Osteonecrosis of the jaws (ONJ) is an adverse side event of bisphosphonates and denosumab, antiresorptive agents that effectively reduce the incidence of skeletal-related events in patients with metastatic bone cancer and multiple myeloma. Available data suggest that 0-27.5% of individuals exposed to antiresorptive agents can develop ONJ. There is increasing evidence that avoidance of surgical trauma and infection to the jawbones can minimize the risk of ONJ, but there are still a significant number of individuals who develop ONJ in the absence of these risk factors. Bone necrosis is almost irreversible and there is no definitive cure for ONJ with the exclusion, in certain cases, of surgical resection. However, most ONJ individuals are affected by advanced incurable cancer and are often managed with minimally invasive nonsurgical interventions in order to control jawbone infections and painful symptoms. This article summarizes current knowledge of ONJ epidemiology, manifestations, risk-reduction and therapeutic strategies. Further research is needed in order to determine individual predisposition to ONJ and clarify the effectiveness of available treatments.

| INTRODUC TI ONOral lichen planus and lichenoid lesions comprise a group of disorders of the oral mucosa that likely represent a common reaction pattern in response to extrinsic antigens, altered self-antigens or super antigens. 1 Historically, there have been unresolved debates and controversies around the oral lichen planus and lichenoid lesions terminology. The latter term has frequently been used to refer to oral lesions that have clinical and histopathological features similar to oral lichen planus but no risk of malignant transformation, or to indicate an uncertain diagnosis of oral lichen planus. However, definitive clinical and histological diagnostic criteria able to distinguish oral lichen planus from lichenoid lesions are still lacking. 1 Furthermore, there remains no consensus regarding the possible different clinical behavior of the disorders in the oral lichen planus and lichenoid lesions group with respect to cancer development. In dermatology, the concept of 'lichenoid tissue reaction/interface dermatitis' was introduced a long time ago to define a number of distinct inflammatory cutaneous diseases sharing common histopathological features, including liquefactive/vacuolar changes of the basal keratinocytes and a subepithelial band-like array of mononuclear inflammatory cells, including activated T lymphocytes, macrophages, and dendritic cells. 1,2 During the 2006 World Workshop in Oral Medicine IV, it was proposed to classify the oral lichen planus and lichenoid lesions group in 4 distinct disorders, including oral lichen planus, oral lichenoid drug reactions caused by systemic drug exposure, oral lichenoid contact lesions triggered by local hypersensitive reaction to dental materials, and oral lichenoid lesions of graft-vs.-host disease. 3 Although a step forward, this classification failed to provide clear and reliable clinical and histological criteria to properly differentiate these 3 types of lichenoid lesions from oral lichen planus. In addition, several other disease entities characterized by clinical and/or histological features of lichenoid tissue reaction/interface dermatitis were excluded from the classification. Other authors have proposed alternative classifications. 4-6 Overall, there remains no consensus on classification, diagnostic criteria, clinical behavior, and management of the oral lichen planus and lichenoid lesions. 7-9In this review, we have attempted to (i) update the classification of oral lichen planus and lichenoid lesions, (ii) suggest pragmatic diagnostic criteria, and (iii) define a management strategy. Table 1 lists the main disorders displaying histological and/or clinical characteristics of this oral lichen planus and lichenoid lesions group. | CL A SS IFIC ATI ONSome of these disorders are apparently uncommon whereas others are poorly defined or may simply represent a misnomer. | OR AL LI CHEN PL AN USOral lichen planus is the prototype disorder of the group. Despite the lack of reliable epidemiological data, oral lichen planus is thought to be relatively commo...

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