117PEDIATRIC DENTAL JOURNAL 19(1): 117–122, 2009

117

Received on September 1, 2008

Accepted on December 3, 2008

Impacted primary second molar with odontoma identifiedin the adjacent tissue

Naofumi Kamakura*1, Kazuhiko Nakano*1, Rena Okawa*1, Ryota Nomura*1,Michiyo Matsumoto*1, Yasuo Fukuda*2 and Takashi Ooshima*1

*1 Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry,*2 Clinical Laboratory, Osaka University Dental Hospital

1-8 Yamada-oka, Suita, Osaka 565-0871, JAPAN

Abstract A case of impacted tooth due to the presence of an odontomaidentified in a 5Y7M-old girl is presented. An intraoral examination showedthat the maxillary right second primary molar had not emerged into the oralcavity, while a periapical X-ray photograph revealed a small round radiopaquemass with a diameter of approximately 2 mm. The calcified mass was suspectedto interfere with eruption of the affected tooth and enucleation of the tissue wascarried out under local anesthesia. Histopathological examination results showedthat the calcified mass consisted of dental enamel, odontogenic epithelium, andpulp-like tissue, and it was diagnosed as an odontoma. At 6Y1M of age, thetooth had not emerged into the oral cavity due to the possibility of interferencein the distal cervical area of the adjacent first primary molar or that of strongtension of the gingiva above the affected tooth. Thus, fenestration of the gingivaover the impacted tooth crown was performed and the tooth crown of theaffected tooth appeared in the oral cavity at the age of 6Y6M.

eruption of affected teeth3,4). In addition, orthodonticapproaches are applied in some cases, which forcesthe affected tooth to successfully locate in theappropriate position5,6).

Herein, we report a rare case of delayed eruptionof the maxillary second primary molar due to asmall odontoma at the occlusal site of an affectedimpacted tooth.

Case Report

A 5Y7M-old girl was referred to the PedodonticClinic, Osaka University Dental Hospital, with thechief complaint of delayed eruption of the maxillaryleft second primary molar. Her parents were informedof the delayed eruption by a general practitionerapproximately 1 year prior to coming to our clinic,during which time periodical examinations had beencarried out. Our intraoral examination showed thatthere were 18 primary teeth, including a fused toothin the mandibular anterior region, and that the

Introduction

Impaction of primary teeth is an uncommon findingand the presence of an odontoma is considered tobe one of the possible causes of interference withthe eruption of the affected teeth1). Odontomasare hamartomatous developmental manifestations ofdental tissues, and considered to arise from epithe-lium and ectomesenchymal odontogenic tissues2).The most frequently detected age group is generallyin the second decade, and patients in primarydentition are considered to be rare. As for thoseless than 5 years of age, most of the lesions are foundin cases of impaction of the maxillary anteriorprimary teeth, especially the primary canines3,4). Asfor treatment modalities, early enucleation of thelesion is generally chosen to remove the eruptiondisturbance, which can accelerate the spontaneous

Key wordsDelayed eruption,Eruption disturbance,Impacted tooth,Odontoma,Primary dentition

Case Report

118 Kamakura, N., Nakano, K., Okawa, R. et al.

maxillary second primary molar could not be seen inthe oral cavity (Fig. 1). According to her parents, nosystemic disorders except for bronchial asthma wereknown in the patient, and no family members werereported to be complicated with systemic diseases or

problems with tooth eruption.A periapical X-ray photograph revealed a small

round radiopaque mass with a diameter of approxi-mately 2 mm (Fig. 2A), while an orthopantomographshowed that the position of the impacted primary

Fig. 1 Intraoral photographs taken at 5Y7M

Arrows indicate the region of delayed eruption.

Fig. 2 Periapical X-ray photographs

(A) 1 month prior to enucleation, (B) 3 months after enucleation, (C) 5 months after enucleation, and (D) 10 months afterenucleation. The arrow shows the radiopaque mass, which was suspected to interfere with eruption of the affected tooth.

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molar was below the peak of the alveolar bone (Fig.3A). Root formation of the affected molar and thetooth germ of the permanent successor were unclear,because they overlapped on the X-ray photographimage. We considered that the calcified mass wouldinterfere with eruption of the affected tooth andenucleation of the tissue was carried out under alocal anesthesia, after which the excised mass wassubmitted to routine histopathological examinations.

Histopathological analysis showed that the cal-cified mass consisted of dental enamel, odontogenicepithelium and pulp-like tissue, and the lesion wasdiagnosed as an odontoma (Fig. 4). At the age of5Y11M, the affected tooth had not emerged intothe oral cavity (Fig. 5A), though a periapical X-rayphotograph image showed that the position of theaffected tooth had moved toward the oral cavity(Fig. 2B). Two months later, the tooth had notappeared in the oral cavity (Fig. 5B), and periapicalX-ray photograph image indicated the possibilityof eruption disturbance due to interference in thedistal cervical area of the adjacent first primarymolar (Fig. 2C). Therefore, we decided to excise the

Fig. 3 Orthopantomographs

(A) 1 month prior to enucleation and (B) 6 months afterenucleation.

