Dens invaginations are a rare developmental defect most commonly affecting maxillary lateral incisors, with very few reported cases in mandibular teeth. We describe a rare case of bilateral first mandibular premolar dens invaginations type I, where apparently health teeth presented with periapical pathology.
A 25-year-old medically fit and well male patient presented twice within a two-week period at a dental emergency clinic. First presentation was due to a 7-day history of constant aching pain affecting the left side of his face, and the patient could isolate the pain to the left mandible. Extraoral and intraoral soft tissue examination was unremarkable. Periodontally there were no pathological pockets, and oral hygiene was good. Dentally the patient had an unrestored adult dentition with absent third molars and no detectable caries. The lower left first premolar tooth was markedly tender to percussion, and a long-cone periapical radiograph (LCPA) revealed a significant periapical radiolucency (Figure
Long-cone periapical radiographs showing the left 1(a) and right 1(b) mandibular premolars. Well-demarcated periapical radiolucencies can be seen associated with the first premolar teeth bilaterally. The white arrows indicate radiolucent “invaginations” on the occlusal surfaces of the teeth.
Two weeks later, the patient reattended the same dental emergency clinic complaining of constant aching pain affecting the lower right mandible. Once again, no decay or periodontal issues were found clinically, but LCPA examination of the lower right quadrant showed periapical pathology associated with the mandibular right first premolar tooth (Figure
With two teeth loosing vitality without any obvious coronal or periodontal pathology, our differential diagnosis included trauma or developmental defects. There was no history of trauma, and indeed this site would be an unusual location for a traumatised tooth, usually affecting more anterior teeth. Developmental defects were suspected, and on examination of the radiographs, radiolucent voids were seen on the occlusal surfaces of the premolar teeth. Our diagnosis was of dens invaginations (DIs) of the first mandibular premolars (
DI is a dental developmental abnormality arising during early odontogenesis and before calcification. Invagination of a portion of the enamel organ into the dental papilla forms infoldings lined by enamel into the crown of the tooth [
DI’s are most commonly classified into three groups depending on the depth of invagination. In type I (79%), the invagination is limited to the crown, not extending past the amelocemental junction (ACJ). In type II (15%), the invagination extends past the ACJ into the root but does not communicate with the periodontal ligament. In type III (5%), the invagination extends through the root and either connects with the periodontal ligament laterally (type IIIA) or apically through the apical foramen (type IIIB) [
Embryology, trauma, and infection have been suggested as potential causes of DI, but the aetiology remains disputed [
Clinically DI is difficult to diagnose as coronal anatomy can appear normal, as in this reported case. Signs suggestive of DI include deep foramen caecum, exaggerated cingulum pits, penetrating fissures, grooved palatal enamel, talon cusps, and incisal notching [
Radiographic features can be easier to distinguish. The following appearances have been described: alterations in enamel morphology, radiolucent pocket, tear-shaped loop, undilated fissure, pseudocanal, blunting of pulp horns, and gross alteration of internal anatomy of the crown or root [
If DI is suspected, early intervention is advocated to prevent pulpal necrosis. Fissure sealant or flowable composite application to suspect areas of newly erupted teeth is essential [
If, like in this case, DI is only diagnosed following pulpal necrosis, endodontic therapy to save the tooth is required. This may require specialist referral as endodontic treatment of DI-affected teeth is often complex due to altered internal anatomy of affected teeth [
This paper highlights a rare presentation of bilateral mandibular premolar DI and shows that although DI affected teeth are anatomically abnormal, clinically this can be difficult to detect. Despite this difficulty, all general dental practitioners should be aware of the possible clinical and radiographic signs, should carefully evaluate all suspect teeth, and where appropriate treat prophylactically with a view to preventing loss of pulp vitality.
The authors declare no conflict of intrests.
R. holliday is an Academic Clinical Fellow/Specialty Registrar in Restorative Dentistry.