Introduction A.Z. Zengin, P. Celenk, K. Gunduz, M. Canger Fusion is a developmental anomaly defined as the union Faculty of Dentistry, Department of Oral and Maxillofacial Radiology of two normally separated tooth buds with the dentins University of Ondokuz Mayis, Turkey at any stage of their development. They may be fused or separated, depending on the development stages of e-mail: [email protected] dental pulp and canal. Tooth gemination is the separation of a single tooth germ. Teeth with large single or bifid crown have a normal root or root canal. As a general rule, when the affected tooth is regarded as one, if in Primary double teeth the arch there is one tooth less than the normal count it is called fusion, while when the normal number of teeth and their effect is present it is termed gemination [Duncan and Helpin, 1987]. However, literature shows that the differential on permanent diagnosis between fusion and gemination is difficult (in some cases, fusion with supernumerary tooth) [Duncan successors and Helpin, 1987; Shafer et al., 1974]. The term “double teeth” is often used to describe both anomalies [Brook and Winter, 1970; Buenviaje and Rapp, 1984; Tasa and Lukacs, 2001]. The prevalence of abstract double teeth varies between 0.1 and 3% [Duncan and Helpin, 1987; Tasa and Lukacs, 2001]. Double teeth are Aim Understanding the effects of primary double more common in primary than in permanent dentition tooth (PDT) on permanent successors is important to (0.6% of primary dentition and 0.1% of permanent ensure healthy permanent occlusion and aesthetics. dentition in Caucasians) [Duncan and Helpin, 1987]. The aim of this study is to determine the prevalence The prevalence of double teeth is more common in and type of PDT, their effect on permanent successors, some races (Mongoloid) than Caucasians [Brook and and the accompanying dental anomalies/pathologies Winter, 1970]. It is more frequent in the maxilla than in in a Turkish population. the mandible [Ravn, 1971]. Although, cases have been Materials and Methods Study Design: The records reported in the posterior region, incisors and canines are of 63 PDTs in 54 healthy Caucasian children among more susceptible [Yuen et al., 1987]. It usually occurs 10,000 patients were investigated. PDTs were classified unilaterally or bilaterally [Brook and Winter, 1970; Levitas according to Aguilo’s classification. ,1965] but the latter is very rare [Milano et al., 1999]. Results The prevalence of PDT was 0.6%. Of the 63 The studies and case reports investigating the PDTs, 14.3% were type I, 11.1% were type II, 31.7% relationship between primary double tooth (PDT) and were type III, and 41.3% were type IV; one (1.6%) permanent successors are limited [Aguilo et al., 1999; was a triple tooth. Aplasia of the permanent lateral Gellin,1984; Nik Hussein and Abdul Majid, 1996; Yuen incisor was observed most frequently in association et al., 1987]. These studies have reported that dental with type I (56%) PDT. All PDTs associated with a anomalies in primary dentition may lead to congenital supernumerary permanent tooth were type IV. Dental deficiency (aplasia), supernumerary teeth or repeated anomalies/pathologies such as odontoma, talon cusp double teeth formation in permanent dentition. were observed. Caries involvement was observed most The aims of this study, which analyses data from 10,000 frequently in type IV (58.3%) PDT. Statistics: The chi- Turkish children, are to determine the prevalence of PDT, squared test was used to determine whether successor their relationship with their successors and to investigate aplasia depended on PDT type, and contingency the associated abnormalities/pathologies, if any. coefficients (%) were calculated to determine the degree of association between aplasia and PDT type. Conclusion Clinicians should assess PDT clinically Material and methods and radiographically to determine whether they are associated with aplasia of permanent lateral incisors The study was conducted in 10,000 paediatric patients (type I) or supernumerary permanent teeth (type IV). (aged 5-12) referring to the Oral and Maxillofacial Type IV of PDT should be sealed with sealant or resin. Radiology Clinic between 2004 and 2008. Dental reports and panoramic/periapical (if any occlusal) radiographs of those children were analysed retrospectively. Children Keywords Dental anomalies; Primary double teeth; with a history of systemic disease or trauma and those Supernumerary teeth. with poor data were excluded from the study. Clinical and radiographic records of PDT were evaluated by two

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fig. 1 fig. 2 a Periapical image of PDT in type 1- Bifid crown, Single root . a Periapical image of PDT in type 2- Large crown, Large root. B Diagramatic representation of PDT in type 1. B Diagramatic representation of PDT in type 2.

