Abstract
This study reports a rare case of a dentigerous cyst in a malformed tooth in the mandible of a 5-year-old Japanese boy. Panoramic radiography revealed a cystic lesion with hard tissues inside. The patient underwent surgery under general anesthesia. The histopathological diagnosis was dentigerous cyst associated with a malformed tooth.
Keywords: Dentigerous cyst, Odontogenic cyst, Malformed tooth, Mandible, Child
Introduction
Dentigerous cysts are relatively common cysts that develop within the jawbone and typically have a favorable prognosis with surgical procedures, such as extraction [1]. These cysts usually surround the crown of a buried or overburdened tooth, presenting a normal tooth structure. Conversely, malformed teeth are relatively rare, and malformed teeth with cysts are even more rarely reported. Although abnormalities in genes involved in tooth assembly have been implicated in the development of malformed teeth, the potential influence of external physical after birth has also been suggested. However, the exact cause remains unknown [2, 3].
This study presents a rare case of a dentigerous cyst with a malformed tooth in the mandible of a child, showcasing an interesting developmental process.
Case Report
A 5-year-old Japanese boy was referred to the Department of Oral and Maxillofacial Surgery, University of Tsukuba Hospital, with complaints of discomfort and swelling in the right mandible. The patient had an uncomplicated history of Kawasaki disease. Intraoral examination revealed painless swelling with a normal mucosal surface on the buccal side of the right mandibular molar. Extraoral examination revealed slight swelling of the right mandible. Panoramic radiography revealed a cystic transmission from the right mandibular second molar to the submandibular margin, with an irregularly shaped hard tissue structure. A normal tooth embryo did not form in the second premolar of the right mandible. No defects or morphological abnormalities were observed in the other teeth (Fig. 1). Computed tomography (CT) revealed a well-defined and unifocal cystic lesion enlarged to 33 mm in the right mandible. It contained hard tissues. Magnetic resonance imaging (MRI) showed a homogeneous internal unifocal mass on T2-weighted images. The clinical diagnosis was a suspected mandibular tumor or odontogenic cyst. Since the patient was a child, preoperative biopsy under local anesthesia was not performed. The patient underwent mandibular disease removal under general anesthesia. Intraoperative findings revealed no adhesions between the disease and the surrounding bone, and dissection was easy. The excised specimen had a very thin fibrous capsule with clear, slightly pale-yellow serous fluid and contained hard tissue with a bowl-shaped morphology. The histopathological diagnosis was dentigerous cyst associated with a malformed tooth. The excised specimen was a 25 × 18 × 8 mm large, surface-smooth, monoblastic cystic lesion containing hard tissue that was diagnosed using a demineralized specimen. Histologically, the cyst was composed of (1) thinning nonkeratinizing stratified squamous epithelium lining the lumen, (2) subepithelial edematous stroma and reticulate odontogenic epithelium, (3) enamel-like cuboidal epithelium, (4) enamel (weak enamel or voids lost by demineralization), (5) dentin (with dentin tubules), (6) dentinblast-like cells in a small portion, and (7) fibrous stroma. Dentoblast-like cells, which are normally present on the pulpal side, were found on the outer side, and enamel epithelial-like cells were found on the inner side, resulting in a malformed tooth with a cystic appearance (Fig. 2). The patient is doing well two years after surgery, with no recurrence.
Fig. 1.
Imaging findings at initial examination, A Panoramic X-ray findings, B CT findings (horizontal section), C CT findings (coronal section), D Contrast-enhanced MR findings (T2-weighted images)
Fig. 2.
