Spontaneous regression of dentigerous cyst in a impacted mandibular first permanent molar with eruptive potential: a case report

Abstract

Background

Surgery is the main treatment for dentigerous cysts. Although the treatment concept has shifted from radical lesion removal to function‑preserving strategies, surgical trauma and related risks are still hard to avoid completely. The strategy of spontaneous fenestration may be preferred in a few dentigerous cysts in children.

Case presentation

A 6-year-old boy was referred because of the delayed eruption of a left mandibular posterior tooth. Panoramic radiographic examination revealed a well-defined radiolucent area measuring approximately 22 × 18 mm around the crown of the left mandibular first permanent molar (tooth 36), which was vertically impacted at Nolla stage 7 and extended to the distal root of the left mandibular second primary molar. A dentigerous cyst of tooth 36 was diagnosed. Because the tooth 36 presented eruptive potential and no obvious coronal bony barrier, only regular follow-up was adopted. At 6‑month follow‑up the cyst decreased to about 16 × 11 × 14 mm on CBCT。After two years, tooth 36 had erupted spontaneously and the cyst had completely resolved.

Conclusions

The tooth 36 had an immature root with no bony obstruction coronally and a small-to-medium cyst volume and lack of adverse effects, and thus conservative monitoring was adopted. During follow-up, the cyst progressively decreased in size and the affected tooth showed a clear tendency for occlusal eruption, ultimately resulting in complete resolution of the cyst and spontaneous eruption of the tooth, confirming that this strategy may be a feasible option.

We also reviewed relevant literature and analyzed the underlying mechanisms, providing evidence for more conservative clinical management strategy of dentigerous cysts in children.

Background

Dentigerous cysts are the second most common type of odontogenic cysts after radicular cysts. Among 1,038 odontogenic jaw cysts, Du et al. [1] reported that dentigerous cysts accounted for 23.22%, of which 39.4% occurred in children and adolescents, frequently associated with obstructed eruption of permanent teeth during the mixed dentition. Aldelaimi et al. [2] found that 68.4% of patients in their 76 cases were aged ≤ 18 years, confirming the high prevalence in this age group, with a male-to-female ratio of approximately 2:1 [1, 2]. Pathologically, these cysts are characterized by complete encasement of the crown of the unerupted tooth, with the cystic epithelium attached at the cementoenamel junction. The mandibular third molar is most commonly affected, followed by maxillary canine, maxillary third molar, and mandibular second premolar [2]. In mixed dentition, these lesions are usually asymptomatic and are frequently discovered incidentally through radiographic examinations performed due to delayed permanent tooth eruption.

Although benign histologically, dentigerous cysts can nevertheless progressively enlarge if left untreated, leading to jaw expansion and possibly invading adjacent structures such as the maxillary sinus and inferior alveolar nerve canal. This would increase the difficulty of subsequent surgery and the risk of various complications [3]. Furthermore, Cystic compression may also cause root resorption, displacement of adjacent teeth, and interfere with normal eruption and the development of occlusal system [4]. Besides, these dentigerous cysts have a certain potential for neoplastic transformation, with possible progression to odontogenic tumors such as ameloblastoma and adenomatoid odontogenic tumors [5]. Although malignant transformation is extremely rare, cases of primary intraosseous squamous cell carcinoma or mucoepidermoid carcinoma have been reported [6].

Surgery is still the primary treatment method for dentigerous cysts. Traditional procedures such as cyst enucleation with extraction of the involved tooth can completely remove the lesion, but in children they often sacrifice the permanent tooth germ, leading to long‑term complications such as missing teeth, jaw growth disturbances, and occlusal problems [7]. In recent years, function‑preserving surgery, particularly decompression via marsupialization, has become the mainstream choice. These techniques create a continuous drainage pathway between the cystic cavity and the oral cavity, reduce intracystic pressure, and promote regression of the cyst and spontaneous eruption of the involved tooth [8, 9]. However, decompression requires a long treatment period and frequent follow‑up visits, demanding good compliance from the child and parents, and some cases still need a second‑stage enucleation.

