Although there were Western case series included in the SR, significantly more were excluded in comparison with the higher proportion of East Asian case series included in the SR. This may simply reflect an increased awareness of OOC by East Asian reporters. The four SR-included reports on five communities,35,39,46,53
which focused solely on the OOC, were from the East Asian global group. This degree of interest in the OOC was in marked contrast to Western case series; however, they recorded, proportionally, significantly more OOCs within their keratocyst case series (refer to the SR on KCOTs11
). The four East Asian reports36,40,47,55
focused on the OOC were intrigued by its different character from the majority of keratocysts.
The marked absence of SR-included reports on OOCs from the sub-Saharan global group was consistent with the SR on KCOT. These findings are a marked contrast to the SR of another odontogenic lesion, the ameloblastoma.9,10
This has already been discussed in the SR on KCOTs.11
There was no significant difference between the reports excluded from the SR on the basis of, language of publication or source.
stated that OOCs did not occur in naevoid basal cell carcinoma syndrome, Bolbaran and et al49,50
reported one case that did.
In only the second decade exhibited a preponderance of females in the overall synthesis. As this decade coincides with the menarche this could suggest that there may be a hormonal element to the occurrence of this lesion in females at this age. On closer examination it can be observed that this phenomenon is largely owing to el Hajj et al's Western report.44
The significantly shorter period between first awareness of the lesion and first presentation for treatment among the Hong Kong Chinese60
compared with an earlier Malaysian report36
may suggest a greater awareness of the need to treat oral and maxillary lesions in the former community. On the other hand, a recent report indicated that although the Hong Kong Chinese reported a memory of a painful episode affecting the mouth, few actually took action.62
The significantly shorter period between first awareness of the lesion and first presentation for its treatment was also noted with regards to KCOT affecting the same community.60
The reason for this unexpected phenomenon has already been discussed.60
48% of OOC were discovered as incidental findings, 41% first presented with swellings and 24% first presented with pain. These differ not only between global groups, but also within a clearly defined global group, such as the East Asian group. All 5 cases in the Hong Kong Chinese report60
presented with symptoms, whereas 75% of the 12 OOC cases in the Vuhalula et al Japanese report40
were discovered as incidental findings. This suggests that the Japanese patients presented for reasons other than OOC. Nevertheless, the East Asian global group was significantly associated with swelling, as the primary presenting symptom, even when the Vuhahula et al report40
was included. Although this suggests that OOCs affecting the East Asian global group might be more aggressive, it was only the Western group that reported recurrences.
All global groups displayed a predilection for the mandible, particularly the posterior sextants; however, the 68% association with unerupted third molars was not expected, particularly as the largest of such reports was an American report.39
A possible explanation for this is that this report may not have been affected by the routine prophylactic removal of third molars. Vuhahula et al40
described most of the OOCs as dentigerous cysts with orthokeratinization. The association with unerupted teeth suggests that many OOCs may have first developed during adolescence, when the third molars were developing, and were only noticed later either owing to the development of symptoms or as an incidental discovery during investigation of another dental problem.
shows the important statistical differences between the present SR and that of the KCOT.11
The KCOT's incidence is more than eight times that of the OOC, reflecting the 10% proportion of OOCs of the formerly known odontogenic keratocyst (refer to the SR on KCOTs11
). The lack of difference between the two SRs, regarding the range of years of the reports they included, is not surprising as the majority of SR-included reports for both SRs were the same. The mean age at first presentation of KCOTs was 3 years older than that of OOC; this difference was not significant. Although the OOC is more likely to present in males, this is not significant. 28% of KCOTs recur in contrast to the 4% recurrence rate of OOC. The margins of all cases of the two small case series of OOCs, reported so far, were well-defined, whereas over a third of KCOTs first presented were poorly defined. KCOT first presented with swelling significantly more frequently than OOCs, but OOCs were significantly more associated with unerupted teeth.
Comparison between keratocystic odontogenic tumour (KCOT) and orthokeratinized odontogenic cyst (OOC): systematic review - number of radiological features per SR-included reports in relation to global groups