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Dentigerous cyst: a retrospective clinicopathological analysis of 2082 dentigerous cysts in British Columbia, Canada
Int. J. Oral Maxillofac. Surg. 2010; 39: 878–882 doi:10.1016/j.ijom.2010.04.048, available online at http://www.sciencedirect.com
Clinical Paper Clinical Pathology
Dentigerous cyst: a retrospective clinicopathological analysis of 2082 dentigerous cysts in British Columbia, Canada
L. L. Zhang1,2, R. Yang2, L. Zhang2, W. Li1, D. MacDonald-Jankowski2, C. F. Poh2 1 State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China; 2 Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, BC, Canada
L. L. Zhang, R. Yang, L. Zhang, W. Li, D. MacDonald-Jankowski, C. F. Poh: Dentigerous cyst: a retrospective clinicopathological analysis of 2082 dentigerous cysts in British Columbia, Canada. Int. J. Oral Maxillofac. Surg. 2010; 39: 878–882. # 2010 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. 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 cemento0901-5027/090878 + 05 $36.00/0
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
Keywords: dentigerous cyst; multiple cysts; prevalence; clinicopathological analysis. Accepted for publication 27 April 2010 Available online 3 June 2010
keratocyst (keratocystic odontogenic tumour, KCOT) or unicystic ameloblastoma on histological analysis3,4. De novo DCs can also transform into more serious lesions, such as unicystic ameloblastoma7. DCs may not always look typical and
# 2010 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
A clinicopathological analysis of dentigerous cysts radiographically can resemble other lesions18. 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 dysplasia9,15,22. Recently, that perception has changed. In Chile in 2007, OCHSENIUS 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 conditions13. This is the largest study in the literature5. 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.
879
Fig. 1. Age and gender distribution of 2029 patients with DCs.
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.
Fig. 2. Panoramic radiograph of a patient with two unilocular radiolucencies enclosing the cemento-enamel junction at the bilateral mandibular third molars. Both cysts showed DC histologically.
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
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
Fig. 3. Location distribution of 2082 DCs.
(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
880
Zhang et al.
Fig. 4. Photomicrographs of a DC (A) and associated odontoma (B, decalcified section) (haematoxylin–eosin staining, original magnification 100).
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). Discussion
The frequency of DCs in the literature, in studies with at least 50 DCs reported, varied from 9% to 38%1,11,12,21,23. The incidence of DCs in biopsy samples at BC OBS in the 10-year period (1998– 2007) was high, accounting for 33% of all jaw cysts. The variation in the frequency amongst reports is intriguing.
Some population may have a lower incidence of DCs. The number can be underreported due to the clinician’s confidence in diagnosis, not wanting to pay the extra fee for the service involved, or the benign nature of the cyst when no samples are submitted for pathology review. The BC OBS provides a free service so the frequency of DCs reported here may be closer to the true value. Most reports showed a peak incidence of DCs in the second and third decades of life2,6,13,21, although some indicated the fifth decade8. The present study supports the majority results and showed a peak incidence in the second (23% of all DCs) and third (20%) decades. A significant percentage of cases also occurred in the fourth, fifth and sixth decades of life (17%, 17% and 12%, respectively). Only a very small percentage of DCs occurred in those in their first decade or the seventh decade and above. The peak age incidence must
Fig. 5. Photomicrograph of a case with co-existence of 2 cysts: the lining epithelium is characterized as an odontogenic keratocyst (*right upper) and a DC (left lower) (haematoxylin–eosin staining, original magnification 100).