fig. 3 fig. 4 a Periapical image of PDT in type 3-Two fused crowns, Double a Periapical image of PDT in type 4- Two fused crowns, Two fused conical root. B Diagramatic representation of PDT in type 3. roots. B Diagramatic representation of PDT in type 4. experienced oral radiologist. Gender variables, clinical - Type III: two fused crowns, double conical root. positions (maxilla, mandible, unilateral, bilateral) and type Two fused crowns with a partial or total vertical of double teeth were examined. Any increase or decrease groove extending cervically; the crowns may be in the number of teeth on the arch was recorded. The symmetrical or show distinct differences, and the effect of PDT on permanent successors was recorded as pulp chambers may be separate. One large conical normal, supernumerary teeth, aplasia or missing teeth, root. The coronal and radicular portions of the pulp repeated double teeth formation. The complications canal may be fused, or the coronal portion may be caused by double teeth were analysed. The condition of shared and end in two radicular canals (Fig. 3). PDT and their successors were re-evaluated by careful - Type IV: two fused crowns, two fused roots. Two examination of periapical and/ or occlusal intraoral films crowns (as in type III) and two distinct, joined roots and panoramic radiographs on a light box. Each PDT was with separate root canals (Fig. 4). classified according to Aguilo et al. [1999], as follows. The chi-squared test was used to determine whether - Type I: bifid crown, single root. A large crown with a successor aplasia depended on PDT type, and contingency notch on the incisal edge and a bifid pulp chamber, coefficients (%) were calculated to determine the degree with normal dimensions of the root and radicular of association between aplasia and PDT type. canal and cervical widening (Fig. 1). - Type II: large crown, large root. A large crown, usually lacking a groove or notch, with single, Results shared, large root canal and pulp chamber and a wider than normal root (Fig. 2). PDT was detected in 54 cases (0.5%) of 10,000

310 European Journal of Paediatric Dentistry vol. 15/3-2014 Primary double teeth

Caucasian patients. The mean age was 8.5. Of these mandibular and two (33.3%) were maxillary. Of the anomalies, 9 (16.7%) were bilateral and 44 (% 83.7) three permanent double teeth, one (33.3%) was were unilateral. Therefore, the total number of PDTs maxillary and two (66.7%) were mandibular; two was 63. The prevalence of PDT was 0.6%. (66.6%) associated PDTs were type IV and one was Of the Caucasian patients, 18 were female and 36 were type II. Double formation was common in type-2 and in male. This anomaly was more common in males than in type-4 respectively. Bilateral PDT was found in 9 patients females (p <0.001); and in mandible (n = 42, 66.7%) (0.09%). Seven (77.8%) of these cases were located than in maxillary teeth (n = 21, 33.3%) (p < 0.001). in the mandible and two (22.2%) were in the maxilla; All were in the anterior region. The most frequently seven (77.8%) were symmetrical and two (22.2%) were affected teeth were the lateral incisors, followed by the asymmetrical. Four (44.4%) bilateral PDTs involved central incisors and canines. No significant difference missing teeth, and two (11.1%) were associated with in PDT location was observed between the right (n = supernumerary teeth (hiperdonti) in the same region. 27, 43%) and left (n = 36, 57%) sides of the jaw (p Most bilateral PDTs were type III (n = 8, 44.4%) and = 0.105). We observed type IV PDT most frequently, type IV (n = 8, 44.4%). The distribution of anomalies/ followed in order by types II, I, and III. The distribution of pathologies associated with PDT is presented in Table 63 PDT with respect to types and location was shown in 4. Delayed permanent tooth eruption was observed in Table 1. The relationship between PDT and permanent only one case, in combination with odontoma. Caries successors was examined as follows. was present at the line of demarcation in 12 PDT a) Normal. [(maxilla, n = 9 (75%), (mandible, n = 3 (25%)]. Type b) Increase in the number of teeth (supernumerary IV (n = 7, 58.3% of decayed