Notably, spontaneous fenestration, a very rare phenomenon has been observed in a few dentigerous cysts in children. The unerupted tooth spontaneously penetrates the cortical bone or communicates with the oral cavity, allowing natural decompression and gradual resolution of the cyst [10, 11]. This suggests that in carefully selected cases, any iatrogenic intervention might be avoided, achieving true self‑healing. Here we report a case of dentigerous cyst involving the left mandibular first permanent molar during mixed dentition that completely resolved after the tooth erupted spontaneously, with good root development. With a review of the literature, we discuss the possible mechanisms and clinical implications of this rare self‑healing process, aiming to provide a reference for individualised and conservative management.

Case presentation

A 6‑year‑old boy was referred because of delayed eruption of the left mandibular posterior tooth. His medical history was unremarkable, with no systemic diseases, allergies, or relevant family history. Intraoral examination revealed a mixed dentition, with mandibular first permanent molar (tooth 36) not yet erupted, while teeth 16, 26 and 46 had already erupted. Panoramic radiograph showed a vertically impacted tooth 36 at Nolla stage 7. A well‑defined pericoronal radiolucent area measured approximately 22 × 18 mm in maximum diameter and extended to the distal root of tooth 75, where slight root resorption was noted (Fig. 1). The maximum width of pericoronal space was 5.84 mm. A diagnosis of dentigerous cyst associated with tooth 36 was made.

Fig. 1.

Initial panoramic radiograph of the 6‑year‑old patient. Tooth 36 is at Nolla stage 7, with a pericoronal radiolucent area and no coronal bone coverage

Given the immature root development of tooth 36, the absence of coronal bony obstruction, and no signs of adjacent tooth displacement or jaw expansion, we decided against any invasive intervention and a 6-month follow-up was recommended. At the 6-month follow up, tooth 36 had still not erupted intraorally. A panoramic radiograph reconstructed from Cone beam computed tomography (CBCT) showed that tooth 36 remained vertically impacted but had moved occlusally compared with the previous radiograph and it was now at Nolla stage 8 (Fig. 2). CBCT also showed that the pericoronal radiolucent area had decreased in size, measuring approximately 16 × 11 × 14 mm, borders were still well defined, the buccal bone plate was discontinuous, and about two‑thirds of the distal root of tooth 75 had been resorbed (Fig. 3). Because the cyst had reduced in size and tooth 36 showed a clear occlusal migration with remaining eruptive potential, we advised continued close follow-up every 6 months. However, the patient did not attend the scheduled visits.

Fig. 2.

Panoramic radiograph (synthesised from CBCT) taken after 6 months. Tooth 36 shows obvious occlusal movement compared with the previous radiograph

Fig. 3.

CBCT images after 6 months. A: axial view; B: sagittal view; C: coronal view. The buccal bone plate of tooth 36 is discontinuous (A, C). About two‑thirds of the distal root of tooth 75 has been resorbed (B)

One and a half years later, at 8 years of age, the boy returned. Intraoral examination showed that tooth 36 was partially erupted. Its mesial marginal ridge contacted the cervical area of the distal root of tooth 75 and the gingival flap covered the distal occlusal surface of tooth 36. Tooth 75 exhibited grade II mobility and the buccal gingival margin was red and swollen (Fig. 4). Panoramic radiograph showed that tooth 36 had progressed to Nolla stage 9. The radiolucent area had completely disappeared with no periapical abnormality. The distal crown and most of the root of tooth 75 had been resorbed and tooth 35 was at Nolla stage 7 (Fig. 5).

Fig. 4.

Intraoral photographs at the 2‑year follow‑up. A: right lateral view; B: frontal view; C: left lateral view; D: maxillary occlusal view; E: mandibular occlusal view. Tooth 36 is partially erupted; its mesial marginal ridge contacts the cervical area of the distal root of tooth 75

Fig. 5.

Panoramic radiograph at the 2‑year follow‑up. Tooth 36 is at Nolla stage 9; the radiolucent area has disappeared. The distal crown and most of the root of tooth 75 have been resorbed

Discussion

Dentigerous cyst, also called follicular cyst, is one of the most common odontogenic cysts of the jaws. Its typical radiographic appearance is a unilocular radiolucent area around the crown of an unerupted tooth, with well‑defined, often sclerotic borders [12]. Based on pathogenesis, dentigerous cysts are classified into developmental and inflammatory types [13]. In our case, neither the associated tooth 36 nor the adjacent teeth exhibited clinical or radiographic evidence of pulpitis or periapical disease, which is more consistent with a developmental origin. Of course, histopathological confirmation was absent because no surgical specimen was obtained in our patient.