be interpreted with caution. Currently many dentists in British Columbia encourage young people to have their unerupted teeth extracted. Consequently, people in the fourth decade and older may have fewer unerupted teeth, and the lower incidence of DCs in the older population may reflect this. A further population based prospective study is required to confirm the value of the prophylactic removal of unerupted/impacted teeth14. The present results demonstrated that males had a slightly higher incidence of DCs than females (1.6:1). This finding is similar to that in previous studies2,11,13. The reason for this gender predilection is not clear. DALEY et al.2 suggested that it might be related to a smaller jaw size and a greater tendency for prophylactic extraction of third molars in females. Caucasians were more likely to develop DCs than Asians. When the ethnicity distribution of the authors’ data (all 10 years, year 2006 and year 2001) with those of BC population from Statistic Canada Census (year 2006 and year 2001), the proportion of DCs in Caucasians was significantly higher than in Asians (all P < 0.0001)19,20. The annual incidence rate for Caucasians was 65–84 per million population; for Asians it was 23–27 per million population. Few studies have reported the incidence of DCs in different ethnic groups, but SHEAR & SPEIGHT17 indicated that Caucasians were more likely to develop DCs compared with Blacks. To the authors’ knowledge, this is the first report to compare the incidence of DC between Caucasians and Asians. The data suggest a higher need for prophylactic extraction of DCs in Caucasians. The present data showed that most DCs (77%) were located in the mandibular third molar region. This concurs with
A clinicopathological analysis of dentigerous cysts
881
is supported by Clinician Scientist Award of Canadian Institute of Health Research and Scholar Award from the Michael Smith Foundation for Health Research. Ethical approval
The study was approved by the Clinical Research Ethics Board at the University of British Columbia (H08-02037). References
Fig. 6. Photomicrograph of an evolving cystic ameloblastoma from a DC. The epithelial cell at the most superficial layer (*) has become enlarged and squamoid shaped with a prominent nucleus and the cells at the basal cell layer have become palisading with a suggestion of reverse polarity of the nucleus (haematoxylin–eosin staining, original magnification 200).
the majority of studies. Mandibular 3rd molars or molars (specific site not stated) are the most common site for DCs. One study from Italy found DCs were most commonly seen in the mandibular premolar region with only 4 (3%) of the 149 DCs in the mandibular molar region21. The proportion of DCs in the mandibular third molars varies in different countries: 77% in Canada2, 73% in the UK8, 51% in South Africa16, 45% in Mexico11, 43% in Brazil6, 39% in Turkey10 and 29% in Chile13. The reasons for this remain speculative. One suggestion is that DCs in Anglo-Saxons predominantly occur in the mandibular third molar region. Most patients only had one DC, but 3% (N = 51) of patients had DCs at multiple locations, predominantly (98%) involving wisdom teeth, particularly mandibular wisdom teeth. Multiple DCs have rarely been reported and are thought to be associated almost exclusively with patients with syndromes or systemic diseases9,15,22. The present results concur with recent reports5,13 but contradicted this conventional notion as none of the 51 patients had known systemic diseases/ syndromes, confirmed by telephone calls to the submitting clinicians. It is possible that the occurrence of multiple DCs is not rare but publications about them are. About 0.5% (N = 11) of cases in the present study were associated with concurrent pathology in the opposite side of the jaw (all five at the opposite mandibular third molar region: three calcifying cystic odontogenic tumor, one KCOT and one glandular odontogenic cyst) or at the same location (six odontomas, one central giant cell granulomas and one KCOT). To the best of the authors’ knowledge, there are
