Abstract
The aim of this research is to analyze the prevalence of dentigerous cysts (DCs) in a population-based cohort in British Columbia, Canada, and to report unusual cases associated with DC. The database of the British Columbia Oral Biopsy Service was searched from 1998 to 2007. 2082 histologically confirmed DCs from 2029 patients were retrieved and retrospectively analyzed for incidence, age, gender and ethnicity. The results show that this is a common jaw cyst with male predilection, has a peak incidence in younger adults and is more common in Caucasians. Multiple DCs, representing 2.5% of the cases, are not associated with any syndromes or systemic conditions. 0.5% DCs were associated with other cysts or tumours at the same site or the opposite side of the jaw. The authors report the first series of cases presenting clinically as bilateral DCs, but histologically as an odontogenic tumour or another type of odontogenic cyst. DCs can co-exist with other more serious conditions, such as odontogenic keratocyst or cystic ameloblastoma. This association with more significant conditions indicates the importance of histologically confirming any jaw cyst, even when it presents clinically as a classic DC.
Dentigerous cyst (DC) is the most common cyst in the jaw. A typical DC presents clinically as an asymptomatic unilocular radiolucency enclosing the crown of an unerupted or impacted tooth; the radiolucency usually arises in the cemento-enamel junction (CEJ) of the tooth. In most cases, the diagnosis of a DC is straightforward; but even a radiographically ‘typical’ DC can be found to be something else, such as a dental follicle, hyperplastic dental follicle, odontogenic keratocyst (keratocystic odontogenic tumour, KCOT) or unicystic ameloblastoma on histological analysis . De novo DCs can also transform into more serious lesions, such as unicystic ameloblastoma . DCs may not always look typical and radiographically can resemble other lesions . Histological diagnosis of these lesions is therefore critical.
Multiple DCs were thought to be rare and exclusively associated with syndromes or systemic conditions, such as mucopolysaccharidosis and cleidocranial dysplasia . Recently, that perception has changed. In Chile in 2007, O chsenius et al. analyzed 2944 odontogenic cysts and identified 61 (11%) multiple DCs from 546 patients with DCs; none of these cases had a known association with syndromes or systemic conditions . This is the largest study in the literature .
In British Columbia, Canada, there is a province-wide Oral Biopsy Service (BC OBS). BC OBS has provided free services for dentists and otorhinolaryngology surgeons throughout the province since 1985. Biopsy samples and often the associated radiographs are received. The objectives of this study are to report the largest and longest (1998–2007) population-based cohort of histologically diagnosed DCs in North America and to present some first-ever rare cases from this cohort.
Materials and methods
All the samples are from the BC OBS. The pathology database of the BC OBS was reviewed from 1998 to 2007. The inclusion criterion for sample selection was a histological diagnosis of DC. The data collected included the patients’ demographic information (age, gender and ethnicity) and associated tooth location. All the DCs have been reviewed histologically to confirm the diagnosis. The study was approved by the Clinical Research Ethics Board at the University of British Columbia (H08-02037).
Fisher’s exact test was used for categorical variables and t -test for continuous variables. All tests were two-sided. P < 0.05 was considered to be statistically significant.
Results
From 1998 to 2007, 38,579 cases of oral biopsies were diagnosed at the BC OBS. Of these, 6807 (18%) were jaw bone cysts and 2029 were DCs, representing 5% of all biopsies and 30% of jaw cysts. There was a wide variation in age distribution amongst patients with DC, ranging from 6 to 99 years with an average 35 ± 17 years ( Fig. 1 ). DCs were rare in the first decade and most common in the second and third decades and the frequency declined with age. Figure 1 also illustrates the gender distribution. Males accounted for 61% of the patients. Amongst these, 1181 (58%) cases had information on ethnic origin: 85% were Caucasian, 13% were Asian, and there were 2% others.
Most patients had single DC (98%) and 51 (3%) patients had multiple DCs (see example in Fig. 2 ). The total number of DCs was 2082; the majority (82%) of which were located in the lower jaw ( Fig. 3 ), mostly at the mandibular third molar (77%), followed by the maxillary third molar (11%), the maxillary canine (5%), and very rarely in the remaining 26 tooth locations (6%). 11 DCs were associated with impacted supernumerary teeth (1%).
Several interesting findings were identified with the association of these DCs. Five patients with concurrent biopsy samples submitted from bilateral radiolucencies in the mandibular third molar regions all had clinical diagnoses of bilateral DCs. For each of these patients, one radiolucency showed DC, the other showed pathologies other than DC: three calcifying ghost cell odontogenic cysts (calcifying cystic odontogenic tumor), one glandular odontogenic cyst, and one KCOT. In another separate six cases, the DC was co-existed with other pathologies: five with odontomas (see example in Fig. 4 ), one with central giant cell granuloma, and one KCOT (see example in Fig. 5 ). The authors also identified 2 rare DCs with unicystic ameloblastoma derived from DC (see example in Fig. 6 ).
Results
From 1998 to 2007, 38,579 cases of oral biopsies were diagnosed at the BC OBS. Of these, 6807 (18%) were jaw bone cysts and 2029 were DCs, representing 5% of all biopsies and 30% of jaw cysts. There was a wide variation in age distribution amongst patients with DC, ranging from 6 to 99 years with an average 35 ± 17 years ( Fig. 1 ). DCs were rare in the first decade and most common in the second and third decades and the frequency declined with age. Figure 1 also illustrates the gender distribution. Males accounted for 61% of the patients. Amongst these, 1181 (58%) cases had information on ethnic origin: 85% were Caucasian, 13% were Asian, and there were 2% others.
