecta (DGI) is also a genetic condition and is characterised by discoloured teeth that can chip easily. It mainly affects primary teeth more severely and shows unique patterns on X-rays, such as short roots and early pulp destruction. Distinguishing DGI from DDI is important, as they present different clinical features despite some common genetic mutations. Other dental anomalies to consider include regional odontodysplasia, which affects a few teeth with large pulp chambers, and amelogenesis imperfecta, which leads to enamel defects but normally structured roots.

Genetic testing can identify mutations related to DDI and assist in diagnosis. Management of DDI focuses on preventive care and maintaining teeth. Treatment options include endodontic procedures, though these can be complex due to root problems. In severe cases, extraction and prosthetic rehabilitation may be needed. Prognosis relies on accurate diagnosis and timely management, with the potential for significant improvement through prosthetic solutions after jaw growth completion.