Fig. 4 Histopathological appearance of the lesion following hematoxylin-eosin staining

Lower (A) to higher (D) magnification. Magnified areas in B, C, and D are enclosed in squares. The lesioncorresponding to radiopaque mass consists of odontogenic epithelium (C), enamel rod (D), and pulp-liketissue (*). Arrows and arrowhead indicate odontogenic epithelium and estimated enamel protein, respectively.

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gingival tissue under a local anesthesia to acceleratespontaneous eruption of the affected tooth (Fig.5C). Finally, the tooth crown of the affected toothappeared in the oral cavity at the age of 6Y6M (Fig.2D, Fig. 5D and Fig. 6).

Discussion

Tooth impaction due to the presence of an odontomais sometimes encountered in the field of pediatricdentistry, with most of the cases found in teenagers.

Analysis odontoma cases in Japan showed thatapproximately half were in patients aged 10–19years old, with the detection rate in those below 10reported to be approximately 10%3). In addition, alarge-scale survey conducted in the United Statesanalyzed odontoma detection rates and classifiedthem into narrower ranges of ages. They found thatone-third of all cases were identified in childrenaged 11–15 years, while the detection rate in thosebelow the age of 5 was extremely low at approxi-mately 2% of all cases7). Thus, the odontoma lesion

Fig. 5 Photographs of the affected region

(A) 3 months after enucleation, (B) 5 months after enucleation, (C) 6 months after enucleation, and (D) 10 months after enucleation.Arrows indicate the affected region.

Fig. 6 Intraoral photographs taken at 1 year after enucleation

Arrows indicate the affected region.

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found in the present 5-year-old patient is consideredto be a rare occurrence.

The size of the present calcified mass wasestimated to be 2 mm in diameter in periapical X-rayphotograph images. Brunetto et al.6) reported thateven a small sized (3.0 mm by 1.5 mm) odontomainterfered with eruption of a maxillary canine in a4-year-old girl. It is difficult to identify small sizeodontoma lesions on X-ray photographs, even whentheir presence is suspected. Fortunately, a periapicalX-ray photographic examination revealed the calci-fied mass above the occlusal surface of the impactedprimary second molar in the present case. Sinceremoval led to eruption of the impacted tooth, itis reasonable to speculate that even a small sizedodontoma can interfere with tooth eruption.

The parents of our patient were informed ofthe delayed tooth eruption by a general practitionerapproximately 1 year prior to coming to our clinic,after which no treatments and only periodicalexaminations were performed. It is possible thatthe lesion was too small to be identified in X-rayphotographic examinations performed during thattime. Our histopathological examination resultsrevealed that the mass consisted of dental enamel,odontogenic epithelium, and pulp-like tissue, whereasneither dentin nor cementum could be identified,presumably due to the small size of the lesion.In addition, eosinophilic accelular matrix that wasbounded laterally around odontogenic epitheliumwas found in the histopathological sections (Fig. 4C).Thus, we estimated the matrix as enamel protein andthe odontoma in the present case was considered tobe in the process of maturation, which also supportsthe notion that an extremely small lesion existed 1year prior to coming to our clinic.

Odontoma cases in children are rarely reported,with the youngest patient aged 1Y2M, in whoman odontoma lesion interfered with eruption of themaxillary primary central incisor8). As for odontomasin the primary molar region, Long et al.9) reportedthat a lesion located between the maxillary primaryfirst and second molars in a 2Y6M-old boy causedasymmetry in the maxillary dental arch. In addition,the case of a 3Y-old boy reported by Motokawaet al.5) is similar to the present case, in which themaxillary left primary second molar was impactedbecause of a dentigerous cyst and the presence ofan odontoma.

It is interesting to consider whether odontomalesions develop as young patients grow. In a report

describing the development of an odontoma in aJapanese boy aged 6Y2M10), the calcified legion wasnot observed in X-ray photographs taken at the firstexamination or 8 months later (6Y10M), whereas aX-ray photograph taken at 7Y2M showed a smallround radiopaque mass, which was confirmed to bedeveloping at the ages of 7Y7M and 7Y10M. Basedon those findings, it is possible to speculate thatthe present lesion was too small to be confirmed1 year prior to coming to our clinic and that itwas still developing when we carried out our firstexamination.

In the present case, the parents of the patientwere not aware of the impacted tooth until the age of4Y7M. It is reported that maxillary primary secondmolars in Japanese children generally emerge intothe oral cavity at an average age of 2Y6M, whilethe latest reported age of eruption of that toothis 3Y8M11). Earlier identification and removal ofodontoma lesions are recommended for affectedchildren in order to obtain satisfactory alignment ofthe teeth12,13). It is important to keep in mind theappropriate order for tooth eruptions as well as theaverage age of exfoliation of primary teeth.

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Kamakura, N., Nakano, K., Okawa, R. et al.