Histopathological findings, The excised specimen was a 25 × 18 × 8 mm large, surface-smooth, monoblastic cystic lesion containing hard tissue that was diagnosed using a demineralized specimen
Discussion
This is a relatively rare case of a dentigerous cyst associated with a malformed tooth. However, dentigerous cysts are commonly encountered in daily clinical practice, and conventional extraction is the recommended treatment, making the healing process not particularly noteworthy. What is unique in this case is that the odontogenic hard tissue (malformed tooth) that caused the cyst was interesting from an embryological perspective. The patient, a normally developing 5-year-old boy, showed panoramic radiographic findings indicating that tooth embryo formation had progressed to the second premolar. However, the normal tooth embryo of the right mandibular second premolar, which corresponded to the cystic area of the right mandible, was missing. This abnormality may have occurred during the development of the right mandibular second premolar. While the extremely unlikely possibility of a cyst arising in an overexpressed tooth embryo and a congenital defect of the right lower 5 (concomitant hypodontia and hyperodontia) cannot be ruled out [4], it is nearly impossible to prove. Regarding the diagnosis of malformed teeth, the conventional WHO classification of “dilated odontoma,” a subtype of odontoma, or “malformed teeth” including endodontia, and others, were considered. Although there have been some reports of similar cases, it is difficult to distinguish between the two because the histological components of both types of odontomas are identical. Dilated odontoma is no longer included in the WHO classification [5], and a diagnosis of malformed teeth was made in this case.
Table 1 shows 9 reported cases of malformed teeth or dilated odontoma (including the present case) [4–6], of which three cases were associated with dentigerous cysts [7, 8]. The mechanism of occurrence is thought to be that the odontogenic epithelium is deposited on the papillary side of the tooth during the development process, enamel is formed from the inside, and dentin and cementum are formed on the outer layer. In this case, the histopathological findings of the hard tissue portion of the tooth revealed dentinoblast-like cells on the outer side and enamel epithelial-like cells on the inner side, which should normally exist on the pulp side. A malformed tooth structure with inverted inner and outer sides was observed, which was consistent with other reported cases. Possible causes such as abnormal pressures, (trauma, inflammation, cysts, and tooth eruption defects) have been suggested [6, 9]. Additionally, the potential involvement of morphogenetic genes has been suggested [10]. All selected cases had good postoperative outcomes, with no reports of recurrence in cases with cysts, aligning with previous studies.
Table 1.
Reported cases of malformed teeth with/without dentigerous cyst
| Author | Issue | Age（year） | Sex | Site | Histopathological diagnosis | Presence of dentigerous cyst | |
|---|---|---|---|---|---|---|---|
| 1 | Ikarashi et al. | 2003 | 7 | Male | rt. lower molar | malformed teeth | + |
| 2 | Matsusue et al. | 2011 | 14 | Female | lt. lower molar | dilated odontoma | |
| 3 | Sebastian et al. | 2013 | 30 | Female | bi. upper anterior teeth | dilated odontoma | |
| 4 | Sharma et al. | 2015 | 18 | Male | rt. upper anterior teeth | dilated odontoma | |
| 5 | Jayachandran et al. | 2016 | 16 | Male | rt. lower molar | dilated odontoma | + |
| 6 | 24 | Male | rt. upper molar | dilated odontoma | |||
| 7 | Galvez et al. | 2021 | 7 | Female | rt. lower molar | dilated odontoma | |
| 8 | Zara et al. | 2021 | 11 | Male | lt. lower molar | dilated odontoma | |
| 9 | Present case | 2024 | 5 | Male | rt. lower molar | malformed teeth | + |
The limitations of this report include the rarity of this disease, the scarcity of reported cases, and the impracticability of prospective follow-up due to developmental abnormalities.
In conclusion, this rare case of a dentigerous cyst associated with malformed teeth represents an interesting disease with an interesting developmental process. However, it was difficult to prove the cause, such as a genetic abnormality, in this case alone. There is much room for further research from an embryological standpoint.
Acknowledgements
We acknowledge Dr. Natsumi Kawamatsu of the Department of Pathology, University of Tsukuba Hospital, for her invaluable help to prepare this manuscript.
Funding
None.
Declarations
Conflict of interest
None.
Ethical approval
Approved, R5-203.
Patient consent
Patient consent has been obtained.
Footnotes
Publisher's Note
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