Early recognition and monitoring
The dental follicle is part of the tooth germ, which originates from the odontogenic ectomesenchyme. Once a tooth has fully developed, the coronal part of the follicle, which is termed the pericoronal sac or follicle, can occasionally sit adjacent to the crown of unerupted teeth.6 It is made up of fibrous connective tissue and frequently contains epithelial residues of odontogenesis, which could be the start of pathology.7 Radiographically, unerupted/impacted wisdom teeth may present with a surrounding thin pericoronal radiolucency, the thickness of which considered ‘normal’ being reported as less than 2.5–3 mm.8,9,10 However, there is no generally accepted consensus on the clinical criteria to differentiate between normal and pathological conditions based on radiographic features.
Even with this ‘normal’ value in mind, various studies have reported pathological changes between 23% and 58.5% with pericoronal follicles that are 2.5 mm or less, particularly those associated with the lower third molar.11,12
Dentigerous cysts are the most common pathological change identified in dental follicular tissue, with impacted third molar pathological follicular tissues reported as being 70–86%.13,14 Ameloblastomas are the second most frequently seen pathological change, with up to 20% of all unicystic ameloblastomas forming within the wall of a dentigerous cyst.15 Several aetiological factors have been proposed for the explanation of this change, and include trauma, inflammation, nutritional deficiency and viral infections.16
There have also been reports of other pathological entities found in the pericoronal follicle of an unerupted or impacted tooth, such as calcifying odontogenic cysts, odontogenic keratocysts, myxomas, odontogenic fibromas, muco-epidermoid carcinoma and fibrosarcomas.11,12,13,14,15,16,17
The growth rate of such pathologies would be dependent on its histological nature, with a meta-analysis reporting the ameloblastoma specific growth rate as 87.84%/year.18 Dentigerous cysts can also exhibit rapid growth, having been reported as up to 5 cm over 3–4 years.19
In 2012 and 2013, the size of the follicle in our patient was 5–6 mm, and at re-attendance in 2017, this had increased to 40 mm (transverse) x 60 mm (craniocaudal), an approximate growth of 54 mm over 4 years (13.5 mm growth/year or 78%/year). It is unknown whether the tumour grew at a uniform rate during this time or whether there was a rapid period of growth preceding the patient's symptoms because the patient did not attend for regular reviews of the cyst with his GDP as advised. A systematic review and meta-analysis found that many patients with large ameloblastomas reported slow growth over a period of years, before a short episode of rapid growth which prompted them to seek medical attention. It is thought that the growth pattern is not linear, but begins slowly before accelerating.18 However, it is difficult to study the growth of ameloblastomas as treatment is initiated immediately following detection. Few case studies where a patient has refused surgical intervention, thereby allowing the growth to be monitored, have been reported, leading to low quality of evidence.
On presentation, the patient described a ‘crackling sound’ when yawning, crepitus was also found on palpation of the swelling. This phenomenon is referred to as ‘egg shell cracking’ and is an important diagnostic feature of an ameloblastoma. The slow bucco-lingual expansion of an ameloblastoma allows the periosteum to form a thin layer of bone around the expanding lesion, this bone cracks on palpation leading to crepitus.20
It can be difficult to monitor these lesions radiographically due to their tendency to expand bucco-lingually. We appreciate our case was above the recommended normal follicular size of 2.5–3 mm; however, studies have shown radiographically normal follicular radiolucencies associated with pathological entities on histological assessment. GDPs should habitually assess the size of dental follicles when reporting on radiographs, such as DPTs. Where there are concerns regarding enlargement of the follicle, regular radiographic monitoring is ideal, and we suggest these radiographic reviews be at annual or bi-annual intervals initially, with longer intervals if there are no changes. Previous imaging, CBCT and clinical assessment should also be considered.
Therefore, the role of the GDP is to ensure clinical assessment for signs of expansion in areas of impacted or unerupted teeth, carrying out peri-apical or DPT radiographic review if required, with comparison to previous imaging, and referral to secondary care oral and maxillofacial departments where there is any concern. If a DPT image has been taken in the secondary care setting, it would be valuable to have this available at the general dental practice for reference.