Radiographic assessment of the pericoronal space is important for differentiating a normal dental follicle from a pathological lesion.Studies have indicated that the pericoronal space greater than 3 to 4 mm suggest a higher likelihood of cystic change [12].In the present case, the maximum width was 5.84 mm. Although no universally accepted classification system exists for dentigerous cyst size, a clinical study of odontogenic cysts in the mixed dentition classified lesions by their maximum radiolucent diameter as small (10–20 mm), medium (20–30 mm), or large (> 30 mm) [14]. The present lesion measured 22 × 18 mm at the initial visit and was therefore classified as medium-sized. In contrast, another study defined cysts with a maximum diameter of < 5.5 cm as small and those ≥ 5.5 cm as large [15], under which our case would be classified as a small dentigerous cyst.

Dentigerous cysts typically exhibit benign expansile growth with a smooth cystic wall. In contrast, odontogenic keratocysts (OKCs) characteristically grow in the anteroposterior direction and may become multilocular or develop satellite cysts when large. Unicystic ameloblastomas (UAs) often exhibit irregular mural nodules, a lobulated contour, or scalloped bone resorption. These aggressive features help distinguish them from dentigerous cysts [16, 17]. Besides, the follicular variant of adenomatoid odontogenic tumor (AOT) may also mimic a dentigerous cyst by presenting as a unilocular radiolucency surrounding the crown of an impacted tooth. However, characteristic “snowflake” calcifications and extension of the lesion beyond the cementoenamel junction to partially envelop the root are key distinguishing features [18]. Calcifying odontogenic cyst (COC) may likewise resemble a dentigerous cyst radiographically, and definitive diagnosis often requires histopathological examination [19].

Traditionally, complete removal of the cyst wall together with the involved tooth was adopted in order to obtain the low recurrence. In children during mixed dentition, this often leads to missing teeth and occlusal dysfunction. Because of these drawbacks, decompression has become the preferred function‑preserving procedure [8]. Decompression continuously reduces intracystic pressure, stops cyst expansion, accelerates bone regeneration, and allows spontaneous eruption of the involved tooth. Berberi et al. [9] reported a case of a large dentigerous cyst in a child during mixed dentition that completely resolved after decompression, with several involved teeth erupting successfully and good bone healing at the 5‑year follow‑up. A systematic review [20] showed that treatment usually takes 1–2 years, requires long‑term patient compliance for cavity irrigation, and some patients still need a second enucleation of residual cyst tissue. Cobo-Vázquez et al. [21] reported no recurrence over a mean follow-up of 33 months after conservative treatment in children, suggesting a low recurrence risk after complete healing. Nevertheless, longer follow-up is required to confirm long-term outcomes.

A dentigerous cyst in a child may undergo spontaneous fenestration. the impacted tooth penetrates the bone and communicates with the oral cavity, the intracystic pressure decreases naturally, and the lesion regresses without any intervention. Ewbank et al. [10] described a 12‑year‑old child with an impacted mandibular canine and an associated dentigerous cyst that resolved spontaneously over 4 years. Xu et al. [11] also reported a case in which a dentigerous cyst spontaneously fenestrated because of gingival discharge and follow‑up showed marked reduction of the cyst and improvement of the impacted tooth position without significant medical intervention.

The spontaneous eruption of the affected tooth observed in the present case may also be explained by the biological mechanisms underlying tooth eruption. Increased expression of OPG, decreased expression of RANKL, and a reduced RANKL/OPG ratio within the cyst lining may inhibit osteoclastic bone resorption overlying the crown, thereby impeding the formation of an eruption pathway [22–24]. In addition, the persistent pressure exerted by the cystic fluid on the surrounding bone is considered another important factor hindering tooth eruption [25]. Decompression, whether surgical or spontaneous, relieves the physical obstruction caused by intracystic fluid pressure, restores normal signalling from the follicle, and directs coronal bone resorption. Meanwhile, the young permanent tooth continues root development, providing the driving force for eruption.

