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Trauma, solitary bone cyst and delayed eruption of permanent mandibular incisors. An unusual case in a 7-year-old patient.


Solitary bone cysts (SBC) are classified as non-neoplastic lesions related to the bone by the WHO in 1992. They are defined as "intra-osseous cysts having a tenuous lining of connective tissue without epithelial lining" [Chapman and Romaniuk, 1985]. SBCs are also known as "traumatic bone cysts", "simple bone cysts", "haemorrhagic bone cysts", "extravasation cysts", unicameral bone cyst and progressive bone cavity [Donkor and Punnia-Moorthy, 1994; Xanthinaki et al, 2006]. Most cysts present in the mandible, beneath the teeth anterior to the ramus or between the mental foramina in the anterior region of the mandible. A smaller percentage of the cysts are reported in the ramus, condyle and the maxilla, mainly in the anterior part (3.4%) [Fielding et al., 1999; Harnet et al., 2008]. They are usually found in patients between 10 and 20 years old (75%). Males and females are affected almost equally [Harnet et al., 2008]. The aetiology of SBC is still obscure; however several theories have been suggested such as abnormality of bone growth, trauma and intra-osseous vascular abnormalities [Harnet et al., 2008].


Most SBCs present no functional signs. Between 60-80% of the patients remain asymptomatic and the cyst is discovered accidentally during a routine radiographic examination. However, some patients complain about pain and swelling [Copete et al., 1998]. Pain is the most frequent presenting symptom, affecting the 10-30% of patients. Tooth sensitivity, fistulas, paraesthesia, delayed tooth eruption and pathological fracture of the mandible have also been reported. The radiographic examination reveals a well-defined radiolucency with a very typical "scalloped" appearance which extends between the roots of the adjacent teeth. Sometimes, the appearance of the cyst does not present with these characteristic features [Horner et al., 1988; Harnet et al., 2008].

Case report

A 7-year-old Caucasian boy, free of any remarkable medical history, was referred by his general dental practitioner to the Department of Paediatric Dentistry of Aristotle University of Thessaloniki. The main complaint was a delay in the eruption of the permanent mandibular central incisors. Clinically, there was no pain or swelling in the region. The panoramic radiographic examination presented a large, radiolucent lesion, which extended in the anterior region of the mandible between the roots of the permanent incisor teeth, largely displacing them and preventing their eruption (Figure 1). A history of trauma in the anterior region of the mandible at 3 years of age was recalled by his parents. They reported that the child had fallen from his bed and he had injured his chin, and that his primary incisors were luxated. Their GDP advised a soft diet for a period of two weeks and after a 3-month follow-up, no further treatment or radiographic examination was suggested at that time.



The treatment of choice was the surgical exploration of the cyst. This was carried out under general anaesthesia due to the patient's age and lack of adequate cooperation. Following the elevation of a mucoperiosteal flap and removal of the underlying buccal bone, an empty cavity without any discernible lining was revealed. Curettage of the cavity wall was performed and some specimens were sent for histological examination. The pathology report revealed normal bone spicules containing fibrous connective tissue and granulation tissue with lymphocytes and multinucleate giant cells (Figure 2a-b).


Close follow-up was planned and, in the two years following the initial operation, there was radiographic evidence of considerable bony regeneration (Figure 3a). Clinically, the mandibular permanent central incisors erupted in their normal position and they were vital. A characteristic discolouration of the enamel of the left central mandibular incisor was noted which was attributed to trauma to its tooth germ (Figure 3b).


The aetiology of this type of cyst is not clear. The most popular theory is the traumatic-haemorrhagic theory, whereby intra-medullary haemorrhage occurs following trauma which is too slight to cause a fracture. The subsequent clot fails to organise and remodeling does not occur leaving an empty cavity within the bone [Kuttenberger et al., 1992]. The present case can be explained according to this theory because the child had sustained trauma 4 years before the initial examination. The history of trauma was consistent with the localised enamel discolouration present in one of the erupting permanent incisors.

When taking a medical and dental history for most cases of SBC, a previous injury of the affected region of the jaws existed despite problems in objectivity of recording the trauma history. The time elapsed between injury and the discovery of SBC varied from 1 week to 20 years [Xanthinaki et al., 2006].


