Radiolucencies

For a dental professional who looks at dental radiographs frequently, coming face to face with a radiolucent lesion in the alveolar bone of our patients is an extremely common occurrence. Most often, these lesions are associated with teeth that are in need of endodontic treatment.  In fact, according to a recent article in the Journal of Endodontics,* over 90% of radiolucent lesions associated with teeth are either a cyst, apical granuloma, or an abscess.  Sometimes these lesions are affectionately referred to as LEOs (Lesions of Endodontic Origin). 

While it is clear that most radiolucent jaw lesions are LEOs, the literature is anything but clear on the distribution of the various types.  For example, different studies have reported the incidence of cysts to be anywhere from 6% to 55% and that of granulomas to be anywhere from 46% to 94%.  Such wide ranges make it difficult to predict with any accuracy the exact nature of a radiolucent lesion.  However, does it really matter whether the lesion in question is a cyst, granuloma or abscess?  Historically, this question may have been more pressing because most experts believed that surgical enucleation of cysts was necessary in addition to non-surgical root canal treatment, whereas teeth with associated granulomas could be effectively treated with root canal treatment alone.  

However, recent data suggest that even some cysts can resolve with proper non-surgical root canal treatment utilizing stringent infection control.* But what should be done when the lesion doesn’t heal (i.e. the lesion is still present radiographically with or without accompanying symptoms)?  A non-healing lesion should be followed closely to assure no changes take place over time.  If the lesion remains unchanged and the tooth remains asymptomatic, close follow-up without additional treatment may be justified.    However, it is also important to bear in mind that while they are the most common, LEOs are only one entity in a long list of entities that can cause radiolucent lesions in the jaws.   The aforementioned article in the Journal of Endodontics describes a study which utilized data from the Department of Oral Pathology at the University of Minnesota School of Dentistry. The data in this study came from biopsy samples that were analyzed over a period of 15 years representing a total of 9,723 radiolucent lesions in the jaws.  Lesions that were on the ramus or angle of the mandible were excluded.  

The researchers found a wide variety of diagnoses associated with these lesions.  In fact, 30 distinct entities were identified.In the final analysis, 73% of the biopsy samples analyzed were diagnosed as either a cyst or granuloma.  While this seems to contradict the statement made earlier that over 90% of radiolucencies are LEOs, it is important to remember that these samples were from mostly non-healing lesions.  This would result in fewer LEOs because many LEOs resolve following root canal treatment.                       

So what type of lesions made up the other 27% of biopsy samples?  Keratocystic odontogenic tumors (KOT, formerly known as odondogenic keratocyst or OKC) were the most common, making up 8.8% of the samples. Other lesions occurring in the 1-2% range included Central Giant Cell Lesions (CGCL), ameloblastomas and cemento-osseous dysplasia.  Metastatic lesions were identified in less than  1% of the samples.  As mentioned above, many other types of lesions were identified but most at less than 1%.  In summary, it is important to remember that most radiolucent lesions associated with teeth are of endodontic origin.  

However, many other entities exist and must be considered in the differential diagnosis.  Sensibility testing (percussion, palpation, thermal testing) should be performed on all teeth with associated radiolucent lesions.  An abnormal relationship between pulpal diagnosis and radiographic appearance may help identify an entity as not of endodontic origin (e.g. a vital tooth with a large radiolucency).  Non-healing lesions or lesions which don’t seem consistent with pulpal diagnosis should be followed closely and considered for biopsy.     

*Frequency and Distribution of Radiolucent Jaw Lesions: A Retrospective Analysis of 9,723 Cases.  Journal of Endodontics, Volume 38, Issue 6, Pages 729-732, June 2012.