Anatomical redesign for the treatment of dens invaginatus type III with open apexes
A literature review and case presentation
Adrian Silberman, DDS,
Nestor Cohenca, DDS and
James H. Simon, DDS
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ABSTRACT
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Background. Dens invaginatus is a rare dental anomaly that may give rise to many complex anatomical forms. The complexity of the internal anatomy may create challenges for the complete removal of the diseased pulpal tissue and the subsequent sealing of the canal system.
Case Description. The authors discuss the modification of the internal anatomy under the operating microscope, allowing the clinician better access to treat predictably the canal system with conventional or alternative techniques.
Conclusion and Clinical Implications. Considering the anatomical variations and the challenges that a dens invaginatus may present, a practitioner may consider a modification of the internal anatomy of the canal system to gain better access for proper instrumentation, disinfection and sealing of the root canal system using conventional or contemporary techniques.
Key Words: Dens invaginatus; anatomical variation; treatment; microscope; mineral trioxide aggregate
Dens invaginatus is a developmental malformation of teeth, showing a wide spectrum of anatomical variations. Salter1 first described anatomical anomaly in 1855 as "a tooth within a tooth." The etiology is controversial and remains unclear2; however, most authors concur that dens invaginatus results from an infolding of the papilla during tooth development.2,3 Other theories include an incomplete lateral fusion of two germs, the distortion of the enamel organ during tooth development, abnormal pressure from the surrounding tissues during tooth formation, the constriction of the dental arch in the enamel organ and a retardation or acceleration of growth of the internal enamel epithelium.4–9
Histologic examination shows that, whereas the enamel and dentin of the "outer" tooth is not affected, the enamel covering the invagination is most defective. In some areas enamel, as well as dentin, may be completely missing, causing a direct communication between the bottom of the invagination and the pulp.5
This developmental malformation is more common than we generally thought. According to the literature, the frequency varies from 0.04 to 10 percent10 and the most affected permanent teeth are the maxillary lateral incisors, frequently bilateral (43 percent),11 followed by central incisors, canines, premolars and molars.4 It also can appear in primary teeth.12 Of the three classifications designed for dens invaginatus,6,13,14 clinicians most commonly use the one proposed by Oehlers6:
- – type I—an enamel-lined invagination within the crown and not extending beyond the cementoenamel junction (CEJ);
- – type II—the enamel invagination into the root, beyond the CEJ, ending as a blind sac;
- – type III—the extension of the enamel-lined invagination through the root to form an additional apical or lateral foramen; usually, there is no direct communication with the pulp.
Teeth with dens invaginatus are prone to early development of caries and subsequent necrosis of the pulp. As a matter of prevention, clinicians are encouraged to seal the invagination prophylactically with resin.15 In cases in which the bacterial invasion has reached the pulp and necrosis is established, nonsurgical root canal treatment remains the treatment of choice. Depending on the type of malformation and the communication of the invagination with the pulp, the clinician may confine the endodontic therapy to the invaginated portion and, as a result, preserve pulp vitality.16,17 However, in most cases, the endodontic treatment must include both the invagination and the root canals.18–20 The task can become difficult, considering the anatomical variations that a dens invaginatus may present within the root canal system. Complete débridement of the root canal system is compromised by limited access; consequently, some areas may be completely untouchable when a conventional technique is used. To overcome these limitations, some researchers21 have suggested that the dens invaginatus be removed under the operating microscope. If nonsurgical endodontic therapy fails, a combined approach with apical surgery may be indicated.22
This article presents a case of a patient with dens invaginatus type III with suppurative apical periodontitis. The condition was treated by means of nonsurgical root canal retreatment using the operating microscope and an apical plug of mineral trioxide aggregate (MTA).
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CASE REPORT
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A 17-year-old boy was referred by his dentist for evaluation and treatment of a persistent infection arising from the maxillary left lateral incisor. The patient’s medical history was noncontributory. A review of the dental history revealed an account of trauma to the maxillary left lateral incisor three years prior; the tooth had been subluxated as a result of a fight. A few months after the injury, the patient underwent endodontic therapy performed by his general dentist.