Clinically, the cyst is nearly always asymptomatic. Occasionally the patients complain of pain and swelling but cortical expansion of the mandible does not occur [Xanthinaki et al., 2006]. When it does, it is indicative of a more aggressive benign or odontogenic neoplasm. Less commonly, root resorption, disturbed labial sensation and pathologic fracture of the mandible have been described [Copete et al., 1998].

In the present case the cyst had caused a large displacement and a delay in the eruption of the permanent mandibular incisors. Radiographically, a well-defined radiolucency with a scalloped appearance is evident, when the cyst involves the roots of the adjacent teeth. This finding is not pathognomonic. Thus differential diagnosis from other types of cysts such as dentigerous, residual and radicular cysts must be made. However, the lamina dura around the involved roots in SBCs remains intact and root resorption is almost never found [Horner et al., 1988]. Due to failure of permanent eruption, the present case implies that SBC should be included in the differential diagnosis of radiolucent lesions associated with unerupted teeth, especially when there is a history of trauma.

The definite diagnosis of the SBC can be achieved only during the surgery when an empty bone cavity is observed and after the histopathology results. Most histological findings reveal normal bone and fibrous connective tissue. There is no evidence of epithelial lining. Also, sometimes, erythrocytes, lymphocytes and occasional giant cells can be found adjacent to the bone surface. The pathological report of the present case supported the evidence that this cystic lesion was a solitary cyst [Copete et al., 1998].

The current treatment of choice is surgical exploration of the cyst with curettage of the bony cavity. Curettage promotes bleeding and haematoma formation, which leads to bony regeneration. Although resolution of the cyst without treatment has been reported, the watch-and-wait policy is not recommended, as SBC may become symptomatic or may cause a pathologic mandibular fracture [Tong et al., 2003].

Following treatment, the patient must be closely followed-up to confirm bony regeneration and early detection of a possible recurrence [Fielding et al., 1999]. Recurrence is not uncommon with rates varying between 2-20%. The patient must be followed-up clinically and radiographically every 1-2 years until healing occurs. More frequent examination is not necessary since recurrent lesions, even if present, grow extremely slowly [Suei et al., 2007]. The surgical treatment of the present case of SBC led to complete healing and eruption of the mandibular permanent incisors.


Clinicians should be aware that SBC is associated with trauma, mainly of the mandible, and with a possible delay of eruption of the corresponding teeth. Dentists, oral and maxilio-facial surgeons should be aware of SBCs, the collection of accurate data of which could lead to more definite conclusions regarding the aetiology.


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Horner K, Forman GH, Smith NJ. Atypical Simple Bone Cysts of the Jaws. I: Recurrent Lesions. Clin Radiol 1988; 39:53-57.

Kuttenberger JJ, Farmand M, Stoss H. Recurrence of a solitary bone cyst of the mandibular condyle in a bone graft. Oral Surg Oral Med Oral Pathol 1992; 74:550-556.

Suei Y, Taguchi A, Tanimoto K. Simple bone cyst of the jaws: Evaluation of treatment outcome by review of 132 cases. J Oral Maxillofac Surg 2007; 65:918-923.

Tong AC, Ng IO, Yan BS. Variations in clinical presentations of the simple bone cyst: report of cases. J Oral Maxillofac Surg 2003; 12:1487-1491.

Xanthinaki AA, Choupis KI, Tosios K, Pagkalos VA, Papanikolaou SI. Traumatic bone cyst of the mandible of possible iatrogenic origin: a case report and brief review of the literature. Head Face Med 2006; 12:40.

D. Lazaridou *, A. Arhakis *, M. Lazaridou **, N. Kotsanos *, K. Antoniadis **

Depts of * Paediatric Dentistry, Dental School and ** Oral and Maxillofacial Surgery, Dental School, Aristotle University of Thessaloniki, Thessaloniki, Greece

Postal address: Dr D. Lazaridou, Dept Paediatric Dentistry, Dental School, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.

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Author:Lazaridou, D.; Arhakis, A.; Lazaridou, M.; Kotsanos, N.; Antoniadis, K.
Publication:European Archives of Paediatric Dentistry
Article Type:Case study
Geographic Code:4EUGR
Date:Oct 1, 2011
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