Introduction
Tooth formation is a highly regulated, intricate biological process that depends on a number of variables for its eventual success. Clinical alterations or modifications will be visible if tooth growth is interrupted in any way. One of the main effects of developmental disruptions is a change in size, where teeth might seem bigger, smaller, or even entirely different from what is expected in terms of their clinical appearance. Throughout this article, one such developmental anomaly is further discussed.
What Is Dens Invaginatus?
Dens invaginatus (DI) or "dens in dente" is defined as a developmental disturbance of the tooth during odontogenesis (stage of tooth development) characterized by enamel invagination (turning inside to form a cavity-like appearance). If the invagination is observed, along with the presence of a foramen cecum, it gives the diagnostic probability that there is a communication between the cavity of the invagination and the pulp chamber or root canal chamber of the tooth. In such cases, a treatment procedure called root canal pulp capping may be required.
Dens invaginatus is less frequent or relatively less observed in the primary dentition than in the permanent dentition. According to traditional literature, the prevalence rate of dens invaginatus (DI) in permanent dentition varies from around 0.04 to10 percent. Reports of severe forms of dens invaginatus are extremely rare or less common. DI has a 3:1 male-to-female predilection.
What Are the Different Types of Dens Invaginatus?
The invagination in DI may be categorized as follows-
i. Coronal Type
In this type, the pitting is either slight or prominent and is confined only to the crown of the tooth and does not involve the tooth root. Hence the chances of communication to the root canal or pulp chamber of the tooth are less and restorative modalities can be adopted by the dentist to correct them, especially if the pitting is minimal.
ii. Radicular Type
This type of DI involves most of the crown and root wherein clear communication or breaches in the pulp chamber or root canal is possible. In severe cases of DI, tooth extraction may be required. In contrast, if the tooth shows bacterial ingression and decay along with symptoms of pain or inflammation, the dentist can do endodontic treatment or root canal treatment.
The difference between these two types is that while the coronal type of invagination is lined only with enamel, the radicular type of invagination is lined with the cementum layer of the tooth. On clinical examination, as mentioned earlier, suspicion of an extremely deep fissure or pit on the lingual surface of anterior teeth or in the occlusal pits or surfaces of the posterior teeth will be a visual diagnostic criterion. However, the only reliable diagnostic criterion remains radiographic examination using three-dimensional or two-dimensional imaging like CBCT (cone beam computed tomography) or OPG (orthopantomogram) to diagnose this anomaly definitively.
In the popular classification system used to classify Dens invaginatus given by Oehlers, the basis of categorizing is upon the extent of invaginations:
i. Type 1: The invagination extends to or ends as a blind sac within the crown, tooth enamel, and dentin region.
ii. Type 2: The invagination extends into the root, i.e., apically beyond the cementoenamel junction.
iii. Type 3: The invagination extends even beyond the cementoenamel junction wherein a second "apical foramen" (other than the original foramen of the tooth that contains nerve and blood vessels) is evident.
iv. Radicular Dens Invaginatus (RDI): In this type, the invagination originates in the root, caused by the infolding of Hertwig's root sheath epithelium into the root, post the completion of crown development.
What Is the Clinical Significance of Dens Invaginatus?
The clinical significance of dens invaginatus is the risk of pulpal inflammation. Although enamel may line the coronal defects that may appear quite simple or superficial, these areas lined by the enamel are thin, fragile, and affected or even missing in the crown portion of the teeth. The cavity is thus only separated from the pulp chamber or the root canals by a thin wall that creates a passage into the external oral environment through a narrow constriction. As a result, patients may not only complain of food lodgement and sensitivity but maintaining oral hygiene is difficult when it comes to brushing or keeping the affected tooth's pit areas clean, creating favorable conditions for the development of dental caries. Deep dental carious lesions may thus rapidly involve the pulp and cause various dental caries symptoms such as pain and sensitivity.
How Is Dens Invaginatus Diagnosed?
Dens invaginatus is usually diagnosed incidentally or during a routine dental examination. Upon clinical examination, the dental surgeon can visualize dens invaginatus in the permanent maxillary lateral incisors, which is the most commonly affected tooth by this condition. Deep lingual pits usually prompt the dentist to investigate further to differentiate between a deep pit and a Dens invaginatus. However, anterior teeth with dens invaginatus always have a normal shape and size in terms of crown structure. In the posterior teeth like premolars and molars, these teeth may possess an anomalous appearance when the pit is deepened palatally. Dens invaginatus commonly affects the maxillary lateral incisors, and case reports of occurrence in the mandibular anterior or posterior teeth are relatively rare in the dental literature.
Two-dimensional imaging, be it through intraoral periapical or panoramic radiographs, remains a commonly used radiographic method for detecting endodontic involvement of the invagination. If the tooth in question exhibits pulpal or periapical disease symptoms, then endodontic therapy is needed. However, three-dimensional images formed by computed tomography (CT) or CBCT (Cone beam computed tomography) are more reliable than these two-dimensional radiographs in diagnosing this developmental condition. That is because detailed information or analysis can be made before treatment about the internal root canal anatomy that may vary from individual to individual. With the widespread usage of CBCT imaging in endodontics, the diagnosis, and management of DI are easier for the dental surgeon to plan preoperatively and have an added advantage in analyzing complex root canal systems using low radiation dose compared to traditional CT scanning.
How Is Dens Invaginatus Treated?
The dental surgeon may consider extraction of the tooth only when endodontic treatment fails to control symptoms or in hopeless prognosis cases wherein the tooth decay is severe and considered a failure for endodontic sitting. However, endodontic or root canal treatment remains the first choice when the patient complains of pain or food lodgement. Furthermore, according to the reports, in cases of dens invaginatus, using a composite resin, amalgam, or glass ionomer cement as filling material in the long term results in the possibility of chronic irritation to the pulp or microleakage leading to pulp vitality loss. This is why most dentists prefer endodontic therapy to simple restorative treatment, especially in moderate to severe cases of DI.
Conclusion
Dens invaginatus requires a proper radiographic diagnosis, preferably by three-dimensional imaging, and also a timely treatment-based approach by the dentist or the endodontist wherein the treatment or endodontic approach is dependent only upon the extent of caries and pulpal inflammation inflicted by the invagination created in the tooth crown or root.
Frequently Asked Questions