Shear's Cysts of the Oral and Maxillofacial Regions. Paul M. Speight

Location Distal or disto‐buccal Buccal Proportion in males 70% 55% Proportion bilateral 4% 25% Clinical features History of pericoronitis on a partially erupted tooth. Cyst is continuous with the pericoronal pocket Swelling, painful. May be signs of infection and suppuration. Tooth tipped buccally, deep pockets in continuity with cyst lumen Radiology Well‐demarcated disto‐buccal radiolucency, superimposed over roots. Distal follicular space preserved Well‐demarcated radiolucency over buccal aspect of roots, buccal expansion with corticated outline

      ^a Frequency as a proportion of inflammatory collateral cysts.

      ^b Frequency as a proportion of all odontogenic cysts.

Table 4.1 Selected papers, with a wide geographical distribution, showing the frequency of inflammatory collateral cysts as a proportion of total odontogenic cysts. Based on Philipsen et al. (2004).

	Country	n	ICC (%)
Data from references in Table 1.3
Meningaud et al. (2006 )	France	695	0
Tortorici et al. (2008 )	Italy (Sicily)	1273	0
Ali (2011 )	Kuwait	196	0
Ramachandra et al. (2011 )	India	252	0
Manor et al. (2012 )	Israel	285	0
Bhat et al. (2019 )	India	125	0
Soluk Tekkeşin et al. (2012b )	Turkey	5003	0.2
Daley et al. (1994 )	Canada	6847	0.5
Grossmann et al. (2007 )	Brazil	2812	0.7
Tamiolakis et al. (2019 )	Greece	5165	1.1
Mosqueda‐Taylor et al. (2002 )	Mexico	856	1.4
Aquilanti et al. (2021 )	Italy	2150	1.5
Sharifian and Khalili (2011 )	Iran	1227	1.8
Ochsenius et al. (2007 )	Chile	2944	3.8
Jones et al. (2006 )	UK	7121	5.6
Kammer et al. (2020 )	Brazil	406	13.6
Data from references in Table 4.2
Ackermann et al. (1989)	South Africa	1852	3.0
Craig (1976 )	UK	1051	4.7
De Sousa et al. (2001 )	Brazil	1256	4.3

      ICC, inflammatory collateral cysts; n, total number of odontogenic cysts in each study.

      Few studies have determined separately the frequencies of paradental cysts and mandibular buccal bifurcation cysts. Tamiolakis et al. (2019 ) reviewed 5165 odontogenic cysts and found only 57 (1.1%) inflammatory collateral cysts. Of these, 53 were paradental cysts on third molars and only 4 were mandibular buccal bifurcation cysts in children, suggesting frequencies of 1.0% and 0.1%, respectively. Jones et al. (2006 ) used the term paradental cyst to encompass both types of inflammatory collateral cyst, but found only 15 cases in their paediatric population (patients ≤16 years), representing 2.7% of odontogenic cysts in children (n = 553) and only 0.2% of all odontogenic cysts (n = 7121). Paradental cysts in adults comprised 376 cases, representing 5.2% of odontogenic cysts. These data suggest that paradental cysts are about 10–20 times more common than mandibular buccal bifurcation cysts.

      Overall, the data from these studies (Table 4.1) suggest that inflammatory collateral cysts represent about 4% of odontogenic cysts. It is probable, however, that they are under‐reported, because many cases received within pathology departments may have insufficient clinical or radiological information to establish the diagnosis and many may have been diagnosed as inflamed dentigerous cysts, pericoronitis, or inflamed follicles. In departments where the diagnosis is made on a regular basis, the paradental cyst appears to be a common lesion. In the series of Colgan et al. (2002 ), paradental cysts comprised 15 of 60 (25%) cystic lesions associated with lower third molars. This was the second most common diagnosis after dentigerous cyst (30%).

      In an analysis of pericoronal tissues from extracted third molars, Costa et al. (2014 ) found that 73.5% (83 of 113) showed pathological changes and of these, 55 (66.2%) were diagnosed as paradental cysts and 21 (25.3%) as dentigerous cysts. It should be noted, however, that the majority of lesions were associated with erupted or partially erupted teeth (85.5%), and only seven teeth were unerupted, suggesting that a number of dentigerous cysts were diagnosed in association with partially erupted impacted third molars. Mohammed et al. (2019 ) undertook a similar