Oral health risks in users of new generation nicotine/tobacco products (NGPs): Systematic review and qualitative meta-analyses

Abstract

Background Use of traditional tobacco products, including combustible cigarettes (CCs) and smokeless oral products, is an established risk factor for various oral diseases. A potential oral health risk of using new generation tobacco/nicotine products (NGPs) such as electronic cigarettes (ECs), heated tobacco products (HTPs) and oral nicotine pouches (ONPs) is not yet well established. Methods In this systematic review, we evaluated published human studies on detrimental oral health effects in NGP users compared to CC smokers and non-users (NU). We identified 52 studies, of which almost all investigations were on EC users. The studies were extremely heterogeneous in terms of design, subjects, endpoints and quality. Reported outcomes, based on both single and grouped endpoints were qualitatively evaluated by comparing NGP users with NU and CC users. Significant increases (indicating a worsening in oral health), significant decreases (indicating an improvement) and no significant difference between groups were assigned scores of + 1, -1 and 0, respectively. Results With this approach, comparisons of EC versus NU yielded mean scores of 0.29 (pre-cancerous lesions, N = 14 observations), 0.27 (inflammatory processes, N = 83), 0.43 (oral clinical parameters, N = 93) and 0.70 (shifts in the oral microbiome, N = 10). The corresponding values for the EC versus CC comparisons amounted to: -0.33 (N = 15), -0.14 (N = 76), -0.27 (N = 78) and 0.57 (N = 7). Most of the evaluated studies have severe limitations in terms of group sizes, duration of NGP use and validity of self-reported exclusive NGP use. In particular, any dual use (EC + CC) was mostly not adequately taken into account. Conclusions The evaluated studies suggest that use of ECs is associated with some improvement of oral health effects compared to cigarette smoking (CC), but oral health is still found to be worse compared to NU. These results have to be interpreted with caution due to a number of limitations and uncertainties in the underlying studies.