Introduction

Swedish snus is a widely used smokeless tobacco product and has been used as an alternative to combustible cigarettes. However, adverse oral effects, including gingival hyperplasia and snus-induced lesions (SILs), are commonly observed among snus users [1]. Tobacco products have also been associated with effects on periodontal tissues, including the cementum, alveolar bone, and periodontal ligament, as well as with periodontal disease [2].

In recent years, the use of non-tobacco-based nicotine pouches (NPs) has increased substantially. These products are available in different nicotine strengths, flavors, and formulations. The present study investigated two commercially available nicotine pouch products, ZYN® Dry (dry formulation) and ZYN® Moist (moist formulation), which differ in moisture content and pouch composition. Unlike conventional snus, nicotine pouches do not contain tobacco leaf and therefore lack several tobacco-specific harmful constituents, such as nitrosamines and polycyclic aromatic hydrocarbons [3].

Previous studies have demonstrated differences in nicotine release and uptake between conventional snus and nicotine pouch products, with considerable inter-individual variability reported [4–7].

Given the established effects of snus on the oral mucosa, concerns have been raised regarding whether nicotine pouches may induce similar oral changes. A previous clinical study reported that substitution of regular snus with a dry nicotine pouch product was associated with improvement of pre-existing snus-induced lesions [8]. However, limited information is available regarding the effects of nicotine pouches on the oral environment, particularly with respect to histopathological findings, inflammatory responses, and salivary biomarkers.

Therefore, the primary objective of the present study was to evaluate the effects of two non-tobacco-based nicotine pouch formulations (dry and moist) on the severity of pre-existing oral mucosal lesions following four weeks of exclusive use. Clinical, histopathological, and immunological assessments were performed at baseline and after 28 days of product substitution.