no reported cases presenting clinically as bilateral DCs, but histologically as an odontogenic tumour or another type of odontogenic cyst at one side and DC at the other. This study did not check the proportion of unicystic ameloblastoma or KCOT that had part of the cystic lining of a DC microscopically. The authors saw one KCOT (Fig. 5) and one cystic ameloblastoma (Fig. 6) with a portion of cystic lining consistent with a DC. This supports the notion that DC could evolve into more serious disease and shows the importance of submitting samples for pathology examination even when cysts present clinically as classical DC. In conclusion, this is the largest number of DCs reported from a population-based cohort in the literature. The results support previous findings that this is a very common jaw cyst with male predilection, a peak incidence in the second and third decades and a prevalence in Caucasians. DC could give rise to more serious diseases such as KCOT and cystic ameloblastoma. Multiple DCs were not extremely rare as previously suggested and DC could be associated with another pathology, either at the same site or at another jaw location. Competing interests
We affirm that we have no financial affiliation (e.g., employment, direct payment, stock holdings, consultancies, honoraria, ownership of shares). Any other potential conflict of interest is disclosed. Funding
LLZ is sponsored by the State Scholarship Fund of China Scholarship Council. CFP
1. Bataineh AB, Rawashdeh MA, Al Qudah MA. The prevalence of inflammatory and developmental odontogenic cysts in a Jordanian population: a clinicopathologic study. Quintessence Int 2004: 35: 815–819. 2. Daley TD, Wysocki GP, Pringle GA. Relative incidence of odontogenic tumors and oral and jaw cysts in a Canadian population. Oral Surg Oral Med Oral Pathol 1994: 77: 276–280. 3. Dunsche A, Babendererde O, Lu¨ttges J, Springer IN. Dentigerous cyst versus unicystic ameloblastoma— differential diagnosis in routine histology. J Oral Pathol Med 2003: 32: 486–489. 4. Farah CS, Savage NW. Pericoronal radiolucencies and the significance of early detection. Aust Dent J 2002: 47: 262–265. 5. Freitas DQ, Tempest LM, Sicoli E, Lopes-Neto FC. Bilateral dentigerous cysts: review of the literature and report of an unusual case. Dentomaxillofac Radiol 2006: 35: 464–468. 6. Grossmann SM, Machado VC, Xavier GM, Moura MD, Gomez RS, Aguiar MC, Mesquita RA. Demographic profile of odontogenic and selected nonodontogenic cysts in a Brazilian population. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007: 104: e35–41. 7. Houston GD. Oral pathology. Ameloblastoma arising in a dentigerous cyst. J Okla Dent Assoc 2007: 98: 28–29. 8. Jones AV, Craig GT, Franklin CD. Range and demographics of odontogenic cysts diagnosed in a UK population over a 30-year period. J Oral Pathol Med 2006: 35: 500–507. 9. Ko KS, Dover DG, Jordan RC. Bilateral dentigerous cysts—report of an unusual case and review of the literature. J Can Dent Assoc 1999: 65: 49–51. 10. Koseoglu BG, Atalay B, Erdem MA. Odontogenic cysts: a clinical study of 90 cases. J Oral Sci 2004: 46: 253–257. 11. Ledesma-Montes C, Herna´ndezGuerrero JC, Garce´s-Ortı´z M. Clinico-pathologic study of odontogenic cysts in a Mexican sample population. Arch Med Res 2000: 31: 373–376. 12. Mosqueda Taylor A, Irigoyen Camacho ME, Dı´az Franco MA, Torres Tejero MA. Odontogenic cysts. Analysis of 856 cases. Med Oral 2002: 7: 89–96.
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13. Ochsenius G, Escobar E, Godoy L, Pen˜afiel C. Odontogenic cysts: analysis of 2,944 cases in Chile. Med Oral Patol Oral Cir Bucal 2007: 12: E85–91. 14. Rakprasitkul S. Pathologic changes in the pericoronal tissues of unerupted third molars. Quintessence Int 2001: 32: 633– 638. 15. Shah N, Thuau H, Beale I. Spontaneous regression of bilateral dentigerous cysts associated with impacted mandibular third molars. Br Dent J 2002: 192: 75–76. 16. Shear M, Altini M. Odontogenic and non-odontogenic cysts of the jaws. J Dent Assoc S Afr 1983: 38: 555–560 562–564. 17. Shear M, Speight P. Dentigerous cyst. In: Shear M, ed: Cysts of the oral and maxillofacial regions 4th ed. St. Louis: Oxford Wright Inc. 2007: 59–75. 18. Slater LJ. Dentigerous cyst versus paradental cyst versus eruption pocket cyst. J Oral Maxillofac Surg 2003: 61: 149. 19. STATISTICS CANADA, Census of Population. Population by selected ethnic ori-
gins, by province and territory (2001 Census) (British Columbia). http:// www40.statcan.gc.ca/l01/cst01/demo26 k-eng.htm [Accessibility verified July 27, 2009]. 20. STATISTICS CANADA, 2006 Census of Population. British Columbia: Ethnic Origin, Single and Multiple Ethnic Origin Responses. http://www12.statcan. ca/english/census06/data/topics/ RetrieveProductTable.cfm?ALEVEL =3&APATH=3&CATNO=& DETAIL=0&DIM=&DS=99&FL=0 &FREE=0&GAL=0&GC=99& GID=838062&GK=NA&GRP= 1&IPS=&METH=0&ORDER=1& PID=92333&PTYPE=88971&RL= 0&S=1&SUB=0&ShowAll=No& StartRow=1&Temporal=2006& Theme=80&VID=0&VNAMEE=& VNAMEF=#FN4 [Accessibility verified July 27, 2009]. 21. Tortorici S, Amodio E, Massenti MF, Buzzanca ML, Burruano F, Vitale F. Prevalence and distribution of odonto-
