href="#ulink_edac6bef-a938-51a0-8bdf-48c28b9c783e">Sex
Site
Clinical Presentation
Radiological Features Radiological Differential Diagnosis
Pathogenesis Relationship of the Paradental Cyst to the Dentigerous Cyst
Inflammatory collateral cysts are cysts of inflammatory origin that are found towards the buccal aspect of the roots of partially or recently erupted teeth. They arise as a result of inflammation in the pericoronal tissues, but the pathogenesis and the epithelium of origin remain uncertain. Although it is possible for a collateral cyst to arise on any erupting tooth, the vast majority are associated with mandibular molars, with about 60% on third molars and most of the remainder seen on the buccal aspect of first or second molars. Thus, two main types of inflammatory collateral cyst are recognised: the paradental cyst, found predominantly on mandibular third molars, and the mandibular buccal bifurcation cyst, found on first or second molars (Speight and Soluk Tekkeşin 2022b ). In some respects the collateral cysts remain controversial, since it is clear that in some quarters their very existence is questioned. There are a number of papers reporting lesions associated with impacted third molars that do not include a single case of paradental cyst (Curran et al. 2002 ; Stathopoulos et al. 2011 ), while other series of pericoronal lesions on mandibular third molars have suggested that more than 50% may be paradental cysts (Costa et al. 2014 ). One reason for these discrepancies may be the very nature of the cyst itself. The lesion presents as a ballooning of the pericoronal tissues to form a pocket (Ackermann et al. 1987 ; Slater 2003 ) that some may not regard as a true cyst, while others regard it as a simple variant of a dentigerous cyst. Nevertheless, the clinical and radiological features are those of a cystic lesion and the inflammatory collateral cysts are widely accepted as an entity and are included in the World Health Organization (WHO) classification of jaw cysts (WHO 2022a ; Speight and Soluk Tekkeşin 2022b ).
Classification and Terminology of Inflammatory Collateral Cysts
In 1970 Main proposed a classification of jaw cysts based on a review and analysis of 274 odontogenic cysts. He found eight cysts (2.9%) that arose ‘alongside a vital tooth involved in pericoronitis’, which he called an inflammatory collateral cyst, in recognition of their association with chronic inflammation and a location on the lateral aspect of a tooth. This term also distinguishes it from a radicular cyst associated with a lateral accessory root canal of a non‐vital tooth, and from a developmental lateral periodontal cyst. Seven of his eight cases arose on mandibular third molars, and one on an impacted upper canine (Main 1970 ). Main's 1970 paper is often cited as the first report of this cyst, but Philipsen et al. (2004 ) found that Hofrath in 1930 had reported several jaw cysts on mandibular third molars affected by pericoronitis. Hofrath called these cysts ‘marginal wisdom tooth cyst’, but all the features were consistent with the inflammatory collateral cyst described by Main (1970 ) and the paradental cyst as currently defined.
The first detailed account of inflammatory collateral cysts was by Craig (1976 ), who described a cyst of inflammatory origin that occurred on the lateral aspect of the roots of partially erupted mandibular third molars where there was an associated history of pericoronitis. He recognised that these cysts were the same clinicopathological entity as the inflammatory collateral cyst described by Main (1970 ), but he was the first to suggest the term paradental cyst. He felt this was more appropriate for this lesion because it emphasised the odontogenic associations of the cyst and its location adjacent to a tooth.
Craig's series consisted of 49 cysts in 48 patients, which represented about 5% of odontogenic cysts seen in his department over a 21‐year period. In all cases the involved tooth was partially erupted and was associated with a history of pericoronitis. In terms of location, 26 cysts were on the buccal aspect of the roots, 19 were distal, and 4 were mesial, but Craig was of the opinion that there was some buccal involvement even in those cysts designated clinically as of mesial or distal location. Macroscopically, the cysts were firmly attached to the bifurcation area on the buccal aspects of the roots, and extended up to the cementoenamel junction. Craig's description of the paradental cyst associated with third molar teeth has become the defining feature of this lesion.
Craig's paper on the paradental cyst was, for a number of years, the only detailed account of the entity. Subsequently, however, Ackermann et al. (1987 ) described 50 cases, all of which arose on impacted third molars and had similar features to those described by Craig. This was soon followed by a report of 6 cases by Fowler and Brannon (1989 ) and 15 cases by Vedtofte and Praetorius (1989 ), and then by numerous case reports and a number of case series or reviews (de Sousa et al. 2001 ; Colgan et al. 2002 ; Philipsen et al. 2004 ; Mohammed et al. 2019 ).
In 1983, Stoneman and Worth described 17 cases of a lesion that was similar to the inflammatory collateral cyst (Main 1970 ) and the paradental cyst (Craig 1976 ), but that arose primarily on the buccal aspect of mandibular first and second molars in children. They named this entity the mandibular infected buccal cyst to emphasise its origin in inflamed periodontal tissues of partially or fully erupted molars. Stoneman and Worth (1983 ) did not refer to the reports of Main or Craig and although they emphasised their lesion as being on first and second molars, three of their cases involved the third molar region. It seems therefore that the mandibular infected buccal cyst and paradental cyst share similar clinical and histological features and should be regarded as variants of the same lesion. This is suggested by more recent papers that have reappraised these cysts and consider them to be the same entity (Packota et al. 1990 ; Wolf and Hietanen 1990 ; Thurnwald et al. 1994 ; Pompura et al. 1997 ; Thompson et al. 1997 ; Chrcanovic et al. 2011 ; Ramos et al. 2012 ). Pompura et al. (1997 ) suggested the term mandibular buccal bifurcation cyst for these lesions, since it described the location of the cyst and reflected the fact that not all lesions are overtly infected.
None of these cysts appeared in the first (1972) edition of the WHO classification of odontogenic tumours and cysts, but they were included in the second edition (Kramer et al. 1992 ). The 1992 WHO classification used the term paradental cyst, but included inflammatory collateral cyst and mandibular infected buccal cyst as synonyms. The classification did however make a distinction between cysts arising in association with third molars and a distinctive variant arising on the buccal aspect of first molars in children.
In a review of the world literature, Philipsen et al. (2004 ) concurred with this view, but found that the literature included at least 16 names for these cysts, including marginal wisdom tooth cyst (Hofrath 1930 ), inflammatory collateral cyst (Main 1970 ), paradental cyst (Craig 1976 ), mandibular infected buccal cyst (Stoneman and Worth 1983 ), and mandibular buccal bifurcation cyst (Pompura et al. 1997 ). Slater (2003 ) had suggested eruption pocket cyst, which nicely describes the association with an erupting tooth as well the morphological feature of a pocket cyst. Nevertheless, this name was never used again in the literature. Philipsen et al. (2004 ) preferred to use the term inflammatory paradental cyst to encompass all the collateral cysts of inflammatory origin. They pointed out, however, that differences in clinical presentation and appearance justify separating the cyst into clinicopathological variants. In the literature up to 2004 they identified reports of 342 patients with 377
