CASE REPORT Complex endodontic treatment of an immature type III dens invaginatus. A case report E. R. Fregnani 1,2 , L. F. B. Spinola 2 , J. R. O. So ˆ nego 2 , C. E. S. Bueno 2 & A. S. De Martin 2 1 Department of Stomatology, A. C. Camargo Cancer Hospital, Sa ˜o Paulo; and 2 Sa ˜ o Leopoldo Mandic Dental Research Centre, Campinas, Sa ˜ o Paulo, Brazil Abstract Fregnani ER, Spinola LFB, So ˆ nego JRO, Bueno CES, De Martin AS. Complex endodontic treatment of an immature type III dens invaginatus. A case report. International Endodontic Journal, 41, 913–919, 2008. Aim To report the endodontic treatment of an immature maxillary central incisor with dens invaginatus. Summary Dens invaginatus is a rare malformation of teeth, probably resulting from an infolding of the dental papilla during tooth development. The present case describes the complex endodontic treatment of a type III dens invaginatus in an immature maxillary central incisor with a necrotic pulp and abscess formation. The initial treatment goal was to achieve apexification of the pseudocanal root and conservative root canal treatment in the main canal. Following 1-year of treatment with calcium hydroxide dressings, radiography revealed a healing response, but no sign of a hard tissue barrier at the apex. Periapical surgery with the placement of a zinc oxide cement (IRM) root-end filling was considered successful at the 4-year follow-up. Key learning points • The complexity of the canal system and open apex in dens invaginatus present a challenge to endodontic treatment. • Correct diagnosis and treatment planning are fundamental to treatment of dens invaginatus. • Periapical surgery is indicated in cases of unsuccessful apexification in immature teeth with dens invaginatus and nonvital pulp. Keywords: calcium hydroxide, dens invaginatus, endodontic treatment. Received 8 July 2007; accepted 4 February 2008 doi:10.1111/j.1365-2591.2008.01414.x Correspondence: Dr Eduardo Fregnani, Rua Alves Guimara ˜ es, 150/1307, Sa ˜ o Paulo, SP 05410-000, Brazil (Tel.: 55 11 2189-5129; fax: 55 11 2189 -5100; e-mail: erfreg@terra.com.br). ª 2008 International Endodontic Journal International Endodontic Journal, 41, 913–919, 2008 913