Background To clinicopathologically characterize the diagnosis of oral lichenoid disease (OLD) and its main subtypes: oral lichen planus (OLP) and oral lichenoid lesion (OLL), in order to correctly asses their prognosis. Material and Methods Ambispective cohort study of 384 patients with diagnosis of OLD, based on pre-established clinical and histopathological criteria. We have analysed 272 (70.8%) women and 112 (29.2%), whose mean age was 57.1+/-11.8 years (range 21-90); minimum follow-up time was 36 months. A specific protocol was designed for this study, where we gathered the data of each patient, including malignant transformation. Results OLP was diagnosed in 229 cases (77.9%) and OLL in 85 (22.1%). Tobacco consumption was found in 20.3% of the patients and alcohol intake in 41.1%. Liver pathology was present in 10.7% of the cases, thyroid pathology in 11.5%, arterial hypertension in 15.6%, diabetes mellitus in 7.6%, psycho-emotional disorders in 33.3%, skin involvement in 12% and genital involvement in 4.9%. Ten patients (2.6%) developed an oral squamous cell carcinoma, 5 (1.7%) with OLP and 5 (5.9%) with OLL. Conclusions OLD is a potentially malignant disorder of the oral mucosa which has to be correctly diagnosed as either OLP or OLL, since the risk of malignancy of these subtypes is significantly different. Key words: Oral lichenoid disease, oral lichen planus, oral lichenoid lesion, diagnosis, malignant transformation, prognosis.

Oral lichenoid lesions (OLLs) are linked to a heterogeneous group of pathologies involving the oral mucosa that cannot be distinguished from the oral lichen planus excepting the fact that direct causal factors such as silver amalgam restorations (SARs) can be allocated to them. Purpose: To analyze the prevalence of mucosal lesions associated with SAR in a group of SAR carrying patients in the Basque Country. Study Design: A clinical prospective study was carried out on 100 adult patients over 30 years of age at the UPV/EHU Clinical Odontology Service whose rear teeth had at least one SAR. Patients were identified and mucosal lesions and amalgam restorations were characterized. Patch tests were performed on patients with lesions and amalgams were replaced with composite material. A statistical and comparative analysis was performed with the resulting data. Results: OLLs were found in 7 patients whose predominant lesion was bilateral, asymmetrical and asymptomatic white papule-macule. Lesions were related to old and corroded SARs. Patch testing was positive in two cases. SAR substitution produced an improvement in 5 cases. Conclusions: The presence of lichenoid lesions associated with SARs is infrequent in our environment and is preferentially related to old and corroded restorations. Key words:Oral mucosa, lichenoid lesions, restoration, silver amalgam, patch test.

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