Alkhatib et al. [26] treated 16 children aged 6–12 years with dentigerous cysts by simple decompression alone; after 8–24 months of follow‑up, all involved permanent teeth had erupted completely and the cystic bone defects had healed fully. However, not all cases allow spontaneous eruption after decompression. Studies indicate that younger age, immature root development, small tooth angulation, small cyst volume, and a superficially impacted position are favourable factors for spontaneous eruption after decompression. In contrast, older age, nearly completed root development, and large tooth angulation often require orthodontic traction after decompression [4, 27, 28].

At the initial presentation of our patient, the lesion had not caused any adverse effects such as displacement of adjacent teeth or jaw expansion. In addition, the cortical bone overlying the crown of tooth 36 was already discontinuous, providing a basis for spontaneous fenestration. Moreover, the tooth had an immature root, small angulation angle, and good eruptive potential, all of which are considered favourable factors for spontaneous eruption. Based on these clinical and radiographic findings, a conservative approach consisting of regular clinical and radiographic follow-up was adopted. Therefore we decided against any iatrogenic intervention and only scheduled regular follow‑up. Similar strategies of dynamic observation have been reported to be feasible in a limited number of previous case reports [10, 11]. In the present case, the spontaneous regression of lesion and a clear coronal eruptive movement of tooth 36 was found after 6 months of follow-up. After 2 years, tooth 36 had erupted, the cyst cavity had disappeared, bone healing was good, and function was normal. This outcome further supports the feasibility of conservative observation under strict case selection.

Nevertheless, this case has several limitations limitations. At the initial presentation, the dentigerous cyst associated with tooth 36 slightly involved the distal root of tooth 75 without obvious root resorption. By the 6-month follow-up, marked distal root resorption of tooth 75 had developed. Whether this resulted from prolonged cystic compression or the altered eruption pathway of tooth 36 remains unclear. The patient was then lost to follow-up and returned 1.5 years later, when tooth 75 showed complete root resorption and tooth 36 had erupted ectopically in a mesial direction. Finally, tooth 75 was extracted, followed by space maintenance. This case underscores that, even with conservative observation, close follow-up is essential to monitor eruption and adjacent teeth, allowing timely intervention if ectopic eruption occurs to prevent secondary arch complications. In addition, aspiration or fine-needle aspiration cytology (FNAC) may aid the differential diagnosis of dentigerous cysts. However, neither examination was performed because of the limited patient cooperation, representing another limitation of this case.

In summary, both surgical decompression and spontaneous fenestration appear to share the similar mechanism by converting a closed cyst into an open one. Therefore, in carefully selected children during the mixed dentition period, conservative observation with dynamic follow-up may be a feasible strategy for dentigerous cysts associated with young permanent molars, maximizing preservation of the permanent tooth germ and dental arch integrity. However, this approach depends on close, regular follow-up with clearly defined criteria for timely intervention. Further studies are needed to clarify the underlying mechanisms and facilitate individualized management of dentigerous cysts in children.

Abbreviations

CBCT

Cone beam computed tomography

OKCs

Odontogenic keratocysts

UAs

Unicystic Ameloblastomas

AOT

Adenomatoid odontogenic tumor

COC

Calcifying odontogenic cyst

FNAC

Fine-needle aspiration cytology

Authors’ contributions

This study was conceived by ZCH and CHY who also wrote the manuscript. MZT.CJ and GT .CYM—interpreted the radiologic data and analyzed the manuscript.LPP—recorded and analyzed the clinical information and revised the manuscript. All authors read and approved the final manuscript.

Funding

This study was supported by the Youth Science Foundation Project of Shandong Natural Science Foundation(No.ZR2024QC113).

Data availability

The data used to support the findings of this study are available from the corresponding author upon request.

Declarations

Ethics approval and consent to participate

Not applicable. Clinical trial number Not applicable.

Consent for publication

A written informed consent for publication was obtained from the patient to publish all clinical details and any accompanying images.

Competing interests

The authors declare no competing interests.