genic cysts in Sicily: 1986–2005. J Oral Sci 2008: 50: 15–18. 22. Ustuner E, Fitoz S, Atasoy C, Erden I, Akyar S. Bilateral maxillary dentigerous cysts: a case report. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003: 95: 632–635. 23. Weir JC, Davenport WD, Skinner RL. A diagnostic and epidemiologic survey of 15,783 oral lesions. J Am Dent Assoc 1987: 115: 439–442. Address: Catherine F. Poh Department of Oral Biological and Medical Sciences Faculty of Dentistry University of British Columbia 2199 Wesbrook Mall Vancouver V6T 1Z3 BC Canada Tel.: +1 604 822 7344 fax: +1 604 675 8079 E-mail: [email protected]
Clinical Paper Clinical Pathology
Dentigerous cyst: a retrospective clinicopathological analysis of 2082 dentigerous cysts in British Columbia, Canada
L. L. Zhang1,2, R. Yang2, L. Zhang2, W. Li1, D. MacDonald-Jankowski2, C. F. Poh2 1 State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China; 2 Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, BC, Canada
L. L. Zhang, R. Yang, L. Zhang, W. Li, D. MacDonald-Jankowski, C. F. Poh: Dentigerous cyst: a retrospective clinicopathological analysis of 2082 dentigerous cysts in British Columbia, Canada. Int. J. Oral Maxillofac. Surg. 2010; 39: 878–882. # 2010 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. 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 cemento0901-5027/090878 + 05 $36.00/0
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
Keywords: dentigerous cyst; multiple cysts; prevalence; clinicopathological analysis. Accepted for publication 27 April 2010 Available online 3 June 2010
keratocyst (keratocystic odontogenic tumour, KCOT) or unicystic ameloblastoma on histological analysis3,4. De novo DCs can also transform into more serious lesions, such as unicystic ameloblastoma7. DCs may not always look typical and
# 2010 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
A clinicopathological analysis of dentigerous cysts radiographically can resemble other lesions18. 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 dysplasia9,15,22. Recently, that perception has changed. In Chile in 2007, OCHSENIUS 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 conditions13. This is the largest study in the literature5. 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.
879
Fig. 1. Age and gender distribution of 2029 patients with DCs.
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.
Fig. 2. Panoramic radiograph of a patient with two unilocular radiolucencies enclosing the cemento-enamel junction at the bilateral mandibular third molars. Both cysts showed DC histologically.
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
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
Fig. 3. Location distribution of 2082 DCs.
(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
880
Zhang et al.
Fig. 4. Photomicrographs of a DC (A) and associated odontoma (B, decalcified section) (haematoxylin–eosin staining, original magnification 100).
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). Discussion
The frequency of DCs in the literature, in studies with at least 50 DCs reported, varied from 9% to 38%1,11,12,21,23. The incidence of DCs in biopsy samples at BC OBS in the 10-year period (1998– 2007) was high, accounting for 33% of all jaw cysts. The variation in the frequency amongst reports is intriguing.
Some population may have a lower incidence of DCs. The number can be underreported due to the clinician’s confidence in diagnosis, not wanting to pay the extra fee for the service involved, or the benign nature of the cyst when no samples are submitted for pathology review. The BC OBS provides a free service so the frequency of DCs reported here may be closer to the true value. Most reports showed a peak incidence of DCs in the second and third decades of life2,6,13,21, although some indicated the fifth decade8. The present study supports the majority results and showed a peak incidence in the second (23% of all DCs) and third (20%) decades. A significant percentage of cases also occurred in the fourth, fifth and sixth decades of life (17%, 17% and 12%, respectively). Only a very small percentage of DCs occurred in those in their first decade or the seventh decade and above. The peak age incidence must
Fig. 5. Photomicrograph of a case with co-existence of 2 cysts: the lining epithelium is characterized as an odontogenic keratocyst (*right upper) and a DC (left lower) (haematoxylin–eosin staining, original magnification 100).
