CASE REPORT 145 pyri Co gh Not for Publicationt b y Q u Dennis J Koenen, Dieter Pahncke i N n o t t r f e o ssence Gemination or fusion: use of a CT scan to assist in diagnosis and endodontic treatment of a maxillary second molar – a case report Dennis J Koenen Dieter Pahncke both Klinik und Polikliniken für Zahn-, Mund- und Key words dental anatomy, fusion, gemination, hyperdontia, supernumerary teeth Kieferheilkunde ‘Hans Moral’, Department of Operative Dentistry, University of Rostock, A 21-year-old female patient was referred to the Department of Operative Dentistry of the University Germany of Rostock because of complaints in the right maxilla indicating pulpitis in a maxillary molar. Tooth 17 Correspondence to: had an extra cusp with an additional root on the buccal aspect. The point of fusion of the additional root DJ Koenen, Polikliniken für Zahnerhaltung, with the regular tooth created an environment conducive to caries. The pulp chamber of the super- Postfach 10 08 88, numerary root was opened during caries excavation and the clinical examination suggested a separate, D-18055 Rostock, Germany Tel: +49 381 494 - 6531 supernumerary root canal. A standard radiograph showed no extraordinary root canal configuration, so Fax: - 6509 during the first appointment only the supernumerary root canal was treated. Owing to continuing dis- Email: dennis.koenen @uni-rostock.de comfort, a more precise radiological diagnosis was made using computed tomography (CT). The CT scan clearly showed that the separate root canal under the extra cusp communicated with the regular root canal system. Therefore, the diagnosis ‘double teeth with incomplete gemination’ was made and fol- lowed by root canal treatment for all the root canals. Introduction variations in morphology, and several pulp cavities and root canals are a challenge regarding root canal Anomalies of tooth morphology develop from a fail- treatment. Therefore, a precise diagnosis and detailed ure in the regular processes of invagination during treatment planning are required. odontogenesis1. If there is a failure in odontogenesis Whereas hyperdontia less frequently occurs in by an over- or under-production in the dental ridge1 primary rather than in permanent teeth1,4,5, the preva- and if increased invaginations occur, additional conse- lence in the permanent dentition of anomalies such as quences will be anomalies of tooth numbers in addi- gemination and fusion seems to be considerably tion to gemination, fusion, concrescence or dens lower6-8. However, these anomalies are very rare: invaginatus1-3. Teeth with a large number of possible 0.5% in primary and 0.1% in permanent teeth9 or ENDO (Lond Engl) 2008;2(2):145–151 146 Koenen/Pahncke Gemination or fusion pyrig Fig 1 (left) Not forCo Publicationh Tooth 17 with extra t cusp, initial situation. b y Q u i N n o t t r f e o ssence Fig 2 (right) Open pulp cavity of the supernumerary root. Fig 3 Diagnostic radio- 0.6 to 2.8% for the first and 0.1 to 1% for the second graph with a root canal 8 instrument inserted into dentition . Most often, maxillary as well as mandibu- the buccal root canal. lar incisors are affected. Anomalies in molars, however, Rubber dam was fixed are extremely rare. using wedges. Reports about the prevalence of hyperdontia vary according to author and examined group of patients, between 0.2 to 1% in primary and 2.1 to 3.8% in per- manent teeth1,4,5. In almost half of these cases of supernumerary teeth, there is a mesiodens in the max- illa and patients are eight times more frequently male. Currently, the aetiology of these malformations is unknown. Local metabolic interferences, that occur during morpho-differentiation of the tooth germ10, heredity11 and genetic predisposition2 are discussed as well as traumatic incidents12. Fig 4 Gutta-percha cone inserted in the extra root canal. ENDO (Lond Engl) 2008;2(2):145–151 Koenen/Pahncke Gemination or fusion 147 pyri Co gh Not for Publicationt b y Q u i N n o t t r f e o ssence Fig 5a Computed tomography showing the communicating root canals. Case report performed using computed tomography (CT) to verify A 21-year-old female patient from Wismar with no any communication between the additional root canal relevant medical history was referred to the Depart- and the root canal system of the regular pulp. To ment of Operative Dentistry of the University of Ros- achieve better diagnostic assessments, a gutta-percha tock, Germany, because of complaints in the right cone was inserted into the buccal root canal (Fig 4). maxilla indicating inflammation of the pulp. Tooth 17 The CT scan clearly showed a separate root canal showed an extra cusp with root at the buccal aspect under the extra cusp, communicating with the regu- (Fig 1). The point of fusion of the additional root with lar pulp (Fig 5). Therefore, the diagnosis ‘double teeth the regular tooth appeared to be a location with a with incomplete gemination’ was made, with root predilection for caries. The patient had suffered from canal treatment for all root canals planned as a conse- spontaneous, intense pain for several days, and had quence. taken an analgesic. The tooth was highly responsive After rubber dam had been applied, preparation to thermal tests (cold and warm) and also slightly of the access cavity and extirpation of the vital pulp tender to percussion. Probing depths were in the range tissue was carried out under local anaesthesia. of 2 to 3 mm and there was no swelling around the Inspection of the pulp chamber floor revealed three tooth. The pulp chamber of the supernumerary root further root canals. Working length was determined was opened during caries excavation (Fig 2). The clin- electronically (Raypex 5, VDW, Munich, Germany), ical examination suggested a separate, supernumerary supported by the information gained from the CT root canal. The periapical radiograph revealed no scan. Preparation of all root canals with manual stain- extraordinary root canal configuration (Fig 3), so only less steel K-files (VDW) up to ISO #55 for the palatal the supernumerary root canal was treated during the and ISO #40 for the buccal canals was performed, first appointment. using a step-back technique. Because of the patient’s continuing complaints of Fig 6 shows the orifices of the extra root canal extreme thermal hypersensitivity and recurrent, and the palatal root canal. Fig 7 shows that the reg- intense and long-lasting spontaneous pain, indicating ular mesio- and disto-buccal root canals have an irreversible pulpitis of the yet untreated root canal merged at the bottom of the pulp cavity. The gutta- system, a more precise radiological assessment was percha cone inserted in the additional root canal ENDO (Lond Engl) 2008;2(2):145–151 148 Koenen/Pahncke Gemination or fusion pyrig Fig 5b Computed Not forCo Publicationh tomography showing t the communicating b y root canals. Q u i N n o t t r f e o ssence 1 7 13 19 2 3 ENDO (Lond Engl) 2008;2(2):145–151 Koenen/Pahncke Gemination or fusion 149 pyrig Not forCo PublicationFig 6 h(left) The extrat and the palatal rootb canal. y Q u i N n o t t r f e o ssence Fig 7 (right) The merged mesio- and disto-buccal canals. Fig 8 (left) Gutta-percha cone indi- cating the fusion of the root canals. Fig 9 (right) Corresponding enlarge- ment of Fig 8. Fig 10 Root canal fill- clearly shows the communication of the supernu- ing performed in lateral merary root canal with the regular pulp (Fig 8, and condensation tech- nique. the corresponding enlargement Fig 9). After cleaning, shaping and irrigating all root canals with 1% sodium hypochlorite, calcium hydroxide was placed as an intracanal dressing and the access cavity was temporarily sealed with CavitTM W (3M Espe, Seefeld, Germany). A week later, the dressing was changed and the root canal system was irrigated again with 1% sodium hypochlorite. At the fourth appointment the patient was symptom-free, and the root canals were obturated with gutta- percha cones (ISO #55 and #40, VDW) and AH Plus® (Dentsply DeTrey, Konstanz, Germany) as sealer using the lateral condensation technique (Fig 10). ENDO (Lond Engl) 2008;2(2):145–151 150 Koenen/Pahncke Gemination or fusion pyrig Fig 11 (left) Accesses to Not forCo Publicationh root canals were filled t using the adhesive b y bonding technique. Q u i N n o t t r f e o ssence Fig 12 (right) Review radiograph of root canal filling. Finally, the access cavities were cleaned and sealed In that case, the complement of teeth is exceeded by with RebildaTM white (Voco, Cuxhaven, Germany) the twin tooth1. In order to differentiate, Brook and using the adhesive bonding technique (Fig 11). Winter suggested the term ‘double teeth’7. Despite differences in aetiology, the clinical appearance of teeth with altered morphology is very Discussion similar. Even conventional radiographs are often not sufficient to show the degree of merging or cleavage. In some cases, it is difficult to distinguish between Advanced technology such as CT may provide impor- gemination and fusion. Classically, one single tooth tant preoperative information on the inner tooth germ with extra invaginations indicates gemination, anatomy in such cases6. In the present case, the exact whereas fusion (synodontia or false gemination) is configuration of the root canal system, necessary to defined as a union between the dentine of two or perform an adequate root canal treatment, was deter- more separately developing teeth1,2,6. On the mined with the help of CT. assumption that fusion is the incomplete attempt of A review of the radiograph after root canal filling two tooth buds to fuse into one, and that gemina- (Fig 12) suggests that a separate mesiobuccal part of tion is the incomplete attempt of one tooth bud to the root canal system is not entirely obturated in the divide into two9,13, one can distinguish between both apical part.