The patient’s primary concern was the presence of hyperplastic tissue in his gingiva that had been present for two years. On clinical examination, the clinician (A.S.) diagnosed an intraoral sinus tract buccal to the maxillary left lateral incisor (Figure 1
). The tooth was tender to percussion and nonmobile. Periodontal probing affirmed normal attachment, with no reading greater than three millimeters. The maxillary left lateral incisor did not respond to vitality testing, though the adjacent maxillary left central incisor and canine responded within normal limits. The color of the tooth did not differ from that of the adjacent teeth, and the total number of teeth in the anterior region was normal. The clinician used a gutta-percha point to trace the sinus tract and took a periapical radiograph to confirm the etiology of the lesion (Figure 2). Radiographic examination revealed a poorly condensed root canal filling and evidence of a large radiolucency apical to the maxillary left lateral incisor. The anatomy of the maxillary left lateral incisor was consistent with a type III dens invaginatus.
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Figure 2. Periapical radiograph showing the previous root canal treatment and a gutta-percha point tracing the sinus tract.
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The clinician planned nonsurgical endodontic retreatment. He advised the patient and his parents that surgery or extraction would be an option if the nonsurgical treatment failed. Under rubber dam isolation and the use of a dental-operating microscope, the clinician performed access preparation. Initial treatment included the removal of gutta-percha from the main canal, at which point a pale yellowish exudate became apparent; this drained continuously throughout the appointment. The main canal was contained within a central cylindrical mass of hard tissue. The clinician then accessed a second area distal to the main canal. Length determination was established using radiographs, paper points and an electronic apex locator (Root ZX, J Morita, Osaka, Japan). He irrigated the root canal system with 5.25 percent sodium hypochlorite solution and 17 percent ethylenediaminetetra-acetic acid (EDTA) (Moyco Union Broach-Thompson, Montgomeryville, Pa.), then dressed them with calcium hydroxide (Ultracal XS, Ultradent Products, South Jordan, Utah) as an intracanal medication. The clinician then temporarily sealed access with Cavit Temporary Filling Material (3M ESPE, Seefeld, Germany).
Owing to a limitation in the patient’s schedule, he returned every two months for treatment over a total of six months. At the second appointment, the sinus tract was still present. Under rubber dam isolation, the clinician located a third undisclosed area mesial to the main canal system. Dark staining of the overlying dentin provided clues to its location (Figure 3). Access to the canal system included three separate entities (Figure 4). The clinician confirmed root canal lengths radiographically (Figure 5) and electronically. The mesial and distal lateral canal spaces were crescent-shaped, terminating buccally and lingually because of the fusion of the central hard-tissue cylinder with the normal root dentin. The clinician performed copious irrigation of the canals with 5.25 percent sodium hypochlorite and 17 percent EDTA throughout the procedure. He medicated the root canal system with calcium hydroxide and restored the access with a temporary sealing compound.
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Figure 3. The dark-stained dentin that provided clues to the location of the distal canal space (arrow).
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Figure 4. The access opening prior to removal of the central hard-tissue core (note alternate openings).
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When the patient returned for the third appointment for evaluation and treatment, the sinus tract had healed and the patient remained asymptomatic. In light of the complexity of the internal anatomy and the challenges it presented for the cleaning and sealing of the individual canal spaces, the clinician decided to remove the central dentinal core and create a single canal space. Under magnification and illumination, he removed the dentinal core using ultrasonic instrumentation (P5, Satelec, Pierre Rolland Phils. Corp., Merignac, France) (Figure 6). The clinician repeated the irrigation protocol previously described, dressed the canal with calcium hydroxide and placed a temporary restoration.
