CASE REPORT  145

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Dennis J Koenen, Dieter Pahncke i N

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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 – a case report

Dennis J Koenen Dieter Pahncke

both Klinik und Polikliniken für Zahn-, Mund- und Key words dental anatomy, fusion, gemination, , supernumerary teeth Kieferheilkunde ‘Hans Moral’, Department of Operative , 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. 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 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, 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

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pyrig Fig 1 (left) Not for PublicationCo h Tooth 17 with extra t

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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.

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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

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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).

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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. However, the CT scan (Fig 5) does not on the basis of the resulting number of teeth: if the show a separate root canal in the apical part of the anomalous tooth is counted as one6 resulting in a full buccal root. As the patient was free of symptoms after dentition, it usually means that the phenomenon completion of treatment, a retreatment was not nec- represents gemination; less than a full complement essary. of teeth usually indicates fusion3,9. There are diag- Unfortunately, the patient could not attend for the nostic difficulties if fusion of a ‘normal’ tooth and a usual follow-up examination after 12 months. Never- supernumerary tooth occurs, resulting in a full com- theless, she reported that she was symptom-free plement of teeth and having the clinical appearance during the year after treatment. of gemination9. Another distinctive feature is the morphology of the root canals, which normally separate in fusion but  Conclusions communicate or merge in gemination2,9. However, there are difficulties of differentiation if complete Regarding the difficulties in distinguishing between gemination is assumed, also known as schizodontia. fusion and gemination as described above, in the pres-

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opyrig ent case CT, which is not a standard method in den- 4. Brook AH. Dental anomalies of number, form andNot size: for their PublicationC h prevalence in British schoolchildren. J Int Assoc Dent Child t

tistry, gave reliable information on the exact configu- 1974;5:37-53. b y ration of the root canals and the pulp cavities. 5. Fernández Montenegro P, Valmaseda Castellón E, BeriniQ Aytés L, Gay Escoda C. Retrospective study of 145 supernumeraryu

Whereas on the basis of the radiograph and clinical teeth. Med Oral Patol Oral Cir Bucal 2006;11:339-344.i N n o

t t 6. Kremeier K, Hülsmann M. Fusion and gemination of teeth: r f impression, a fusion with separate pulp cavities was es o e review of the literature, treatment considerations, and report senc expected, the CT scan revealed an incomplete gemi- of cases. ENDO (Lond Engl) 2007;1:11-23. nation, thus making treatment of all identified root 7. Brook AH, Winter GB. Double teeth. A retrospective study of ‘geminated’ and ‘fused’ teeth in children. Br Dent J 1970; canals necessary. 129:123-130. 8. Schuurs AH, van Loveren C. Double teeth: review of the lit- erature. ASDC J Dent Child 2000;67:313-324. 9. Kelly JR. Gemination, fusion, or both? Oral Surg Oral Med Oral Pathol 1978;45:655-656.  10. Grover PS, Lorton L. Gemination and twinning in the permanent References dentition. Oral Surg Oral Med Oral Pathol 1985;59: 313-318. 1. Gängler P, Hoffmann T, Willershausen B, Schwenzer N, 11. Garvey MT, Barry HJ, Blake M. Supernumerary teeth: an Ehrenfeld M. Konservierende Zahnheilkunde und Parodon- overview of classification, diagnosis and management. J Can tologie. Stuttgart: Thieme, 2005. Dent Assoc 1999;65:612-616. 2. Pindborg JJ. Pathology of the Dental Hard Tissues. Copen- 12. Lyroudia K, Mikrogeorgis G, Nikopoulos N, Samakovitis G, hagen: Munksgaard, 1970. Molyvdas I, Pitas I. Computerized 3-D reconstruction of two 3. Tannenbaum KA, Alling EE. Anomalous tooth development. ‘double teeth’. Endod Dent Traumatol 1997;13:218-222. Case reports of gemination and twinning. Oral Surg Oral 13. Patel JR. Gemination. Oral Surg Oral Med Oral Pathol 1984; Med Oral Pathol 1963;16:883-887. 57:232.

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