Figure 1: Classification of dens invaginatus, adapted from Oehlers (1957) class I (a); class II (b, c); class III (d)
Adrian Espinoza Muñoz, Jorge Paredes Vieyra, Fabian Ocampo Acosta and Francisco Javier Jiménez Enriquez review dens invaginatus in root canals, and measure how best to approach the condition.
Dens invaginatus (DI) is a growth-related malformation resulting from invagination of the crown before calcification has developed (Hüllsmann, 1997). As the hard tissues are created, the invaginated enamel organ creates a small tooth inside the forthcoming pulp chamber. In the severe type of dens invaginatus, there is a folding of Hertwig’s epithelial sheath into the developing root (Bhaskar, 1986).
The etiology of this dental malformation remains controversial, and although many hypotheses have been proposed, none have been supported or widely accepted. Numerous issues have been suggested to explain this uncommon dental formation, including trauma, infection, inhibition of the growth of specific cells, disruption of factors that regulate the formation of the enamel organ, and links to genetic factors (Hüllsmann, 1997; Alani and Bishop, 2008; Hosey and Bedi, 1996).
Salter (1855) described a radiographic image that seems to be ‘a tooth within tooth’. DI can be catalogued according to its complexity, with the well documented classification of Oehlers (1957) describing three forms according to the complexity of the invagination into the root: Type I is limited to the crown, whereas type II invagination extended inside the root, ending as a blind pod. Type III invagination invades the entire root and exit apically or laterally (Figure 1). Its occurrence varies from 0.3% to 10% (Hovland and Block, 1977), with the upper lateral incisor the most frequently affected tooth followed by the upper central incisor.
Teeth with DI pose a problem for root canal therapy because of their complex anatomy. Numerous clinical procedures have been proposed such as nonsurgical root canal treatment (Hovland and Block, 1977), combined root canal and surgical treatment (Benenati, 1994), planned replantation (Lindner et al, 1995) and extraction (Rotstein et al, 1987). However, planned replantation and extraction are often the last decision. Outcome studies for the management of teeth with DI are, however, unavailable due to the rarity of the condition.
The following clinical condition describes the combined orthodontic-endodontic treatment of a maxillary central incisor diagnosed with infected dens invaginatus (Oehlers’ type III) and associated apical periodontitis. A surgical operating microscope was used as an aid for both diagnosis and the planning of treatment.
An 11-year-old female patient presented at the Orthodontic Graduate School in Tijuana, México with a story of pain and tenderness in the maxillary left anterior area. The principal condition was the un-erupted left maxillary central incisor (UL1).