Two months later, the patient returned for completion of the nonsurgical endodontic retreatment. Under rubber dam isolation, the clinician performed a final irrigation using 10 cubic centimeters of 5.25 percent sodium hypochlorite. The clinician sealed the apical one-third of the root canal with 3 to 4 mm of gray MTA (ProRoot MTA, Dentsply Tulsa Dental, Tulsa, Okla.). He then sealed the middle one-third of the root canal using Kerr pulp canal sealer EWT (Kerr, Romulus, Mich.) and thermoplasticized gutta-percha (Obtura, Fenton, Mo.). The clinician placed the filling material incrementally and condensed it to the level of the middle and coronal thirds of the canal, up to a level of 3 mm below the CEJ. He condensed composite resin (XRV Herculite, Kerr, Orange, Calif.) to the level of the gutta-percha, consciously placing it below the osseous level to increase the resistance to fracture and to create a permanent seal of the coronal access (Figure 7).
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Figure 7. Immediate posoperative periapical radiograph taken after final canal obturation and placement of a coronal seal.
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During the nine-month follow-up period, the patient remained asymptomatic. Clinically, the tooth was not tender to percussion or palpation and the findings of the periodontal examination were within normal limits. The radiograph demonstrates evidence of advanced apical bone healing (Figure 8).
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DISCUSSION
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The literature includes only a few reports of cases involving endodontic retreatment of a dens invaginatus.23,24 The case described here demonstrated the anatomical difficulties that can lead endodontic failure and the development of periapical pathology.
The successful management of a dens invaginatus depends mainly on the ability to gain access to and disinfect the root canal system in light of its complex and variable presentation and unpredictable morphology. Moreover, the root canal filling also can become a challenge, considering the restricted access and the irregular shape of the root canal system. In cases of dens invaginatus type III, the removal of the dens or central hard tissue, under the use of the operating microscope, may enhance the clinician’s ability to disinfect and seal that irregular space with a more predictable outcome.
In this case, the clinician used MTA as an apical plug owing to the periapical inflammatory resorptive process that resulted in an irregular apex and made sealing the root system with conventional gutta-percha compaction clinically challenging and unpredictable. The use of MTA as an apical seal for immature roots, or resorbed apexes, has been reported in the literature in the last several years.25–29 The results of those studies showed that MTA produced apical hard-tissue formation with significantly greater consistency owing to its good sealability and high degree of biocompatibility. Therefore, it has become an excellent alternative to conventional long-term calcium hydroxide therapy. In addition, the procedure allows the immediate rehabilitation of the crown, thus increasing the resistance to fracture and enhancing the esthetic result.30
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CONCLUSION
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Using the fundamental concepts regarding the etiology of endodontic infections and current instrumentation techniques, we have presented an alternative approach for the treatment of teeth with complex anatomy. Considering the anatomical variations of root canal systems and the challenges they present for treatment, a practitioner may decide to modify the internal anatomy of the canal system to gain better access for proper instrumentation, disinfection and sealing using conventional or contemporary techniques. Future developments in instrumentation and disinfecting medicaments may provide alternatives to the techniques described.
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FOOTNOTES
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When this article was written, Dr. Silberman was a postgraduate resident in endodontics, Division of Surgical, Therapeutic and Bioengineering Sciences, University of Southern California School of Dentistry, Los Angeles. He now maintains a private practice in Murrieta, Calif.
Dr. Cohenca is an assistant clinical professor, Department of Endodontics, School of Dentistry, University of Washington, Seattle. Address reprint requests to Dr. Cohenca at Department of Endodontics, School of Dentistry, University of Washington, 1959 NE Pacific St., PO Box 357448, Seattle, Wash. 98195-7448, e-mail "cohenca{at}u.washington.edu".
Dr. Simon is the Wayne G. and Margaret L. Bemis Professor and director, Post-Graduate Endodontics, Division of Surgical, Therapeutic and Bio-engineering Sciences, University of Southern California School of Dentistry, Los Angeles.
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REFERENCES
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ABSTRACT
CASE REPORT
