Dens invaginatus (DI), often called “tooth within a tooth,” is a rare developmental dental anomaly affecting tooth structure. This condition occurs when the tooth’s outer surface folds inward during its formation, resulting in a complex internal anatomy. While often asymptomatic, this altered structure significantly increases the risk of severe dental complications. This article explains the formation, classification, risks, and management approaches for DI.
Defining the Anomaly
The formation of dens invaginatus begins early in tooth development, characterized by an infolding of the enamel organ into the dental papilla. This folding creates a pocket or indentation that becomes lined with enamel and dentin as the tooth mineralizes. This structural defect creates an abnormal pathway extending from the tooth’s surface deep into the internal structure, sometimes reaching the pulp chamber. The resulting cavity can be complex. Although DI can affect any tooth, it is most frequently observed in the permanent maxillary lateral incisors.
Types and Severity Classification
The complexity of the anomaly is commonly classified using the Oehlers system, which divides the condition into three main types based on how far the fold extends from the crown toward the root. Type I is the mildest form, confined entirely to the tooth crown and not extending past the cementoenamel junction. Type II is more extensive, with the invagination extending into the root structure, remaining contained within the root canal space. Type III is the most severe form, where the invagination penetrates through the root and establishes a direct communication with the periodontal ligament.
Detection and Associated Risks
Dens invaginatus is frequently asymptomatic and is often discovered during a routine dental radiographic examination (X-ray). Clinically, affected teeth may appear slightly malformed, sometimes presenting with a distinct deep pit or groove on the surface. However, many cases show no external signs, making radiography the primary diagnostic tool.
The invagination acts as a sheltered space that traps bacteria and debris, making the tooth highly susceptible to decay. Because the enamel lining the internal fold is often thin, porous, or defective, bacteria can rapidly penetrate the structure. This allows for a quick progression of dental caries and subsequent infection of the pulp tissue, leading to pulp necrosis and the development of a periapical abscess.
Therapeutic Approaches
Treatment for dens invaginatus depends on the classification type, the depth of the invagination, and whether the pulp tissue is infected. For mild cases, such as an asymptomatic Type I, the primary goal is prevention. This involves prophylactically sealing the opening of the invagination with a filling material to block the entry of bacteria and debris.
If the invagination is deeper but the pulp remains healthy, restorative procedures are used to seal the defect and prevent future infection. When infection has occurred, leading to pulp necrosis or an abscess, non-surgical root canal therapy is required. This procedure is complex due to the intricate and aberrant anatomy of the invaginated tooth, often requiring specialized techniques to clean the internal spaces. For immature teeth, regenerative endodontic procedures may be attempted to promote further root development. If the tooth is severely damaged or the infection cannot be resolved with conservative methods, surgical intervention or extraction may be necessary.