teeth) PDT were most tooth, hyperdonti). frequently affected by caries (p < 0.05). c) Reduction in the number of teeth (aplasia/missing tooth, hypodontia). d) Repeated double teeth formation. Discussion and conclusion Dental anomalies were observed in the permanent successors of 23 (36.5%) PDT (Table 2), including Numerous studies have examined the prevalence of six (9.5%) supernumerary teeth, 17 (27%) aplasia/ PDT in populations throughout the world [Boyne, 1955; missing teeth, and three (4.8%) repeated double teeth formation. The distribution of the relationship between PDT and permanent successors with respect to types Normal Supernume- Aplasia Repeated was also given (Table 3). rary teeth or double Permanent tooth aplasia was observed in 55.6% of missing teeth all type I PDTs, and was most prevalent in this type (p < teeth formation 0.05). PDT type was thus associated significantly with Type 1 4 - 5 - successor aplasia. Type 2 5 - 1 1 All six supernumerary permanent teeth were associated with type IV PDT; four (66.7%) were Type 3 14 - 6 - Type 4 13 6 5 2 Total 36 6 17 3 Type I Type II Type III Type IV Total Maxilla 1 2 7 10 20 tabLE 3 Distribution of the relationship between double teeth and Mandible 8 5 13 16 42 permanent teeth with respect to types (one triple tooth was excluded). Total 9 7 20 26 62 N % tabLE 1 Distribution of PDT with respect to type and location. One Hyperdontia* 8 28.6 triple tooth was excluded. Hypodontia* 16 57.1 Normal Supernu- Aplasia Repeated Total Taurodontism* 2 7.1 merary or double Odontoma** (delayed eruption) 1 3.6 teeth missing teeth Talon cusp** 1 3.6 teeth formation Total 28 100 n 37 6 17 3 63 * unrelated region % 58.7 9.5 27 4.8 100 **related region tabLE 2 Dental anomalies observed in the permanent successors of PDT. tabLE 4 Distribution of dental anomalies/pathologies associated with PDT.

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Duncan and Helpin, 1987; Nisvander and Sujaku, 1983; associated with such teeth were of type IV. Ravn, 1971; Tasa and Lukacs, 2001; Wu et al., 2010]. In this study, repeated double teeth formation in The frequency of this anomaly is lower in Caucasians permanent successors was associated with two type (0.1–1.6%) [Boyne, 1955; Ravn, 1971] than in Taiwan and IV PDTs and one type II PDT. We found no significant Japanese populations (0.72–3%) [Nisvander and Sujaku, relationship between PDT type and this successor 1983; Wu et al., 2010]. We found a 0.6% prevalence of anomaly, perhaps due to its low incidence (n = 3) in our PDT in this Turkish population, which is similar to that sample. PDT is susceptible to caries because the labial and found in Caucasians [Boyne, 1955; Ravn, 1971]. lingual vertical grooves are difficult to clean [Duncan and We found that PDT affects twice as many males than Crawford PJ, 1996; Himelhoch, 1988; Nik Hussein and females, in agreement with previous findings of male Salcedo, 1987]. Caries involvement has been reported in predominance [Razak and Nik-Hussein, 1986; Yuen 56% of maxillary and 7% of mandibular PDT [Aguilo et et al., 1987]. However, other studies have found no al., 1999]. We observed caries in 42.9% of maxillary and sex difference in PDT prevalence [Aguilo et al., 1999; 7.1% of mandibular PDT, most frequently in type IV PDT. Brook and Winter, 1970; Ravn, 1971]. We also found Given this high risk of caries involvement in type IV that PDTs were located predominantly in the mandible PDT, we suggest sealing of the labial and lingual grooves (mandible:maxilla = 2:1), in agreement with previous of these teeth. reports [Razak and Nik-Hussein,1986; Yuen et al., 1987; Wu et al., 2010]. Aguilo et al. [1999] found that the lateral incisors Acknowledgements were most frequently affected by PDT [Aguilo et al., 1999]. Similarly, the most frequently affected teeth We thank to Soner CANKAYA for the statistical analysis. in the present study were the lateral incisors, followed by the central incisors and canines. We used the PDT classification of Aguilo et al. [1999], which is based References on root and crown morphology, because it is easy to understand and readily applied. We observed type IV › Aguiló L, Gandia JL, Cibrian R, et