Osseous dysplasia (OD), a rare and benign fibro-osseous lesion of the jaws, can mimic a radiolucent endodontic periapical lesion in the early stage of its maturation. Whereas differentiating such conditions in a vital tooth can be relatively straightforward, the situation becomes more complex when faced with endodontically-treated teeth, especially in cases of presumed inadequate treatments. Correct differential diagnosis is thus of paramount importance for the clinician, in order to avoid unnecessary iatrogenic dental treatments.
Florid osseous dysplasia (FOD) is the widespread form of osseous dysplasia; periapical OD is confined to the anterior mandible; focal OD occurs in a single sextant and familial gigantiform cementoma is an uncommon variant encountered preferentially in young patients that can lead to considerable bone expansion [8, 9].
In FOD, the molar and premolar teeth are the most frequently involved. FOD is usually asymptomatic and thus an incidental finding during a routine dental radiographic examination. The rare clinical symptoms observed are pain, swelling and local drainage but these are only encountered in cases of secondary infection, when the calcified masses are exposed in the oral cavity.
FOD follows an ethnic distribution, as shown in the systematic review of MacDonald-Jankowski in 2003: 59% of cases arise in African patients, 37% in Asians and 3% in Caucasians. In our patient series, collected within a French Parisian hospital, 92% of cases arose in African patients. Women are more affected than men and the disease occurring mostly around the fourth decade [10]. Several autosomal dominant cases of FOD have also been reported in the literature [5, 8]. Interestingly and similarly to the third case previously presented, simple bone cysts have been reported in association with FOD, but no conclusive explanation for such association has been found yet [11].
Because of its typical clinico-radiographic presentation, diagnosis of FOD is usually straightforward and does not require any additional investigations. For instance, the discovery of multiple periapical radiolucencies on vital teeth in different quadrants is a sufficient argument to evoke the diagnosis of Florid Osseous Dysplasia. There is no need for a biopsy in typical cases, especially considering the risk of secondary infection of these hypovascularized lesions. Nevertheless, when in doubt, a biopsy can be performed to rule out other fibro-osseous lesions or bone diseases [7].
Differential diagnosis of early stage FOD (Fig. 1) should include others periapical radiolucent lesions especially apical periodontitis, whereas radiopaque FOD lesions (Figs. 2 and 3) should be differentiated from chronic diffuse osteomyelitis, Paget disease and other fibro-osseous lesions such as ossifying fibroma (Fig. 6) and fibrous dysplasia [5, 7, 10, 12, 13]. In particular, differential diagnosis with ossifying fibroma can be difficult when faced with a small solitary lesion, both entities sharing near-identical radiological features.
As FOD is a benign usually self-limiting disease, treatment of such condition mostly consists of simple monitoring of the lesions, with an annual long-term clinical and radiographic follow-up [4, 5, 14, 15]. Patients should be informed of the slowly growing nature of FOD as well as the self-limiting behavior of the lesions. Complications of such disease are rare, mostly local surinfection of the lesions. In case of local FOD lesion infection, a surgical resection of the dysplastic fibro-osseous bone can be carried out under antibiotic treatment, taking into consideration the poor tissue diffusion of the antibiotic because of the avascular nature of these lesions. Symptomatic cases with swelling and deformation require a more complex management, usually a partial resection of the lesions to alleviate the symptoms. Several cases of osteomyelitis have been reported as a possible complication of FOD [16,17,18].
FOD is a condition of significant importance for the endodontist and general dental practitioner. Endodontic lesions and FOD may co-exist (Figs. 2 and 3) and FOD can affect the diagnosis, prognosis and monitoring of endodontic lesions [19]. For instance, when FOD lesions become radiopaque, the periodontal ligament space becomes invisible on radiographic examinations and can no more serve as an aid in determining accurate working length of the tooth. In cases where periapical surgery is required, clinicians must be aware of the risk of secondary infection of FOD lesions because of their avascular nature, strongly impairing periapical healing.
A classic clinical conundrum for the dental clinician is trying to accurately diagnose the radiolucent periapical lesion in an endodontically-treated tooth in a patient presenting with FOD. Several questions arise: Is the periapical lesion a FOD lesion, an apical periodontitis or a surinfection of a FOD lesion? Is the endodontic treatment a consequence of a misdiagnosed FOD lesion or an adequate treatment of a superinfected FOD lesion? Indeed, reports of lesions mimicking periapical endodontic lesions leading to inappropriate endodontic treatments are frequent in the literature [15].
In this paper, we presented several clinical cases of patients presenting typical FOD lesions, in healthy teeth, endodontically-treated teeth or decayed teeth (Figs. 1, 2 and 3). As previously illustrated, diagnosis and management of such lesions can be quite challenging especially in stage 1 osteolytic FOD lesions, which can perfectly mimic apical periodontitis [20]. Whereas three-dimensional CBCT examination is of little use in typical FOD lesions (easily diagnosed on simple two-dimensional radiographs), it can be a significant aid in elucidating the nature of periapical pathology observed in FOD patients. Indeed, CBCT can provide useful information about the lesion’s limits, local extension and radiopacity [19]. For instance, thin cross-sections may underline faint differences regarding the radiodensity of stage 1 OD, which may seem slightly denser in contrast with the trabecular space or that can include minute micro-opacities (Fig. 5). Moreover, FOD lesions are self-limited above the mandibular canal (Fig. 3) and below the hard palate junction in the maxilla thus always limited to the alveolar process [3]. On the contrary, other fibro-osseous lesions such as ossifying fibroma (Fig. 6) show a more aggressive and expansive behavior, useful in differentiating the two conditions.
