LITMIR.BIZ

Figure 4.3 Mandibular buccal bifurcation cysts involving (a) an erupting first permanent molar and (b) a second permanent molar. The cysts are well demarcated and corticated and overly the buccal and periapical aspects of the tooth roots. The periodontal ligament and lamina dura are intact (arrows).

      Sources: (a) Courtesy of Dr Douglas W Stoneman. (b) Courtesy of Prof Paul Speight (Previously published: El‐Naggar AK 2017, Courtesy of IARC).

      Buccal expansion is often apparent and with involvement of the periosteum new bone may be laid down, either as a single linear band or in a laminated pattern (Figure 4.4). This pattern of laminated new bone is seen as a result of periostitis and is also seen in chronic osteomyelitis. Wolf and Hietanen (1990 ) noted this feature and suggested that clinically and radiographically, the mandibular buccal bifurcation cyst may be similar to osteomyelitis, and that in some cases the cyst may be a cause of chronic osteomyelitis, (sometimes referred to as Garré's osteomyelitis or periostitis ossificans).

      CBCT is especially useful in the diagnosis of mandibular buccal bifurcation cysts because it allows the buccal expansion and extent of the lesion to be fully visualised (Ramos et al. 2012 ; Bautista et al. 2019 ; Dave et al. 2020 ). Magnetic resonance imaging (MRI) can also be useful, but although it has the advantage of lower radiation dosage, it has very limited use in routine examination of jaw lesions in dentistry. CBCT shows a hypodense, well‐demarcated, and often spherical cystic lesion with a corticated outline, which is always located on the buccal aspect of the tooth. CBCT and occlusal radiographs show that the affected tooth is tilted buccally and transverse views show the apices abutting and occasionally eroding the lingual cortical plate (Figure 4.4; Bautista et al. 2019 ).

      Inflammatory collateral cysts at other sites show similar radiological features. The four cases associated with premolars, reported by Morimoto et al. (2004 ), showed well‐demarcated radiolucencies overlying the buccal aspect of erupting and incompletely formed premolars. There was buccal expansion and in all cases the teeth were displaced lingually. Cysts in the globulomaxillary region present as a well‐demarcated radiolucency between the lateral incisor and the canine tooth. The cyst has an ‘inverted pear’ shape and the tooth roots are displaced and diverge. All eight cases reported by Vedtofte and Holmstrup (1989 ) showed these features and in all cases both the canine and incisor tooth were fully erupted.

Radiological Differential Diagnosis

      The histological features of inflammatory collateral cysts are not specific, but taken together the clinical and radiological features should allow an accurate diagnosis (Box 4.2). In virtually all cases the cysts arise on the buccal or disto‐buccal aspect of a partially erupted or recently erupted tooth with characteristic radiological features. The associated tooth is vital. Nevertheless, as discussed previously, there is great variation in the relative frequency of these cysts in different studies and it is apparent that some workers do not recognise it as an entity. For the most part this is probably due to lack of clear diagnostic criteria and uncertainty about the pathogenesis. The key features of these lesions and diagnostic criteria are suggested in Box 4.2.