Overview

Dentin dysplasia type I (DD-I), also known as radicular dentin dysplasia, is a rare genetic disorder that affects dentin, a mineralised tissue beneath the enamel that forms the body of the tooth. DD-I affects both baby teeth and adult teeth. In dentin dysplasia type 1, the teeth usually look normal in shape and colour. However, key characteristics of this disease include extremely wobbly teeth and early tooth loss. DD-I was first reported by Ballschmiedel in 1922.¹ He described a family with six children whose teeth had short, rounded roots and changes in the inner canal. He referred to these as ‘rootless teeth’ .¹

According to Shield’s classification, dentin dysplasia is divided into dentin dysplasia type I and dentin dysplasia type II or anomalous dysplasia of dentin.² Dentin dysplasia II affects both the primary and the permanent dentition. The colour of the primary dentition changes. 

Pathogenesis of DD-I

DD-I is an autosomal dominant condition, meaning only one copy of a gene is needed to cause significant symptoms.^3,5 The mechanisms of this condition are still not well understood, and several studies have suggested many theories. Researchers have suggested that DD-I includes abnormal development of tooth roots and dentin (Hertwig epithelial root sheath and dental papilla), which has a knock-on effect on the other, causing the visual changes described by Ballschmiedel.⁵ The genes involved in dentin formation include dentin sialophosphoprotein (DSPP), which is commonly mutated in various inherited dental disorders.⁶

Clinical features

In DD-I, teeth appear normal visually. However, teeth may be hypermobile (very wobbly) and may fall out earlier than expected. When these teeth are examined, their roots are short, hence the term ‘rootless teeth’. In DD-I, both genders are equally affected, and both sets of teeth (milk and adult) are affected, which may result in permanent tooth loss. In some cases, teeth can appear more see-through (translucent) than normal.^5,7

Radiographic features

During an X-ray, the roots of the teeth appear sharp, narrow and pointy. Typically, the pulp of a tooth appears darker inside, while harder parts such as enamel and dentin appear whiter. However, X-rays of baby teeth with DD-I show that the inside of the tooth contains a calcified tissue. X-ray images of adult teeth before they erupt show a thin, crescent-shaped space, indicating a pulpal remnant. In some cases, taurodontism can be seen in molars of DD-I patients, where the pulp space appears enlarged, and roots appear short.^5,7

Histopathologic features

A microscope is used to examine structural cellular changes in the teeth of individuals with DD-I. 

The enamel and primary dentin layer (mantle dentin) appear normal. Deeper layers of dentin lack a defined structure, with areas of nodular masses of abnormal dentin. The characteristic appearance is described as “lava flowing around boulders”. Pulpal remnants can be seen between the normal and abnormal dentin.⁷

Differential diagnosis

DD-I should be differentiated from other diseases or conditions, such as DD-II, dentinogenesis imperfecta, and regional odontodysplasia, based on the teeth involved, hereditary patterns and structural differences. A comparison of each condition is shown in the table below:⁴

Table 1: A comparison of how DD-I presents alongside similar dental conditions

Management of DD-I

Treatment and management options depend on an individual’s age and the severity of their condition. Practising excellent oral hygiene, such as regular brushing and flossing, can maintain or improve current tooth health. Protective measures, such as stainless steel caps and composite veneers, can help protect baby teeth from wear and damage. It is important for dentists to treat infections and damage to adult teeth; however, due to structural changes in the tooth interior and roots, this can be challenging, and removal of the affected teeth may be required to prevent severe infections. If teeth need to be removed, replacements, including dentures and implants, are considered to restore function. Additional procedures may be required to facilitate replacements, such as ridge augmentation and bone grafts to ensure implants fit correctly.⁵

Summary

DD-I is a rare disorder which causes disturbances in the dentin formation. The teeth appear normal in colour, with short or absent roots. The characteristic features include hypermobility and premature tooth loss. DD-I is an autosomal dominant disorder, where both baby and adult teeth are affected. The radiographic features include blockage of the pulp and root canals. DD-I should be recognised from other conditions such as DD-II, dentinogenesis imperfecta and regional odontodysplasia. Proper oral hygiene measures are necessary to maintain oral health. Dentists play a crucial role in educating people about the importance of oral hygiene and early intervention in dental care.