al. Primary double teeth. A retrospective clinical study PDT most frequently, followed in order by types II, I, and of their morphological characteristics and associated anomalies. Int J Paediatr Dent 1999;9:175-183. III; these results were identical to those of Aguilo et al. › Boyne PJ.Gemination; report of two cases. J Am Dent Assoc 1955;50:194. [1999]. They reported that type I was found only in the › Brook AH, Winter GB. Double teeth. A retrospective study of 'geminated' and 'fused' maxilla, types II and III were found only in the mandible, teeth in children. Br Dent J 1970;129:123-130. and type IV was most frequently seen in the maxilla; this › Buenviaje TM, Rapp R. Dental anomalies in children: a clinical and radiographic survey. ASDC J Dent Child 1984;51:42-46. distribution differs from our observations. In the present › Duncan WK, Helpin ML. Bilateral fusion and gemination: a literature analysis and case study, the prevalence of bilateral PDT was 0.09%, which report. Oral Surg Oral Med Oral Pathol 1987;64:82-87. is higher than that reported by Duncan and Helpin [1987] › Gellin ME. The distribution of anomalies of primary anterior teeth and their effect on (0.02%), and lower than that reported by Wu et al. the permanent successors. Dent Clin North Am1984;28:69-80. [2010] (0.12%). › Himelhoch DA. Separation of fused primary incisors: report of case. ASDC J Dent Child 1988;55:294-297. PDT is of interest because it is related to aesthetic › Levitas TC. Gemination, Fusion, Twinning and Concrescence. ASDC J Dent Child and functional problems, such as caries involvement, 1965;32:93-100. delayed exfoliation [Brook and Winter, 1970; Himelhoch, › Milano M, Seybold SV, McCandless G, Cammarata R. Bilateral fusion of the mandibular 1988; Peretz and Brezniak, 1992], and anomalies in the primary incisors: report of case. ASDC J Dent Child 1999;66:280-282. › Nik-Hussein NN, Abdul Majid Z. Dental anomalies in the primary dentition: distribution, permanent dentition [Himelhoch, 1988; Levitas, 1965; and correlation with the permanent teeth. J Clin Pediatr Dent 1996;21:15-19. Yuen et al., 1987]. Dental anomalies such as aplasia › Nik-Hussein NN, Salcedo AH. Double teeth with hypodontia in identical twins. ASDC (lateral incisor, 32.1%) [Aguilo et al., 1999], hypodontia J Dent Child 1987;54:179-181. (51.5%) [Wu et al., 2010], hyperdontia (11.3%) [Aguilo › Niswander JD, Sujaku C. Congenital anomalies of teeth in Japanese children. Am J et al., 1999], peg-shaped incisors (1.5%) [Wu et al., Phys Anthropol 1963;21:569-574. › Peretz B, Brezniak N. Fusion of primary mandibular teeth: report of case. ASDC J Dent 2010], and double tooth formation (2.9%) [Wu et al., Child 1992;59:366-368. 2010] have been found in up to 59% of permanent › Ravn JJ. Aplasia, supernumerary teeth and fused teeth in the primary dentition. An successors [Nik Hussein and Abdul Majid, 1996, Wu et epidemiologic study. Scand J Dent Res 1971;79:1-6. al., 2010]. We detected dental anomalies in 36.5% of › Razak IA, Nik-Hussein NN. A retrospective study of double teeth in the primary dentition. Ann Acad Med Singapore 1986;15:393-396. the permanent successors of PDT, including aplasia of › Shafer WG, Hine MK, Levy BM: A textbook of Oral Pathology, ed.3,Philadelphia 1974, the lateral incisors (27%), supernumerary teeth (9.5%), WB Saunders Company. pp. 36. and repeated double tooth formation (4.8%). Although › Tasa GL, Lukacs JR. The prevalence and expression of primary double teeth in western successor aplasia had been previously associated with India. ASDC J Dent Child. 2001;68:196-200. type III PDT [Aguilo et al., 1999], our results suggest a › Wu CW, Lin YT, Lin YT. Double primary teeth in children under 17 years old and their correlation with permanent successors. Chang Gung Med J. 2010;33:188-193. relationship with type I PDT. No relationship has been › Yuen SW, Chan JC, Wei SH. Double primary teeth and their relationship with the reported between supernumerary permanent teeth and permanent successors: a radiographic study of 376 cases. Pediatr Dent. 1987;9:42- PDT type [Aguilo et al., 1999], we observed that all PDT 48.

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