be interpreted with caution. Currently many dentists in British Columbia encourage young people to have their unerupted teeth extracted. Consequently, people in the fourth decade and older may have fewer unerupted teeth, and the lower incidence of DCs in the older population may reflect this. A further population based prospective study is required to confirm the value of the prophylactic removal of unerupted/impacted teeth14. The present results demonstrated that males had a slightly higher incidence of DCs than females (1.6:1). This finding is similar to that in previous studies2,11,13. The reason for this gender predilection is not clear. DALEY et al.2 suggested that it might be related to a smaller jaw size and a greater tendency for prophylactic extraction of third molars in females. Caucasians were more likely to develop DCs than Asians. When the ethnicity distribution of the authors’ data (all 10 years, year 2006 and year 2001) with those of BC population from Statistic Canada Census (year 2006 and year 2001), the proportion of DCs in Caucasians was significantly higher than in Asians (all P < 0.0001)19,20. The annual incidence rate for Caucasians was 65–84 per million population; for Asians it was 23–27 per million population. Few studies have reported the incidence of DCs in different ethnic groups, but SHEAR & SPEIGHT17 indicated that Caucasians were more likely to develop DCs compared with Blacks. To the authors’ knowledge, this is the first report to compare the incidence of DC between Caucasians and Asians. The data suggest a higher need for prophylactic extraction of DCs in Caucasians. The present data showed that most DCs (77%) were located in the mandibular third molar region. This concurs with
A clinicopathological analysis of dentigerous cysts
881
is supported by Clinician Scientist Award of Canadian Institute of Health Research and Scholar Award from the Michael Smith Foundation for Health Research. Ethical approval
The study was approved by the Clinical Research Ethics Board at the University of British Columbia (H08-02037). References
Fig. 6. Photomicrograph of an evolving cystic ameloblastoma from a DC. The epithelial cell at the most superficial layer (*) has become enlarged and squamoid shaped with a prominent nucleus and the cells at the basal cell layer have become palisading with a suggestion of reverse polarity of the nucleus (haematoxylin–eosin staining, original magnification 200).
the majority of studies. Mandibular 3rd molars or molars (specific site not stated) are the most common site for DCs. One study from Italy found DCs were most commonly seen in the mandibular premolar region with only 4 (3%) of the 149 DCs in the mandibular molar region21. The proportion of DCs in the mandibular third molars varies in different countries: 77% in Canada2, 73% in the UK8, 51% in South Africa16, 45% in Mexico11, 43% in Brazil6, 39% in Turkey10 and 29% in Chile13. The reasons for this remain speculative. One suggestion is that DCs in Anglo-Saxons predominantly occur in the mandibular third molar region. Most patients only had one DC, but 3% (N = 51) of patients had DCs at multiple locations, predominantly (98%) involving wisdom teeth, particularly mandibular wisdom teeth. Multiple DCs have rarely been reported and are thought to be associated almost exclusively with patients with syndromes or systemic diseases9,15,22. The present results concur with recent reports5,13 but contradicted this conventional notion as none of the 51 patients had known systemic diseases/ syndromes, confirmed by telephone calls to the submitting clinicians. It is possible that the occurrence of multiple DCs is not rare but publications about them are. About 0.5% (N = 11) of cases in the present study were associated with concurrent pathology in the opposite side of the jaw (all five at the opposite mandibular third molar region: three calcifying cystic odontogenic tumor, one KCOT and one glandular odontogenic cyst) or at the same location (six odontomas, one central giant cell granulomas and one KCOT). To the best of the authors’ knowledge, there are
no reported cases presenting clinically as bilateral DCs, but histologically as an odontogenic tumour or another type of odontogenic cyst at one side and DC at the other. This study did not check the proportion of unicystic ameloblastoma or KCOT that had part of the cystic lining of a DC microscopically. The authors saw one KCOT (Fig. 5) and one cystic ameloblastoma (Fig. 6) with a portion of cystic lining consistent with a DC. This supports the notion that DC could evolve into more serious disease and shows the importance of submitting samples for pathology examination even when cysts present clinically as classical DC. In conclusion, this is the largest number of DCs reported from a population-based cohort in the literature. The results support previous findings that this is a very common jaw cyst with male predilection, a peak incidence in the second and third decades and a prevalence in Caucasians. DC could give rise to more serious diseases such as KCOT and cystic ameloblastoma. Multiple DCs were not extremely rare as previously suggested and DC could be associated with another pathology, either at the same site or at another jaw location. Competing interests
We affirm that we have no financial affiliation (e.g., employment, direct payment, stock holdings, consultancies, honoraria, ownership of shares). Any other potential conflict of interest is disclosed. Funding
LLZ is sponsored by the State Scholarship Fund of China Scholarship Council. CFP
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