A Retrospective Study of 23 Cases: Are Lichenoid Lesions of the Labial Mucosa Induced?

Background Lichen planus (LP) is a pathology that affects the skin and the mucosa. The lips are rarely involved but represent a diagnostic challenge in those cases. Oral lichenoid lesions (OLL) are defined as lesions that resemble oral lichen planus (OLP) but do not fully meet the clinical and/or histologic criteria for OLP. This study aimed to present our case series and to study the correlation between the location of the lesion and the dental factor (resin composite, amalgams, crowns, abrasive teeth, and mandibular crossbite) that could cause the lesion. Methods We conducted a retrospective observational study of 23 patients with LP/OLL of the lips treated in the Department of Oral Mucosal Pathology of the Department of Stomatology and Maxillofacial Surgery of the Pitié-Salpêtrière Hospital in Paris between January 2017 and February 2021. We noted the location of the lesion (upper, lower, or both lips), medical history, treatments, smoking habits, and the aspect of the teeth facing the lesion. Patients received a local corticoid treatment and were monitored via follow-up. Results Sixteen patients had lesions on the upper lip, two on the lower lip, and five on both lips, and most patients (n = 14, 60.1%) had a dental factor facing the lesion (e.g., abrasive teeth, resin composites, dental crowns, and mandibular crossbite). Six patients received clobetasol propionate, and 15 patients received a preparation combining betamethasone and benzocaine (Orabase, ConvaTec, Deeside, UK). Fourteen patients returned for post-treatment follow-up consultations approximately two months after treatment. Seven patients saw clinical improvement, five had partial improvement, and two had no improvement. Conclusions Lesions of the labial mucosa appear to be a rare condition in LP/OLL. The difference between LP and OLL can be difficult, even with histological analysis. Its pathogenesis remains unknown, although some studies found evidence of lichenoid reactions of the lips in contact with dental composite restorations. In our study, 14 of our patients had a dental factor facing the lesions. However, our study failed to show a correlation between the presence of an inducing factor and the lesion. In a future study, the potential effect of dental inducing factor removal could be studied. This topic requires further investigations, particularly regarding the inducing factor and the optimal therapeutic approach.